Initial commit.

## Launch Checklist

This PR increases coverage by adding unit tests to lib folde, replace
the skipped end to end placeholder with actual tests and adds more end
to end tests.

This was mostly done by AI (Claude opus 4.8) and I reviewed it and
requested changes where needed.

 - [x] Briefly describe the changes in this PR.
 - [x] Link to related issues.
- [x] Include before/after visuals or gifs if this PR includes visual
changes.
 - [x] Write tests for all new functionality.
 - [x] Add an entry to `CHANGELOG.md` under the `## main` section.

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Co-authored-by: Copilot Autofix powered by AI <62310815+github-advanced-security[bot]@users.noreply.github.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

.github/workflows/ci.yml

@@ -96,7 +96,6 @@ jobs:
         with:
           node-version-file: '.nvmrc'
       - run: npm ci
-      - run: npx playwright install --with-deps chromium
       - run: npm run test-unit-ci
       - name: Upload coverage reports to Codecov
         uses: codecov/codecov-action@fb8b3582c8e4def4969c97caa2f19720cb33a72f # v7.0.0
@@ -164,8 +163,3 @@ jobs:
         run: npm run test-e2e
         env:
           E2E_NO_WEBSERVER: "1"
-      - name: Upload coverage reports to Codecov
-        uses: codecov/codecov-action@fb8b3582c8e4def4969c97caa2f19720cb33a72f # v7.0.0
-        with:
-          files: ${{ github.workspace }}/coverage/coverage-final.json
-          verbose: true

AGENTS.md

@@ -36,7 +36,7 @@ Then run the end-to-end tests (Playwright starts the dev server automatically):
 npm run test
 ```
 
-Run the unit and component tests with Vitest:
+Run the unit tests with Vitest:
 
 ```
 npm run test-unit
@@ -45,3 +45,106 @@ npm run test-unit
 ## Pull Requests
 
 - Pull requests should update `CHANGELOG.md` with a short description of the change.
+
+## Testing
+
+### Prefer end-to-end tests
+
+Most of this codebase is React components, and they are only reachable from an
+end-to-end test. E2E coverage is the primary signal.
+
+Reach for a unit test only for pure logic that e2e cannot cheaply reach (parsers,
+sorting, watchers, stores). Before writing one, check whether e2e already covers
+the file — a unit test that duplicates existing e2e coverage adds test code and
+almost no coverage:
+
+```
+npx nyc report --reporter=text --include="src/libs/style.ts"
+```
+
+Do **not** merge the Vitest (v8) and e2e (istanbul) coverage reports locally. They
+produce conflicting statement maps for the same files and the combined percentage
+is meaningless. Codecov merges the two uploads server-side; that is the number to
+trust. Locally, read them separately:
+
+- e2e: `npx playwright test` then `npx nyc report --reporter=text-summary` (reads `.nyc_output/`)
+- unit: `npx vitest run --coverage` (writes `coverage/`)
+
+### E2E layering
+
+Three layers, and the boundaries matter:
+
+- `e2e/playwright-helper.ts` — generic, app-agnostic browser actions. **The only
+  file allowed to import `@playwright/test`** (besides `e2e/utils/fixtures.ts`).
+- `e2e/maputnik-driver.ts` — domain actions (layers, filters, functions, the
+  style). Knows nothing about `page` or Playwright.
+- `e2e/modal-driver.ts` — actions scoped to a modal, exposed as `when.modal.*`.
+
+Specs get a driver at describe scope and assert fluently:
+
+```ts
+describe("layer editor", () => {
+  const { given, get, when, then } = new MaputnikDriver();
+  ...
+  await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({ layers: [{ id, type: "fill" }] });
+});
+```
+
+New UI interactions belong in a driver, not inline in a spec.
+
+### Writing assertions
+
+- `shouldDeepNestedInclude` is a recursive partial match (`toMatchObject`): nested
+  objects are matched as subsets, arrays and primitives must match exactly
+  (including array length).
+- Assert against the whole style, not an extracted slice. Avoid
+  `get.styleFromLocalStorage().then(style => style.layers.find(...))` — it moves
+  test logic into the test. Compare the real object instead.
+- `Query.then()` is lazy and returns a new `Query`, **not** a Promise. `await
+  get.styleFromLocalStorage()` hangs forever. Use `.get()` to await it directly,
+  or pass the Query to `then(...)`.
+
+### One behaviour per test
+
+If a test needs comments narrating "and now this…", it is several tests. Split it,
+and hoist the shared setup into a nested `describe` + `beforeEach`.
+
+### Test ids
+
+Test ids use the `data-wd-key` attribute and are read via `get.elementByTestId`.
+
+The `Input*` components already accept `data-wd-key` and render it on the real
+`<input>`; the `Field*` wrappers forward it through their `{...props}` spread. So
+passing `data-wd-key` to a `Field*` component is usually enough. Do **not** also
+add it to `Block`/`Fieldset` — the id then matches two elements and locators fail
+in strict mode.
+
+Note `InputNumber` renders `<key>-text` and `<key>-range` when `allowRange` is set,
+and `<key>` otherwise.
+
+### Input commit semantics (common source of "the value didn't save")
+
+- `InputString` only fires its `onChange` on **blur** or **Enter**. Typing alone
+  fires `onInput`. A driver that calls `fill()` must then call `blur()`, or the
+  value never reaches the style.
+- `InputNumber` commits on every change; no blur needed.
+- The autocomplete inputs (layer source, add-layer source) are controlled
+  downshift comboboxes. Keystroke typing is dropped/reordered — `{selectall}` then
+  typing `raster` yields `"exampleaster"`. Use `fill()`, which dispatches a single
+  input event, then pick from the filtered menu.
+- CodeMirror auto-closes brackets and quotes, and types over its own closers, so
+  inserting a well-formed JSON fragment stays well-formed. To break JSON on
+  purpose, insert a bare word.
+
+### Fixtures
+
+Style fixtures live in `e2e/fixtures/`. A new one must be registered in two places
+in `maputnik-driver.ts`: the list in `given.setupMockBackedResponses` and the
+`styleFileByKey` map in `when.setStyle`.
+
+### Verify a new test can fail
+
+A test that passes for the wrong reason is worse than no test. After writing one,
+mutate the expected value and confirm it fails. This has caught real mistakes
+(e.g. a driver that never committed its input, so the assertion was matching a
+value written by the *previous* step).

e2e/access-tokens.spec.ts

@@ -0,0 +1,60 @@
+import { test, expect, describe, beforeEach } from "./utils/fixtures";
+import { MaputnikDriver } from "./maputnik-driver";
+import tokens from "../src/config/tokens.json" with { type: "json" };
+
+describe("access tokens", () => {
+  const { given, when } = new MaputnikDriver();
+
+  const tileJson = {
+    tilejson: "2.2.0",
+    tiles: ["https://example.local/{z}/{x}/{y}.pbf"],
+    minzoom: 0,
+    maxzoom: 14,
+  };
+
+  beforeEach(async () => {
+    await given.setupMockBackedResponses();
+  });
+
+  test("uses the thunderforest token for a thunderforest source", async () => {
+    await given.interceptAndMockResponse({
+      method: "GET",
+      url: /tile\.thunderforest\.com\/.*/,
+      response: tileJson,
+      alias: "thunderforest",
+    });
+
+    await when.setStyle("access_tokens");
+
+    const request = await when.waitForResponse("thunderforest");
+    expect(request.url()).toContain(`apikey=${tokens.thunderforest}`);
+  });
+
+  test("uses the locationiq token for a locationiq source", async () => {
+    await given.interceptAndMockResponse({
+      method: "GET",
+      url: /tiles\.locationiq\.com\/.*/,
+      response: tileJson,
+      alias: "locationiq",
+    });
+
+    await when.setStyle("access_tokens");
+
+    const request = await when.waitForResponse("locationiq");
+    expect(request.url()).toContain(`key=${tokens.locationiq}`);
+  });
+
+  test("appends the stadia token as a query parameter", async () => {
+    await given.interceptAndMockResponse({
+      method: "GET",
+      url: /tiles\.stadiamaps\.com\/.*/,
+      response: tileJson,
+      alias: "stadia",
+    });
+
+    await when.setStyle("access_tokens");
+
+    const request = await when.waitForResponse("stadia");
+    expect(request.url()).toContain("?api_key=stadia-test-token");
+  });
+});

e2e/accessibility.spec.ts

@@ -1,16 +1,16 @@
-import { test } from "./fixtures";
+import { test, describe, beforeEach } from "./utils/fixtures";
 import { MaputnikDriver } from "./maputnik-driver";
 
-test.describe("accessibility", () => {
+describe("accessibility", () => {
   const { given, get, when, then } = new MaputnikDriver();
 
-  test.beforeEach(async () => {
+  beforeEach(async () => {
     await given.setupMockBackedResponses();
     await when.setStyle("both");
   });
 
-  test.describe("skip links", () => {
-    test.beforeEach(async () => {
+  describe("skip links", () => {
+    beforeEach(async () => {
       await when.setStyle("layer");
     });
 

e2e/code-editor.spec.ts

@@ -1,10 +1,10 @@
-import { test } from "./fixtures";
+import { beforeEach, describe, test } from "./utils/fixtures";
 import { MaputnikDriver } from "./maputnik-driver";
 
-test.describe("code editor", () => {
+describe("code editor", () => {
   const { given, get, when, then } = new MaputnikDriver();
 
-  test.beforeEach(async () => {
+  beforeEach(async () => {
     await given.setupMockBackedResponses();
     await when.setStyle("both");
   });

e2e/coverage.ts

@@ -1,30 +0,0 @@
-import fs from "node:fs";
-import path from "node:path";
-import type { Page } from "@playwright/test";
-
-const OUTPUT_DIR = path.resolve(process.cwd(), ".nyc_output");
-
-/**
- * Reads the istanbul coverage object (injected by vite-plugin-istanbul) from the
- * given page. Returns `null` when the page has not been instrumented.
- */
-export async function readCoverage(page: Page): Promise<unknown | null> {
-  try {
-    return await page.evaluate(() => (window as unknown as { __coverage__?: unknown }).__coverage__ ?? null);
-  } catch {
-    // Page might be navigating/closed.
-    return null;
-  }
-}
-
-/**
- * Persists a coverage chunk to `.nyc_output` so that `nyc report` can merge it.
- * istanbul-lib-coverage (used by nyc) sums the hit counts across every file it
- * finds, so writing one file per chunk is enough to accumulate coverage across
- * navigations and tests.
- */
-export function writeCoverage(coverage: unknown, id: string): void {
-  if (!coverage) return;
-  fs.mkdirSync(OUTPUT_DIR, { recursive: true });
-  fs.writeFileSync(path.join(OUTPUT_DIR, `playwright-${id}.json`), JSON.stringify(coverage));
-}

e2e/fixtures.ts

@@ -1,46 +0,0 @@
-import { test as base, expect, type Page } from "@playwright/test";
-import { readCoverage, writeCoverage } from "./coverage";
-
-let activePage: Page | undefined;
-const coverageChunks: unknown[] = [];
-
-/** The page for the currently running test. Throws if used outside a test. */
-export function currentPage(): Page {
-  if (!activePage) {
-    throw new Error("No active page: a MaputnikDriver method was called outside of a running test.");
-  }
-  return activePage;
-}
-
-/** Records a coverage snapshot (called before navigations, which reset __coverage__). */
-export function recordCoverageChunk(chunk: unknown): void {
-  if (chunk) coverageChunks.push(chunk);
-}
-
-/**
- * Auto fixture that binds the current test's page for the (page-lazy)
- * MaputnikDriver, auto-accepts confirm dialogs, and writes the istanbul
- * coverage collected during the test to `.nyc_output`.
- */
-export const test = base.extend<{ maputnikPage: void }>({
-  maputnikPage: [
-    async ({ page }, use, testInfo) => {
-      activePage = page;
-      coverageChunks.length = 0;
-      // Accept confirm dialogs (e.g. the "replace current style" prompt). These
-      // are dismissed by default, which would cancel loading a style via URL.
-      page.on("dialog", (dialog) => dialog.accept().catch(() => undefined));
-
-      await use();
-
-      const finalCoverage = await readCoverage(page);
-      if (finalCoverage) coverageChunks.push(finalCoverage);
-      coverageChunks.forEach((chunk, index) => writeCoverage(chunk, `${testInfo.testId}-${index}`));
-      coverageChunks.length = 0;
-      activePage = undefined;
-    },
-    { auto: true },
-  ],
-});
-
-export { expect };

e2e/fixtures/access-token-style.json

@@ -0,0 +1,22 @@
+{
+  "version": 8,
+  "name": "Access token style",
+  "metadata": {
+    "maputnik:stadia_access_token": "stadia-test-token"
+  },
+  "sources": {
+    "thunderforest_transport": {
+      "type": "vector",
+      "url": "https://tile.thunderforest.com/thunderforest.transport-v2.json?apikey={key}"
+    },
+    "stadia_outdoors": {
+      "type": "vector",
+      "url": "https://tiles.stadiamaps.com/data/openmaptiles.json"
+    },
+    "locationiq": {
+      "type": "vector",
+      "url": "https://tiles.locationiq.com/v3/pbf/tiles.json?key={key}"
+    }
+  },
+  "layers": []
+}

e2e/history.spec.ts

@@ -1,13 +1,13 @@
-import { test } from "./fixtures";
+import { beforeEach, describe, test } from "./utils/fixtures";
 import { MaputnikDriver } from "./maputnik-driver";
 
-test.describe("history", () => {
+describe("history", () => {
   const { given, get, when, then } = new MaputnikDriver();
 
   const undoKeyCombo = process.platform === "darwin" ? "{meta}z" : "{ctrl}z";
   const redoKeyCombo = process.platform === "darwin" ? "{meta}{shift}z" : "{ctrl}y";
 
-  test.beforeEach(async () => {
+  beforeEach(async () => {
     await given.setupMockBackedResponses();
     await when.setStyle("both");
   });

e2e/i18n.spec.ts

@@ -1,15 +1,15 @@
-import { test } from "./fixtures";
+import { beforeEach, describe, test } from "./utils/fixtures";
 import { MaputnikDriver } from "./maputnik-driver";
 
-test.describe("i18n", () => {
+describe("i18n", () => {
   const { given, get, when, then } = new MaputnikDriver();
 
-  test.beforeEach(async () => {
+  beforeEach(async () => {
     await given.setupMockBackedResponses();
     await when.setStyle("both");
   });
 
-  test.describe("language detector", () => {
+  describe("language detector", () => {
     test("English", async () => {
       await when.visit("?lng=en");
       await then(get.elementByTestId("maputnik-lang-select")).shouldHaveValue("en");
@@ -21,8 +21,8 @@ test.describe("i18n", () => {
     });
   });
 
-  test.describe("language switcher", () => {
-    test.beforeEach(async () => {
+  describe("language switcher", () => {
+    beforeEach(async () => {
       await when.setStyle("layer");
     });
 

e2e/keyboard.spec.ts

@@ -1,16 +1,16 @@
-import { test } from "./fixtures";
+import { beforeEach, describe, test } from "./utils/fixtures";
 import { MaputnikDriver } from "./maputnik-driver";
 
-test.describe("keyboard", () => {
+describe("keyboard", () => {
   const { given, get, when, then } = new MaputnikDriver();
 
-  test.beforeEach(async () => {
+  beforeEach(async () => {
     await given.setupMockBackedResponses();
     await when.setStyle("both");
   });
 
-  test.describe("shortcuts", () => {
-    test.beforeEach(async () => {
+  describe("shortcuts", () => {
+    beforeEach(async () => {
       await given.setupMockBackedResponses();
       await when.setStyle("");
     });

e2e/layer-editor.spec.ts

@@ -1,11 +1,11 @@
 import { v1 as uuid } from "uuid";
-import { test } from "./fixtures";
+import { beforeEach, describe, test } from "./utils/fixtures";
 import { MaputnikDriver } from "./maputnik-driver";
 
-test.describe("layer editor", () => {
+describe("layer editor", () => {
   const { given, get, when, then } = new MaputnikDriver();
 
-  test.beforeEach(async () => {
+  beforeEach(async () => {
     await given.setupMockBackedResponses();
     await when.setStyle("both");
     await when.modal.open();
@@ -25,7 +25,18 @@ test.describe("layer editor", () => {
     return id;
   }
 
-  test.skip("expand/collapse", () => {});
+  test("expand/collapse", async () => {
+    const bgId = await createBackground();
+    await when.click("layer-list-item:background:" + bgId);
+
+    await then(get.elementByTestId("layer-editor.layer-id.input")).shouldBeVisible();
+
+    await when.toggleGroupInLayerEditor("Layer");
+    await then(get.elementByTestId("layer-editor.layer-id.input")).shouldNotBeVisible();
+
+    await when.toggleGroupInLayerEditor("Layer");
+    await then(get.elementByTestId("layer-editor.layer-id.input")).shouldBeVisible();
+  });
 
   test("id", async () => {
     const bgId = await createBackground();
@@ -41,7 +52,7 @@ test.describe("layer editor", () => {
     });
   });
 
-  test.describe("source", () => {
+  describe("source", () => {
     test("should show error when the source is invalid", async () => {
       await when.modal.fillLayers({
         type: "circle",
@@ -53,10 +64,10 @@ test.describe("layer editor", () => {
     });
   });
 
-  test.describe("min-zoom", () => {
+  describe("min-zoom", () => {
     let bgId: string;
 
-    test.beforeEach(async () => {
+    beforeEach(async () => {
       bgId = await createBackground();
       await when.click("layer-list-item:background:" + bgId);
       await when.setValue("min-zoom.input-text", "1");
@@ -76,12 +87,20 @@ test.describe("layer editor", () => {
         layers: [{ id: "background:" + bgId, type: "background", minzoom: 1 }],
       });
     });
+
+    test("the range slider adjusts min-zoom", async () => {
+      await when.focus("min-zoom.input-range");
+      await when.typeKeys("{rightarrow}");
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        layers: [{ id: "background:" + bgId, type: "background", minzoom: 2 }],
+      });
+    });
   });
 
-  test.describe("max-zoom", () => {
+  describe("max-zoom", () => {
     let bgId: string;
 
-    test.beforeEach(async () => {
+    beforeEach(async () => {
       bgId = await createBackground();
       await when.click("layer-list-item:background:" + bgId);
       await when.setValue("max-zoom.input-text", "1");
@@ -95,11 +114,11 @@ test.describe("layer editor", () => {
     });
   });
 
-  test.describe("comments", () => {
+  describe("comments", () => {
     let bgId: string;
     const comment = "42";
 
-    test.beforeEach(async () => {
+    beforeEach(async () => {
       bgId = await createBackground();
       await when.click("layer-list-item:background:" + bgId);
       await when.setValue("layer-comment.input", comment);
@@ -118,8 +137,8 @@ test.describe("layer editor", () => {
       });
     });
 
-    test.describe("when unsetting", () => {
-      test.beforeEach(async () => {
+    describe("when unsetting", () => {
+      beforeEach(async () => {
         await when.clear("layer-comment.input");
         await when.click("min-zoom.input-text");
       });
@@ -132,9 +151,9 @@ test.describe("layer editor", () => {
     });
   });
 
-  test.describe("color", () => {
+  describe("color", () => {
     let bgId: string;
-    test.beforeEach(async () => {
+    beforeEach(async () => {
       bgId = await createBackground();
       await when.click("layer-list-item:background:" + bgId);
       await when.click("spec-field:background-color");
@@ -145,11 +164,18 @@ test.describe("layer editor", () => {
         layers: [{ id: "background:" + bgId, type: "background" }],
       });
     });
+
+    test("typing a hex value updates the paint color", async () => {
+      await when.setColorValue("background-color", "#ff0000");
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        layers: [{ id: "background:" + bgId, type: "background", paint: { "background-color": "#ff0000" } }],
+      });
+    });
   });
 
-  test.describe("opacity", () => {
+  describe("opacity", () => {
     let bgId: string;
-    test.beforeEach(async () => {
+    beforeEach(async () => {
       bgId = await createBackground();
       await when.click("layer-list-item:background:" + bgId);
       await when.type("spec-field-input:background-opacity", "0.");
@@ -165,33 +191,343 @@ test.describe("layer editor", () => {
     });
   });
 
-  test.describe("filter", () => {
-    test.skip("expand/collapse", () => {});
-    test.skip("compound filter", () => {});
+  describe("filter", () => {
+    let id: string;
+
+    beforeEach(async () => {
+      id = await when.modal.fillLayers({ type: "fill", layer: "example" });
+      await when.addFilter();
+    });
+
+    test("should add a filter item", async () => {
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        layers: [{ id, type: "fill", source: "example", filter: ["all", ["==", "name", ""]] }],
+      });
+    });
+
+    test("should change the filter operator", async () => {
+      await when.selectFilterOperator("!=");
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        layers: [{ id, filter: ["all", ["!=", "name", ""]] }],
+      });
+    });
+
+    test("should extend the compound filter with a second item", async () => {
+      await when.addFilter();
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        layers: [{ id, filter: ["all", ["==", "name", ""], ["==", "name", ""]] }],
+      });
+    });
+
+    test("should change the combining operator", async () => {
+      await when.selectFilterCombiningOperator("any");
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        layers: [{ id, filter: ["any", ["==", "name", ""]] }],
+      });
+    });
+
+    test("should delete a filter item", async () => {
+      await when.addFilter();
+      await when.deleteFilterItem();
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        layers: [{ id, filter: ["all", ["==", "name", ""]] }],
+      });
+    });
+
+    describe("when converted to an expression", () => {
+      beforeEach(async () => {
+        await when.convertFilterToExpression();
+      });
+
+      test("should migrate the filter to an expression", async () => {
+        // A single-item "all" collapses to the bare comparison when migrated.
+        await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+          layers: [{ id, filter: ["==", ["get", "name"], ""] }],
+        });
+      });
+
+      test("should restore the default filter when the expression is deleted", async () => {
+        await when.deleteFilterExpression();
+        await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+          layers: [{ id, filter: ["all"] }],
+        });
+      });
+    });
   });
 
-  test.describe("layout", () => {
+  describe("functions", () => {
+    let id: string;
+
+    describe("zoom function", () => {
+      beforeEach(async () => {
+        id = await when.modal.fillLayers({ type: "circle", layer: "example" });
+        await when.makeZoomFunction("circle-radius");
+      });
+
+      test("should convert the property to a zoom function", async () => {
+        await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+          layers: [
+            { id, type: "circle", source: "example", paint: { "circle-radius": { stops: [[6, 5], [10, 5]] } } },
+          ],
+        });
+      });
+
+      test("should add a stop", async () => {
+        await when.addFunctionStop("circle-radius");
+        await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+          layers: [{ id, paint: { "circle-radius": { stops: [[6, 5], [10, 5], [11, 5]] } } }],
+        });
+      });
+
+      test("should delete the first stop", async () => {
+        // A function needs more than two stops, otherwise deleting one collapses
+        // it back into a plain value.
+        await when.addFunctionStop("circle-radius");
+        await when.deleteFunctionStop("circle-radius");
+        await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+          layers: [{ id, paint: { "circle-radius": { stops: [[10, 5], [11, 5]] } } }],
+        });
+      });
+
+      test("should set the base", async () => {
+        await when.setFunctionBase("circle-radius", "2");
+        await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+          layers: [{ id, paint: { "circle-radius": { base: 2, stops: [[6, 5], [10, 5]] } } }],
+        });
+      });
+
+      test("should edit the zoom of a stop", async () => {
+        await when.setFunctionStopValue("circle-radius", "Zoom", 0, "3");
+        await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+          layers: [{ id, paint: { "circle-radius": { stops: [[3, 5], [10, 5]] } } }],
+        });
+      });
+
+      test("should edit the output value of a stop", async () => {
+        await when.setFunctionStopValue("circle-radius", "Output value", 0, "9");
+        await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+          layers: [{ id, paint: { "circle-radius": { stops: [[6, 9], [10, 5]] } } }],
+        });
+      });
+
+      test("should convert to an expression", async () => {
+        await when.makeExpression("circle-radius");
+        await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+          layers: [{ id, paint: { "circle-radius": ["interpolate", ["linear"], ["zoom"], 6, 5, 10, 5] } }],
+        });
+      });
+
+      describe("when converted to a data function", () => {
+        beforeEach(async () => {
+          // Any non-interpolate scale turns the zoom function into a data one.
+          await when.selectFunctionType("circle-radius", "categorical");
+        });
+
+        test("should carry the stops over as zoom/value pairs", async () => {
+          await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+            layers: [
+              {
+                id,
+                paint: {
+                  "circle-radius": {
+                    property: "",
+                    type: "exponential",
+                    stops: [[{ zoom: 6, value: 0 }, 5], [{ zoom: 10, value: 0 }, 5]],
+                  },
+                },
+              },
+            ],
+          });
+        });
+
+        test("should convert back to a zoom function", async () => {
+          await when.selectFunctionType("circle-radius", "interpolate");
+          await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+            layers: [{ id, paint: { "circle-radius": { stops: [[6, 5], [10, 5]] } } }],
+          });
+        });
+      });
+    });
+
+    describe("data function", () => {
+      beforeEach(async () => {
+        id = await when.modal.fillLayers({ type: "circle", layer: "example" });
+        await when.setValue("spec-field-input:circle-blur", "1");
+        await when.makeDataFunction("circle-blur");
+      });
+
+      test("should convert the property to a data function", async () => {
+        await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+          layers: [
+            {
+              id,
+              type: "circle",
+              source: "example",
+              paint: {
+                "circle-blur": {
+                  property: "",
+                  type: "exponential",
+                  stops: [[{ zoom: 6, value: 0 }, 1], [{ zoom: 10, value: 0 }, 1]],
+                },
+              },
+            },
+          ],
+        });
+      });
+
+      test("should add a stop", async () => {
+        await when.addFunctionStop("circle-blur");
+        await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+          layers: [
+            {
+              id,
+              paint: {
+                "circle-blur": {
+                  stops: [[{ zoom: 6, value: 0 }, 1], [{ zoom: 10, value: 0 }, 1], [{ zoom: 11, value: 0 }, 1]],
+                },
+              },
+            },
+          ],
+        });
+      });
+
+      test("should delete the first stop", async () => {
+        await when.addFunctionStop("circle-blur");
+        await when.deleteFunctionStop("circle-blur");
+        await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+          layers: [
+            {
+              id,
+              paint: {
+                "circle-blur": {
+                  stops: [[{ zoom: 10, value: 0 }, 1], [{ zoom: 11, value: 0 }, 1]],
+                },
+              },
+            },
+          ],
+        });
+      });
+
+      test("should set the property", async () => {
+        await when.setFunctionProperty("circle-blur", "myprop");
+        await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+          layers: [{ id, paint: { "circle-blur": { property: "myprop" } } }],
+        });
+      });
+
+      test("should set the default", async () => {
+        await when.setFunctionDefault("circle-blur", "0.5");
+        await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+          layers: [{ id, paint: { "circle-blur": { default: 0.5 } } }],
+        });
+      });
+
+      test("should edit the input value of a stop", async () => {
+        await when.setFunctionStopValue("circle-blur", "Input value", 0, "7");
+        await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+          layers: [
+            {
+              id,
+              paint: {
+                "circle-blur": {
+                  stops: [[{ zoom: 6, value: 7 }, 1], [{ zoom: 10, value: 0 }, 1]],
+                },
+              },
+            },
+          ],
+        });
+      });
+
+      test("should change the function type", async () => {
+        await when.selectFunctionType("circle-blur", "categorical");
+        await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+          layers: [{ id, paint: { "circle-blur": { type: "categorical" } } }],
+        });
+      });
+    });
+
+    describe("expression", () => {
+      beforeEach(async () => {
+        id = await when.modal.fillLayers({ type: "circle", layer: "example" });
+        await when.setValue("spec-field-input:circle-blur", "1");
+        await when.makeExpression("circle-blur");
+      });
+
+      test("should wrap the property value in a literal expression", async () => {
+        await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+          layers: [{ id, paint: { "circle-blur": ["literal", 1] } }],
+        });
+      });
+
+      test("should restore the plain value when reverted", async () => {
+        await when.undoExpression("circle-blur");
+        await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+          layers: [{ id, paint: { "circle-blur": 1 } }],
+        });
+      });
+
+      test("should fall back to the spec default when deleted", async () => {
+        await when.deleteExpression("circle-blur");
+        await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+          layers: [{ id, paint: { "circle-blur": 0 } }],
+        });
+      });
+    });
+  });
+
+  describe("layout", () => {
     test("text-font", async () => {
       await when.setStyle("font");
       await when.collapseGroupInLayerEditor();
       await when.collapseGroupInLayerEditor(1);
       await when.collapseGroupInLayerEditor(2);
-      await when.doWithin("spec-field:text-font", async () => {
-        await get.element(".maputnik-autocomplete input").first().click();
-      });
+      await when.clickWithin("spec-field:text-font", ".maputnik-autocomplete input");
       await then(get.element(".maputnik-autocomplete-menu-item")).shouldBeVisible();
       await then(get.element(".maputnik-autocomplete-menu-item")).shouldHaveLength(3);
     });
   });
 
-  test.describe("paint", () => {
-    test.skip("expand/collapse", () => {});
-    test.skip("color", () => {});
-    test.skip("pattern", () => {});
-    test.skip("opacity", () => {});
+  describe("paint", () => {
+    let id: string;
+
+    beforeEach(async () => {
+      id = await when.modal.fillLayers({ type: "fill", layer: "example" });
+    });
+
+    test("expand/collapse", async () => {
+      await then(get.elementByTestId("spec-field:fill-color")).shouldBeVisible();
+
+      await when.toggleGroupInLayerEditor("Paint properties");
+      await then(get.elementByTestId("spec-field:fill-color")).shouldNotBeVisible();
+
+      await when.toggleGroupInLayerEditor("Paint properties");
+      await then(get.elementByTestId("spec-field:fill-color")).shouldBeVisible();
+    });
+
+    test("color", async () => {
+      await when.setColorValue("fill-color", "#ff0000");
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        layers: [{ id, type: "fill", source: "example", paint: { "fill-color": "#ff0000" } }],
+      });
+    });
+
+    test("pattern", async () => {
+      await when.setStringValue("fill-pattern", "some-pattern");
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        layers: [{ id, type: "fill", source: "example", paint: { "fill-pattern": "some-pattern" } }],
+      });
+    });
+
+    test("opacity", async () => {
+      await when.setValue("spec-field-input:fill-opacity", "0.4");
+      await when.click("layer-editor.layer-id");
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        layers: [{ id, type: "fill", source: "example", paint: { "fill-opacity": 0.4 } }],
+      });
+    });
   });
 
-  test.describe("json-editor", () => {
+  describe("json-editor", () => {
     test("add", async () => {
       const id = await when.modal.fillLayers({
         type: "circle",
@@ -202,15 +538,34 @@ test.describe("layer editor", () => {
         layers: [{ id, type: "circle", source: "example" }],
       });
 
-      const sourceText = get.elementByText('"source"');
-      await sourceText.click();
+      await when.clickByText('"source"');
       await when.typeKeys('"');
 
       await then(get.element(".cm-lint-marker-error")).shouldExist();
     });
 
-    test.skip("expand/collapse", () => {});
-    test.skip("modify", () => {});
+    test("expand/collapse", async () => {
+      const bgId = await createBackground();
+      await when.click("layer-list-item:background:" + bgId);
+
+      await then(get.element(".cm-content")).shouldBeVisible();
+
+      await when.toggleGroupInLayerEditor("JSON Editor");
+      await then(get.element(".cm-content")).shouldNotBeVisible();
+
+      await when.toggleGroupInLayerEditor("JSON Editor");
+      await then(get.element(".cm-content")).shouldBeVisible();
+    });
+
+    test("modify", async () => {
+      const bgId = await createBackground();
+      await when.click("layer-list-item:background:" + bgId);
+
+      await when.appendToJsonEditorLine('"background"', ',\n"minzoom": 5');
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        layers: [{ id: "background:" + bgId, type: "background", minzoom: 5 }],
+      });
+    });
 
     test("parse error", async () => {
       const bgId = await createBackground();
@@ -227,7 +582,7 @@ test.describe("layer editor", () => {
     });
   });
 
-  test.describe("sticky header", () => {
+  describe("sticky header", () => {
     test("should keep layer header visible when scrolling properties", async () => {
       // Setup: Create a layer with many properties (e.g. symbol layer)
       await when.modal.fillLayers({
@@ -239,9 +594,7 @@ test.describe("layer editor", () => {
       const header = get.elementByTestId("layer-editor.header");
       await then(header).shouldBeVisible();
 
-      await get
-        .element(".maputnik-scroll-container")
-        .evaluate((el) => el.scrollTo(0, el.scrollHeight));
+      await when.scrollToBottom(get.element(".maputnik-scroll-container"));
       await when.wait(200);
 
       await then(header).shouldBeVisible();

e2e/layers-list.spec.ts

@@ -1,18 +1,18 @@
-import { test } from "./fixtures";
+import { beforeEach, describe, test } from "./utils/fixtures";
 import { MaputnikDriver } from "./maputnik-driver";
 
-test.describe("layers list", () => {
+describe("layers list", () => {
   const { given, get, when, then } = new MaputnikDriver();
 
-  test.beforeEach(async () => {
+  beforeEach(async () => {
     await given.setupMockBackedResponses();
     await when.setStyle("both");
     await when.modal.open();
   });
 
-  test.describe("ops", () => {
+  describe("ops", () => {
     let id: string;
-    test.beforeEach(async () => {
+    beforeEach(async () => {
       id = await when.modal.fillLayers({ type: "background" });
     });
 
@@ -22,8 +22,8 @@ test.describe("layers list", () => {
       });
     });
 
-    test.describe("when clicking delete", () => {
-      test.beforeEach(async () => {
+    describe("when clicking delete", () => {
+      beforeEach(async () => {
         await when.click("layer-list-item:" + id + ":delete");
       });
       test("should empty layers in local storage", async () => {
@@ -33,8 +33,8 @@ test.describe("layers list", () => {
       });
     });
 
-    test.describe("when clicking duplicate", () => {
-      test.beforeEach(async () => {
+    describe("when clicking duplicate", () => {
+      beforeEach(async () => {
         await when.click("layer-list-item:" + id + ":copy");
       });
       test("should add copy layer in local storage", async () => {
@@ -47,8 +47,8 @@ test.describe("layers list", () => {
       });
     });
 
-    test.describe("when clicking hide", () => {
-      test.beforeEach(async () => {
+    describe("when clicking hide", () => {
+      beforeEach(async () => {
         await when.click("layer-list-item:" + id + ":toggle-visibility");
       });
 
@@ -58,8 +58,8 @@ test.describe("layers list", () => {
         });
       });
 
-      test.describe("when clicking show", () => {
-        test.beforeEach(async () => {
+      describe("when clicking show", () => {
+        beforeEach(async () => {
           await when.click("layer-list-item:" + id + ":toggle-visibility");
         });
 
@@ -70,9 +70,9 @@ test.describe("layers list", () => {
         });
       });
 
-      test.describe("when selecting a layer", () => {
+      describe("when selecting a layer", () => {
         let secondId: string;
-        test.beforeEach(async () => {
+        beforeEach(async () => {
           await when.modal.open();
           secondId = await when.modal.fillLayers({
             id: "second-layer",
@@ -89,7 +89,7 @@ test.describe("layers list", () => {
     });
   });
 
-  test.describe("background", () => {
+  describe("background", () => {
     test("add", async () => {
       const id = await when.modal.fillLayers({ type: "background" });
       await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
@@ -97,10 +97,18 @@ test.describe("layers list", () => {
       });
     });
 
-    test.skip("modify", () => {});
+    test("modify", async () => {
+      const id = await when.modal.fillLayers({ type: "background" });
+      await when.click("layer-list-item:" + id);
+      await when.setValue("spec-field-input:background-opacity", "0.4");
+      await when.click("layer-editor.layer-id");
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        layers: [{ id, type: "background", paint: { "background-opacity": 0.4 } }],
+      });
+    });
   });
 
-  test.describe("fill", () => {
+  describe("fill", () => {
     test("add", async () => {
       const id = await when.modal.fillLayers({ type: "fill", layer: "example" });
       await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
@@ -108,11 +116,16 @@ test.describe("layers list", () => {
       });
     });
 
-    // TODO: Change source
-    test.skip("change source", () => {});
+    test("change source", async () => {
+      const id = await when.modal.fillLayers({ type: "fill", layer: "example" });
+      await when.changeLayerSource("raster");
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        layers: [{ id, type: "fill", source: "raster" }],
+      });
+    });
   });
 
-  test.describe("line", () => {
+  describe("line", () => {
     test("add", async () => {
       const id = await when.modal.fillLayers({ type: "line", layer: "example" });
       await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
@@ -121,7 +134,6 @@ test.describe("layers list", () => {
     });
 
     test("groups", async () => {
-      await when.modal.open();
       const id1 = await when.modal.fillLayers({ id: "aa", type: "line", layer: "example" });
 
       await when.modal.open();
@@ -151,7 +163,7 @@ test.describe("layers list", () => {
     });
   });
 
-  test.describe("symbol", () => {
+  describe("symbol", () => {
     test("add", async () => {
       const id = await when.modal.fillLayers({ type: "symbol", layer: "example" });
       await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
@@ -189,7 +201,7 @@ test.describe("layers list", () => {
     });
   });
 
-  test.describe("raster", () => {
+  describe("raster", () => {
     test("add", async () => {
       const id = await when.modal.fillLayers({ type: "raster", layer: "raster" });
       await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
@@ -198,7 +210,7 @@ test.describe("layers list", () => {
     });
   });
 
-  test.describe("circle", () => {
+  describe("circle", () => {
     test("add", async () => {
       const id = await when.modal.fillLayers({ type: "circle", layer: "example" });
       await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
@@ -207,7 +219,7 @@ test.describe("layers list", () => {
     });
   });
 
-  test.describe("fill extrusion", () => {
+  describe("fill extrusion", () => {
     test("add", async () => {
       const id = await when.modal.fillLayers({ type: "fill-extrusion", layer: "example" });
       await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
@@ -216,7 +228,7 @@ test.describe("layers list", () => {
     });
   });
 
-  test.describe("hillshade", () => {
+  describe("hillshade", () => {
     test("add", async () => {
       const id = await when.modal.fillLayers({ type: "hillshade", layer: "example" });
       await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
@@ -267,7 +279,7 @@ test.describe("layers list", () => {
     });
   });
 
-  test.describe("color-relief", () => {
+  describe("color-relief", () => {
     test("add", async () => {
       const id = await when.modal.fillLayers({ type: "color-relief", layer: "example" });
       await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
@@ -285,7 +297,7 @@ test.describe("layers list", () => {
     });
   });
 
-  test.describe("groups", () => {
+  describe("groups", () => {
     test("simple", async () => {
       await when.setStyle("geojson");
 
@@ -308,9 +320,8 @@ test.describe("layers list", () => {
     });
   });
 
-  test.describe("drag and drop", () => {
+  describe("drag and drop", () => {
     test("move layer should update local storage", async () => {
-      await when.modal.open();
       const firstId = await when.modal.fillLayers({ id: "a", type: "background" });
       await when.modal.open();
       const secondId = await when.modal.fillLayers({ id: "b", type: "background" });
@@ -329,10 +340,12 @@ test.describe("layers list", () => {
     });
   });
 
-  test.describe("sticky header", () => {
+  describe("sticky header", () => {
     test("should keep header visible when scrolling layer list", async () => {
       // Setup: Create multiple layers to enable scrolling
-      for (let i = 0; i < 20; i++) {
+      // The modal is already open (beforeEach) for the first layer.
+      await when.modal.fillLayers({ id: "layer-0", type: "background" });
+      for (let i = 1; i < 20; i++) {
         await when.modal.open();
         await when.modal.fillLayers({ id: `layer-${i}`, type: "background" });
       }
@@ -342,7 +355,7 @@ test.describe("layers list", () => {
       await then(header).shouldBeVisible();
 
       // Scroll the layer list container
-      await get.elementByTestId("layer-list").evaluate((el) => el.scrollTo(0, el.scrollHeight));
+      await when.scrollToBottom(get.elementByTestId("layer-list"));
       await when.wait(200);
       await then(header).shouldBeVisible();
       await then(get.elementByTestId("layer-list:add-layer")).shouldBeVisible();

e2e/map.spec.ts

@@ -1,15 +1,15 @@
-import { test } from "./fixtures";
+import { beforeEach, describe, test } from "./utils/fixtures";
 import { MaputnikDriver } from "./maputnik-driver";
 
-test.describe("map", () => {
+describe("map", () => {
   const { given, get, when, then } = new MaputnikDriver();
 
-  test.beforeEach(async () => {
+  beforeEach(async () => {
     await given.setupMockBackedResponses();
     await when.setStyle("both");
   });
 
-  test.describe("zoom level", () => {
+  describe("zoom level", () => {
     test("via url", async () => {
       const zoomLevel = 12.37;
       await when.setStyle("geojson", zoomLevel);
@@ -38,14 +38,14 @@ test.describe("map", () => {
     });
   });
 
-  test.describe("search", () => {
+  describe("search", () => {
     test("should exist", async () => {
       await then(get.searchControl()).shouldBeVisible();
     });
   });
 
-  test.describe("popup", () => {
-    test.beforeEach(async () => {
+  describe("popup", () => {
+    beforeEach(async () => {
       await when.setStyle("rectangles");
       await then(get.locationHash()).shouldExist();
     });

e2e/maputnik-driver.ts

@@ -1,270 +1,31 @@
-import fs from "node:fs";
-import path from "node:path";
-import { fileURLToPath } from "node:url";
-import { expect, type Locator, type Page, type Request } from "@playwright/test";
-import { readCoverage } from "./coverage";
-import { currentPage, recordCoverageChunk } from "./fixtures";
+import { PlaywrightHelper } from "./playwright-helper";
 import { ModalDriver } from "./modal-driver";
 
 const baseUrl = "http://localhost:8888/";
-const FIXTURES_DIR = path.join(path.dirname(fileURLToPath(import.meta.url)), "fixtures");
-const DATA_ATTRIBUTE = "data-wd-key";
-
 const isMac = process.platform === "darwin";
 
-function testIdSelector(testId: string): string {
-  return `[${DATA_ATTRIBUTE}="${testId}"]`;
-}
+/**
+ * The maputnik-specific driver. It builds on the generic {@link PlaywrightHelper}
+ * — spreading its `given`/`when`/`get` primitives and adding domain concepts
+ * (loading a style, the add-layer modal, the JSON editor, …). All Playwright
+ * access goes through the helper; the driver never touches `page` directly.
+ */
+export class MaputnikDriver {
+  private readonly helper = new PlaywrightHelper();
+  private readonly modalDriver = new ModalDriver();
 
-export function readFixture(name: string): any {
-  const contents = fs.readFileSync(path.join(FIXTURES_DIR, name), "utf-8");
-  return JSON.parse(contents);
-}
+  then = this.helper.then;
 
-/** Reads the maputnik style currently persisted in localStorage. */
-function styleFromLocalStorage(page: Page): Promise<any> {
-  return page.evaluate(() => {
-    const styleId = window.localStorage.getItem("maputnik:latest_style");
-    const styleItemKey = `maputnik:style:${styleId}`;
-    const styleItem = window.localStorage.getItem(styleItemKey);
+  /** Reads the maputnik style currently persisted in localStorage. */
+  private async readStoredStyle(): Promise<any> {
+    const styleId = await this.helper.get.localStorageItem("maputnik:latest_style");
+    const styleItem = await this.helper.get.localStorageItem(`maputnik:style:${styleId}`);
     if (!styleItem) throw new Error("Could not get styleItem from localStorage");
     return JSON.parse(styleItem);
-  });
-}
-
-async function retry(assertion: () => Promise<void> | void, timeout = 10000, interval = 100): Promise<void> {
-  const start = Date.now();
-  let lastError: unknown;
-  for (;;) {
-    try {
-      await assertion();
-      return;
-    } catch (error) {
-      lastError = error;
-      if (Date.now() - start > timeout) throw lastError;
-      await new Promise((resolve) => setTimeout(resolve, interval));
-    }
   }
-}
-
-/**
- * A lazily-evaluated value (e.g. the style in localStorage). Assertions on a
- * Query re-read the value until they pass, mirroring Cypress' retry-ability.
- */
-export class Query<T> {
-  readonly __maputnikQuery = true as const;
-  constructor(private readonly getter: () => Promise<T>) {}
-
-  get(): Promise<T> {
-    return this.getter();
-  }
-
-  then<U>(mapper: (value: T) => U | Promise<U>): Query<U> {
-    return new Query<U>(async () => mapper(await this.getter()));
-  }
-}
-
-function isQuery(target: unknown): target is Query<unknown> {
-  return typeof target === "object" && target !== null && (target as Query<unknown>).__maputnikQuery === true;
-}
-
-function isLocator(target: unknown): target is Locator {
-  return (
-    typeof target === "object" &&
-    target !== null &&
-    typeof (target as Locator).count === "function" &&
-    typeof (target as Locator).boundingBox === "function"
-  );
-}
-
-/** Asserts that every top-level key in `expected` deep-equals its counterpart in `actual`. */
-function assertDeepNestedInclude(actual: any, expected: Record<string, unknown>): void {
-  for (const key of Object.keys(expected)) {
-    expect(actual?.[key], `property "${key}"`).toEqual(expected[key]);
-  }
-}
-
-export class MaputnikAssertable<T> {
-  constructor(private readonly target: T, private readonly page?: Page) {}
-
-  private locator(): Locator {
-    if (!isLocator(this.target)) throw new Error("Expected a Locator target for this assertion");
-    return this.target;
-  }
-
-  private async assertValue(assertion: (value: any) => void): Promise<void> {
-    const target = this.target;
-    if (isQuery(target)) {
-      await retry(async () => assertion(await target.get()));
-    } else {
-      assertion(await (target as any));
-    }
-  }
-
-  // Element assertions (auto-retrying via Playwright web-first assertions).
-  shouldBeVisible = () => expect(this.locator().first()).toBeVisible();
-  // Some testids resolve to many elements that are always rendered but hidden
-  // (e.g. per-field documentation panels); "not visible" means none is visible.
-  shouldNotBeVisible = () => expect(this.locator().filter({ visible: true })).toHaveCount(0);
-  shouldExist = async () => {
-    if (isLocator(this.target)) {
-      await expect(this.locator().first()).toBeAttached();
-    } else {
-      await this.assertValue((value) => expect(value).toBeTruthy());
-    }
-  };
-  shouldNotExist = () => expect(this.locator()).toHaveCount(0);
-  shouldBeFocused = () => expect(this.locator().first()).toBeFocused();
-  shouldNotBeFocused = () => expect(this.locator().first()).not.toBeFocused();
-  shouldHaveValue = (value: string) => expect(this.locator().first()).toHaveValue(value);
-  shouldContainText = async (text: string) => {
-    const locator = this.locator();
-    // Prefer the visible element when a testid resolves to several (only the
-    // open documentation panel is visible; the rest are hidden in the DOM).
-    const target = (await locator.count()) > 1 ? locator.filter({ visible: true }).first() : locator.first();
-    await expect(target).toContainText(text);
-  };
-  shouldHaveText = (text: string) => expect(this.locator().first()).toHaveText(text);
-  shouldHaveLength = (length: number) => expect(this.locator()).toHaveCount(length);
-  shouldHaveCss = (property: string, value: string) => expect(this.locator().first()).toHaveCSS(property, value);
-
-  // Value assertions (auto-retrying for Query targets).
-  shouldEqual = (value: any) => this.assertValue((actual) => expect(actual).toBe(value));
-
-  shouldInclude = (value: any) =>
-    this.assertValue((actual) => {
-      if (typeof value === "object" && value !== null) {
-        expect(actual).toMatchObject(value);
-      } else {
-        expect(String(actual)).toContain(String(value));
-      }
-    });
-
-  shouldDeepNestedInclude = (value: Record<string, unknown>) =>
-    this.assertValue((actual) => assertDeepNestedInclude(actual, value));
-
-  /**
-   * Asserts that the object under test (a fixture / response body) contains every
-   * top-level property of the style currently stored in localStorage.
-   */
-  shouldEqualToStoredStyle = async () => {
-    if (!this.page) throw new Error("shouldEqualToStoredStyle requires a page-bound assertable");
-    const expected = await (this.target as any);
-    await retry(async () => {
-      const stored = await styleFromLocalStorage(this.page!);
-      assertDeepNestedInclude(expected, stored);
-    });
-  };
-}
-
-/**
- * Translates a Cypress-style key sequence (e.g. "{meta}z", "{esc}", "0.") into
- * Playwright keyboard actions on the currently focused element.
- */
-async function typeSequence(page: Page, text: string): Promise<void> {
-  const tokens = text.match(/\{[^}]+\}|[^{]+/g) ?? [];
-  const modifierMap: Record<string, string> = { meta: "Meta", ctrl: "Control", shift: "Shift", alt: "Alt" };
-  const namedKeys: Record<string, string> = {
-    esc: "Escape",
-    enter: "Enter",
-    backspace: "Backspace",
-    del: "Delete",
-    tab: "Tab",
-  };
-
-  for (let i = 0; i < tokens.length; i++) {
-    const token = tokens[i];
-    if (!token.startsWith("{") || !token.endsWith("}")) {
-      await page.keyboard.type(token);
-      continue;
-    }
-    const name = token.slice(1, -1).toLowerCase();
-    if (name === "selectall") {
-      await page.keyboard.press(isMac ? "Meta+a" : "Control+a");
-    } else if (namedKeys[name]) {
-      await page.keyboard.press(namedKeys[name]);
-    } else if (modifierMap[name]) {
-      const modifiers = [modifierMap[name]];
-      let j = i + 1;
-      while (j < tokens.length && /^\{(meta|ctrl|shift|alt)\}$/i.test(tokens[j])) {
-        modifiers.push(modifierMap[tokens[j].slice(1, -1).toLowerCase()]);
-        j++;
-      }
-      const key = tokens[j] ?? "";
-      await page.keyboard.press([...modifiers, key].join("+"));
-      i = j;
-    }
-  }
-}
-
-async function centerOf(locator: Locator): Promise<{ x: number; y: number }> {
-  const box = await locator.boundingBox();
-  if (!box) throw new Error("Element has no bounding box");
-  return { x: box.x + box.width / 2, y: box.y + box.height / 2 };
-}
-
-export class MaputnikDriver {
-  private scope: Locator | null = null;
-  private readonly recordedRequests = new Map<string, Request[]>();
-  private readonly modalDriver = new ModalDriver(this);
-
-  /**
-   * The page for the currently running test. Resolved lazily so a single driver
-   * instance can be created once per `describe` and reused across its tests.
-   */
-  private get page(): Page {
-    return currentPage();
-  }
-
-  // ---- Element access ------------------------------------------------------
-
-  private root(): Page | Locator {
-    return this.scope ?? this.page;
-  }
-
-  private testId(testId: string): Locator {
-    return this.root().locator(testIdSelector(testId));
-  }
-
-  then = <T>(target: T) => new MaputnikAssertable(target, this.page);
-
-  // ---- given ---------------------------------------------------------------
 
   public given = {
-    fixture: (_name: string, _alias?: string) => {
-      // Fixtures are read directly from disk in Playwright, no registration needed.
-    },
-
-    intercept: async (url: string, alias: string, _method = "GET") => {
-      this.recordedRequests.set(alias, []);
-      // Convert the Cypress-style glob (which may contain "?" in a query string)
-      // into a regex so query parameters match reliably.
-      const pattern = new RegExp(
-        "^" + url.replace(/[.+^${}()|[\]\\?]/g, "\\$&").replace(/\*/g, ".*") + "$"
-      );
-      await this.page.route(pattern, (route) => {
-        this.recordedRequests.get(alias)!.push(route.request());
-        route.continue();
-      });
-    },
-
-    interceptAndMockResponse: async (options: {
-      method?: string;
-      url: string | RegExp;
-      response: unknown | { fixture: string };
-      alias?: string;
-    }) => {
-      const { url, response, alias } = options;
-      if (alias) this.recordedRequests.set(alias, []);
-      await this.page.route(url, (route) => {
-        if (alias) this.recordedRequests.get(alias)!.push(route.request());
-        const body =
-          response && typeof response === "object" && "fixture" in (response as any)
-            ? readFixture((response as { fixture: string }).fixture)
-            : response;
-        route.fulfill({ json: body });
-      });
-    },
+    ...this.helper.given,
 
     setupMockBackedResponses: async () => {
       const styleFixtures = [
@@ -277,18 +38,19 @@ export class MaputnikDriver {
         "example-style-with-fonts.json",
         "example-style-with-zoom-7-and-center-0-51.json",
         "example-style-with-zoom-5-and-center-50-50.json",
+        "access-token-style.json",
       ];
       for (const fixture of styleFixtures) {
-        await this.given.interceptAndMockResponse({
+        await this.helper.given.interceptAndMockResponse({
           method: "GET",
           url: baseUrl + fixture,
           response: { fixture },
           alias: fixture === "example-style.json" ? "example-style.json" : undefined,
         });
       }
-      await this.given.interceptAndMockResponse({ method: "GET", url: /example\.local\//, response: [] });
-      await this.given.interceptAndMockResponse({ method: "GET", url: /example\.com\//, response: [] });
-      await this.given.interceptAndMockResponse({
+      await this.helper.given.interceptAndMockResponse({ method: "GET", url: /example\.local\//, response: [] });
+      await this.helper.given.interceptAndMockResponse({ method: "GET", url: /example\.com\//, response: [] });
+      await this.helper.given.interceptAndMockResponse({
         method: "GET",
         url: "https://www.glyph-server.com/*",
         response: ["Font 1", "Font 2", "Font 3"],
@@ -296,97 +58,11 @@ export class MaputnikDriver {
     },
   };
 
-  // ---- when ----------------------------------------------------------------
-
   public when = {
+    ...this.helper.when,
+
     modal: this.modalDriver.when,
 
-    visit: async (url: string) => {
-      // Snapshot coverage before navigating, since a full page load resets it.
-      recordCoverageChunk(await readCoverage(this.page));
-      const target = url.startsWith("http") ? url : new URL(url, baseUrl).toString();
-      await this.page.goto(target);
-    },
-
-    wait: (ms: number) => this.page.waitForTimeout(ms),
-
-    tab: () => this.page.keyboard.press("Tab"),
-
-    typeKeys: (keys: string) => typeSequence(this.page, keys),
-
-    doWithin: async (selector: string, fn: () => Promise<void> | void) => {
-      const previous = this.scope;
-      this.scope = (previous ?? this.page).locator(testIdSelector(selector));
-      try {
-        await fn();
-      } finally {
-        this.scope = previous;
-      }
-    },
-
-    click: async (testId: string, index = 0) => {
-      // Documentation buttons are wrapped in a <label>/.maputnik-doc-target that
-      // Playwright treats as intercepting the click; bypass the check for them.
-      const force = testId.startsWith("field-doc-button-");
-      await this.testId(testId).nth(index).click({ force });
-    },
-
-    realClick: async (testId: string) => {
-      await this.testId(testId).click();
-    },
-
-    hover: async (testId: string) => {
-      await this.testId(testId).hover();
-    },
-
-    focus: async (testId: string) => {
-      await this.testId(testId).focus();
-    },
-
-    clear: async (testId: string) => {
-      await this.testId(testId).clear();
-    },
-
-    select: async (testId: string, value: string) => {
-      await this.testId(testId).selectOption(value);
-    },
-
-    selectWithin: async (selector: string, value: string) => {
-      await this.root().locator(testIdSelector(selector)).locator("select").selectOption(value);
-    },
-
-    setValue: async (testId: string, text: string) => {
-      const input = this.testId(testId);
-      await input.fill("");
-      await input.fill(text);
-    },
-
-    type: async (testId: string, text: string) => {
-      await this.testId(testId).focus();
-      // Place the caret at the start of the field (matching how the original
-      // Cypress suite typed), so a leading "{backspace}" is a no-op rather than
-      // clearing an already-committed value.
-      await this.page.keyboard.press("Home");
-      await typeSequence(this.page, text);
-    },
-
-    setValueToPropertyArray: async (selector: string, value: string) => {
-      await this.when.doWithin(selector, async () => {
-        const input = this.root().locator(".maputnik-array-block-content input").last();
-        await input.focus();
-        await typeSequence(this.page, "{selectall}" + value);
-      });
-    },
-
-    addValueToPropertyArray: async (selector: string, value: string) => {
-      await this.when.doWithin(selector, async () => {
-        await this.root().locator(".maputnik-array-add-value").click();
-        const input = this.root().locator(".maputnik-array-block-content input").last();
-        await input.focus();
-        await typeSequence(this.page, "{selectall}" + value);
-      });
-    },
-
     setStyle: async (
       styleProperties:
         | "geojson"
@@ -396,6 +72,7 @@ export class MaputnikDriver {
         | "rectangles"
         | "font"
         | "zoom_7_center_0_51"
+        | "access_tokens"
         | "",
       zoom?: number
     ) => {
@@ -407,6 +84,7 @@ export class MaputnikDriver {
         rectangles: "rectangles-style.json",
         font: "example-style-with-fonts.json",
         zoom_7_center_0_51: "example-style-with-zoom-7-and-center-0-51.json",
+        access_tokens: "access-token-style.json",
       };
 
       const url = new URL(baseUrl);
@@ -417,163 +95,264 @@ export class MaputnikDriver {
         url.hash = `${zoom}/41.3805/2.1635`;
       }
 
-      await this.when.visit(url.toString());
+      await this.helper.when.visit(url.toString());
 
-      const toolbarLink = this.testId("toolbar:link");
+      const toolbarLink = this.helper.get.elementByTestId("toolbar:link");
       await toolbarLink.scrollIntoViewIfNeeded();
-      await expect(toolbarLink).toBeVisible();
+      await this.then(toolbarLink).shouldBeVisible();
     },
 
     openASecondStyleWithDifferentZoomAndCenter: async () => {
-      await this.page.getByRole("button", { name: "Open" }).click();
-      const input = this.testId("modal:open.url.input");
-      await expect(input).toBeEnabled();
+      await this.helper.when.clickButtonByName("Open");
+      const input = this.helper.get.elementByTestId("modal:open.url.input");
       await input.fill("http://localhost:8888/example-style-with-zoom-5-and-center-50-50.json");
       await input.press("Enter");
     },
 
     chooseExampleFile: async () => {
-      await this.openFileByFixture("example-style.json", "modal:open.dropzone", "modal:open.file.input");
-      await this.when.wait(200);
+      await this.helper.when.openFileByFixture("example-style.json", "modal:open.dropzone");
+      await this.helper.when.wait(200);
+    },
+
+    /** Picks the example style through the browser's native file chooser. */
+    chooseExampleFileFromPicker: async () => {
+      await this.helper.when.chooseFileFromPicker("example-style.json", "modal:open.dropzone");
+      await this.helper.when.wait(200);
     },
 
     dropExampleFile: async () => {
-      await this.dropFileByFixture("example-style.json", "modal:open.dropzone");
-      await this.when.wait(200);
+      await this.helper.when.dropFileByFixture("example-style.json", "modal:open.dropzone");
+      await this.helper.when.wait(200);
     },
 
     clickZoomIn: async () => {
-      await this.page.locator(".maplibregl-ctrl-zoom-in").click();
+      await this.helper.get.element(".maplibregl-ctrl-zoom-in").click();
     },
 
     closePopup: async () => {
-      await this.page.locator(".maplibregl-popup-close-button").click();
-    },
-
-    clickCenter: async (testId: string) => {
-      const { x, y } = await centerOf(this.testId(testId));
-      await this.page.mouse.move(x, y);
-      await this.page.mouse.down();
-      await this.when.wait(200);
-      await this.page.mouse.up();
+      await this.helper.get.element(".maplibregl-popup-close-button").click();
     },
 
     collapseGroupInLayerEditor: async (index = 0) => {
-      await this.page.locator(".maputnik-layer-editor-group__button").nth(index).click();
+      await this.helper.get.element(".maputnik-layer-editor-group__button").nth(index).click();
+    },
+
+    /** Expands/collapses a layer-editor group by its title, e.g. "Paint properties". */
+    toggleGroupInLayerEditor: async (title: string) => {
+      await this.helper.when.click("layer-editor-group:" + title);
+    },
+
+    /**
+     * Picks a source for the selected layer from the source autocomplete.
+     * The autocomplete is a controlled (downshift) input, so the value has to be
+     * filled rather than typed key by key, then chosen from the filtered menu.
+     */
+    changeLayerSource: async (sourceId: string) => {
+      const input = this.helper.get.elementByTestId("layer-editor.layer-source").locator("input");
+      await input.fill(sourceId);
+      await this.helper.get.element(".maputnik-autocomplete-menu-item").first().click();
     },
 
     appendTextInJsonEditor: async (text: string) => {
-      await this.page.locator(".cm-line").first().click();
+      await this.helper.get.element(".cm-line").first().click();
       // Move to the very start of the document so the inserted text breaks the
       // root JSON structure (CodeMirror auto-closes brackets otherwise).
-      await this.page.keyboard.press("Home");
-      await typeSequence(this.page, text);
+      await this.helper.when.typeKeys("{home}");
+      await this.helper.when.typeText(text);
     },
 
     setTextInJsonEditor: async (text: string) => {
-      const firstLine = this.page.locator(".cm-line").first();
-      await firstLine.click();
-      await this.page.keyboard.press(isMac ? "Meta+a" : "Control+a");
-      await this.page.keyboard.type(text);
+      await this.helper.get.element(".cm-line").first().click();
+      await this.helper.when.typeKeys("{selectall}");
+      await this.helper.when.typeText(text);
     },
 
-    dragAndDropWithWait: async (source: string, target: string) => {
-      const from = await centerOf(this.testId(source));
-      const to = await centerOf(this.testId(target));
-      await this.page.mouse.move(from.x, from.y);
-      await this.page.mouse.down();
-      await this.page.mouse.move(from.x, from.y + 10);
-      await this.page.mouse.move(to.x, to.y, { steps: 10 });
-      await this.when.wait(100);
-      await this.page.mouse.up();
+    setValueToPropertyArray: async (selector: string, value: string) => {
+      const input = this.helper.get.elementByTestId(selector).locator(".maputnik-array-block-content input").last();
+      await input.focus();
+      await this.helper.when.typeKeys("{selectall}");
+      await this.helper.when.typeText(value);
     },
 
-    waitForResponse: async (alias: string) => {
-      const requests = this.recordedRequests.get(alias);
-      if (!requests) throw new Error(`No intercept registered for alias "${alias}"`);
-      await retry(async () => {
-        if (requests.length === 0) throw new Error(`No request recorded for alias "${alias}"`);
-      });
-      return requests[requests.length - 1];
+    addValueToPropertyArray: async (selector: string, value: string) => {
+      const block = this.helper.get.elementByTestId(selector);
+      await block.locator(".maputnik-array-add-value").click();
+      const input = block.locator(".maputnik-array-block-content input").last();
+      await input.focus();
+      await this.helper.when.typeKeys("{selectall}");
+      await this.helper.when.typeText(value);
     },
 
-    waitForExampleFileResponse: () => this.when.waitForResponse("example-style.json"),
+    makeZoomFunction: async (fieldName: string) => {
+      const container = this.helper.get.elementByTestId("spec-field-container:" + fieldName);
+      await container.scrollIntoViewIfNeeded();
+      await container.locator(".maputnik-make-zoom-function").last().click({ force: true });
+    },
 
-    clearLocalStorage: () => this.page.evaluate(() => window.localStorage.clear()),
+    makeDataFunction: async (fieldName: string) => {
+      const container = this.helper.get.elementByTestId("spec-field-container:" + fieldName);
+      await container.scrollIntoViewIfNeeded();
+      await container.locator(".maputnik-make-data-function").click({ force: true });
+    },
+
+    addFunctionStop: async (fieldName: string) => {
+      const container = this.helper.get.elementByTestId("spec-field-container:" + fieldName);
+      await container.locator(".maputnik-add-stop").first().click({ force: true });
+    },
+
+    deleteFunctionStop: async (fieldName: string) => {
+      const container = this.helper.get.elementByTestId("spec-field-container:" + fieldName);
+      await container.locator(".maputnik-delete-stop").first().click({ force: true });
+    },
+
+    /** Turns the property into a raw style expression. */
+    makeExpression: async (fieldName: string) => {
+      const container = this.helper.get.elementByTestId("spec-field-container:" + fieldName);
+      await container.scrollIntoViewIfNeeded();
+      // In the plain spec field the expression button shares the zoom-function
+      // class and comes first; inside a function editor it has its own test id.
+      const inFunctionEditor = container.locator("[data-wd-key='convert-to-expression']");
+      const button =
+        (await inFunctionEditor.count()) > 0
+          ? inFunctionEditor
+          : container.locator(".maputnik-make-zoom-function").first();
+      await button.click({ force: true });
+    },
+
+    /** Reverts an expression back to a plain value. */
+    undoExpression: async (fieldName: string) => {
+      const container = this.helper.get.elementByTestId("spec-field-container:" + fieldName);
+      await container.locator("[data-wd-key='undo-expression']").click({ force: true });
+    },
+
+    /** Removes an expression, restoring the property's spec default. */
+    deleteExpression: async (fieldName: string) => {
+      const container = this.helper.get.elementByTestId("spec-field-container:" + fieldName);
+      await container.locator("[data-wd-key='delete-expression']").click({ force: true });
+    },
+
+    /** Picks the function scale (categorical/interval/exponential/identity/interpolate). */
+    selectFunctionType: async (fieldName: string, type: string) => {
+      const container = this.helper.get.elementByTestId("spec-field-container:" + fieldName);
+      await container.locator("[data-wd-key='function-type'] select").selectOption(type);
+    },
+
+    /** Sets the "Base" input of a zoom/data function. */
+    setFunctionBase: async (fieldName: string, value: string) => {
+      const container = this.helper.get.elementByTestId("spec-field-container:" + fieldName);
+      await container.locator("[data-wd-key='function-base'] input").fill(value);
+    },
+
+    /**
+     * Sets the data property a data function keys off of. This is an InputString,
+     * which only commits its value on blur, so typing alone is not enough.
+     */
+    setFunctionProperty: async (fieldName: string, value: string) => {
+      const container = this.helper.get.elementByTestId("spec-field-container:" + fieldName);
+      const input = container.locator("[data-wd-key='function-property'] input");
+      await input.fill(value);
+      await input.blur();
+    },
+
+    /** Sets the fallback value used when a feature has no matching stop. */
+    setFunctionDefault: async (fieldName: string, value: string) => {
+      const container = this.helper.get.elementByTestId("spec-field-container:" + fieldName);
+      await container.locator("[data-wd-key='function-default'] input").fill(value);
+    },
+
+    /** Edits one cell of a function's stop table ("Zoom", "Input value" or "Output value"). */
+    setFunctionStopValue: async (fieldName: string, column: string, index: number, value: string) => {
+      const container = this.helper.get.elementByTestId("spec-field-container:" + fieldName);
+      await container.locator(`[aria-label="${column}"]`).nth(index).fill(value);
+    },
+
+    addFilter: async () => {
+      const button = this.helper.get.elementByTestId("layer-filter-button");
+      await button.scrollIntoViewIfNeeded();
+      await button.click({ force: true });
+    },
+
+    selectFilterOperator: async (value: string) => {
+      await this.helper.get.element(".maputnik-filter-editor-operator select").first().selectOption(value);
+    },
+
+    /** Chooses how the filter items combine: all / none / any. */
+    selectFilterCombiningOperator: async (value: string) => {
+      await this.helper.when.selectWithin("filter-combining-operator", value);
+    },
+
+    deleteFilterItem: async (index = 0) => {
+      await this.helper.get
+        .element(".maputnik-filter-editor-block-action .maputnik-icon-button")
+        .nth(index)
+        .click();
+    },
+
+    /** Converts the simple filter editor into a raw expression editor. */
+    convertFilterToExpression: async () => {
+      await this.helper.when.click("filter-convert-to-expression");
+    },
+
+    /**
+     * Deletes the filter expression, restoring the simple filter editor.
+     * The filter group precedes the paint group, so its button comes first.
+     */
+    deleteFilterExpression: async () => {
+      await this.helper.get.element("[data-wd-key='delete-expression']").first().click();
+    },
+
+    setColorValue: async (fieldName: string, value: string) => {
+      const input = this.helper.get.elementByTestId("spec-field:" + fieldName).locator(".maputnik-color");
+      await input.fill(value);
+    },
+
+    /** Sets a plain string spec field (e.g. a pattern), which has no dedicated input test id. */
+    setStringValue: async (fieldName: string, value: string) => {
+      const input = this.helper.get.elementByTestId("spec-field:" + fieldName).locator("input.maputnik-string");
+      await input.fill(value);
+      await input.blur();
+    },
+
+    /**
+     * Appends text to the end of the JSON editor line holding `lineText`.
+     * CodeMirror types over its own auto-inserted closing quotes/brackets, so a
+     * well-formed fragment stays well-formed.
+     */
+    appendToJsonEditorLine: async (lineText: string, text: string) => {
+      await this.helper.when.clickByText(lineText);
+      await this.helper.when.typeKeys("{end}");
+      await this.helper.when.typeText(text);
+    },
+
+    waitForExampleFileResponse: () => this.helper.when.waitForResponse("example-style.json"),
+
+    /** Fill localStorage until we get a QuotaExceededError. */
+    fillLocalStorage: () => this.helper.when.fillLocalStorageUntilQuota("maputnik:fill-"),
   };
 
-  // ---- get -----------------------------------------------------------------
-
   public get = {
+    ...this.helper.get,
+
     isMac: () => isMac,
 
-    element: (selector: string) => this.root().locator(selector),
+    canvas: () => this.helper.get.element("canvas"),
 
-    elementByTestId: (testId: string) => this.testId(testId),
+    searchControl: () => this.helper.get.element(".maplibregl-ctrl-geocoder"),
 
-    elementByText: (text: string) => this.root().getByText(text),
+    skipTargetLayerList: () => this.helper.get.elementByTestId("skip-target-layer-list"),
 
-    elementByAttribute: (attribute: string, value: string) =>
-      this.root().locator(`[${attribute}="${value}"]`),
+    skipTargetLayerEditor: () => this.helper.get.elementByTestId("skip-target-layer-editor"),
 
-    canvas: () => this.page.locator("canvas"),
+    styleFromLocalStorage: () => this.helper.query(() => this.readStoredStyle()),
 
-    searchControl: () => this.page.locator(".maplibregl-ctrl-geocoder"),
-
-    skipTargetLayerList: () => this.testId("skip-target-layer-list"),
-
-    skipTargetLayerEditor: () => this.testId("skip-target-layer-editor"),
-
-    inputValue: (testId: string) => new Query<string>(() => this.testId(testId).first().inputValue()),
-
-    elementsText: (testId: string) => new Query<string>(() => this.testId(testId).first().innerText()),
-
-    locationHash: () => new Query<string>(async () => new URL(this.page.url()).hash),
-
-    styleFromLocalStorage: () => new Query<any>(() => styleFromLocalStorage(this.page)),
-
-    fixture: (name: string) => Promise.resolve(readFixture(name)),
+    fixture: (name: string) => this.helper.readFixture(name),
 
     responseBody: (alias: string) => {
       // Our mocked style responses always return the matching fixture.
       const name = alias.endsWith(".json") ? alias : `${alias}.json`;
-      return Promise.resolve(readFixture(name));
+      return this.helper.readFixture(name);
     },
 
     exampleFileUrl: () => baseUrl + "example-style.json",
   };
-
-  // ---- file open helpers ---------------------------------------------------
-
-  private async openFileByFixture(fixture: string, buttonTestId: string, inputTestId: string): Promise<void> {
-    const content = JSON.stringify(readFixture(fixture));
-    const hasPicker = await this.page.evaluate(() => "showOpenFilePicker" in window);
-    if (hasPicker) {
-      await this.page.evaluate((fileContent) => {
-        (window as any).showOpenFilePicker = async () => [
-          { getFile: async () => ({ text: async () => fileContent }) },
-        ];
-      }, content);
-      await this.testId(buttonTestId).click();
-    } else {
-      await this.testId(inputTestId).setInputFiles({
-        name: fixture,
-        mimeType: "application/json",
-        buffer: Buffer.from(content),
-      });
-    }
-  }
-
-  private async dropFileByFixture(fixture: string, dropzoneTestId: string): Promise<void> {
-    const content = JSON.stringify(readFixture(fixture));
-    const dataTransfer = await this.page.evaluateHandle((fileContent) => {
-      const dt = new DataTransfer();
-      dt.items.add(new File([fileContent], "example-style.json", { type: "application/json" }));
-      return dt;
-    }, content);
-    const dropzone = this.testId(dropzoneTestId);
-    await dropzone.dispatchEvent("dragenter", { dataTransfer });
-    await dropzone.dispatchEvent("dragover", { dataTransfer });
-    await dropzone.dispatchEvent("drop", { dataTransfer });
-  }
 }

e2e/modal-driver.ts

@@ -1,27 +1,24 @@
 import { v1 as uuid } from "uuid";
-import { expect } from "@playwright/test";
-import type { MaputnikDriver } from "./maputnik-driver";
+import { PlaywrightHelper } from "./playwright-helper";
 
 export class ModalDriver {
-  constructor(private readonly driver: MaputnikDriver) {}
+  private readonly helper = new PlaywrightHelper();
 
   public when = {
     fillLayers: async (opts: { type: string; layer?: string; id?: string }) => {
-      const { when, get } = this.driver;
+      const { when, get, then } = this.helper;
       const id = opts.id ?? `${opts.type}:${uuid()}`;
 
       await when.select("add-layer.layer-type.select", opts.type);
       await when.type("add-layer.layer-id.input", id);
 
       if (opts.layer) {
-        await when.doWithin("add-layer.layer-source-block", async () => {
-          const input = get.element("input");
-          await input.click();
-          await input.fill(opts.layer!);
-          // The source input is a controlled downshift combobox; wait for React
-          // to settle on the typed value before submitting.
-          await expect(input).toHaveValue(opts.layer!);
-        });
+        const input = get.elementByTestId("add-layer.layer-source-block").locator("input");
+        await input.click();
+        await input.fill(opts.layer);
+        // The source input is a controlled downshift combobox; wait for React to
+        // settle on the typed value before submitting.
+        await then(input).shouldHaveValue(opts.layer);
         // Close the autocomplete menu so it does not intercept the add button.
         await get.elementByTestId("add-layer.layer-id.input").click();
       }
@@ -31,15 +28,51 @@ export class ModalDriver {
     },
 
     open: async () => {
-      // No-op when the add-layer modal is already open (some specs call open()
-      // both in a beforeEach and at the start of the test body).
-      const modal = this.driver.get.elementByTestId("modal:add-layer").first();
-      if (await modal.isVisible()) return;
-      await this.driver.when.click("layer-list:add-layer");
+      await this.helper.when.click("layer-list:add-layer");
     },
 
     close: async (key: string) => {
-      await this.driver.when.click(key + ".close-modal");
+      await this.helper.when.click(key + ".close-modal");
+    },
+
+    /**
+     * Adds a source of the given type from the sources modal, keeping whatever
+     * defaults that type's editor prefills.
+     */
+    addSource: async (sourceId: string, sourceType: string) => {
+      const { when } = this.helper;
+      await when.setValue("modal:sources.add.source_id", sourceId);
+      await when.select("modal:sources.add.source_type", sourceType);
+      await when.click("modal:sources.add.add_source");
+      await when.wait(200);
+    },
+
+    /** Adds one of the predefined public sources listed in the sources modal. */
+    addPublicSource: async (index = 0) => {
+      await this.helper.get.element(".maputnik-public-source-select").nth(index).click();
+    },
+
+    deleteFirstActiveSource: async () => {
+      await this.helper.get.element(".maputnik-active-source-type-editor-header-delete").first().click();
+    },
+
+    /** Fills one number box of a coordinate pair in the image/video source editor. */
+    setCoordinateValue: async (index: number, value: string) => {
+      const input = this.helper.get
+        .elementByTestId("modal:sources")
+        .locator(".maputnik-array input")
+        .nth(index);
+      await input.fill(value);
+      await input.blur();
+    },
+
+    exportCreateHtml: async () => {
+      await this.helper.get.element(".maputnik-modal-export-buttons button").last().click();
+    },
+
+    exportSaveStyle: async () => {
+      await this.helper.stubSaveFilePicker();
+      await this.helper.get.element(".maputnik-modal-export-buttons button").first().click();
     },
   };
 }

e2e/modals.spec.ts

@@ -1,20 +1,18 @@
-import { test, expect } from "./fixtures";
+import { test, expect, describe, beforeEach } from "./utils/fixtures";
 import { MaputnikDriver } from "./maputnik-driver";
 import tokens from "../src/config/tokens.json" with { type: "json" };
 
-test.describe("modals", () => {
+describe("modals", () => {
   const { given, get, when, then } = new MaputnikDriver();
 
-  test.beforeEach(async () => {
+  beforeEach(async () => {
     await given.setupMockBackedResponses();
-    // Load a style first so it is persisted to localStorage, then reset the URL
-    // to the root (no style param) — several tests read the stored style.
     await when.setStyle("both");
     await when.setStyle("");
   });
 
-  test.describe("open", () => {
-    test.beforeEach(async () => {
+  describe("open", () => {
+    beforeEach(async () => {
       await when.click("nav:open");
     });
 
@@ -25,16 +23,16 @@ test.describe("modals", () => {
 
     test("upload", async () => {
       await when.chooseExampleFile();
-      await then(get.fixture("example-style.json")).shouldEqualToStoredStyle();
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude(get.fixture("example-style.json"));
     });
 
     test("upload via drag and drop", async () => {
       await when.dropExampleFile();
-      await then(get.fixture("example-style.json")).shouldEqualToStoredStyle();
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude(get.fixture("example-style.json"));
     });
 
-    test.describe("when click open url", () => {
-      test.beforeEach(async () => {
+    describe("when click open url", () => {
+      beforeEach(async () => {
         const styleFileUrl = get.exampleFileUrl();
 
         await when.setValue("modal:open.url.input", styleFileUrl);
@@ -42,12 +40,22 @@ test.describe("modals", () => {
         await when.wait(200);
       });
       test("load from url", async () => {
-        await then(get.responseBody("example-style.json")).shouldEqualToStoredStyle();
+        await then(get.styleFromLocalStorage()).shouldDeepNestedInclude(get.responseBody("example-style.json"));
+      });
+    });
+
+    describe("without the File System Access API", () => {
+      test("upload via the file chooser", async () => {
+        await given.noFileSystemAccessApi();
+        await when.setStyle("");
+        await when.click("nav:open");
+        await when.chooseExampleFileFromPicker();
+        await then(get.styleFromLocalStorage()).shouldDeepNestedInclude(get.fixture("example-style.json"));
       });
     });
   });
 
-  test.describe("shortcuts", () => {
+  describe("shortcuts", () => {
     test("open/close", async () => {
       await when.setStyle("");
       await when.typeKeys("?");
@@ -56,8 +64,8 @@ test.describe("modals", () => {
     });
   });
 
-  test.describe("export", () => {
-    test.beforeEach(async () => {
+  describe("export", () => {
+    beforeEach(async () => {
       await when.click("nav:export");
     });
 
@@ -66,18 +74,44 @@ test.describe("modals", () => {
       await then(get.elementByTestId("modal:export")).shouldNotExist();
     });
 
-    // TODO: Work out how to download a file and check the contents
-    test.skip("download", () => {});
+    test("download HTML and save the style", async () => {
+      // Generate the standalone HTML export (triggers a file download).
+      await when.modal.exportCreateHtml();
+      await then(get.elementByTestId("modal:export")).shouldExist();
+
+      // Saving the style closes the export modal.
+      await when.modal.exportSaveStyle();
+      await then(get.elementByTestId("modal:export")).shouldNotExist();
+    });
   });
 
-  test.describe("sources", () => {
-    test.beforeEach(async () => {
+  describe("sources", () => {
+    beforeEach(async () => {
       await when.setStyle("layer");
       await when.click("nav:sources");
     });
 
-    test.skip("active sources", () => {});
-    test.skip("public source", () => {});
+    test("active sources are listed and can be deleted", async () => {
+      await when.setStyle("both");
+      await when.click("nav:sources");
+      const before = Object.keys(get.fixture("geojson-raster-style.json").sources).length;
+      await when.modal.deleteFirstActiveSource();
+      await then(
+        get.styleFromLocalStorage().then((style) => Object.keys(style.sources).length)
+      ).shouldEqual(before - 1);
+    });
+
+    test("public source", async () => {
+      await when.modal.addPublicSource();
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        sources: {
+          openmaptiles: {
+            type: "vector",
+            url: `https://api.maptiler.com/tiles/v3-openmaptiles/tiles.json?key=${tokens.openmaptiles}`,
+          },
+        },
+      });
+    });
 
     test("add new source", async () => {
       const sourceId = "n1z2v3r";
@@ -86,8 +120,8 @@ test.describe("modals", () => {
       await when.select("modal:sources.add.scheme_type", "tms");
       await when.click("modal:sources.add.add_source");
       await when.wait(200);
-      await then(get.styleFromLocalStorage().then((style) => style.sources[sourceId])).shouldInclude({
-        scheme: "tms",
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        sources: { [sourceId]: { scheme: "tms" } },
       });
     });
 
@@ -120,13 +154,115 @@ test.describe("modals", () => {
       await when.setValue("modal:sources.add.tile_size", "128");
       await when.click("modal:sources.add.add_source");
       await when.wait(200);
-      await then(get.styleFromLocalStorage().then((style) => style.sources[sourceId])).shouldInclude({
-        tileSize: 128,
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        sources: { [sourceId]: { tileSize: 128 } },
+      });
+    });
+
+    test("add new geojson url source", async () => {
+      await when.modal.addSource("geojsonurl", "geojson_url");
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        sources: {
+          geojsonurl: { type: "geojson", data: "http://localhost:3000/geojson.json" },
+        },
+      });
+    });
+
+    test("add new geojson json source", async () => {
+      await when.modal.addSource("geojsonjson", "geojson_json");
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        sources: {
+          geojsonjson: { type: "geojson", cluster: false, data: "" },
+        },
+      });
+    });
+
+    test("add new tilejson vector source", async () => {
+      await when.modal.addSource("tilejsonvector", "tilejson_vector");
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        sources: {
+          tilejsonvector: { type: "vector", url: "http://localhost:3000/tilejson.json" },
+        },
+      });
+    });
+
+    test("add new tilejson raster source", async () => {
+      await when.modal.addSource("tilejsonraster", "tilejson_raster");
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        sources: {
+          tilejsonraster: { type: "raster", url: "http://localhost:3000/tilejson.json" },
+        },
+      });
+    });
+
+    test("add new tilejson raster-dem source", async () => {
+      await when.modal.addSource("tilejsonrasterdem", "tilejson_raster-dem");
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        sources: {
+          tilejsonrasterdem: { type: "raster-dem", url: "http://localhost:3000/tilejson.json" },
+        },
+      });
+    });
+
+    test("add new tile xyz raster-dem source", async () => {
+      await when.modal.addSource("tilexyzrasterdem", "tilexyz_raster-dem");
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        sources: {
+          tilexyzrasterdem: {
+            type: "raster-dem",
+            tiles: ["http://localhost:3000/{x}/{y}/{z}.png"],
+            minzoom: 0,
+            maxzoom: 14,
+            tileSize: 512,
+          },
+        },
+      });
+    });
+
+    test("add new image source", async () => {
+      await when.modal.addSource("imagesource", "image");
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        sources: {
+          imagesource: {
+            type: "image",
+            url: "http://localhost:3000/image.png",
+            coordinates: [[0, 0], [0, 0], [0, 0], [0, 0]],
+          },
+        },
+      });
+    });
+
+    test("add new video source", async () => {
+      await when.modal.addSource("videosource", "video");
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        sources: {
+          videosource: {
+            type: "video",
+            urls: ["http://localhost:3000/movie.mp4"],
+            coordinates: [[0, 0], [0, 0], [0, 0], [0, 0]],
+          },
+        },
+      });
+    });
+
+    test("edit the corner coordinates of an image source", async () => {
+      const sourceId = "imagecoords";
+      await when.setValue("modal:sources.add.source_id", sourceId);
+      await when.select("modal:sources.add.source_type", "image");
+      // The first corner is the first two number boxes of the coordinate arrays.
+      await when.modal.setCoordinateValue(0, "1");
+      await when.modal.setCoordinateValue(1, "2");
+      await when.click("modal:sources.add.add_source");
+      await when.wait(200);
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        sources: {
+          [sourceId]: { type: "image", coordinates: [[1, 2], [0, 0], [0, 0], [0, 0]] },
+        },
       });
     });
   });
 
-  test.describe("inspect", () => {
+  describe("inspect", () => {
     test("toggle", async () => {
       // There is no assertion in this test
       await when.setStyle("geojson");
@@ -134,13 +270,13 @@ test.describe("modals", () => {
     });
   });
 
-  test.describe("style settings", () => {
-    test.beforeEach(async () => {
+  describe("style settings", () => {
+    beforeEach(async () => {
       await when.click("nav:settings");
     });
 
-    test.describe("when click name filed spec information", () => {
-      test.beforeEach(async () => {
+    describe("when click name filed spec information", () => {
+      beforeEach(async () => {
         await when.click("field-doc-button-Name");
       });
 
@@ -149,8 +285,8 @@ test.describe("modals", () => {
       });
     });
 
-    test.describe("when set name and click owner", () => {
-      test.beforeEach(async () => {
+    describe("when set name and click owner", () => {
+      beforeEach(async () => {
         await when.setValue("modal:settings.name", "foobar");
         await when.click("modal:settings.owner");
         await when.wait(200);
@@ -163,8 +299,8 @@ test.describe("modals", () => {
       });
     });
 
-    test.describe("when set owner and click name", () => {
-      test.beforeEach(async () => {
+    describe("when set owner and click name", () => {
+      beforeEach(async () => {
         await when.setValue("modal:settings.owner", "foobar");
         await when.click("modal:settings.name");
         await when.wait(200);
@@ -206,8 +342,8 @@ test.describe("modals", () => {
       const apiKey = "testing123";
       await when.setValue("modal:settings.maputnik:openmaptiles_access_token", apiKey);
       await when.click("modal:settings.name");
-      await then(get.styleFromLocalStorage().then((style) => style.metadata)).shouldInclude({
-        "maputnik:openmaptiles_access_token": apiKey,
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        metadata: { "maputnik:openmaptiles_access_token": apiKey },
       });
     });
 
@@ -215,8 +351,8 @@ test.describe("modals", () => {
       const apiKey = "testing123";
       await when.setValue("modal:settings.maputnik:thunderforest_access_token", apiKey);
       await when.click("modal:settings.name");
-      await then(get.styleFromLocalStorage().then((style) => style.metadata)).shouldInclude({
-        "maputnik:thunderforest_access_token": apiKey,
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        metadata: { "maputnik:thunderforest_access_token": apiKey },
       });
     });
 
@@ -224,8 +360,8 @@ test.describe("modals", () => {
       const apiKey = "testing123";
       await when.setValue("modal:settings.maputnik:stadia_access_token", apiKey);
       await when.click("modal:settings.name");
-      await then(get.styleFromLocalStorage().then((style) => style.metadata)).shouldInclude({
-        "maputnik:stadia_access_token": apiKey,
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        metadata: { "maputnik:stadia_access_token": apiKey },
       });
     });
 
@@ -233,29 +369,67 @@ test.describe("modals", () => {
       const apiKey = "testing123";
       await when.setValue("modal:settings.maputnik:locationiq_access_token", apiKey);
       await when.click("modal:settings.name");
-      await then(get.styleFromLocalStorage().then((style) => style.metadata)).shouldInclude({
-        "maputnik:locationiq_access_token": apiKey,
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        metadata: { "maputnik:locationiq_access_token": apiKey },
+      });
+    });
+
+    test("map view defaults", async () => {
+      await when.setValue("modal:settings.zoom", "4");
+      await when.setValue("modal:settings.bearing", "12");
+      await when.setValue("modal:settings.pitch", "30");
+      await when.click("modal:settings.name");
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        zoom: 4,
+        bearing: 12,
+        pitch: 30,
+      });
+    });
+
+    test("light intensity", async () => {
+      await when.setValue("modal:settings.light-intensity", "0.7");
+      await when.click("modal:settings.name");
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        light: { intensity: 0.7 },
+      });
+    });
+
+    test("terrain source and exaggeration", async () => {
+      await when.setValue("modal:settings.maputnik:terrain_source", "terrain");
+      await when.setValue("modal:settings.terrain-exaggeration", "1.5");
+      await when.click("modal:settings.name");
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        terrain: { source: "terrain", exaggeration: 1.5 },
+      });
+    });
+
+    test("transition delay and duration", async () => {
+      await when.setValue("modal:settings.transition-delay", "100");
+      await when.setValue("modal:settings.transition-duration", "500");
+      await when.click("modal:settings.name");
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        transition: { delay: 100, duration: 500 },
       });
     });
 
     test("style projection mercator", async () => {
       await when.select("modal:settings.projection", "mercator");
-      await then(get.styleFromLocalStorage().then((style) => style.projection)).shouldInclude({
-        type: "mercator",
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        projection: { type: "mercator" },
       });
     });
 
     test("style projection globe", async () => {
       await when.select("modal:settings.projection", "globe");
-      await then(get.styleFromLocalStorage().then((style) => style.projection)).shouldInclude({
-        type: "globe",
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        projection: { type: "globe" },
       });
     });
 
     test("style projection vertical-perspective", async () => {
       await when.select("modal:settings.projection", "vertical-perspective");
-      await then(get.styleFromLocalStorage().then((style) => style.projection)).shouldInclude({
-        type: "vertical-perspective",
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+        projection: { type: "vertical-perspective" },
       });
     });
 
@@ -273,7 +447,7 @@ test.describe("modals", () => {
       await when.click("modal:settings.close-modal");
       await when.click("nav:open");
 
-      await get.elementByAttribute("aria-label", "MapTiler Basic").click();
+      await when.clickByAttribute("aria-label", "MapTiler Basic");
       await when.wait(1000);
       await when.click("nav:settings");
 
@@ -284,7 +458,7 @@ test.describe("modals", () => {
       await then(get.inputValue("modal:settings.maputnik:renderer")).shouldEqual("ol");
 
       await given.intercept(
-        "https://api.maptiler.com/tiles/v3-openmaptiles/tiles.json?key=*",
+        /https:\/\/api\.maptiler\.com\/tiles\/v3-openmaptiles\/tiles\.json\?key=.*/,
         "tileRequest",
         "GET"
       );
@@ -299,8 +473,8 @@ test.describe("modals", () => {
     });
   });
 
-  test.describe("add layer", () => {
-    test.beforeEach(async () => {
+  describe("add layer", () => {
+    beforeEach(async () => {
       await when.setStyle("layer");
       await when.modal.open();
     });
@@ -313,12 +487,8 @@ test.describe("modals", () => {
     });
   });
 
-  test.describe("sources placeholder", () => {
-    test.skip("toggle", () => {});
-  });
-
-  test.describe("global state", () => {
-    test.beforeEach(async () => {
+  describe("global state", () => {
+    beforeEach(async () => {
       await when.click("nav:global-state");
     });
 
@@ -374,7 +544,7 @@ test.describe("modals", () => {
     });
   });
 
-  test.describe("error panel", () => {
+  describe("error panel", () => {
     test("not visible when no errors", async () => {
       await then(get.element("maputnik-message-panel-error")).shouldNotExist();
     });
@@ -389,40 +559,18 @@ test.describe("modals", () => {
     });
   });
 
-  test.describe("Handle localStorage QuotaExceededError", () => {
-    test("handles quota exceeded error when opening style from URL", async ({ page }) => {
+  describe("Handle localStorage QuotaExceededError", () => {
+    test("handles quota exceeded error when opening style from URL", async () => {
       // Clear localStorage to start fresh
       await when.clearLocalStorage();
-
-      // fill localStorage until we get a QuotaExceededError
-      await page.evaluate(() => {
-        let chunkSize = 1000;
-        const chunk = new Array(chunkSize).join("x");
-        let index = 0;
-
-        // Keep adding until we hit the quota
-        for (;;) {
-          try {
-            const key = `maputnik:fill-${index++}`;
-            window.localStorage.setItem(key, chunk);
-          } catch (e: any) {
-            // Verify it's a quota error
-            if (e.name === "QuotaExceededError") {
-              if (chunkSize <= 1) return;
-              chunkSize /= 2;
-              continue;
-            }
-            throw e; // Unexpected error
-          }
-        }
-      });
+      await when.fillLocalStorage();
 
       // Open the style via URL input
       await when.click("nav:open");
       await when.setValue("modal:open.url.input", get.exampleFileUrl());
       await when.click("modal:open.url.button");
 
-      await then(get.responseBody("example-style.json")).shouldEqualToStoredStyle();
+      await then(get.styleFromLocalStorage()).shouldDeepNestedInclude(get.responseBody("example-style.json"));
       await then(get.styleFromLocalStorage()).shouldExist();
     });
   });

e2e/playwright-helper.ts

@@ -0,0 +1,453 @@
+import fs from "node:fs";
+import path from "node:path";
+import { fileURLToPath } from "node:url";
+import { expect, type Locator, type Page, type Request } from "@playwright/test";
+import { currentPage, recordCoverageChunk } from "./utils/fixtures";
+
+const DATA_ATTRIBUTE = "data-wd-key";
+const FIXTURES_DIR = path.join(path.dirname(fileURLToPath(import.meta.url)), "fixtures");
+const isMac = process.platform === "darwin";
+
+function testIdSelector(testId: string): string {
+  return `[${DATA_ATTRIBUTE}="${testId}"]`;
+}
+
+/** Retries `assertion` until it stops throwing */
+async function retry(
+  assertion: () => Promise<void> | void,
+  timeout = 10000,
+  interval = 100
+): Promise<void> {
+  const start = Date.now();
+  let lastError: unknown;
+  while (true) {
+    try {
+      await assertion();
+      return;
+    } catch (error) {
+      lastError = error;
+      if (Date.now() - start > timeout) throw lastError;
+      await new Promise((resolve) => setTimeout(resolve, interval));
+    }
+  }
+}
+
+/**
+ * A lazily-evaluated value (e.g. the style in localStorage). Assertions on a
+ * Query re-read the value until they pass.
+ */
+class Query<T> {
+  readonly __query = true as const;
+  constructor(private readonly getter: () => Promise<T>) {}
+
+  get(): Promise<T> {
+    return this.getter();
+  }
+
+  then<U>(mapper: (value: T) => U | Promise<U>): Query<U> {
+    return new Query<U>(async () => mapper(await this.getter()));
+  }
+}
+
+function isQuery(target: unknown): target is Query<unknown> {
+  return typeof target === "object" && target !== null && (target as Query<unknown>).__query === true;
+}
+
+function isLocator(target: unknown): target is Locator {
+  return (
+    typeof target === "object" &&
+    target !== null &&
+    typeof (target as Locator).count === "function" &&
+    typeof (target as Locator).boundingBox === "function"
+  );
+}
+
+/**
+ * Asserts that `actual` recursively contains everything in `expected`: nested
+ * objects are matched as subsets, while arrays and primitives must match exactly.
+ */
+function assertDeepNestedInclude(actual: any, expected: Record<string, unknown> | unknown[]): void {
+  expect(actual).toMatchObject(expected);
+}
+
+/**
+ * Fluent, auto-retrying assertions over a Playwright Locator or a lazily
+ * evaluated value/Query. This is the generic base that the maputnik-specific
+ * assertable extends.
+ */
+export class Assertable<T> {
+  constructor(private readonly target: T) {}
+
+  private locator(): Locator {
+    if (!isLocator(this.target)) throw new Error("Expected a Locator target for this assertion");
+    return this.target;
+  }
+
+  protected async assertValue(assertion: (value: any) => void): Promise<void> {
+    const target = this.target;
+    if (isQuery(target)) {
+      await retry(async () => assertion(await target.get()));
+    } else {
+      assertion(await (target as any));
+    }
+  }
+
+  // Element assertions (auto-retrying via Playwright web-first assertions).
+  shouldBeVisible = () => expect(this.locator().first()).toBeVisible();
+  // Some testids resolve to many elements that are always rendered but hidden
+  // (e.g. per-field documentation panels); "not visible" means none is visible.
+  shouldNotBeVisible = () => expect(this.locator().filter({ visible: true })).toHaveCount(0);
+  shouldExist = async () => {
+    if (isLocator(this.target)) {
+      await expect(this.locator().first()).toBeAttached();
+    } else {
+      await this.assertValue((value) => expect(value).toBeTruthy());
+    }
+  };
+  shouldNotExist = () => expect(this.locator()).toHaveCount(0);
+  shouldBeFocused = () => expect(this.locator().first()).toBeFocused();
+  shouldNotBeFocused = () => expect(this.locator().first()).not.toBeFocused();
+  shouldHaveValue = (value: string) => expect(this.locator().first()).toHaveValue(value);
+  shouldContainText = async (text: string) => {
+    const locator = this.locator();
+    // Prefer the visible element when a testid resolves to several (only the
+    // open documentation panel is visible; the rest are hidden in the DOM).
+    const target = (await locator.count()) > 1 ? locator.filter({ visible: true }).first() : locator.first();
+    await expect(target).toContainText(text);
+  };
+  shouldHaveText = (text: string) => expect(this.locator().first()).toHaveText(text);
+  shouldHaveLength = (length: number) => expect(this.locator()).toHaveCount(length);
+  shouldHaveCss = (property: string, value: string) => expect(this.locator().first()).toHaveCSS(property, value);
+
+  // Value assertions (auto-retrying for Query targets).
+  shouldEqual = (value: any) => this.assertValue((actual) => expect(actual).toBe(value));
+
+  shouldInclude = (value: any) =>
+    this.assertValue((actual) => {
+      if (typeof value === "object" && value !== null) {
+        expect(actual).toMatchObject(value);
+      } else {
+        expect(String(actual)).toContain(String(value));
+      }
+    });
+
+  shouldDeepNestedInclude = (value: Record<string, unknown> | unknown[]) =>
+    this.assertValue((actual) => assertDeepNestedInclude(actual, value));
+}
+
+async function typeSequence(page: Page, text: string): Promise<void> {
+  const tokens = text.match(/\{[^}]+\}|[^{]+/g) ?? [];
+  const modifierMap: Record<string, string> = { meta: "Meta", ctrl: "Control", shift: "Shift", alt: "Alt" };
+  const namedKeys: Record<string, string> = {
+    esc: "Escape",
+    enter: "Enter",
+    backspace: "Backspace",
+    del: "Delete",
+    tab: "Tab",
+    home: "Home",
+    end: "End",
+    rightarrow: "ArrowRight",
+  };
+
+  for (let i = 0; i < tokens.length; i++) {
+    const token = tokens[i];
+    if (!token.startsWith("{") || !token.endsWith("}")) {
+      await page.keyboard.type(token);
+      continue;
+    }
+    const name = token.slice(1, -1).toLowerCase();
+    if (name === "selectall") {
+      await page.keyboard.press(isMac ? "Meta+a" : "Control+a");
+    } else if (namedKeys[name]) {
+      await page.keyboard.press(namedKeys[name]);
+    } else if (modifierMap[name]) {
+      const modifiers = [modifierMap[name]];
+      let j = i + 1;
+      while (j < tokens.length && /^\{(meta|ctrl|shift|alt)\}$/i.test(tokens[j])) {
+        modifiers.push(modifierMap[tokens[j].slice(1, -1).toLowerCase()]);
+        j++;
+      }
+      const key = tokens[j] ?? "";
+      await page.keyboard.press([...modifiers, key].join("+"));
+      i = j;
+    }
+  }
+}
+
+async function centerOf(locator: Locator): Promise<{ x: number; y: number }> {
+  const box = await locator.boundingBox();
+  if (!box) throw new Error("Element has no bounding box");
+  return { x: box.x + box.width / 2, y: box.y + box.height / 2 };
+}
+
+/**
+ * This is where all plywright-specific test helpers live.
+ * It is used by the MaputnikDriver to implement the Maputnik-specific test helpers.
+ */
+export class PlaywrightHelper {
+  private readonly recordedRequests = new Map<string, Request[]>();
+
+  private get page(): Page {
+    return currentPage();
+  }
+
+  private testId(testId: string): Locator {
+    return this.page.locator(testIdSelector(testId));
+  }
+
+  /** Reads and parses a JSON fixture from the fixtures directory. */
+  public readFixture(name: string): any {
+    return JSON.parse(fs.readFileSync(path.join(FIXTURES_DIR, name), "utf-8"));
+  }
+
+  /** Wraps a lazily-evaluated value so assertions on it auto-retry. */
+  public query<T>(getter: () => Promise<T>): Query<T> {
+    return new Query<T>(getter);
+  }
+
+  /** Stubs the File System Access "save" picker so file saves complete headlessly. */
+  public stubSaveFilePicker(): Promise<void> {
+    return this.page.evaluate(() => {
+      (window as any).showSaveFilePicker = async () => ({
+        createWritable: async () => ({ write: async () => {}, close: async () => {} }),
+      });
+    });
+  }
+
+  /** Entry point for fluent assertions over a Locator or a value/Query. */
+  public then = <T>(target: T): Assertable<T> => new Assertable(target);
+
+  public given = {
+    /**
+     * Removes the File System Access API so the app falls back to a plain
+     * <input type="file">, the way Firefox and Safari behave. Must be called
+     * before the page under test is loaded.
+     */
+    noFileSystemAccessApi: async () => {
+      await this.page.addInitScript(() => {
+        delete (window as any).showOpenFilePicker;
+        delete (window as any).showSaveFilePicker;
+      });
+    },
+
+    intercept: async (pattern: RegExp, alias: string, _method = "GET") => {
+      this.recordedRequests.set(alias, []);
+      await this.page.route(pattern, (route) => {
+        this.recordedRequests.get(alias)!.push(route.request());
+        route.continue();
+      });
+    },
+
+    interceptAndMockResponse: async (options: {
+      method?: string;
+      url: string | RegExp;
+      response: unknown | { fixture: string };
+      alias?: string;
+    }) => {
+      const { url, response, alias } = options;
+      if (alias) this.recordedRequests.set(alias, []);
+      await this.page.route(url, (route) => {
+        if (alias) this.recordedRequests.get(alias)!.push(route.request());
+        const body =
+          response && typeof response === "object" && "fixture" in (response as any)
+            ? this.readFixture((response as { fixture: string }).fixture)
+            : response;
+        route.fulfill({ json: body });
+      });
+    },
+  };
+
+  public when = {
+    visit: async (url: string) => {
+      // Snapshot coverage before navigating, since a full page load resets it.
+      await recordCoverageChunk(this.page);
+      await this.page.goto(url);
+    },
+
+    wait: (ms: number) => this.page.waitForTimeout(ms),
+
+    tab: () => this.page.keyboard.press("Tab"),
+
+    typeKeys: (keys: string) => typeSequence(this.page, keys),
+
+    /** Types raw text into the focused element (no "{key}" sequence parsing). */
+    typeText: (text: string) => this.page.keyboard.type(text),
+
+    clickButtonByName: async (name: string) => {
+      await this.page.getByRole("button", { name }).click();
+    },
+
+    click: async (testId: string, index = 0) => {
+      // Documentation buttons are wrapped in a <label>/.maputnik-doc-target that
+      // Playwright treats as intercepting the click; bypass the check for them.
+      const force = testId.startsWith("field-doc-button-");
+      await this.testId(testId).nth(index).click({ force });
+    },
+
+    realClick: async (testId: string) => {
+      await this.testId(testId).click();
+    },
+
+    hover: async (testId: string) => {
+      await this.testId(testId).hover();
+    },
+
+    focus: async (testId: string) => {
+      await this.testId(testId).focus();
+    },
+
+    clear: async (testId: string) => {
+      await this.testId(testId).clear();
+    },
+
+    select: async (testId: string, value: string) => {
+      await this.testId(testId).selectOption(value);
+    },
+
+    selectWithin: async (parentTestId: string, value: string) => {
+      await this.testId(parentTestId).locator("select").selectOption(value);
+    },
+
+    clickWithin: async (parentTestId: string, selector: string) => {
+      await this.testId(parentTestId).locator(selector).first().click();
+    },
+
+    clickByText: async (text: string) => {
+      await this.page.getByText(text).click();
+    },
+
+    clickByAttribute: async (attribute: string, value: string) => {
+      await this.page.locator(`[${attribute}="${value}"]`).click();
+    },
+
+    scrollToBottom: async (element: Locator) => {
+      await element.evaluate((el) => el.scrollTo(0, el.scrollHeight));
+    },
+
+    setValue: async (testId: string, text: string) => {
+      const input = this.testId(testId);
+      await input.fill("");
+      await input.fill(text);
+    },
+
+    type: async (testId: string, text: string) => {
+      await this.testId(testId).focus();
+      // Place the caret at the start of the field, so a leading "{backspace}"
+      // is a no-op rather than clearing an already-committed value.
+      await this.page.keyboard.press("Home");
+      await typeSequence(this.page, text);
+    },
+
+    dragAndDropWithWait: async (source: string, target: string) => {
+      const from = await centerOf(this.testId(source));
+      const to = await centerOf(this.testId(target));
+      await this.page.mouse.move(from.x, from.y);
+      await this.page.mouse.down();
+      await this.page.mouse.move(from.x, from.y + 10);
+      await this.page.mouse.move(to.x, to.y, { steps: 10 });
+      await this.page.waitForTimeout(100);
+      await this.page.mouse.up();
+    },
+
+    clickCenter: async (testId: string) => {
+      const { x, y } = await centerOf(this.testId(testId));
+      await this.page.mouse.move(x, y);
+      await this.page.mouse.down();
+      await this.page.waitForTimeout(200);
+      await this.page.mouse.up();
+    },
+
+    /**
+     * Opens a fixture through the File System Access API, which raises no
+     * "filechooser" event and so has to be stubbed. For the <input type="file">
+     * fallback that browsers without the API use, see chooseFileFromPicker.
+     */
+    openFileByFixture: async (fixture: string, buttonTestId: string) => {
+      const content = JSON.stringify(this.readFixture(fixture));
+      await this.page.evaluate((fileContent) => {
+        (window as any).showOpenFilePicker = async () => [
+          { getFile: async () => ({ text: async () => fileContent }) },
+        ];
+      }, content);
+      await this.testId(buttonTestId).click();
+    },
+
+    /**
+     * Clicks a control that opens the browser's native file chooser and answers
+     * it with a fixture. Only works on the <input type="file"> path — the File
+     * System Access API does not raise a "filechooser" event, so pair this with
+     * given.noFileSystemAccessApi().
+     */
+    chooseFileFromPicker: async (fixture: string, triggerTestId: string) => {
+      const content = JSON.stringify(this.readFixture(fixture));
+      const [fileChooser] = await Promise.all([
+        this.page.waitForEvent("filechooser"),
+        this.testId(triggerTestId).click(),
+      ]);
+      await fileChooser.setFiles({
+        name: fixture,
+        mimeType: "application/json",
+        buffer: Buffer.from(content),
+      });
+    },
+
+    dropFileByFixture: async (fixture: string, dropzoneTestId: string) => {
+      const content = JSON.stringify(this.readFixture(fixture));
+      const dataTransfer = await this.page.evaluateHandle((fileContent) => {
+        const dt = new DataTransfer();
+        dt.items.add(new File([fileContent], "example-style.json", { type: "application/json" }));
+        return dt;
+      }, content);
+      const dropzone = this.testId(dropzoneTestId);
+      await dropzone.dispatchEvent("dragenter", { dataTransfer });
+      await dropzone.dispatchEvent("dragover", { dataTransfer });
+      await dropzone.dispatchEvent("drop", { dataTransfer });
+    },
+
+    waitForResponse: async (alias: string) => {
+      const requests = this.recordedRequests.get(alias);
+      if (!requests) throw new Error(`No intercept registered for alias "${alias}"`);
+      await retry(async () => {
+        if (requests.length === 0) throw new Error(`No request recorded for alias "${alias}"`);
+      });
+      return requests[requests.length - 1];
+    },
+
+    clearLocalStorage: () => this.page.evaluate(() => window.localStorage.clear()),
+
+    /** Writes to localStorage under `keyPrefix` until a QuotaExceededError is hit. */
+    fillLocalStorageUntilQuota: (keyPrefix: string) =>
+      this.page.evaluate((prefix) => {
+        let chunkSize = 1000;
+        const chunk = new Array(chunkSize).join("x");
+        let index = 0;
+        while (true) {
+          try {
+            window.localStorage.setItem(`${prefix}${index++}`, chunk);
+          } catch (e: any) {
+            if (e.name === "QuotaExceededError") {
+              if (chunkSize <= 1) return;
+              chunkSize /= 2;
+              continue;
+            }
+            throw e; // Unexpected error
+          }
+        }
+      }, keyPrefix),
+  };
+
+  public get = {
+    element: (selector: string) => this.page.locator(selector),
+
+    localStorageItem: (key: string) =>
+      this.page.evaluate((k) => window.localStorage.getItem(k), key),
+
+    elementByTestId: (testId: string) => this.testId(testId),
+
+    inputValue: (testId: string) => new Query<string>(() => this.testId(testId).first().inputValue()),
+
+    elementsText: (testId: string) => new Query<string>(() => this.testId(testId).first().innerText()),
+
+    locationHash: () => new Query<string>(async () => new URL(this.page.url()).hash),
+  };
+}

e2e/utils/fixtures.ts

@@ -0,0 +1,82 @@
+import { test, expect, type Page } from "@playwright/test";
+import fs from "node:fs";
+import path from "node:path";
+
+let activePage: Page | undefined;
+const coverageChunks: unknown[] = [];
+
+/** The page for the currently running test. Throws if used outside a test. */
+export function currentPage(): Page {
+  if (!activePage) {
+    throw new Error("No active page: a MaputnikDriver method was called outside of a running test.");
+  }
+  return activePage;
+}
+
+const OUTPUT_DIR = path.resolve(process.cwd(), ".nyc_output");
+
+/**
+ * Reads the istanbul coverage object (injected by vite-plugin-istanbul) from the
+ * given page. Returns `null` when the page has not been instrumented.
+ */
+async function readCoverage(page: Page): Promise<unknown | null> {
+  try {
+    return await page.evaluate(() => (window as unknown as { __coverage__?: unknown }).__coverage__ ?? null);
+  } catch {
+    // Page might be navigating/closed.
+    return null;
+  }
+}
+
+/**
+ * Persists a coverage chunk to `.nyc_output` so that `nyc report` can merge it.
+ * istanbul-lib-coverage (used by nyc) sums the hit counts across every file it
+ * finds, so writing one file per chunk is enough to accumulate coverage across
+ * navigations and tests.
+ */
+export function writeCoverage(coverage: unknown, id: string): void {
+  if (!coverage) return;
+  fs.mkdirSync(OUTPUT_DIR, { recursive: true });
+  fs.writeFileSync(path.join(OUTPUT_DIR, `playwright-${id}.json`), JSON.stringify(coverage));
+}
+
+/** Records a coverage snapshot (called before navigations, which reset __coverage__). */
+export async function recordCoverageChunk(page: Page): Promise<void> {
+  const chunk = await readCoverage(page);
+  if (chunk) coverageChunks.push(chunk);
+}
+
+/**
+ * Auto fixture that binds the current test's page for the (page-lazy)
+ * MaputnikDriver, auto-accepts confirm dialogs, and writes the istanbul
+ * coverage collected during the test to `.nyc_output`.
+ */
+const extendedTest = test.extend<{ maputnikPage: void }>({
+  maputnikPage: [
+    async ({ page }, use, testInfo) => {
+      activePage = page;
+      coverageChunks.length = 0;
+      // Accept confirm dialogs (e.g. the "replace current style" prompt). These
+      // are dismissed by default, which would cancel loading a style via URL.
+      page.on("dialog", (dialog) => dialog.accept().catch(() => undefined));
+
+      await use();
+
+      const finalCoverage = await readCoverage(page);
+      if (finalCoverage) coverageChunks.push(finalCoverage);
+      coverageChunks.forEach((chunk, index) => writeCoverage(chunk, `${testInfo.testId}-${index}`));
+      coverageChunks.length = 0;
+      activePage = undefined;
+    },
+    { auto: true },
+  ],
+});
+
+const describe = extendedTest.describe;
+const beforeEach = extendedTest.beforeEach;
+export {
+  expect,
+  describe,
+  extendedTest as test,
+  beforeEach,
+};

eslint.config.js

@@ -32,9 +32,11 @@ export default defineConfig({
     "@stylistic": stylisticTs
   },
   rules: {
+    "react-hooks/rules-of-hooks": "error",
+    "react-hooks/exhaustive-deps": "warn",
     "react-refresh/only-export-components": [
       "warn",
-      { allowConstantExport: true }
+      { allowConstantExport: true, extraHOCs: ["withTranslation"] }
     ],
     "@typescript-eslint/no-explicit-any": "off",
     "@typescript-eslint/no-unused-vars": [

package.json

@@ -28,9 +28,9 @@
   "dependencies": {
     "@codemirror/lang-json": "^6.0.2",
     "@codemirror/lint": "^6.9.7",
-    "@codemirror/state": "^6.7.0",
+    "@codemirror/state": "^6.7.1",
     "@codemirror/theme-one-dark": "^6.1.3",
-    "@codemirror/view": "^6.43.5",
+    "@codemirror/view": "^6.43.6",
     "@dnd-kit/core": "^6.3.1",
     "@dnd-kit/sortable": "^10.0.0",
     "@dnd-kit/utilities": "^3.2.2",
@@ -124,8 +124,6 @@
     "@types/string-hash": "^1.1.3",
     "@types/wicg-file-system-access": "^2023.10.7",
     "@vitejs/plugin-react": "5.2",
-    "@vitest/browser": "^4.1.10",
-    "@vitest/browser-playwright": "^4.1.10",
     "@vitest/coverage-v8": "^4.1.10",
     "cors": "^2.8.6",
     "eslint": "^10.6.0",
@@ -147,7 +145,6 @@
     "uuid": "^14.0.1",
     "vite": "^7.3.2",
     "vite-plugin-istanbul": "^9.0.1",
-    "vitest": "^4.1.10",
-    "vitest-browser-react": "^2.2.0"
+    "vitest": "^4.1.10"
   }
 }

playwright.config.ts

@@ -9,8 +9,8 @@ const baseURL = process.env.E2E_BASE_URL ?? "http://localhost:8888/";
 export default defineConfig({
   testDir: "./e2e",
   testMatch: "**/*.spec.ts",
-  globalSetup: "./e2e/global-setup.ts",
-  globalTeardown: "./e2e/global-teardown.ts",
+  globalSetup: "./e2e/utils/e2e-setup.ts",
+  globalTeardown: "./e2e/utils/e2e-teardown.ts",
   fullyParallel: true,
   forbidOnly: isCI,
   retries: isCI ? 2 : 0,

src/components/AppLayout.tsx

@@ -1,5 +1,5 @@
 import React from "react";
-import ScrollContainer from "./ScrollContainer";
+import { ScrollContainer } from "./ScrollContainer";
 import { type WithTranslation, withTranslation } from "react-i18next";
 import { IconContext } from "react-icons";
 
@@ -13,42 +13,38 @@ type AppLayoutInternalProps = {
   modals?: React.ReactNode
 } & WithTranslation;
 
-class AppLayoutInternal extends React.Component<AppLayoutInternalProps> {
+const AppLayoutInternal: React.FC<AppLayoutInternalProps> = (props) => {
+  document.body.dir = props.i18n.dir();
 
-  render() {
-    document.body.dir = this.props.i18n.dir();
-
-    return <IconContext.Provider value={{size: "14px"}}>
-      <div className="maputnik-layout">
-        {this.props.toolbar}
-        <div className="maputnik-layout-main">
-          {this.props.codeEditor && <div className="maputnik-layout-code-editor">
-            <ScrollContainer>
-              {this.props.codeEditor}
-            </ScrollContainer>
-          </div>
-          }
-          {!this.props.codeEditor && <>
-            <div className="maputnik-layout-list">
-              {this.props.layerList}
-            </div>
-            <div className="maputnik-layout-drawer">
-              <ScrollContainer>
-                {this.props.layerEditor}
-              </ScrollContainer>
-            </div>
-          </>}
-          {this.props.map}
-        </div>
-        {this.props.bottom && <div className="maputnik-layout-bottom">
-          {this.props.bottom}
+  return <IconContext.Provider value={{size: "14px"}}>
+    <div className="maputnik-layout">
+      {props.toolbar}
+      <div className="maputnik-layout-main">
+        {props.codeEditor && <div className="maputnik-layout-code-editor">
+          <ScrollContainer>
+            {props.codeEditor}
+          </ScrollContainer>
         </div>
         }
-        {this.props.modals}
+        {!props.codeEditor && <>
+          <div className="maputnik-layout-list">
+            {props.layerList}
+          </div>
+          <div className="maputnik-layout-drawer">
+            <ScrollContainer>
+              {props.layerEditor}
+            </ScrollContainer>
+          </div>
+        </>}
+        {props.map}
       </div>
-    </IconContext.Provider>;
-  }
-}
+      {props.bottom && <div className="maputnik-layout-bottom">
+        {props.bottom}
+      </div>
+      }
+      {props.modals}
+    </div>
+  </IconContext.Provider>;
+};
 
-const AppLayout = withTranslation()(AppLayoutInternal);
-export default AppLayout;
+export const AppLayout = withTranslation()(AppLayoutInternal);

src/components/AppMessagePanel.tsx

@@ -13,53 +13,49 @@ type AppMessagePanelInternalProps = {
   selectedLayerIndex?: number
 } & WithTranslation;
 
-class AppMessagePanelInternal extends React.Component<AppMessagePanelInternalProps> {
-  static defaultProps = {
-    onLayerSelect: () => { },
-  };
+const AppMessagePanelInternal: React.FC<AppMessagePanelInternalProps> = ({
+  onLayerSelect = () => { },
+  ...props
+}) => {
+  const { t, selectedLayerIndex } = props;
+  const errors = props.errors?.map((error, idx) => {
+    let content;
+    if (error.parsed && error.parsed.type === "layer") {
+      const { parsed } = error;
+      const layerId = props.mapStyle?.layers[parsed.data.index].id;
+      content = (
+        <>
+          {t("Layer")} <span>{formatLayerId(layerId)}</span>: {parsed.data.message}
+          {selectedLayerIndex !== parsed.data.index &&
+            <>
+              &nbsp;&mdash;&nbsp;
+              <button
+                className="maputnik-message-panel__switch-button"
+                onClick={() => onLayerSelect!(parsed.data.index)}
+              >
+                {t("switch to layer")}
+              </button>
+            </>
+          }
+        </>
+      );
+    }
+    else {
+      content = error.message;
+    }
+    return <p key={"error-" + idx} className="maputnik-message-panel-error">
+      {content}
+    </p>;
+  });
 
-  render() {
-    const { t, selectedLayerIndex } = this.props;
-    const errors = this.props.errors?.map((error, idx) => {
-      let content;
-      if (error.parsed && error.parsed.type === "layer") {
-        const { parsed } = error;
-        const layerId = this.props.mapStyle?.layers[parsed.data.index].id;
-        content = (
-          <>
-            {t("Layer")} <span>{formatLayerId(layerId)}</span>: {parsed.data.message}
-            {selectedLayerIndex !== parsed.data.index &&
-              <>
-                &nbsp;&mdash;&nbsp;
-                <button
-                  className="maputnik-message-panel__switch-button"
-                  onClick={() => this.props.onLayerSelect!(parsed.data.index)}
-                >
-                  {t("switch to layer")}
-                </button>
-              </>
-            }
-          </>
-        );
-      }
-      else {
-        content = error.message;
-      }
-      return <p key={"error-" + idx} className="maputnik-message-panel-error">
-        {content}
-      </p>;
-    });
+  const infos = props.infos?.map((m, i) => {
+    return <p key={"info-" + i}>{m}</p>;
+  });
 
-    const infos = this.props.infos?.map((m, i) => {
-      return <p key={"info-" + i}>{m}</p>;
-    });
+  return <div className="maputnik-message-panel">
+    {errors}
+    {infos}
+  </div>;
+};
 
-    return <div className="maputnik-message-panel">
-      {errors}
-      {infos}
-    </div>;
-  }
-}
-
-const AppMessagePanel = withTranslation()(AppMessagePanelInternal);
-export default AppMessagePanel;
+export const AppMessagePanel = withTranslation()(AppMessagePanelInternal);

src/components/AppToolbar.tsx

@@ -31,11 +31,9 @@ type IconTextProps = {
 };
 
 
-class IconText extends React.Component<IconTextProps> {
-  render() {
-    return <span className="maputnik-icon-text">{this.props.children}</span>;
-  }
-}
+const IconText: React.FC<IconTextProps> = (props) => {
+  return <span className="maputnik-icon-text">{props.children}</span>;
+};
 
 type ToolbarLinkProps = {
   className?: string
@@ -43,35 +41,31 @@ type ToolbarLinkProps = {
   href?: string
 };
 
-class ToolbarLink extends React.Component<ToolbarLinkProps> {
-  render() {
-    return <a
-      className={classnames("maputnik-toolbar-link", this.props.className)}
-      href={this.props.href}
-      rel="noopener noreferrer"
-      target="_blank"
-      data-wd-key="toolbar:link"
-    >
-      {this.props.children}
-    </a>;
-  }
-}
+const ToolbarLink: React.FC<ToolbarLinkProps> = (props) => {
+  return <a
+    className={classnames("maputnik-toolbar-link", props.className)}
+    href={props.href}
+    rel="noopener noreferrer"
+    target="_blank"
+    data-wd-key="toolbar:link"
+  >
+    {props.children}
+  </a>;
+};
 
 type ToolbarSelectProps = {
   children?: React.ReactNode
   wdKey?: string
 };
 
-class ToolbarSelect extends React.Component<ToolbarSelectProps> {
-  render() {
-    return <div
-      className='maputnik-toolbar-select'
-      data-wd-key={this.props.wdKey}
-    >
-      {this.props.children}
-    </div>;
-  }
-}
+const ToolbarSelect: React.FC<ToolbarSelectProps> = (props) => {
+  return <div
+    className='maputnik-toolbar-select'
+    data-wd-key={props.wdKey}
+  >
+    {props.children}
+  </div>;
+};
 
 type ToolbarActionProps = {
   children?: React.ReactNode
@@ -79,17 +73,15 @@ type ToolbarActionProps = {
   wdKey?: string
 };
 
-class ToolbarAction extends React.Component<ToolbarActionProps> {
-  render() {
-    return <button
-      className='maputnik-toolbar-action'
-      data-wd-key={this.props.wdKey}
-      onClick={this.props.onClick}
-    >
-      {this.props.children}
-    </button>;
-  }
-}
+const ToolbarAction: React.FC<ToolbarActionProps> = (props) => {
+  return <button
+    className='maputnik-toolbar-action'
+    data-wd-key={props.wdKey}
+    onClick={props.onClick}
+  >
+    {props.children}
+  </button>;
+};
 
 export type MapState = "map" | "inspect" | "filter-achromatopsia" | "filter-deuteranopia" | "filter-protanopia" | "filter-tritanopia";
 
@@ -108,26 +100,16 @@ type AppToolbarInternalProps = {
   renderer?: string
 } & WithTranslation;
 
-class AppToolbarInternal extends React.Component<AppToolbarInternalProps> {
-  state = {
-    isOpen: {
-      settings: false,
-      sources: false,
-      open: false,
-      add: false,
-      export: false,
-    }
-  };
-
-  handleSelection(val: MapState) {
-    this.props.onSetMapState(val);
+const AppToolbarInternal: React.FC<AppToolbarInternalProps> = (props) => {
+  function handleSelection(val: MapState) {
+    props.onSetMapState(val);
   }
 
-  handleLanguageChange(val: string) {
-    this.props.i18n.changeLanguage(val);
+  function handleLanguageChange(val: string) {
+    props.i18n.changeLanguage(val);
   }
 
-  onSkip = (target: string) => {
+  const onSkip = (target: string) => {
     if (target === "map") {
       (document.querySelector(".maplibregl-canvas") as HTMLCanvasElement).focus();
     }
@@ -137,174 +119,171 @@ class AppToolbarInternal extends React.Component<AppToolbarInternalProps> {
     }
   };
 
-  render() {
-    const t = this.props.t;
-    const views = [
-      {
-        id: "map",
-        group: "general",
-        title: t("Map"),
-      },
-      {
-        id: "inspect",
-        group: "general",
-        title: t("Inspect"),
-        disabled: this.props.renderer === "ol",
-      },
-      {
-        id: "filter-deuteranopia",
-        group: "color-accessibility",
-        title: t("Deuteranopia filter"),
-        disabled: !colorAccessibilityFiltersEnabled,
-      },
-      {
-        id: "filter-protanopia",
-        group: "color-accessibility",
-        title: t("Protanopia filter"),
-        disabled: !colorAccessibilityFiltersEnabled,
-      },
-      {
-        id: "filter-tritanopia",
-        group: "color-accessibility",
-        title: t("Tritanopia filter"),
-        disabled: !colorAccessibilityFiltersEnabled,
-      },
-      {
-        id: "filter-achromatopsia",
-        group: "color-accessibility",
-        title: t("Achromatopsia filter"),
-        disabled: !colorAccessibilityFiltersEnabled,
-      },
-    ];
+  const t = props.t;
+  const views = [
+    {
+      id: "map",
+      group: "general",
+      title: t("Map"),
+    },
+    {
+      id: "inspect",
+      group: "general",
+      title: t("Inspect"),
+      disabled: props.renderer === "ol",
+    },
+    {
+      id: "filter-deuteranopia",
+      group: "color-accessibility",
+      title: t("Deuteranopia filter"),
+      disabled: !colorAccessibilityFiltersEnabled,
+    },
+    {
+      id: "filter-protanopia",
+      group: "color-accessibility",
+      title: t("Protanopia filter"),
+      disabled: !colorAccessibilityFiltersEnabled,
+    },
+    {
+      id: "filter-tritanopia",
+      group: "color-accessibility",
+      title: t("Tritanopia filter"),
+      disabled: !colorAccessibilityFiltersEnabled,
+    },
+    {
+      id: "filter-achromatopsia",
+      group: "color-accessibility",
+      title: t("Achromatopsia filter"),
+      disabled: !colorAccessibilityFiltersEnabled,
+    },
+  ];
 
-    const currentView = views.find((view) => {
-      return view.id === this.props.mapState;
-    });
+  const currentView = views.find((view) => {
+    return view.id === props.mapState;
+  });
 
-    return <nav className='maputnik-toolbar'>
-      <div className="maputnik-toolbar__inner">
-        <div
-          className="maputnik-toolbar-logo-container"
+  return <nav className='maputnik-toolbar'>
+    <div className="maputnik-toolbar__inner">
+      <div
+        className="maputnik-toolbar-logo-container"
+      >
+        {/* Keyboard accessible quick links */}
+        <button
+          data-wd-key="root:skip:layer-list"
+          className="maputnik-toolbar-skip"
+          onClick={_e => onSkip("layer-list")}
         >
-          {/* Keyboard accessible quick links */}
-          <button
-            data-wd-key="root:skip:layer-list"
-            className="maputnik-toolbar-skip"
-            onClick={_e => this.onSkip("layer-list")}
-          >
-            {t("Layers list")}
-          </button>
-          <button
-            data-wd-key="root:skip:layer-editor"
-            className="maputnik-toolbar-skip"
-            onClick={_e => this.onSkip("layer-editor")}
-          >
-            {t("Layer editor")}
-          </button>
-          <button
-            data-wd-key="root:skip:map-view"
-            className="maputnik-toolbar-skip"
-            onClick={_e => this.onSkip("map")}
-          >
-            {t("Map view")}
-          </button>
-          <a
-            className="maputnik-toolbar-logo"
-            target="blank"
-            rel="noreferrer noopener"
-            href="https://github.com/maplibre/maputnik"
-          >
-            <img src={maputnikLogo} alt={t("Maputnik on GitHub")} />
-            <h1>
-              <span className="maputnik-toolbar-name">{pkgJson.name}</span>
-              <span className="maputnik-toolbar-version">v{pkgJson.version}</span>
-            </h1>
-          </a>
-        </div>
-        <div className="maputnik-toolbar__actions" role="navigation" aria-label="Toolbar">
-          <ToolbarAction wdKey="nav:open" onClick={() => this.props.onToggleModal("open")}>
-            <MdOpenInBrowser />
-            <IconText>{t("Open")}</IconText>
-          </ToolbarAction>
-          <ToolbarAction wdKey="nav:export" onClick={() => this.props.onToggleModal("export")}>
-            <MdSave />
-            <IconText>{t("Save")}</IconText>
-          </ToolbarAction>
-          <ToolbarAction wdKey="nav:code-editor" onClick={() => this.props.onToggleModal("codeEditor")}>
-            <MdCode />
-            <IconText>{t("Code Editor")}</IconText>
-          </ToolbarAction>
-          <ToolbarAction wdKey="nav:sources" onClick={() => this.props.onToggleModal("sources")}>
-            <MdLayers />
-            <IconText>{t("Data Sources")}</IconText>
-          </ToolbarAction>
-          <ToolbarAction wdKey="nav:settings" onClick={() => this.props.onToggleModal("settings")}>
-            <MdSettings />
-            <IconText>{t("Style Settings")}</IconText>
-          </ToolbarAction>
-          <ToolbarAction wdKey="nav:global-state" onClick={() => this.props.onToggleModal("globalState")}>
-            <MdPublic />
-            <IconText>{t("Global State")}</IconText>
-          </ToolbarAction>
+          {t("Layers list")}
+        </button>
+        <button
+          data-wd-key="root:skip:layer-editor"
+          className="maputnik-toolbar-skip"
+          onClick={_e => onSkip("layer-editor")}
+        >
+          {t("Layer editor")}
+        </button>
+        <button
+          data-wd-key="root:skip:map-view"
+          className="maputnik-toolbar-skip"
+          onClick={_e => onSkip("map")}
+        >
+          {t("Map view")}
+        </button>
+        <a
+          className="maputnik-toolbar-logo"
+          target="blank"
+          rel="noreferrer noopener"
+          href="https://github.com/maplibre/maputnik"
+        >
+          <img src={maputnikLogo} alt={t("Maputnik on GitHub")} />
+          <h1>
+            <span className="maputnik-toolbar-name">{pkgJson.name}</span>
+            <span className="maputnik-toolbar-version">v{pkgJson.version}</span>
+          </h1>
+        </a>
+      </div>
+      <div className="maputnik-toolbar__actions" role="navigation" aria-label="Toolbar">
+        <ToolbarAction wdKey="nav:open" onClick={() => props.onToggleModal("open")}>
+          <MdOpenInBrowser />
+          <IconText>{t("Open")}</IconText>
+        </ToolbarAction>
+        <ToolbarAction wdKey="nav:export" onClick={() => props.onToggleModal("export")}>
+          <MdSave />
+          <IconText>{t("Save")}</IconText>
+        </ToolbarAction>
+        <ToolbarAction wdKey="nav:code-editor" onClick={() => props.onToggleModal("codeEditor")}>
+          <MdCode />
+          <IconText>{t("Code Editor")}</IconText>
+        </ToolbarAction>
+        <ToolbarAction wdKey="nav:sources" onClick={() => props.onToggleModal("sources")}>
+          <MdLayers />
+          <IconText>{t("Data Sources")}</IconText>
+        </ToolbarAction>
+        <ToolbarAction wdKey="nav:settings" onClick={() => props.onToggleModal("settings")}>
+          <MdSettings />
+          <IconText>{t("Style Settings")}</IconText>
+        </ToolbarAction>
+        <ToolbarAction wdKey="nav:global-state" onClick={() => props.onToggleModal("globalState")}>
+          <MdPublic />
+          <IconText>{t("Global State")}</IconText>
+        </ToolbarAction>
 
-          <ToolbarSelect wdKey="nav:inspect">
-            <MdFindInPage />
-            <IconText>{t("View")}
-              <select
-                className="maputnik-select"
-                data-wd-key="maputnik-select"
-                onChange={(e) => this.handleSelection(e.target.value as MapState)}
-                value={currentView?.id}
-              >
-                {views.filter(v => v.group === "general").map((item) => {
+        <ToolbarSelect wdKey="nav:inspect">
+          <MdFindInPage />
+          <IconText>{t("View")}
+            <select
+              className="maputnik-select"
+              data-wd-key="maputnik-select"
+              onChange={(e) => handleSelection(e.target.value as MapState)}
+              value={currentView?.id}
+            >
+              {views.filter(v => v.group === "general").map((item) => {
+                return (
+                  <option key={item.id} value={item.id} disabled={item.disabled} data-wd-key={item.id}>
+                    {item.title}
+                  </option>
+                );
+              })}
+              <optgroup label={t("Color accessibility")}>
+                {views.filter(v => v.group === "color-accessibility").map((item) => {
                   return (
-                    <option key={item.id} value={item.id} disabled={item.disabled} data-wd-key={item.id}>
+                    <option key={item.id} value={item.id} disabled={item.disabled}>
                       {item.title}
                     </option>
                   );
                 })}
-                <optgroup label={t("Color accessibility")}>
-                  {views.filter(v => v.group === "color-accessibility").map((item) => {
-                    return (
-                      <option key={item.id} value={item.id} disabled={item.disabled}>
-                        {item.title}
-                      </option>
-                    );
-                  })}
-                </optgroup>
-              </select>
-            </IconText>
-          </ToolbarSelect>
+              </optgroup>
+            </select>
+          </IconText>
+        </ToolbarSelect>
 
-          <ToolbarSelect wdKey="nav:language">
-            <MdLanguage />
-            <IconText>Language
-              <select
-                className="maputnik-select"
-                data-wd-key="maputnik-lang-select"
-                onChange={(e) => this.handleLanguageChange(e.target.value)}
-                value={this.props.i18n.language}
-              >
-                {Object.entries(supportedLanguages).map(([code, name]) => {
-                  return (
-                    <option key={code} value={code}>
-                      {name}
-                    </option>
-                  );
-                })}
-              </select>
-            </IconText>
-          </ToolbarSelect>
+        <ToolbarSelect wdKey="nav:language">
+          <MdLanguage />
+          <IconText>Language
+            <select
+              className="maputnik-select"
+              data-wd-key="maputnik-lang-select"
+              onChange={(e) => handleLanguageChange(e.target.value)}
+              value={props.i18n.language}
+            >
+              {Object.entries(supportedLanguages).map(([code, name]) => {
+                return (
+                  <option key={code} value={code}>
+                    {name}
+                  </option>
+                );
+              })}
+            </select>
+          </IconText>
+        </ToolbarSelect>
 
-          <ToolbarLink href={"https://github.com/maplibre/maputnik/wiki"}>
-            <MdHelpOutline />
-            <IconText>{t("Help")}</IconText>
-          </ToolbarLink>
-        </div>
+        <ToolbarLink href={"https://github.com/maplibre/maputnik/wiki"}>
+          <MdHelpOutline />
+          <IconText>{t("Help")}</IconText>
+        </ToolbarLink>
       </div>
-    </nav>;
-  }
-}
+    </div>
+  </nav>;
+};
 
-const AppToolbar = withTranslation()(AppToolbarInternal);
-export default AppToolbar;
+export const AppToolbar = withTranslation()(AppToolbarInternal);

src/components/Block.tsx

@@ -1,7 +1,7 @@
-import React, {type CSSProperties, type PropsWithChildren, type SyntheticEvent} from "react";
+import React, {type CSSProperties, type PropsWithChildren, type SyntheticEvent, useRef, useState} from "react";
 import classnames from "classnames";
-import FieldDocLabel from "./FieldDocLabel";
-import Doc from "./Doc";
+import { FieldDocLabel } from "./FieldDocLabel";
+import { Doc } from "./Doc";
 
 export type BlockProps = PropsWithChildren & {
   "data-wd-key"?: string
@@ -14,32 +14,13 @@ export type BlockProps = PropsWithChildren & {
   error?: {message: string}
 };
 
-type BlockState = {
-  showDoc: boolean
-};
-
 /** Wrap a component with a label */
-export default class Block extends React.Component<BlockProps, BlockState> {
-  _blockEl: HTMLDivElement | null = null;
+export const Block: React.FC<BlockProps> = (props) => {
+  const [showDoc, setShowDoc] = useState(false);
+  const blockEl = useRef<HTMLDivElement | null>(null);
 
-  constructor (props: BlockProps) {
-    super(props);
-    this.state = {
-      showDoc: false,
-    };
-  }
-
-  onChange(e: React.BaseSyntheticEvent<Event, HTMLInputElement, HTMLInputElement>) {
-    const value = e.target.value;
-    if (this.props.onChange) {
-      return this.props.onChange(value === "" ? undefined : value);
-    }
-  }
-
-  onToggleDoc = (val: boolean) => {
-    this.setState({
-      showDoc: val
-    });
+  const onToggleDoc = (val: boolean) => {
+    setShowDoc(val);
   };
 
   /**
@@ -48,9 +29,9 @@ export default class Block extends React.Component<BlockProps, BlockState> {
    * causing the picker to reopen. This causes a scenario where the picker can
    * never be closed once open.
    */
-  onLabelClick = (event: SyntheticEvent<any, any>) => {
+  const onLabelClick = (event: SyntheticEvent<any, any>) => {
     const el = event.nativeEvent.target;
-    const contains = this._blockEl?.contains(el);
+    const contains = blockEl.current?.contains(el);
 
     if (event.nativeEvent.target.nodeName !== "INPUT" && !contains) {
       event.stopPropagation();
@@ -60,45 +41,43 @@ export default class Block extends React.Component<BlockProps, BlockState> {
     }
   };
 
-  render() {
-    return <label style={this.props.style}
-      data-wd-key={this.props["data-wd-key"]}
-      className={classnames({
-        "maputnik-input-block": true,
-        "maputnik-input-block--wide": this.props.wideMode,
-        "maputnik-action-block": this.props.action,
-        "maputnik-input-block--error": this.props.error
-      })}
-      onClick={this.onLabelClick}
-    >
-      {this.props.fieldSpec &&
-        <div className="maputnik-input-block-label">
-          <FieldDocLabel
-            label={this.props.label}
-            onToggleDoc={this.onToggleDoc}
-            fieldSpec={this.props.fieldSpec}
-          />
-        </div>
-      }
-      {!this.props.fieldSpec &&
-        <div className="maputnik-input-block-label">
-          {this.props.label}
-        </div>
-      }
-      <div className="maputnik-input-block-action">
-        {this.props.action}
+  return <label style={props.style}
+    data-wd-key={props["data-wd-key"]}
+    className={classnames({
+      "maputnik-input-block": true,
+      "maputnik-input-block--wide": props.wideMode,
+      "maputnik-action-block": props.action,
+      "maputnik-input-block--error": props.error
+    })}
+    onClick={onLabelClick}
+  >
+    {props.fieldSpec &&
+      <div className="maputnik-input-block-label">
+        <FieldDocLabel
+          label={props.label}
+          onToggleDoc={onToggleDoc}
+          fieldSpec={props.fieldSpec}
+        />
       </div>
-      <div className="maputnik-input-block-content" ref={el => {this._blockEl = el;}}>
-        {this.props.children}
+    }
+    {!props.fieldSpec &&
+      <div className="maputnik-input-block-label">
+        {props.label}
       </div>
-      {this.props.fieldSpec &&
-        <div
-          className="maputnik-doc-inline"
-          style={{display: this.state.showDoc ? "" : "none"}}
-        >
-          <Doc fieldSpec={this.props.fieldSpec} />
-        </div>
-      }
-    </label>;
-  }
-}
+    }
+    <div className="maputnik-input-block-action">
+      {props.action}
+    </div>
+    <div className="maputnik-input-block-content" ref={blockEl}>
+      {props.children}
+    </div>
+    {props.fieldSpec &&
+      <div
+        className="maputnik-doc-inline"
+        style={{display: showDoc ? "" : "none"}}
+      >
+        <Doc fieldSpec={props.fieldSpec} />
+      </div>
+    }
+  </label>;
+};

src/components/CodeEditor.tsx

@@ -1,4 +1,4 @@
-import InputJson from "./InputJson";
+import { InputJson } from "./InputJson";
 import React from "react";
 import { withTranslation, type WithTranslation } from "react-i18next";
 import { type StyleSpecification } from "maplibre-gl";
@@ -24,6 +24,4 @@ const CodeEditorInternal: React.FC<CodeEditorProps> = (props) => {
   </>;
 };
 
-const CodeEditor = withTranslation()(CodeEditorInternal);
-
-export default CodeEditor;
+export const CodeEditor = withTranslation()(CodeEditorInternal);

src/components/Collapse.tsx

@@ -9,25 +9,19 @@ type CollapseProps = {
 };
 
 
-export default class Collapse extends React.Component<CollapseProps> {
-  static defaultProps = {
-    isActive: true
-  };
-
-  render() {
-    if (reducedMotionEnabled()) {
-      return (
-        <div style={{display: this.props.isActive ? "block" : "none"}}>
-          {this.props.children}
-        </div>
-      );
-    }
-    else {
-      return (
-        <ReactCollapse isOpened={this.props.isActive}>
-          {this.props.children}
-        </ReactCollapse>
-      );
-    }
+export const Collapse: React.FC<CollapseProps> = ({isActive = true, children}) => {
+  if (reducedMotionEnabled()) {
+    return (
+      <div style={{display: isActive ? "block" : "none"}}>
+        {children}
+      </div>
+    );
   }
-}
+  else {
+    return (
+      <ReactCollapse isOpened={isActive}>
+        {children}
+      </ReactCollapse>
+    );
+  }
+};

src/components/Collapser.tsx

@@ -6,13 +6,11 @@ type CollapserProps = {
   style?: object
 };
 
-export default class Collapser extends React.Component<CollapserProps> {
-  render() {
-    const iconStyle = {
-      width: 20,
-      height: 20,
-      ...this.props.style,
-    };
-    return this.props.isCollapsed ? <MdArrowDropUp style={iconStyle}/> : <MdArrowDropDown style={iconStyle} />;
-  }
-}
+export const Collapser: React.FC<CollapserProps> = (props) => {
+  const iconStyle = {
+    width: 20,
+    height: 20,
+    ...props.style,
+  };
+  return props.isCollapsed ? <MdArrowDropUp style={iconStyle}/> : <MdArrowDropDown style={iconStyle} />;
+};

src/components/DataProperty.tsx

@@ -0,0 +1,371 @@
+import React, { useRef } from "react";
+import {PiListPlusBold} from "react-icons/pi";
+import {TbMathFunction} from "react-icons/tb";
+import latest from "@maplibre/maplibre-gl-style-spec/dist/latest.json";
+
+import { InputButton } from "./InputButton";
+import { InputSpec } from "./InputSpec";
+import { InputNumber } from "./InputNumber";
+import { InputString } from "./InputString";
+import { InputSelect } from "./InputSelect";
+import { Block } from "./Block";
+import { generateUniqueId as docUid } from "../libs/document-uid";
+import { sortNumerically } from "../libs/sort-numerically";
+import {findDefaultFromSpec} from "../libs/spec-helper";
+import { type WithTranslation, withTranslation } from "react-i18next";
+
+import { labelFromFieldName } from "../libs/label-from-field-name";
+import { DeleteStopButton } from "./DeleteStopButton";
+import { type MappedLayerErrors } from "../libs/definitions";
+
+
+
+function setStopRefs(props: DataPropertyInternalProps, state: DataPropertyState) {
+  // This is initialised below only if required to improved performance.
+  let newRefs: {[key: number]: string} | undefined;
+
+  if(props.value && props.value.stops) {
+    props.value.stops.forEach((_val, idx) => {
+      if(!Object.prototype.hasOwnProperty.call(state.refs, idx)) {
+        if(!newRefs) {
+          newRefs = {...state};
+        }
+        newRefs[idx] = docUid("stop-");
+      }
+    });
+  }
+
+  return newRefs;
+}
+
+type DataPropertyInternalProps = {
+  onChange?(fieldName: string, value: any): unknown
+  onDeleteStop?(...args: unknown[]): unknown
+  onAddStop?(...args: unknown[]): unknown
+  onExpressionClick?(...args: unknown[]): unknown
+  onChangeToZoomFunction?(...args: unknown[]): unknown
+  fieldName: string
+  fieldType?: string
+  fieldSpec?: object
+  value?: DataPropertyValue
+  errors?: MappedLayerErrors
+} & WithTranslation;
+
+type DataPropertyState = {
+  refs: {[key: number]: string}
+};
+
+type DataPropertyValue = {
+  default?: any
+  property?: string
+  base?: number
+  type?: string
+  stops: Stop[]
+};
+
+export type Stop = [{
+  zoom: number
+  value: number
+}, number];
+
+const DataPropertyInternal: React.FC<DataPropertyInternalProps> = (props) => {
+  // Kept in a ref rather than state: the original recomputed these on every
+  // render via getDerivedStateFromProps, which as state would mean setting
+  // state during render on every pass.
+  const refs = useRef<{[key: number]: string}>({});
+  // setStopRefs returns undefined when no new stop needs a ref; as in the
+  // original, only replace the map when it actually produced one.
+  const newStopRefs = setStopRefs(props, { refs: refs.current });
+  if (newStopRefs) {
+    refs.current = newStopRefs;
+  }
+
+  function getFieldFunctionType(fieldSpec: any) {
+    if (fieldSpec.expression.interpolated) {
+      return "exponential";
+    }
+    if (fieldSpec.type === "number") {
+      return "interval";
+    }
+    return "categorical";
+  }
+
+  function getDataFunctionTypes(fieldSpec: any) {
+    if (fieldSpec.expression.interpolated) {
+      return ["interpolate", "categorical", "interval", "exponential", "identity"];
+    }
+    else {
+      return ["categorical", "interval", "identity"];
+    }
+  }
+
+  // Order the stops altering the refs to reflect their new position.
+  function orderStopsByZoom(stops: Stop[]) {
+    const mappedWithRef = stops
+      .map((stop, idx) => {
+        return {
+          ref: refs.current[idx],
+          data: stop
+        };
+      })
+    // Sort by zoom
+      .sort((a, b) => sortNumerically(a.data[0].zoom, b.data[0].zoom));
+
+    // Fetch the new position of the stops
+    const newRefs = {} as {[key: number]: string};
+    mappedWithRef
+      .forEach((stop, idx) =>{
+        newRefs[idx] = stop.ref;
+      });
+
+    refs.current = newRefs;
+
+    return mappedWithRef.map((item) => item.data);
+  }
+
+  const onChange = (fieldName: string, value: any) => {
+    if (value.type === "identity") {
+      value = {
+        type: value.type,
+        property: value.property,
+      };
+    }
+    else {
+      const stopValue = value.type === "categorical" ? "" : 0;
+      value = {
+        property: "",
+        type: value.type,
+        // Default props if they don't already exist.
+        stops: [
+          [{zoom: 6, value: stopValue}, findDefaultFromSpec(props.fieldSpec as any)],
+          [{zoom: 10, value: stopValue}, findDefaultFromSpec(props.fieldSpec as any)]
+        ],
+        ...value,
+      };
+    }
+    props.onChange!(fieldName, value);
+  };
+
+  function changeStop(changeIdx: number, stopData: { zoom: number | undefined, value: number }, value: number) {
+    const stops = props.value?.stops.slice(0) || [];
+    // const changedStop = stopData.zoom === undefined ? stopData.value : stopData
+    stops[changeIdx] = [
+      {
+        value: stopData.value,
+        zoom: (stopData.zoom === undefined) ? 0 : stopData.zoom,
+      },
+      value
+    ];
+
+    const orderedStops = orderStopsByZoom(stops);
+
+    const changedValue = {
+      ...props.value,
+      stops: orderedStops,
+    };
+    onChange(props.fieldName, changedValue);
+  }
+
+  function changeBase(newValue: number | undefined) {
+    const changedValue = {
+      ...props.value,
+      base: newValue
+    };
+
+    if (changedValue.base === undefined) {
+      delete changedValue["base"];
+    }
+    props.onChange!(props.fieldName, changedValue);
+  }
+
+  function changeDataType(propVal: string) {
+    if (propVal === "interpolate" && props.onChangeToZoomFunction) {
+      props.onChangeToZoomFunction();
+    }
+    else {
+      onChange(props.fieldName, {
+        ...props.value,
+        type: propVal,
+      });
+    }
+  }
+
+  function changeDataProperty(propName: "property" | "default", propVal: any) {
+    if (propVal) {
+      props.value![propName] = propVal;
+    }
+    else {
+      delete props.value![propName];
+    }
+    onChange(props.fieldName, props.value);
+  }
+
+  const t = props.t;
+
+  if (typeof props.value?.type === "undefined") {
+    props.value!.type = getFieldFunctionType(props.fieldSpec);
+  }
+
+  let dataFields;
+  if (props.value?.stops) {
+    dataFields = props.value.stops.map((stop, idx) => {
+      const zoomLevel = typeof stop[0] === "object" ? stop[0].zoom : undefined;
+      const key  = refs.current[idx];
+      const dataLevel = typeof stop[0] === "object" ? stop[0].value : stop[0];
+      const value = stop[1];
+      const deleteStopBtn = <DeleteStopButton onClick={props.onDeleteStop?.bind(null, idx)} />;
+
+      const dataProps = {
+        "aria-label": t("Input value"),
+        label: t("Data value"),
+        value: dataLevel as any,
+        onChange: (newData: string | number | undefined) => changeStop(idx, { zoom: zoomLevel, value: newData as number }, value)
+      };
+
+      let dataInput;
+      if(props.value?.type === "categorical") {
+        dataInput = <InputString {...dataProps} />;
+      }
+      else {
+        dataInput = <InputNumber {...dataProps} />;
+      }
+
+      let zoomInput = null;
+      if(zoomLevel !== undefined) {
+        zoomInput = <div>
+          <InputNumber
+            aria-label="Zoom"
+            value={zoomLevel}
+            onChange={newZoom => changeStop(idx, {zoom: newZoom, value: dataLevel}, value)}
+            min={0}
+            max={22}
+          />
+        </div>;
+      }
+
+      return <tr key={key}>
+        <td>
+          {zoomInput}
+        </td>
+        <td>
+          {dataInput}
+        </td>
+        <td>
+          <InputSpec
+            aria-label={t("Output value")}
+            fieldName={props.fieldName}
+            fieldSpec={props.fieldSpec}
+            value={value}
+            onChange={(_, newValue) => changeStop(idx, {zoom: zoomLevel, value: dataLevel}, newValue as number)}
+          />
+        </td>
+        <td>
+          {deleteStopBtn}
+        </td>
+      </tr>;
+    });
+  }
+
+  return <div className="maputnik-data-spec-block">
+    <fieldset className="maputnik-data-spec-property">
+      <legend>{labelFromFieldName(props.fieldName)}</legend>
+      <div className="maputnik-data-fieldset-inner">
+        <Block
+          label={t("Function")}
+          key="function"
+          data-wd-key="function-type"
+        >
+          <div className="maputnik-data-spec-property-input">
+            <InputSelect
+              value={props.value!.type}
+              onChange={(propVal: string) => changeDataType(propVal)}
+              title={t("Select a type of data scale (default is 'categorical').")}
+              options={getDataFunctionTypes(props.fieldSpec)}
+            />
+          </div>
+        </Block>
+        {props.value?.type !== "identity" &&
+            <Block
+              label={t("Base")}
+              key="base"
+              data-wd-key="function-base"
+            >
+              <div className="maputnik-data-spec-property-input">
+                <InputSpec
+                  fieldName={"base"}
+                  fieldSpec={latest.function.base as typeof latest.function.base & { type: "number" }}
+                  value={props.value?.base}
+                  onChange={(_, newValue) => changeBase(newValue as number)}
+                />
+              </div>
+            </Block>
+        }
+        <Block
+          label={"Property"}
+          key="property"
+          data-wd-key="function-property"
+        >
+          <div className="maputnik-data-spec-property-input">
+            <InputString
+              value={props.value?.property}
+              title={t("Input a data property to base styles off of.")}
+              onChange={propVal => changeDataProperty("property", propVal)}
+            />
+          </div>
+        </Block>
+        {dataFields &&
+            <Block
+              label={t("Default")}
+              key="default"
+              data-wd-key="function-default"
+            >
+              <InputSpec
+                fieldName={props.fieldName}
+                fieldSpec={props.fieldSpec}
+                value={props.value?.default}
+                onChange={(_, propVal) => changeDataProperty("default", propVal)}
+              />
+            </Block>
+        }
+        {dataFields &&
+            <div className="maputnik-function-stop">
+              <table className="maputnik-function-stop-table">
+                <caption>{t("Stops")}</caption>
+                <thead>
+                  <tr>
+                    <th>{t("Zoom")}</th>
+                    <th>{t("Input value")}</th>
+                    <th rowSpan={2}>{t("Output value")}</th>
+                  </tr>
+                </thead>
+                <tbody>
+                  {dataFields}
+                </tbody>
+              </table>
+            </div>
+        }
+        <div className="maputnik-toolbox">
+          {dataFields &&
+              <InputButton
+                className="maputnik-add-stop"
+                onClick={props.onAddStop?.bind(null)}
+              >
+                <PiListPlusBold style={{ verticalAlign: "text-bottom" }} />
+                {t("Add stop")}
+              </InputButton>
+          }
+          <InputButton
+            className="maputnik-add-stop"
+            data-wd-key="convert-to-expression"
+            onClick={props.onExpressionClick?.bind(null)}
+          >
+            <TbMathFunction style={{ verticalAlign: "text-bottom" }} />
+            {t("Convert to expression")}
+          </InputButton>
+        </div>
+      </div>
+    </fieldset>
+  </div>;
+};
+
+export const DataProperty = withTranslation()(DataPropertyInternal);

src/components/DeleteStopButton.tsx

@@ -0,0 +1,24 @@
+import React from "react";
+
+import { InputButton } from "./InputButton";
+import {MdDelete} from "react-icons/md";
+import { type WithTranslation, withTranslation } from "react-i18next";
+
+
+type DeleteStopButtonInternalProps = {
+  onClick?(...args: unknown[]): unknown
+} & WithTranslation;
+
+
+const DeleteStopButtonInternal: React.FC<DeleteStopButtonInternalProps> = (props) => {
+  const t = props.t;
+  return <InputButton
+    className="maputnik-delete-stop"
+    onClick={props.onClick}
+    title={t("Remove zoom level from stop")}
+  >
+    <MdDelete />
+  </InputButton>;
+};
+
+export const DeleteStopButton = withTranslation()(DeleteStopButtonInternal);

src/components/Doc.tsx

@@ -23,88 +23,84 @@ type DocProps = {
   }
 };
 
-export default class Doc extends React.Component<DocProps> {
-  render () {
-    const {fieldSpec} = this.props;
+export const Doc: React.FC<DocProps> = ({fieldSpec}) => {
+  const {doc, values, docUrl, docUrlLinkText} = fieldSpec;
+  const sdkSupport = fieldSpec["sdk-support"];
 
-    const {doc, values, docUrl, docUrlLinkText} = fieldSpec;
-    const sdkSupport = fieldSpec["sdk-support"];
+  const renderValues = (
+    !!values &&
+    // HACK: Currently we merge additional values into the style spec, so this is required
+    // See <https://github.com/maplibre/maputnik/blob/main/src/components/PropertyGroup.jsx#L16>
+    !Array.isArray(values)
+  );
 
-    const renderValues = (
-      !!values &&
-      // HACK: Currently we merge additional values into the style spec, so this is required
-      // See <https://github.com/maplibre/maputnik/blob/main/src/components/PropertyGroup.jsx#L16>
-      !Array.isArray(values)
-    );
+  const sdkSupportToJsx = (value: string) => {
+    const supportValue = value.toLowerCase();
+    if (supportValue.startsWith("https://")) {
+      return <a href={supportValue} target="_blank" rel="noreferrer">{"#" + supportValue.split("/").pop()}</a>;
+    }
+    return value;
+  };
 
-    const sdkSupportToJsx = (value: string) => {
-      const supportValue = value.toLowerCase();
-      if (supportValue.startsWith("https://")) {
-        return <a href={supportValue} target="_blank" rel="noreferrer">{"#" + supportValue.split("/").pop()}</a>;
+  return (
+    <>
+      {doc &&
+        <div className="SpecDoc">
+          <div className="SpecDoc__doc" data-wd-key='spec-field-doc'>
+            <Markdown components={{
+              a: ({node: _node, href, children, ...props}) => <a href={href} target="_blank" {...props}>{children}</a>,
+            }}>{doc}</Markdown>
+          </div>
+          {renderValues &&
+            <ul className="SpecDoc__values">
+              {Object.entries(values).map(([key, value]) => {
+                return (
+                  <li key={key}>
+                    <code>{JSON.stringify(key)}</code>
+                    <div>{value.doc}</div>
+                  </li>
+                );
+              })}
+            </ul>
+          }
+        </div>
       }
-      return value;
-    };
-
-    return (
-      <>
-        {doc &&
-          <div className="SpecDoc">
-            <div className="SpecDoc__doc" data-wd-key='spec-field-doc'>
-              <Markdown components={{
-                a: ({node: _node, href, children, ...props}) => <a href={href} target="_blank" {...props}>{children}</a>,
-              }}>{doc}</Markdown>
-            </div>
-            {renderValues &&
-              <ul className="SpecDoc__values">
-                {Object.entries(values).map(([key, value]) => {
-                  return (
-                    <li key={key}>
-                      <code>{JSON.stringify(key)}</code>
-                      <div>{value.doc}</div>
-                    </li>
-                  );
+      {sdkSupport &&
+        <div className="SpecDoc__sdk-support">
+          <table className="SpecDoc__sdk-support__table">
+            <thead>
+              <tr>
+                <th></th>
+                {Object.values(headers).map(header => {
+                  return <th key={header}>{header}</th>;
                 })}
-              </ul>
-            }
-          </div>
-        }
-        {sdkSupport &&
-          <div className="SpecDoc__sdk-support">
-            <table className="SpecDoc__sdk-support__table">
-              <thead>
-                <tr>
-                  <th></th>
-                  {Object.values(headers).map(header => {
-                    return <th key={header}>{header}</th>;
-                  })}
-                </tr>
-              </thead>
-              <tbody>
-                {Object.entries(sdkSupport).map(([key, supportObj]) => {
-                  return (
-                    <tr key={key}>
-                      <td>{key}</td>
-                      {Object.keys(headers).map((k) => {
-                        if (Object.prototype.hasOwnProperty.call(supportObj, k)) {
-                          return <td key={k}>{sdkSupportToJsx(supportObj[k as keyof typeof headers])}</td>;
-                        }
-                        else {
-                          return <td key={k}>no</td>;
-                        }
-                      })}
-                    </tr>
-                  );
-                })}
-              </tbody>
-            </table>
-          </div>
-        }
-        {docUrl && docUrlLinkText &&
-          <div className="SpecDoc__learn-more">
-            <a href={docUrl}  target="_blank" rel="noreferrer">{docUrlLinkText}</a>
-          </div>
-        }
-      </>
-    );
-  }
-}
+              </tr>
+            </thead>
+            <tbody>
+              {Object.entries(sdkSupport).map(([key, supportObj]) => {
+                return (
+                  <tr key={key}>
+                    <td>{key}</td>
+                    {Object.keys(headers).map((k) => {
+                      if (Object.prototype.hasOwnProperty.call(supportObj, k)) {
+                        return <td key={k}>{sdkSupportToJsx(supportObj[k as keyof typeof headers])}</td>;
+                      }
+                      else {
+                        return <td key={k}>no</td>;
+                      }
+                    })}
+                  </tr>
+                );
+              })}
+            </tbody>
+          </table>
+        </div>
+      }
+      {docUrl && docUrlLinkText &&
+        <div className="SpecDoc__learn-more">
+          <a href={docUrl}  target="_blank" rel="noreferrer">{docUrlLinkText}</a>
+        </div>
+      }
+    </>
+  );
+};

src/components/ExpressionProperty.tsx

@@ -0,0 +1,85 @@
+import React from "react";
+import {MdDelete, MdUndo} from "react-icons/md";
+import { type WithTranslation, withTranslation } from "react-i18next";
+
+import { Block } from "./Block";
+import { InputButton } from "./InputButton";
+import { labelFromFieldName } from "../libs/label-from-field-name";
+import { FieldJson } from "./FieldJson";
+import type { StylePropertySpecification } from "maplibre-gl";
+import { type MappedLayerErrors } from "../libs/definitions";
+
+
+type ExpressionPropertyInternalProps = {
+  fieldName: string
+  fieldType?: string
+  fieldSpec?: StylePropertySpecification
+  value?: any
+  errors?: MappedLayerErrors
+  onDelete?(...args: unknown[]): unknown
+  onChange(value: object): void
+  onUndo?(...args: unknown[]): unknown
+  canUndo?(...args: unknown[]): unknown
+  onFocus?(...args: unknown[]): unknown
+  onBlur?(...args: unknown[]): unknown
+} & WithTranslation;
+
+const ExpressionPropertyInternal: React.FC<ExpressionPropertyInternalProps> = ({
+  errors = {},
+  onFocus = () => {},
+  onBlur = () => {},
+  ...props
+}) => {
+  const {t, value, canUndo} = props;
+  const undoDisabled = canUndo ? !canUndo() : true;
+
+  const deleteStopBtn = (
+    <>
+      {props.onUndo &&
+        <InputButton
+          key="undo_action"
+          onClick={props.onUndo}
+          disabled={undoDisabled}
+          className="maputnik-delete-stop"
+          data-wd-key="undo-expression"
+          title={t("Revert from expression")}
+        >
+          <MdUndo />
+        </InputButton>
+      }
+      <InputButton
+        key="delete_action"
+        onClick={props.onDelete}
+        className="maputnik-delete-stop"
+        data-wd-key="delete-expression"
+        title={t("Delete expression")}
+      >
+        <MdDelete />
+      </InputButton>
+    </>
+  );
+  let error = undefined;
+  if (errors) {
+    const fieldKey = props.fieldType ? props.fieldType + "." + props.fieldName : props.fieldName;
+    error = errors[fieldKey];
+  }
+  return <Block
+    fieldSpec={props.fieldSpec}
+    label={t(labelFromFieldName(props.fieldName))}
+    action={deleteStopBtn}
+    wideMode={true}
+    error={error}
+  >
+    <FieldJson
+      lintType="expression"
+      spec={props.fieldSpec}
+      className="maputnik-expression-editor"
+      onFocus={onFocus}
+      onBlur={onBlur}
+      value={value}
+      onChange={props.onChange}
+    />
+  </Block>;
+};
+
+export const ExpressionProperty = withTranslation()(ExpressionPropertyInternal);

src/components/FieldArray.tsx

@@ -1,5 +1,5 @@
-import InputArray, { type InputArrayProps } from "./InputArray";
-import Fieldset from "./Fieldset";
+import { InputArray, type InputArrayProps } from "./InputArray";
+import { Fieldset } from "./Fieldset";
 
 type FieldArrayProps = InputArrayProps & {
   name?: string
@@ -8,12 +8,10 @@ type FieldArrayProps = InputArrayProps & {
   }
 };
 
-const FieldArray: React.FC<FieldArrayProps> = (props) => {
+export const FieldArray: React.FC<FieldArrayProps> = (props) => {
   return (
     <Fieldset label={props.label} fieldSpec={props.fieldSpec}>
       <InputArray {...props} />
     </Fieldset>
   );
 };
-
-export default FieldArray;

src/components/FieldAutocomplete.tsx

@@ -1,5 +1,5 @@
-import Block from "./Block";
-import InputAutocomplete, { type InputAutocompleteProps } from "./InputAutocomplete";
+import { Block } from "./Block";
+import { InputAutocomplete, type InputAutocompleteProps } from "./InputAutocomplete";
 
 
 type FieldAutocompleteProps = InputAutocompleteProps & {
@@ -7,12 +7,10 @@ type FieldAutocompleteProps = InputAutocompleteProps & {
 };
 
 
-const FieldAutocomplete: React.FC<FieldAutocompleteProps> = (props) => {
+export const FieldAutocomplete: React.FC<FieldAutocompleteProps> = (props) => {
   return (
     <Block label={props.label}>
       <InputAutocomplete {...props} />
     </Block>
   );
 };
-
-export default FieldAutocomplete;

src/components/FieldCheckbox.tsx

@@ -1,5 +1,5 @@
-import Block from "./Block";
-import InputCheckbox, {type InputCheckboxProps} from "./InputCheckbox";
+import { Block } from "./Block";
+import { InputCheckbox, type InputCheckboxProps } from "./InputCheckbox";
 
 
 type FieldCheckboxProps = InputCheckboxProps & {
@@ -7,12 +7,10 @@ type FieldCheckboxProps = InputCheckboxProps & {
 };
 
 
-const FieldCheckbox: React.FC<FieldCheckboxProps> = (props) => {
+export const FieldCheckbox: React.FC<FieldCheckboxProps> = (props) => {
   return (
     <Block label={props.label}>
       <InputCheckbox {...props} />
     </Block>
   );
 };
-
-export default FieldCheckbox;

src/components/FieldColor.tsx

@@ -1,5 +1,5 @@
-import Block from "./Block";
-import InputColor, {type InputColorProps} from "./InputColor";
+import { Block } from "./Block";
+import { InputColor, type InputColorProps } from "./InputColor";
 
 
 type FieldColorProps = InputColorProps & {
@@ -10,12 +10,10 @@ type FieldColorProps = InputColorProps & {
 };
 
 
-const FieldColor: React.FC<FieldColorProps> = (props) => {
+export const FieldColor: React.FC<FieldColorProps> = (props) => {
   return (
     <Block label={props.label} fieldSpec={props.fieldSpec}>
       <InputColor {...props} />
     </Block>
   );
 };
-
-export default FieldColor;

src/components/FieldComment.tsx

@@ -1,7 +1,7 @@
 import React from "react";
 
-import Block from "./Block";
-import InputString from "./InputString";
+import { Block } from "./Block";
+import { InputString } from "./InputString";
 import { type WithTranslation, withTranslation } from "react-i18next";
 
 type FieldCommentInternalProps = {
@@ -36,5 +36,4 @@ const FieldCommentInternal: React.FC<FieldCommentInternalProps> = (props) => {
   );
 };
 
-const FieldComment = withTranslation()(FieldCommentInternal);
-export default FieldComment;
+export const FieldComment = withTranslation()(FieldCommentInternal);

src/components/FieldDocLabel.tsx

@@ -10,7 +10,7 @@ type FieldDocLabelProps = {
 };
 
 
-const FieldDocLabel: React.FC<FieldDocLabelProps> = (props) => {
+export const FieldDocLabel: React.FC<FieldDocLabelProps> = (props) => {
   const [open, setOpen] = React.useState(false);
 
   const onToggleDoc = (state: boolean) => {
@@ -49,5 +49,3 @@ const FieldDocLabel: React.FC<FieldDocLabelProps> = (props) => {
   }
   return <div />;
 };
-
-export default FieldDocLabel;

src/components/FieldDynamicArray.tsx

@@ -1,16 +1,14 @@
-import InputDynamicArray, {type InputDynamicArrayProps} from "./InputDynamicArray";
-import Fieldset from "./Fieldset";
+import { InputDynamicArray, type InputDynamicArrayProps } from "./InputDynamicArray";
+import { Fieldset } from "./Fieldset";
 
 type FieldDynamicArrayProps = InputDynamicArrayProps & {
   name?: string
 };
 
-const FieldDynamicArray: React.FC<FieldDynamicArrayProps> = (props) => {
+export const FieldDynamicArray: React.FC<FieldDynamicArrayProps> = (props) => {
   return (
     <Fieldset label={props.label}>
       <InputDynamicArray {...props} />
     </Fieldset>
   );
 };
-
-export default FieldDynamicArray;

src/components/FieldEnum.tsx

@@ -1,5 +1,5 @@
-import InputEnum, {type InputEnumProps} from "./InputEnum";
-import Fieldset from "./Fieldset";
+import { InputEnum, type InputEnumProps } from "./InputEnum";
+import { Fieldset } from "./Fieldset";
 
 
 type FieldEnumProps = InputEnumProps & {
@@ -10,12 +10,10 @@ type FieldEnumProps = InputEnumProps & {
 };
 
 
-const FieldEnum: React.FC<FieldEnumProps> = (props) => {
+export const FieldEnum: React.FC<FieldEnumProps> = (props) => {
   return (
     <Fieldset label={props.label} fieldSpec={props.fieldSpec}>
       <InputEnum {...props} />
     </Fieldset>
   );
 };
-
-export default FieldEnum;

src/components/FieldFunction.tsx

@@ -1,9 +1,9 @@
 import React from "react";
 
-import SpecProperty from "./_SpecProperty";
-import DataProperty, { type Stop } from "./_DataProperty";
-import ZoomProperty from "./_ZoomProperty";
-import ExpressionProperty from "./_ExpressionProperty";
+import { SpecProperty } from "./SpecProperty";
+import { DataProperty, type Stop } from "./DataProperty";
+import { ZoomProperty } from "./ZoomProperty";
+import { ExpressionProperty } from "./ExpressionProperty";
 import {function as styleFunction} from "@maplibre/maplibre-gl-style-spec";
 import {findDefaultFromSpec} from "../libs/spec-helper";
 import { type MappedLayerErrors } from "../libs/definitions";
@@ -128,7 +128,7 @@ type FieldFunctionProps = {
 /** Supports displaying spec field for zoom function objects
  * https://www.mapbox.com/mapbox-gl-style-spec/#types-function-zoom-property
  */
-const FieldFunction: React.FC<FieldFunctionProps> = (props) => {
+export const FieldFunction: React.FC<FieldFunctionProps> = (props) => {
   const [dataType, setDataType] = React.useState(
     getDataType(props.value, props.fieldSpec)
   );
@@ -402,5 +402,3 @@ const FieldFunction: React.FC<FieldFunctionProps> = (props) => {
     </div>
   );
 };
-
-export default FieldFunction;

src/components/FieldId.tsx

@@ -1,7 +1,7 @@
 
 import latest from "@maplibre/maplibre-gl-style-spec/dist/latest.json";
-import Block from "./Block";
-import InputString from "./InputString";
+import { Block } from "./Block";
+import { InputString } from "./InputString";
 
 type FieldIdProps = {
   value: string
@@ -10,7 +10,7 @@ type FieldIdProps = {
   error?: {message: string}
 };
 
-const FieldId: React.FC<FieldIdProps> = (props) => {
+export const FieldId: React.FC<FieldIdProps> = (props) => {
   return (
     <Block label="ID" fieldSpec={latest.layer.id}
       data-wd-key={props.wdKey}
@@ -24,5 +24,3 @@ const FieldId: React.FC<FieldIdProps> = (props) => {
     </Block>
   );
 };
-
-export default FieldId;

src/components/FieldJson.tsx

@@ -1,11 +1,9 @@
-import InputJson, {type InputJsonProps} from "./InputJson";
+import { InputJson, type InputJsonProps } from "./InputJson";
 
 
 type FieldJsonProps = InputJsonProps & {};
 
 
-const FieldJson: React.FC<FieldJsonProps> = (props) => {
+export const FieldJson: React.FC<FieldJsonProps> = (props) => {
   return <InputJson {...props} />;
 };
-
-export default FieldJson;

src/components/FieldMaxZoom.tsx

@@ -1,8 +1,8 @@
 import React from "react";
 
 import latest from "@maplibre/maplibre-gl-style-spec/dist/latest.json";
-import Block from "./Block";
-import InputNumber from "./InputNumber";
+import { Block } from "./Block";
+import { InputNumber } from "./InputNumber";
 import { type WithTranslation, withTranslation } from "react-i18next";
 
 type FieldMaxZoomInternalProps = {
@@ -31,5 +31,4 @@ const FieldMaxZoomInternal: React.FC<FieldMaxZoomInternalProps> = (props) => {
   );
 };
 
-const FieldMaxZoom = withTranslation()(FieldMaxZoomInternal);
-export default FieldMaxZoom;
+export const FieldMaxZoom = withTranslation()(FieldMaxZoomInternal);

src/components/FieldMinZoom.tsx

@@ -1,8 +1,8 @@
 import React from "react";
 
 import latest from "@maplibre/maplibre-gl-style-spec/dist/latest.json";
-import Block from "./Block";
-import InputNumber from "./InputNumber";
+import { Block } from "./Block";
+import { InputNumber } from "./InputNumber";
 import { type WithTranslation, withTranslation } from "react-i18next";
 
 type FieldMinZoomInternalProps = {
@@ -31,5 +31,4 @@ const FieldMinZoomInternal: React.FC<FieldMinZoomInternalProps> = (props) => {
   );
 };
 
-const FieldMinZoom = withTranslation()(FieldMinZoomInternal);
-export default FieldMinZoom;
+export const FieldMinZoom = withTranslation()(FieldMinZoomInternal);

src/components/FieldMultiInput.tsx

@@ -1,5 +1,5 @@
-import InputMultiInput, {type InputMultiInputProps} from "./InputMultiInput";
-import Fieldset from "./Fieldset";
+import { InputMultiInput, type InputMultiInputProps } from "./InputMultiInput";
+import { Fieldset } from "./Fieldset";
 
 
 type FieldMultiInputProps = InputMultiInputProps & {
@@ -7,12 +7,10 @@ type FieldMultiInputProps = InputMultiInputProps & {
 };
 
 
-const FieldMultiInput: React.FC<FieldMultiInputProps> = (props) => {
+export const FieldMultiInput: React.FC<FieldMultiInputProps> = (props) => {
   return (
     <Fieldset label={props.label}>
       <InputMultiInput {...props} />
     </Fieldset>
   );
 };
-
-export default FieldMultiInput;

src/components/FieldNumber.tsx

@@ -1,5 +1,5 @@
-import InputNumber, {type InputNumberProps} from "./InputNumber";
-import Block from "./Block";
+import { InputNumber, type InputNumberProps } from "./InputNumber";
+import { Block } from "./Block";
 
 
 type FieldNumberProps = InputNumberProps & {
@@ -10,12 +10,10 @@ type FieldNumberProps = InputNumberProps & {
 };
 
 
-const FieldNumber: React.FC<FieldNumberProps> = (props) => {
+export const FieldNumber: React.FC<FieldNumberProps> = (props) => {
   return (
     <Block label={props.label} fieldSpec={props.fieldSpec}>
       <InputNumber {...props} />
     </Block>
   );
 };
-
-export default FieldNumber;

src/components/FieldSelect.tsx

@@ -1,5 +1,5 @@
-import Block from "./Block";
-import InputSelect, {type InputSelectProps} from "./InputSelect";
+import { Block } from "./Block";
+import { InputSelect, type InputSelectProps } from "./InputSelect";
 
 
 type FieldSelectProps = InputSelectProps & {
@@ -10,12 +10,10 @@ type FieldSelectProps = InputSelectProps & {
 };
 
 
-const FieldSelect: React.FC<FieldSelectProps> = (props) => {
+export const FieldSelect: React.FC<FieldSelectProps> = (props) => {
   return (
     <Block label={props.label} fieldSpec={props.fieldSpec}>
       <InputSelect {...props} />
     </Block>
   );
 };
-
-export default FieldSelect;

src/components/FieldSource.tsx

@@ -1,8 +1,8 @@
 import React from "react";
 
 import latest from "@maplibre/maplibre-gl-style-spec/dist/latest.json";
-import Block from "./Block";
-import InputAutocomplete from "./InputAutocomplete";
+import { Block } from "./Block";
+import { InputAutocomplete } from "./InputAutocomplete";
 import { type WithTranslation, withTranslation } from "react-i18next";
 
 type FieldSourceInternalProps = {
@@ -38,5 +38,4 @@ const FieldSourceInternal: React.FC<FieldSourceInternalProps> = ({
 };
 
 
-const FieldSource = withTranslation()(FieldSourceInternal);
-export default FieldSource;
+export const FieldSource = withTranslation()(FieldSourceInternal);

src/components/FieldSourceLayer.tsx

@@ -1,8 +1,8 @@
 import React from "react";
 
 import {latest} from "@maplibre/maplibre-gl-style-spec";
-import Block from "./Block";
-import InputAutocomplete from "./InputAutocomplete";
+import { Block } from "./Block";
+import { InputAutocomplete } from "./InputAutocomplete";
 import { type WithTranslation, withTranslation } from "react-i18next";
 
 type FieldSourceLayerInternalProps = {
@@ -35,5 +35,4 @@ const FieldSourceLayerInternal: React.FC<FieldSourceLayerInternalProps> = ({
   );
 };
 
-const FieldSourceLayer = withTranslation()(FieldSourceLayerInternal);
-export default FieldSourceLayer;
+export const FieldSourceLayer = withTranslation()(FieldSourceLayerInternal);

src/components/FieldSpec.tsx

@@ -1,6 +1,6 @@
-import Block, { type BlockProps } from "./Block";
-import InputSpec, { type FieldSpecType, type InputSpecProps } from "./InputSpec";
-import Fieldset, { type FieldsetProps } from "./Fieldset";
+import { Block, type BlockProps } from "./Block";
+import { InputSpec, type FieldSpecType, type InputSpecProps } from "./InputSpec";
+import { Fieldset, type FieldsetProps } from "./Fieldset";
 
 function getElementFromType(fieldSpec: { type?: FieldSpecType, values?: unknown[] }): typeof Fieldset | typeof Block {
   switch(fieldSpec.type) {
@@ -36,7 +36,7 @@ function getElementFromType(fieldSpec: { type?: FieldSpecType, values?: unknown[
 
 export type FieldSpecProps = InputSpecProps & BlockProps & FieldsetProps;
 
-const FieldSpec: React.FC<FieldSpecProps> = (props) => {
+export const FieldSpec: React.FC<FieldSpecProps> = (props) => {
   const TypeBlock = getElementFromType(props.fieldSpec!);
 
   return (
@@ -45,5 +45,3 @@ const FieldSpec: React.FC<FieldSpecProps> = (props) => {
     </TypeBlock>
   );
 };
-
-export default FieldSpec;

src/components/FieldString.tsx

@@ -1,5 +1,5 @@
-import Block from "./Block";
-import InputString, {type InputStringProps} from "./InputString";
+import { Block } from "./Block";
+import { InputString, type InputStringProps } from "./InputString";
 
 type FieldStringProps = InputStringProps & {
   name?: string
@@ -9,12 +9,10 @@ type FieldStringProps = InputStringProps & {
   }
 };
 
-const FieldString: React.FC<FieldStringProps> = (props) => {
+export const FieldString: React.FC<FieldStringProps> = (props) => {
   return (
     <Block label={props.label} fieldSpec={props.fieldSpec}>
       <InputString {...props} />
     </Block>
   );
 };
-
-export default FieldString;

src/components/FieldType.tsx

@@ -1,8 +1,8 @@
 import React from "react";
 import {v8} from "@maplibre/maplibre-gl-style-spec";
-import Block from "./Block";
-import InputSelect from "./InputSelect";
-import InputString from "./InputString";
+import { Block } from "./Block";
+import { InputSelect } from "./InputSelect";
+import { InputString } from "./InputString";
 import { type WithTranslation, withTranslation } from "react-i18next";
 import { startCase } from "lodash";
 
@@ -43,5 +43,4 @@ const FieldTypeInternal: React.FC<FieldTypeInternalProps> = ({
   );
 };
 
-const FieldType = withTranslation()(FieldTypeInternal);
-export default FieldType;
+export const FieldType = withTranslation()(FieldTypeInternal);

src/components/FieldUrl.tsx

@@ -1,5 +1,5 @@
-import InputUrl, {type FieldUrlProps as InputUrlProps} from "./InputUrl";
-import Block from "./Block";
+import { InputUrl, type FieldUrlProps as InputUrlProps } from "./InputUrl";
+import { Block } from "./Block";
 
 
 type FieldUrlProps = InputUrlProps & {
@@ -10,12 +10,10 @@ type FieldUrlProps = InputUrlProps & {
 };
 
 
-const FieldUrl: React.FC<FieldUrlProps> = (props) => {
+export const FieldUrl: React.FC<FieldUrlProps> = (props) => {
   return (
     <Block label={props.label} fieldSpec={props.fieldSpec}>
       <InputUrl {...props} />
     </Block>
   );
 };
-
-export default FieldUrl;

src/components/Fieldset.tsx

@@ -1,8 +1,8 @@
 import React, { type PropsWithChildren, type ReactElement } from "react";
 import classnames from "classnames";
-import FieldDocLabel from "./FieldDocLabel";
-import Doc from "./Doc";
-import generateUniqueId from "../libs/document-uid";
+import { FieldDocLabel } from "./FieldDocLabel";
+import { Doc } from "./Doc";
+import { generateUniqueId } from "../libs/document-uid";
 
 export type FieldsetProps = PropsWithChildren & {
   label?: string,
@@ -12,7 +12,7 @@ export type FieldsetProps = PropsWithChildren & {
 };
 
 
-const Fieldset: React.FC<FieldsetProps> = (props) => {
+export const Fieldset: React.FC<FieldsetProps> = (props) => {
   const [showDoc, setShowDoc] = React.useState(false);
   const labelId = React.useRef(generateUniqueId("fieldset_label_"));
 
@@ -49,5 +49,3 @@ const Fieldset: React.FC<FieldsetProps> = (props) => {
     </div>
   );
 };
-
-export default Fieldset;

src/components/FilterEditor.tsx

@@ -1,4 +1,4 @@
-import React from "react";
+import React, { useState } from "react";
 import { TbMathFunction } from "react-icons/tb";
 import { PiListPlusBold } from "react-icons/pi";
 import {isEqual} from "lodash";
@@ -7,13 +7,13 @@ import {migrate, convertFilter} from "@maplibre/maplibre-gl-style-spec";
 import latest from "@maplibre/maplibre-gl-style-spec/dist/latest.json";
 
 import {combiningFilterOps} from "../libs/filterops";
-import InputSelect from "./InputSelect";
-import Block from "./Block";
-import SingleFilterEditor from "./SingleFilterEditor";
-import FilterEditorBlock from "./FilterEditorBlock";
-import InputButton from "./InputButton";
-import Doc from "./Doc";
-import ExpressionProperty from "./_ExpressionProperty";
+import { InputSelect } from "./InputSelect";
+import { Block } from "./Block";
+import { SingleFilterEditor } from "./SingleFilterEditor";
+import { FilterEditorBlock } from "./FilterEditorBlock";
+import { InputButton } from "./InputButton";
+import { Doc } from "./Doc";
+import { ExpressionProperty } from "./ExpressionProperty";
 import { type WithTranslation, withTranslation } from "react-i18next";
 import type { MappedLayerErrors, StyleSpecificationWithId } from "../libs/definitions";
 
@@ -100,221 +100,190 @@ type FilterEditorInternalProps = {
   onChange(value: LegacyFilterSpecification | ExpressionSpecification): void
 } & WithTranslation;
 
-type FilterEditorState = {
-  showDoc: boolean
-  displaySimpleFilter: boolean
-  valueIsSimpleFilter?: boolean
-};
+const FilterEditorInternal: React.FC<FilterEditorInternalProps> = ({ filter = ["all"], ...rest }) => {
+  const props = { filter, ...rest } as FilterEditorInternalProps;
 
-class FilterEditorInternal extends React.Component<FilterEditorInternalProps, FilterEditorState> {
-  static defaultProps = {
-    filter: ["all"],
-  };
+  // Nothing ever toggles this: the Block below renders its own documentation
+  // toggle, so this component's inline doc panel stays hidden (as it did before).
+  const [showDoc] = useState(false);
+  const [displaySimpleFilter, setDisplaySimpleFilter] = useState(() =>
+    checkIfSimpleFilter(combiningFilter(props))
+  );
 
-  constructor (props: FilterEditorInternalProps) {
-    super(props);
-    this.state = {
-      showDoc: false,
-      displaySimpleFilter: checkIfSimpleFilter(combiningFilter(props)),
-    };
+  // Replaces getDerivedStateFromProps. "Upgrade but never downgrade": once the
+  // filter stops being expressible in the simple editor, switch to the
+  // expression editor and stay there.
+  const isSimpleFilter = checkIfSimpleFilter(combiningFilter(props));
+  if (!isSimpleFilter && displaySimpleFilter) {
+    setDisplaySimpleFilter(false);
   }
+  // In the original this was state, but every branch derived it from these two
+  // values alone.
+  const valueIsSimpleFilter = isSimpleFilter && !displaySimpleFilter;
 
   // Convert filter to combining filter
-  onFilterPartChanged(filterIdx: number, newPart: any[]) {
-    const newFilter = combiningFilter(this.props).slice(0) as LegacyFilterSpecification | ExpressionSpecification;
+  function onFilterPartChanged(filterIdx: number, newPart: any[]) {
+    const newFilter = combiningFilter(props).slice(0) as LegacyFilterSpecification | ExpressionSpecification;
     newFilter[filterIdx] = newPart;
-    this.props.onChange(newFilter);
+    props.onChange(newFilter);
   }
 
-  deleteFilterItem(filterIdx: number) {
-    const newFilter = combiningFilter(this.props).slice(0) as LegacyFilterSpecification | ExpressionSpecification;
+  function deleteFilterItem(filterIdx: number) {
+    const newFilter = combiningFilter(props).slice(0) as LegacyFilterSpecification | ExpressionSpecification;
     newFilter.splice(filterIdx + 1, 1);
-    this.props.onChange(newFilter);
+    props.onChange(newFilter);
   }
 
-  addFilterItem = () => {
-    const newFilterItem = combiningFilter(this.props).slice(0) as LegacyFilterSpecification | ExpressionSpecification;
+  const addFilterItem = () => {
+    const newFilterItem = combiningFilter(props).slice(0) as LegacyFilterSpecification | ExpressionSpecification;
     (newFilterItem as any[]).push(["==", "name", ""]);
-    this.props.onChange(newFilterItem);
+    props.onChange(newFilterItem);
   };
 
-  onToggleDoc = (val: boolean) => {
-    this.setState({
-      showDoc: val
-    });
+  const makeFilter = () => {
+    setDisplaySimpleFilter(true);
   };
 
-  makeFilter = () => {
-    this.setState({
-      displaySimpleFilter: true,
-    });
+  const makeExpression = () => {
+    const currentFilter = combiningFilter(props);
+    props.onChange(migrateFilter(currentFilter));
+    setDisplaySimpleFilter(false);
   };
 
-  makeExpression = () => {
-    const filter = combiningFilter(this.props);
-    this.props.onChange(migrateFilter(filter));
-    this.setState({
-      displaySimpleFilter: false,
-    });
+
+  const {errors, t} = props;
+  const fieldSpec={
+    doc: latest.layer.filter.doc + " Combine multiple filters together by using a compound filter."
   };
+  const defaultFilter = ["all"] as LegacyFilterSpecification | ExpressionSpecification;
 
-  static getDerivedStateFromProps(props: Readonly<FilterEditorInternalProps>, state: FilterEditorState) {
-    const displaySimpleFilter = checkIfSimpleFilter(combiningFilter(props));
+  const isNestedCombiningFilter = displaySimpleFilter && hasNestedCombiningFilter(combiningFilter(props));
 
-    // Upgrade but never downgrade
-    if (!displaySimpleFilter && state.displaySimpleFilter === true) {
-      return {
-        displaySimpleFilter: false,
-        valueIsSimpleFilter: false,
-      };
-    }
-    else if (displaySimpleFilter && state.displaySimpleFilter === false) {
-      return {
-        valueIsSimpleFilter: true,
-      };
-    }
-    else {
-      return {
-        valueIsSimpleFilter: false,
-      };
-    }
+  if (isNestedCombiningFilter) {
+    return <div className="maputnik-filter-editor-unsupported">
+      <p>
+        {t("Nested filters are not supported.")}
+      </p>
+      <InputButton
+        onClick={makeExpression}
+        title={t("Convert to expression")}
+      >
+        <TbMathFunction />
+        {t("Upgrade to expression")}
+      </InputButton>
+    </div>;
   }
+  else if (displaySimpleFilter) {
+    const filter = combiningFilter(props);
+    const combiningOp = filter[0];
+    const filters = filter.slice(1) as (LegacyFilterSpecification | ExpressionSpecification)[];
 
-  render() {
-    const {errors, t} = this.props;
-    const {displaySimpleFilter} = this.state;
-    const fieldSpec={
-      doc: latest.layer.filter.doc + " Combine multiple filters together by using a compound filter."
-    };
-    const defaultFilter = ["all"] as LegacyFilterSpecification | ExpressionSpecification;
-
-    const isNestedCombiningFilter = displaySimpleFilter && hasNestedCombiningFilter(combiningFilter(this.props));
-
-    if (isNestedCombiningFilter) {
-      return <div className="maputnik-filter-editor-unsupported">
-        <p>
-          {t("Nested filters are not supported.")}
-        </p>
+    const actions = (
+      <div>
         <InputButton
-          onClick={this.makeExpression}
+          onClick={makeExpression}
           title={t("Convert to expression")}
+          className="maputnik-make-zoom-function"
+          data-wd-key="filter-convert-to-expression"
         >
           <TbMathFunction />
-          {t("Upgrade to expression")}
         </InputButton>
-      </div>;
-    }
-    else if (displaySimpleFilter) {
-      const filter = combiningFilter(this.props);
-      const combiningOp = filter[0];
-      const filters = filter.slice(1) as (LegacyFilterSpecification | ExpressionSpecification)[];
+      </div>
+    );
 
-      const actions = (
-        <div>
-          <InputButton
-            onClick={this.makeExpression}
-            title={t("Convert to expression")}
-            className="maputnik-make-zoom-function"
-          >
-            <TbMathFunction />
-          </InputButton>
+    const editorBlocks = filters.map((f, idx) => {
+      const error = errors![`filter[${idx+1}]`];
+
+      return (
+        <div key={`block-${idx}`}>
+          <FilterEditorBlock key={idx} onDelete={deleteFilterItem.bind(null, idx)}>
+            <SingleFilterEditor
+              properties={props.properties}
+              filter={f}
+              onChange={onFilterPartChanged.bind(null, idx + 1)}
+            />
+          </FilterEditorBlock>
+          {error &&
+              <div key="error" className="maputnik-inline-error">{error.message}</div>
+          }
         </div>
       );
-
-      const editorBlocks = filters.map((f, idx) => {
-        const error = errors![`filter[${idx+1}]`];
-
-        return (
-          <div key={`block-${idx}`}>
-            <FilterEditorBlock key={idx} onDelete={this.deleteFilterItem.bind(this, idx)}>
-              <SingleFilterEditor
-                properties={this.props.properties}
-                filter={f}
-                onChange={this.onFilterPartChanged.bind(this, idx + 1)}
-              />
-            </FilterEditorBlock>
-            {error &&
-              <div key="error" className="maputnik-inline-error">{error.message}</div>
-            }
-          </div>
-        );
-      });
+    });
 
 
-      return (
-        <>
-          <Block
-            key="top"
-            fieldSpec={fieldSpec}
-            label={t("Filter")}
-            action={actions}
-          >
-            <InputSelect
-              value={combiningOp}
-              onChange={(v: [string, any]) => this.onFilterPartChanged(0, v)}
-              options={[
-                ["all", t("every filter matches")],
-                ["none", t("no filter matches")],
-                ["any", t("any filter matches")]
-              ]}
-            />
-          </Block>
-          {editorBlocks}
-          <div
-            key="buttons"
-            className="maputnik-filter-editor-add-wrapper"
-          >
-            <InputButton
-              data-wd-key="layer-filter-button"
-              className="maputnik-add-filter"
-              onClick={this.addFilterItem}
-            >
-              <PiListPlusBold style={{ verticalAlign: "text-bottom" }} />
-              {t("Add filter")}
-            </InputButton>
-          </div>
-          <div
-            key="doc"
-            className="maputnik-doc-inline"
-            style={{display: this.state.showDoc ? "" : "none"}}
-          >
-            <Doc fieldSpec={fieldSpec} />
-          </div>
-        </>
-      );
-    }
-    else {
-      const {filter} = this.props;
-
-      return (
-        <>
-          <ExpressionProperty
-            onDelete={() => {
-              this.setState({displaySimpleFilter: true});
-              this.props.onChange(defaultFilter);
-            }}
-            fieldName="filter"
-            value={filter}
-            errors={errors}
-            onChange={this.props.onChange}
+    return (
+      <>
+        <Block
+          key="top"
+          fieldSpec={fieldSpec}
+          label={t("Filter")}
+          action={actions}
+          data-wd-key="filter-combining-operator"
+        >
+          <InputSelect
+            value={combiningOp}
+            onChange={(v: [string, any]) => onFilterPartChanged(0, v)}
+            options={[
+              ["all", t("every filter matches")],
+              ["none", t("no filter matches")],
+              ["any", t("any filter matches")]
+            ]}
           />
-          {this.state.valueIsSimpleFilter &&
+        </Block>
+        {editorBlocks}
+        <div
+          key="buttons"
+          className="maputnik-filter-editor-add-wrapper"
+        >
+          <InputButton
+            data-wd-key="layer-filter-button"
+            className="maputnik-add-filter"
+            onClick={addFilterItem}
+          >
+            <PiListPlusBold style={{ verticalAlign: "text-bottom" }} />
+            {t("Add filter")}
+          </InputButton>
+        </div>
+        <div
+          key="doc"
+          className="maputnik-doc-inline"
+          style={{display: showDoc ? "" : "none"}}
+        >
+          <Doc fieldSpec={fieldSpec} />
+        </div>
+      </>
+    );
+  }
+  else {
+    const {filter} = props;
+
+    return (
+      <>
+        <ExpressionProperty
+          onDelete={() => {
+            setDisplaySimpleFilter(true);
+            props.onChange(defaultFilter);
+          }}
+          fieldName="filter"
+          value={filter}
+          errors={errors}
+          onChange={props.onChange}
+        />
+        {valueIsSimpleFilter &&
             <div className="maputnik-expr-infobox">
               {t("You've entered an old style filter.")}
               {" "}
               <button
-                onClick={this.makeFilter}
+                onClick={makeFilter}
                 className="maputnik-expr-infobox__button"
               >
                 {t("Switch to filter editor.")}
               </button>
             </div>
-          }
-        </>
-      );
-    }
+        }
+      </>
+    );
   }
-}
+};
 
-const FilterEditor = withTranslation()(FilterEditorInternal);
-export default FilterEditor;
+export const FilterEditor = withTranslation()(FilterEditorInternal);

src/components/FilterEditorBlock.tsx

@@ -1,5 +1,5 @@
 import React, { type PropsWithChildren } from "react";
-import InputButton from "./InputButton";
+import { InputButton } from "./InputButton";
 import {MdDelete} from "react-icons/md";
 import { type WithTranslation, withTranslation } from "react-i18next";
 
@@ -7,25 +7,22 @@ type FilterEditorBlockInternalProps = PropsWithChildren & {
   onDelete(...args: unknown[]): unknown
 } & WithTranslation;
 
-class FilterEditorBlockInternal extends React.Component<FilterEditorBlockInternalProps> {
-  render() {
-    const t = this.props.t;
-    return <div className="maputnik-filter-editor-block">
-      <div className="maputnik-filter-editor-block-content">
-        {this.props.children}
-      </div>
-      <div className="maputnik-filter-editor-block-action">
-        <InputButton
-          className="maputnik-icon-button"
-          onClick={this.props.onDelete}
-          title={t("Delete filter block")}
-        >
-          <MdDelete />
-        </InputButton>
-      </div>
-    </div>;
-  }
-}
+const FilterEditorBlockInternal: React.FC<FilterEditorBlockInternalProps> = (props) => {
+  const t = props.t;
+  return <div className="maputnik-filter-editor-block">
+    <div className="maputnik-filter-editor-block-content">
+      {props.children}
+    </div>
+    <div className="maputnik-filter-editor-block-action">
+      <InputButton
+        className="maputnik-icon-button"
+        onClick={props.onDelete}
+        title={t("Delete filter block")}
+      >
+        <MdDelete />
+      </InputButton>
+    </div>
+  </div>;
+};
 
-const FilterEditorBlock = withTranslation()(FilterEditorBlockInternal);
-export default FilterEditorBlock;
+export const FilterEditorBlock = withTranslation()(FilterEditorBlockInternal);

src/components/FunctionButtons.tsx

@@ -0,0 +1,68 @@
+import React from "react";
+
+import { InputButton } from "./InputButton";
+import {MdFunctions, MdInsertChart} from "react-icons/md";
+import { TbMathFunction } from "react-icons/tb";
+import { type WithTranslation, withTranslation } from "react-i18next";
+
+type FunctionInputButtonsInternalProps = {
+  fieldSpec?: any
+  onZoomClick?(): void
+  onDataClick?(): void
+  onExpressionClick?(): void
+  onElevationClick?(): void
+} & WithTranslation;
+
+const FunctionInputButtonsInternal: React.FC<FunctionInputButtonsInternalProps> = (props) => {
+  const t = props.t;
+
+  if (props.fieldSpec.expression?.parameters.includes("zoom")) {
+    const expressionInputButton = (
+      <InputButton
+        className="maputnik-make-zoom-function"
+        onClick={props.onExpressionClick}
+        title={t("Convert to expression")}
+      >
+        <TbMathFunction />
+      </InputButton>
+    );
+
+    const makeZoomInputButton = <InputButton
+      className="maputnik-make-zoom-function"
+      onClick={props.onZoomClick}
+      title={t("Convert property into a zoom function")}
+    >
+      <MdFunctions />
+    </InputButton>;
+
+    let makeDataInputButton;
+    if (props.fieldSpec["property-type"] === "data-driven") {
+      makeDataInputButton = <InputButton
+        className="maputnik-make-data-function"
+        onClick={props.onDataClick}
+        title={t("Convert property to data function")}
+      >
+        <MdInsertChart />
+      </InputButton>;
+    }
+    return <div>
+      {expressionInputButton}
+      {makeDataInputButton}
+      {makeZoomInputButton}
+    </div>;
+  } else if (props.fieldSpec.expression?.parameters.includes("elevation")) {
+    const inputElevationButton = <InputButton
+      className="maputnik-make-elevation-function"
+      onClick={props.onElevationClick}
+      title={t("Convert property into a elevation function")}
+      data-wd-key='make-elevation-function'
+    >
+      <MdFunctions />
+    </InputButton>;
+    return <div>{inputElevationButton}</div>;
+  } else {
+    return <div></div>;
+  }
+};
+
+export const FunctionInputButtons = withTranslation()(FunctionInputButtonsInternal);

src/components/IconLayer.tsx

@@ -13,7 +13,7 @@ type IconLayerProps = {
   className?: string
 };
 
-const IconLayer: React.FC<IconLayerProps> = (props) => {
+export const IconLayer: React.FC<IconLayerProps> = (props) => {
   const iconProps = { style: props.style };
   switch(props.type) {
     case "fill-extrusion": return <IoMdCube {...iconProps} />;
@@ -29,5 +29,3 @@ const IconLayer: React.FC<IconLayerProps> = (props) => {
     default: return <MdPriorityHigh {...iconProps} />;
   }
 };
-
-export default IconLayer;

src/components/InputArray.tsx

@@ -1,6 +1,6 @@
-import React from "react";
-import InputString from "./InputString";
-import InputNumber from "./InputNumber";
+import React, { useState } from "react";
+import { InputString } from "./InputString";
+import { InputNumber } from "./InputNumber";
 
 export type InputArrayProps = {
   value: (string | number | undefined)[]
@@ -12,106 +12,72 @@ export type InputArrayProps = {
   label?: string
 };
 
-type InputArrayState = {
-  value: (string | number | undefined)[]
-  initialPropsValue: unknown[]
+export const InputArray: React.FC<InputArrayProps> = ({
+  value: propsValue = [],
+  default: propsDefault = [],
+  ...rest
+}) => {
+  const props = { value: propsValue, default: propsDefault, ...rest };
+
+  // The original seeded this from props and then never let props overwrite it
+  // again (its getDerivedStateFromProps assigned the existing state back in
+  // both branches), so the value is owned by this component after mount.
+  const [value, setValue] = useState<(string | number | undefined)[]>(() => propsValue.slice(0));
+
+  function isComplete(val: unknown[]) {
+    return Array(props.length).fill(null).every((_, i) => {
+      const v = val[i];
+      return !(v === undefined || v === "");
+    });
+  }
+
+  function changeValue(idx: number, newValue: string | number | undefined) {
+    const nextValue = value.slice(0);
+    nextValue[idx] = newValue;
+
+    setValue(nextValue);
+
+    if (isComplete(nextValue) && props.onChange) {
+      props.onChange(nextValue);
+    }
+    else if (props.onChange) {
+      // Unset until complete
+      props.onChange(undefined);
+    }
+  }
+
+  const containsValues = (
+    value.length > 0 &&
+    !value.every(val => {
+      return (val === "" || val === undefined);
+    })
+  );
+
+  const inputs = Array(props.length).fill(null).map((_, i) => {
+    if(props.type === "number") {
+      return <InputNumber
+        key={i}
+        default={containsValues || !props.default ? undefined : props.default[i] as number}
+        value={value[i] as number}
+        required={containsValues ? true : false}
+        onChange={(v) => changeValue(i, v)}
+        aria-label={props["aria-label"] || props.label}
+      />;
+    } else {
+      return <InputString
+        key={i}
+        default={containsValues || !props.default ? undefined : props.default[i] as string}
+        value={value[i] as string}
+        required={containsValues ? true : false}
+        onChange={(v) => changeValue(i, v)}
+        aria-label={props["aria-label"] || props.label}
+      />;
+    }
+  });
+
+  return (
+    <div className="maputnik-array">
+      {inputs}
+    </div>
+  );
 };
-
-export default class InputArray extends React.Component<InputArrayProps, InputArrayState> {
-  static defaultProps = {
-    value: [],
-    default: [],
-  };
-
-  constructor (props: InputArrayProps) {
-    super(props);
-    this.state = {
-      value: this.props.value.slice(0),
-      // This is so we can compare changes in getDerivedStateFromProps
-      initialPropsValue: this.props.value.slice(0),
-    };
-  }
-
-  static getDerivedStateFromProps(props: Readonly<InputArrayProps>, state: InputArrayState) {
-    const value: any[] = [];
-    const initialPropsValue = state.initialPropsValue.slice(0);
-
-    Array(props.length).fill(null).map((_, i) => {
-      if (props.value[i] === state.initialPropsValue[i]) {
-        value[i] = state.value[i];
-      }
-      else {
-        value[i] = state.value[i];
-        initialPropsValue[i] = state.value[i];
-      }
-    });
-
-    return {
-      value,
-      initialPropsValue,
-    };
-  }
-
-  isComplete(value: unknown[]) {
-    return Array(this.props.length).fill(null).every((_, i) => {
-      const val = value[i];
-      return !(val === undefined || val === "");
-    });
-  }
-
-  changeValue(idx: number, newValue: string | number | undefined) {
-    const value = this.state.value.slice(0);
-    value[idx] = newValue;
-
-    this.setState({
-      value,
-    }, () => {
-      if (this.isComplete(value) && this.props.onChange) {
-        this.props.onChange(value);
-      }
-      else if (this.props.onChange){
-        // Unset until complete
-        this.props.onChange(undefined);
-      }
-    });
-  }
-
-  render() {
-    const {value} = this.state;
-
-    const containsValues = (
-      value.length > 0 &&
-      !value.every(val => {
-        return (val === "" || val === undefined);
-      })
-    );
-
-    const inputs = Array(this.props.length).fill(null).map((_, i) => {
-      if(this.props.type === "number") {
-        return <InputNumber
-          key={i}
-          default={containsValues || !this.props.default ? undefined : this.props.default[i] as number}
-          value={value[i] as number}
-          required={containsValues ? true : false}
-          onChange={(v) => this.changeValue(i, v)}
-          aria-label={this.props["aria-label"] || this.props.label}
-        />;
-      } else {
-        return <InputString
-          key={i}
-          default={containsValues || !this.props.default ? undefined : this.props.default[i] as string}
-          value={value[i] as string}
-          required={containsValues ? true : false}
-          onChange={this.changeValue.bind(this, i)}
-          aria-label={this.props["aria-label"] || this.props.label}
-        />;
-      }
-    });
-
-    return (
-      <div className="maputnik-array">
-        {inputs}
-      </div>
-    );
-  }
-}

src/components/InputAutocomplete.browser.test.tsx

@@ -1,24 +0,0 @@
-import { expect, test } from "vitest";
-import { render } from "vitest-browser-react";
-import { page } from "vitest/browser";
-import InputAutocomplete from "./InputAutocomplete";
-
-const fruits = ["apple", "banana", "cherry"];
-
-test("filters options when typing", async () => {
-  render(<InputAutocomplete aria-label="Fruit" options={fruits.map((f) => [f, f])} />);
-
-  const input = page.getByLabelText("Fruit");
-  await input.click();
-
-  const menuItems = page.getByRole("option");
-  await expect.element(menuItems.first()).toBeVisible();
-  expect(menuItems.all()).toHaveLength(3);
-
-  await input.fill("ch");
-  await expect.element(page.getByText("cherry")).toBeVisible();
-  expect(page.getByRole("option").all()).toHaveLength(1);
-
-  await page.getByText("cherry").click();
-  await expect.element(input).toHaveValue("cherry");
-});

src/components/InputAutocomplete.tsx

@@ -11,7 +11,7 @@ export type InputAutocompleteProps = {
   "aria-label"?: string
 };
 
-export default function InputAutocomplete({
+export function InputAutocomplete({
   value,
   options = [],
   onChange = () => {},

src/components/InputButton.tsx

@@ -14,20 +14,18 @@ type InputButtonProps = {
   title?: string
 };
 
-export default class InputButton extends React.Component<InputButtonProps> {
-  render() {
-    return <button
-      id={this.props.id}
-      title={this.props.title}
-      type={this.props.type}
-      onClick={this.props.onClick}
-      disabled={this.props.disabled}
-      aria-label={this.props["aria-label"]}
-      className={classnames("maputnik-button", this.props.className)}
-      data-wd-key={this.props["data-wd-key"]}
-      style={this.props.style}
-    >
-      {this.props.children}
-    </button>;
-  }
-}
+export const InputButton: React.FC<InputButtonProps> = (props) => {
+  return <button
+    id={props.id}
+    title={props.title}
+    type={props.type}
+    onClick={props.onClick}
+    disabled={props.disabled}
+    aria-label={props["aria-label"]}
+    className={classnames("maputnik-button", props.className)}
+    data-wd-key={props["data-wd-key"]}
+    style={props.style}
+  >
+    {props.children}
+  </button>;
+};

src/components/InputCheckbox.tsx

@@ -6,32 +6,26 @@ export type InputCheckboxProps = {
   onChange(...args: unknown[]): unknown
 };
 
-export default class InputCheckbox extends React.Component<InputCheckboxProps> {
-  static defaultProps = {
-    value: false,
+export const InputCheckbox: React.FC<InputCheckboxProps> = ({value = false, ...props}) => {
+  const onChange = () => {
+    props.onChange(!value);
   };
 
-  onChange = () => {
-    this.props.onChange(!this.props.value);
-  };
-
-  render() {
-    return <div className="maputnik-checkbox-wrapper">
-      <input
-        className="maputnik-checkbox"
-        type="checkbox"
-        style={this.props.style}
-        onChange={this.onChange}
-        onClick={this.onChange}
-        checked={this.props.value}
-      />
-      <div className="maputnik-checkbox-box">
-        <svg style={{
-          display: this.props.value ? "inline" : "none"
-        }} className="maputnik-checkbox-icon" viewBox='0 0 32 32'>
-          <path d='M1 14 L5 10 L13 18 L27 4 L31 8 L13 26 z' />
-        </svg>
-      </div>
-    </div>;
-  }
-}
+  return <div className="maputnik-checkbox-wrapper">
+    <input
+      className="maputnik-checkbox"
+      type="checkbox"
+      style={props.style}
+      onChange={onChange}
+      onClick={onChange}
+      checked={value}
+    />
+    <div className="maputnik-checkbox-box">
+      <svg style={{
+        display: value ? "inline" : "none"
+      }} className="maputnik-checkbox-icon" viewBox='0 0 32 32'>
+        <path d='M1 14 L5 10 L13 18 L27 4 L31 8 L13 26 z' />
+      </svg>
+    </div>
+  </div>;
+};

src/components/InputColor.tsx

@@ -1,4 +1,4 @@
-import React from "react";
+import React, { useEffect, useMemo, useRef, useState } from "react";
 import Color from "color";
 import ChromePicker from "react-color/lib/components/chrome/Chrome";
 import {type ColorResult} from "react-color";
@@ -20,26 +20,27 @@ export type InputColorProps = {
 };
 
 /*** Number fields with support for min, max and units and documentation*/
-export default class InputColor extends React.Component<InputColorProps> {
-  state = {
-    pickerOpened: false
-  };
-  colorInput: HTMLInputElement | null = null;
+export const InputColor: React.FC<InputColorProps> = (props) => {
+  const [pickerOpened, setPickerOpened] = useState(false);
+  const colorInput = useRef<HTMLInputElement | null>(null);
 
-  constructor (props: InputColorProps) {
-    super(props);
-    this.onChangeNoCheck = lodash.throttle(this.onChangeNoCheck, 1000/30);
-  }
+  // Keep the latest `onChange` available to the throttled callback, which is
+  // created only once so that throttling actually takes effect.
+  const onChangeProp = useRef(props.onChange);
+  useEffect(() => {
+    onChangeProp.current = props.onChange;
+  });
 
-  onChangeNoCheck(v: string) {
-    this.props.onChange(v);
-  }
+  const onChangeNoCheck = useMemo(
+    () => lodash.throttle((v: string) => onChangeProp.current(v), 1000/30),
+    []
+  );
 
   //TODO: I much rather would do this with absolute positioning
   //but I am too stupid to get it to work together with fixed position
   //and scrollbars so I have to fallback to JavaScript
-  calcPickerOffset = () => {
-    const elem = this.colorInput;
+  const calcPickerOffset = () => {
+    const elem = colorInput.current;
     if(elem) {
       const pos = elem.getBoundingClientRect();
       return {
@@ -54,82 +55,80 @@ export default class InputColor extends React.Component<InputColorProps> {
     }
   };
 
-  togglePicker = () => {
-    this.setState({ pickerOpened: !this.state.pickerOpened });
+  const togglePicker = () => {
+    setPickerOpened(opened => !opened);
   };
 
-  get color() {
+  const getColor = () => {
     // Catch invalid color.
     try {
-      return Color(this.props.value).rgb();
+      return Color(props.value).rgb();
     }
     catch(err) {
       console.warn("Error parsing color: ", err);
       return Color("rgb(255,255,255)");
     }
-  }
+  };
 
-  onChange (v: string) {
-    this.props.onChange(v === "" ? undefined : v);
-  }
+  const onChange = (v: string) => {
+    props.onChange(v === "" ? undefined : v);
+  };
 
-  render() {
-    const offset = this.calcPickerOffset();
-    const currentColor = this.color.object();
-    const currentChromeColor = {
-      r: currentColor.r,
-      g: currentColor.g,
-      b: currentColor.b,
-      // Rename alpha -> a for ChromePicker
-      a: currentColor.alpha!
-    };
+  const offset = calcPickerOffset();
+  const currentColor = getColor().object();
+  const currentChromeColor = {
+    r: currentColor.r,
+    g: currentColor.g,
+    b: currentColor.b,
+    // Rename alpha -> a for ChromePicker
+    a: currentColor.alpha!
+  };
 
-    const picker = <div
+  const picker = <div
+    className="maputnik-color-picker-offset"
+    style={{
+      position: "fixed",
+      zIndex: 1,
+      left: offset.left,
+      top: offset.top,
+    }}>
+    <ChromePicker
+      color={currentChromeColor}
+      onChange={c => onChangeNoCheck(formatColor(c))}
+    />
+    <div
       className="maputnik-color-picker-offset"
+      onClick={togglePicker}
       style={{
+        zIndex: -1,
         position: "fixed",
-        zIndex: 1,
-        left: offset.left,
-        top: offset.top,
-      }}>
-      <ChromePicker
-        color={currentChromeColor}
-        onChange={c => this.onChangeNoCheck(formatColor(c))}
-      />
-      <div
-        className="maputnik-color-picker-offset"
-        onClick={this.togglePicker}
-        style={{
-          zIndex: -1,
-          position: "fixed",
-          top: "0px",
-          right: "0px",
-          bottom: "0px",
-          left: "0px",
-        }}
-      />
-    </div>;
+        top: "0px",
+        right: "0px",
+        bottom: "0px",
+        left: "0px",
+      }}
+    />
+  </div>;
 
-    const swatchStyle = {
-      backgroundColor: this.props.value
-    };
+  const swatchStyle = {
+    backgroundColor: props.value
+  };
 
-    return <div className="maputnik-color-wrapper">
-      {this.state.pickerOpened && picker}
-      <div className="maputnik-color-swatch" style={swatchStyle}></div>
-      <input
-        aria-label={this.props["aria-label"]}
-        spellCheck="false"
-        autoComplete="off"
-        className="maputnik-color"
-        ref={(input) => {this.colorInput = input;}}
-        onClick={this.togglePicker}
-        style={this.props.style}
-        name={this.props.name}
-        placeholder={this.props.default}
-        value={this.props.value ? this.props.value : ""}
-        onChange={(e) => this.onChange(e.target.value)}
-      />
-    </div>;
-  }
-}
+  return <div className="maputnik-color-wrapper">
+    {pickerOpened && picker}
+    <div className="maputnik-color-swatch" style={swatchStyle}></div>
+    <input
+      aria-label={props["aria-label"]}
+      spellCheck="false"
+      autoComplete="off"
+      className="maputnik-color"
+      ref={colorInput}
+      onClick={togglePicker}
+      style={props.style}
+      name={props.name}
+      placeholder={props.default}
+      value={props.value ? props.value : ""}
+      onChange={(e) => onChange(e.target.value)}
+    />
+  </div>;
+};

src/components/InputDynamicArray.tsx

@@ -3,13 +3,13 @@ import capitalize from "lodash.capitalize";
 import {MdDelete} from "react-icons/md";
 import { type WithTranslation, withTranslation } from "react-i18next";
 
-import InputString from "./InputString";
-import InputNumber from "./InputNumber";
-import InputButton from "./InputButton";
-import FieldDocLabel from "./FieldDocLabel";
-import InputEnum from "./InputEnum";
-import InputUrl from "./InputUrl";
-import InputColor from "./InputColor";
+import { InputString } from "./InputString";
+import { InputNumber } from "./InputNumber";
+import { InputButton } from "./InputButton";
+import { FieldDocLabel } from "./FieldDocLabel";
+import { InputEnum } from "./InputEnum";
+import { InputUrl } from "./InputUrl";
+import { InputColor } from "./InputColor";
 
 
 export type InputDynamicArrayProps = {
@@ -27,138 +27,130 @@ export type InputDynamicArrayProps = {
 
 type InputDynamicArrayInternalProps = InputDynamicArrayProps & WithTranslation;
 
-class InputDynamicArrayInternal extends React.Component<InputDynamicArrayInternalProps> {
-  changeValue(idx: number, newValue: string | number | undefined) {
-    const values = this.values.slice(0);
-    values[idx] = newValue;
-    if (this.props.onChange) this.props.onChange(values);
-  }
+const InputDynamicArrayInternal: React.FC<InputDynamicArrayInternalProps> = (props) => {
+  const values = props.value || props.default || [];
 
-  get values() {
-    return this.props.value || this.props.default || [];
-  }
-
-  addValue = () => {
-    const values = this.values.slice(0);
-    if (this.props.type === "number") {
-      values.push(0);
-    }
-    else if (this.props.type === "url") {
-      values.push("");
-    }
-    else if (this.props.type === "enum") {
-      const {fieldSpec} = this.props;
-      const defaultValue = Object.keys(fieldSpec!.values)[0];
-      values.push(defaultValue);
-    } else if (this.props.type === "color") {
-      values.push("#000000");
-    } else {
-      values.push("");
-    }
-
-    if (this.props.onChange) this.props.onChange(values);
+  const changeValue = (idx: number, newValue: string | number | undefined) => {
+    const newValues = values.slice(0);
+    newValues[idx] = newValue;
+    if (props.onChange) props.onChange(newValues);
   };
 
-  deleteValue(valueIdx: number) {
-    const values = this.values.slice(0);
-    values.splice(valueIdx, 1);
+  const addValue = () => {
+    const newValues = values.slice(0);
+    if (props.type === "number") {
+      newValues.push(0);
+    }
+    else if (props.type === "url") {
+      newValues.push("");
+    }
+    else if (props.type === "enum") {
+      const {fieldSpec} = props;
+      const defaultValue = Object.keys(fieldSpec!.values)[0];
+      newValues.push(defaultValue);
+    } else if (props.type === "color") {
+      newValues.push("#000000");
+    } else {
+      newValues.push("");
+    }
 
-    if (this.props.onChange) this.props.onChange(values.length > 0 ? values : undefined);
-  }
+    if (props.onChange) props.onChange(newValues);
+  };
 
-  render() {
-    const t = this.props.t;
-    const i18nProps = { t, i18n: this.props.i18n, tReady: this.props.tReady };
-    const inputs = this.values.map((v, i) => {
-      const deleteValueBtn= <DeleteValueInputButton
-        onClick={this.deleteValue.bind(this, i)}
-        {...i18nProps}
+  const deleteValue = (valueIdx: number) => {
+    const newValues = values.slice(0);
+    newValues.splice(valueIdx, 1);
+
+    if (props.onChange) props.onChange(newValues.length > 0 ? newValues : undefined);
+  };
+
+  const t = props.t;
+  const i18nProps = { t, i18n: props.i18n, tReady: props.tReady };
+  const inputs = values.map((v, i) => {
+    const deleteValueBtn= <DeleteValueInputButton
+      onClick={deleteValue.bind(null, i)}
+      {...i18nProps}
+    />;
+    let input;
+    if(props.type === "url") {
+      input = <InputUrl
+        value={v as string}
+        onChange={changeValue.bind(null, i)}
+        aria-label={props["aria-label"] || props.label}
       />;
-      let input;
-      if(this.props.type === "url") {
-        input = <InputUrl
-          value={v as string}
-          onChange={this.changeValue.bind(this, i)}
-          aria-label={this.props["aria-label"] || this.props.label}
-        />;
-      }
-      else if (this.props.type === "number") {
-        input = <InputNumber
-          value={v as number}
-          onChange={this.changeValue.bind(this, i)}
-          aria-label={this.props["aria-label"] || this.props.label}
-        />;
-      }
-      else if (this.props.type === "enum") {
-        const options = Object.keys(this.props.fieldSpec?.values).map(v => [v, capitalize(v)]);
-        input = <InputEnum
-          options={options}
-          value={v as string}
-          onChange={this.changeValue.bind(this, i)}
-          aria-label={this.props["aria-label"] || this.props.label}
-        />;
-      }
-      else if (this.props.type === "color") {
-        input = <InputColor
-          value={v as string}
-          onChange={this.changeValue.bind(this, i)}
-          aria-label={this.props["aria-label"] || this.props.label}
-        />;
-      }
-      else {
-        input = <InputString
-          value={v as string}
-          onChange={this.changeValue.bind(this, i)}
-          aria-label={this.props["aria-label"] || this.props.label}
-        />;
-      }
+    }
+    else if (props.type === "number") {
+      input = <InputNumber
+        value={v as number}
+        onChange={changeValue.bind(null, i)}
+        aria-label={props["aria-label"] || props.label}
+      />;
+    }
+    else if (props.type === "enum") {
+      const options = Object.keys(props.fieldSpec?.values).map(v => [v, capitalize(v)]);
+      input = <InputEnum
+        options={options}
+        value={v as string}
+        onChange={changeValue.bind(null, i)}
+        aria-label={props["aria-label"] || props.label}
+      />;
+    }
+    else if (props.type === "color") {
+      input = <InputColor
+        value={v as string}
+        onChange={changeValue.bind(null, i)}
+        aria-label={props["aria-label"] || props.label}
+      />;
+    }
+    else {
+      input = <InputString
+        value={v as string}
+        onChange={changeValue.bind(null, i)}
+        aria-label={props["aria-label"] || props.label}
+      />;
+    }
 
-      return <div
-        style={this.props.style}
-        key={i}
-        className="maputnik-array-block"
-      >
-        <div className="maputnik-array-block-action">
-          {deleteValueBtn}
-        </div>
-        <div className="maputnik-array-block-content">
-          {input}
-        </div>
-      </div>;
-    });
-
-    return (
-      <div className="maputnik-array">
-        {inputs}
-        <InputButton
-          className="maputnik-array-add-value"
-          onClick={this.addValue}
-        >
-          {t("Add value")}
-        </InputButton>
+    return <div
+      style={props.style}
+      key={i}
+      className="maputnik-array-block"
+    >
+      <div className="maputnik-array-block-action">
+        {deleteValueBtn}
       </div>
-    );
-  }
-}
+      <div className="maputnik-array-block-content">
+        {input}
+      </div>
+    </div>;
+  });
 
-const InputDynamicArray = withTranslation()(InputDynamicArrayInternal);
-export default InputDynamicArray;
+  return (
+    <div className="maputnik-array">
+      {inputs}
+      <InputButton
+        className="maputnik-array-add-value"
+        onClick={addValue}
+      >
+        {t("Add value")}
+      </InputButton>
+    </div>
+  );
+};
 
+export const InputDynamicArray = withTranslation()(InputDynamicArrayInternal);
 type DeleteValueInputButtonProps = {
   onClick?(...args: unknown[]): unknown
 } & WithTranslation;
 
-class DeleteValueInputButton extends React.Component<DeleteValueInputButtonProps> {
-  render() {
-    const t = this.props.t;
-    return <InputButton
-      className="maputnik-delete-stop"
-      onClick={this.props.onClick}
-      title={t("Remove array item")}
-    >
-      <FieldDocLabel
-        label={<MdDelete />}
-      />
-    </InputButton>;
-  }
-}
+const DeleteValueInputButton: React.FC<DeleteValueInputButtonProps> = (props) => {
+  const t = props.t;
+  return <InputButton
+    className="maputnik-delete-stop"
+    onClick={props.onClick}
+    title={t("Remove array item")}
+  >
+    <FieldDocLabel
+      label={<MdDelete />}
+    />
+  </InputButton>;
+};

src/components/InputEnum.tsx

@@ -1,6 +1,6 @@
 import React from "react";
-import InputSelect from "./InputSelect";
-import InputMultiInput from "./InputMultiInput";
+import { InputSelect } from "./InputSelect";
+import { InputMultiInput } from "./InputMultiInput";
 
 
 function optionsLabelLength(options: any[]) {
@@ -25,25 +25,23 @@ export type InputEnumProps = {
 };
 
 
-export default class InputEnum extends React.Component<InputEnumProps> {
-  render() {
-    const {options, value, onChange, name, label} = this.props;
+export const InputEnum: React.FC<InputEnumProps> = (props) => {
+  const {options, value, onChange, name, label} = props;
 
-    if(options.length <= 3 && optionsLabelLength(options) <= 20) {
-      return <InputMultiInput
-        name={name}
-        options={options}
-        value={(value || this.props.default)!}
-        onChange={onChange}
-        aria-label={this.props["aria-label"] || label}
-      />;
-    } else {
-      return <InputSelect
-        options={options}
-        value={(value || this.props.default)!}
-        onChange={onChange}
-        aria-label={this.props["aria-label"] || label}
-      />;
-    }
+  if(options.length <= 3 && optionsLabelLength(options) <= 20) {
+    return <InputMultiInput
+      name={name}
+      options={options}
+      value={(value || props.default)!}
+      onChange={onChange}
+      aria-label={props["aria-label"] || label}
+    />;
+  } else {
+    return <InputSelect
+      options={options}
+      value={(value || props.default)!}
+      onChange={onChange}
+      aria-label={props["aria-label"] || label}
+    />;
   }
-}
+};

src/components/InputFont.tsx

@@ -1,5 +1,5 @@
 import React from "react";
-import InputAutocomplete from "./InputAutocomplete";
+import { InputAutocomplete } from "./InputAutocomplete";
 
 export type InputFontProps = {
   name: string
@@ -11,13 +11,9 @@ export type InputFontProps = {
   "aria-label"?: string
 };
 
-export default class InputFont extends React.Component<InputFontProps> {
-  static defaultProps = {
-    fonts: []
-  };
-
-  get values() {
-    const out = this.props.value || this.props.default || [];
+export const InputFont: React.FC<InputFontProps> = ({fonts = [], ...props}) => {
+  const getValues = () => {
+    const out = props.value || props.default || [];
 
     // Always put a "" in the last field to you can keep adding entries
     if (out[out.length-1] !== ""){
@@ -26,36 +22,36 @@ export default class InputFont extends React.Component<InputFontProps> {
     else {
       return out;
     }
-  }
+  };
 
-  changeFont(idx: number, newValue: string) {
-    const changedValues = this.values.slice(0);
+  const values = getValues();
+
+  const changeFont = (idx: number, newValue: string) => {
+    const changedValues = values.slice(0);
     changedValues[idx] = newValue;
     const filteredValues = changedValues
       .filter(v => v !== undefined)
       .filter(v => v !== "");
 
-    this.props.onChange(filteredValues);
-  }
+    props.onChange(filteredValues);
+  };
 
-  render() {
-    const inputs = this.values.map((value, i) => {
-      return <li
-        key={i}
-      >
-        <InputAutocomplete
-          aria-label={this.props["aria-label"] || this.props.name}
-          value={value}
-          options={this.props.fonts?.map(f => [f, f])}
-          onChange={this.changeFont.bind(this, i)}
-        />
-      </li>;
-    });
+  const inputs = values.map((value, i) => {
+    return <li
+      key={i}
+    >
+      <InputAutocomplete
+        aria-label={props["aria-label"] || props.name}
+        value={value}
+        options={fonts.map(f => [f, f])}
+        onChange={changeFont.bind(null, i)}
+      />
+    </li>;
+  });
 
-    return (
-      <ul className="maputnik-font">
-        {inputs}
-      </ul>
-    );
-  }
-}
+  return (
+    <ul className="maputnik-font">
+      {inputs}
+    </ul>
+  );
+};

src/components/InputJson.tsx

@@ -1,4 +1,4 @@
-import React from "react";
+import React, { useEffect, useRef } from "react";
 import classnames from "classnames";
 import { type WithTranslation, withTranslation } from "react-i18next";
 
@@ -25,88 +25,49 @@ export type InputJsonProps = {
 };
 type InputJsonInternalProps = InputJsonProps & WithTranslation;
 
-type InputJsonState = {
-  isEditing: boolean
-  prevValue: string
-};
+function getPrettyJson(data: any) {
+  return stringifyPretty(data, {indent: 2, maxLength: 40});
+}
 
-class InputJsonInternal extends React.Component<InputJsonInternalProps, InputJsonState> {
-  static defaultProps = {
-    onFocus: () => {},
-    onBlur: () => {},
-    withScroll: false
-  };
-  _view: EditorView | undefined;
-  _el: HTMLDivElement | null = null;
-  _cancelNextChange: boolean = false;
+const InputJsonInternal: React.FC<InputJsonInternalProps> = ({
+  value,
+  className,
+  onChange,
+  onFocus = () => {},
+  onBlur = () => {},
+  lintType,
+  spec,
+  withScroll = false,
+}) => {
+  const el = useRef<HTMLDivElement | null>(null);
+  const view = useRef<EditorView | undefined>(undefined);
+  const cancelNextChange = useRef<boolean>(false);
+  // `isEditing` and `prevValue` are never rendered, they are only read from the
+  // CodeMirror callbacks, so refs keep them up to date without re-rendering.
+  const isEditing = useRef<boolean>(false);
+  const prevValue = useRef<string>(getPrettyJson(value));
+  // Mirrors `prevProps.value` from the previous `componentDidUpdate`.
+  const prevValueProp = useRef<object>(value);
 
-  constructor(props: InputJsonInternalProps) {
-    super(props);
-    this.state = {
-      isEditing: false,
-      prevValue: this.getPrettyJson(this.props.value),
-    };
-  }
-
-  getPrettyJson(data: any) {
-    return stringifyPretty(data, {indent: 2, maxLength: 40});
-  }
-
-  componentDidMount () {
-    this._view = createEditor({
-      parent: this._el!,
-      value: this.getPrettyJson(this.props.value),
-      lintType: this.props.lintType || "layer",
-      onChange: (value:string) => this.onChange(value),
-      onFocus: () => this.onFocus(),
-      onBlur: () => this.onBlur(),
-      spec: this.props.spec
-    });
-  }
-
-  onFocus = () => {
-    if (this.props.onFocus) this.props.onFocus();
-    this.setState({
-      isEditing: true,
-    });
+  const handleFocus = () => {
+    if (onFocus) onFocus();
+    isEditing.current = true;
   };
 
-  onBlur = () => {
-    if (this.props.onBlur) this.props.onBlur();
-    this.setState({
-      isEditing: false,
-    });
+  const handleBlur = () => {
+    if (onBlur) onBlur();
+    isEditing.current = false;
   };
 
-  componentDidUpdate(prevProps: InputJsonProps) {
-    if (!this.state.isEditing && prevProps.value !== this.props.value) {
-      this._cancelNextChange = true;
-      const transactionSpec: TransactionSpec = {
-        changes: {
-          from: 0,
-          to: this._view!.state.doc.length,
-          insert: this.getPrettyJson(this.props.value)
-        }
-      };
-      if (this.props.withScroll) {
-        transactionSpec.selection = this._view!.state.selection;
-        transactionSpec.scrollIntoView = true;
-      }
-      this._view!.dispatch(transactionSpec);
-    }
-  }
-
-  onChange = (_e: unknown) => {
-    if (this._cancelNextChange) {
-      this._cancelNextChange = false;
-      this.setState({
-        prevValue: this._view!.state.doc.toString(),
-      });
+  const handleChange = () => {
+    if (cancelNextChange.current) {
+      cancelNextChange.current = false;
+      prevValue.current = view.current!.state.doc.toString();
       return;
     }
-    const newCode = this._view!.state.doc.toString();
+    const newCode = view.current!.state.doc.toString();
 
-    if (this.state.prevValue !== newCode) {
+    if (prevValue.current !== newCode) {
       let parsedLayer, err;
       try {
         parsedLayer = JSON.parse(newCode);
@@ -116,24 +77,63 @@ class InputJsonInternal extends React.Component<InputJsonInternalProps, InputJso
       }
 
       if (!err) {
-        if (this.props.onChange) this.props.onChange(parsedLayer);
+        if (onChange) onChange(parsedLayer);
       }
     }
 
-    this.setState({
-      prevValue: newCode,
-    });
+    prevValue.current = newCode;
   };
 
-  render() {
-    return <div className="json-editor" data-wd-key="json-editor" aria-hidden="true" style={{cursor: "text"}}>
-      <div
-        className={classnames("codemirror-container", this.props.className)}
-        ref={(el) => {this._el = el;}}
-      />
-    </div>;
-  }
-}
+  // The editor is created once on mount, so its callbacks have to go through a
+  // ref to always see the latest props.
+  const handlers = useRef({handleChange, handleFocus, handleBlur});
+  useEffect(() => {
+    handlers.current = {handleChange, handleFocus, handleBlur};
+  });
 
-const InputJson = withTranslation()(InputJsonInternal);
-export default InputJson;
+  useEffect(() => {
+    view.current = createEditor({
+      parent: el.current!,
+      value: getPrettyJson(value),
+      lintType: lintType || "layer",
+      onChange: () => handlers.current.handleChange(),
+      onFocus: () => handlers.current.handleFocus(),
+      onBlur: () => handlers.current.handleBlur(),
+      spec: spec
+    });
+    // Runs once on mount, mirroring the previous componentDidMount.
+    // eslint-disable-next-line react-hooks/exhaustive-deps -- mount-only: adding deps would rebuild the editor on every change
+  }, []);
+
+  useEffect(() => {
+    // Only react to an actual change of the `value` prop, which also skips the
+    // initial mount (the editor is created with the value already).
+    if (prevValueProp.current === value) return;
+    prevValueProp.current = value;
+
+    if (isEditing.current) return;
+
+    cancelNextChange.current = true;
+    const transactionSpec: TransactionSpec = {
+      changes: {
+        from: 0,
+        to: view.current!.state.doc.length,
+        insert: getPrettyJson(value)
+      }
+    };
+    if (withScroll) {
+      transactionSpec.selection = view.current!.state.selection;
+      transactionSpec.scrollIntoView = true;
+    }
+    view.current!.dispatch(transactionSpec);
+  }, [value, withScroll]);
+
+  return <div className="json-editor" data-wd-key="json-editor" aria-hidden="true" style={{cursor: "text"}}>
+    <div
+      className={classnames("codemirror-container", className)}
+      ref={el}
+    />
+  </div>;
+};
+
+export const InputJson = withTranslation()(InputJsonInternal);

src/components/InputMultiInput.tsx

@@ -9,31 +9,29 @@ export type InputMultiInputProps = {
   "aria-label"?: string
 };
 
-export default class InputMultiInput extends React.Component<InputMultiInputProps> {
-  render() {
-    let options = this.props.options;
-    if(options.length > 0 && !Array.isArray(options[0])) {
-      options = options.map(v => [v, v]);
-    }
-
-    const selectedValue = this.props.value || options[0][0];
-    const radios = options.map(([val, label])=> {
-      return <label
-        key={val}
-        className={classnames("maputnik-button", "maputnik-radio-as-button", {"maputnik-button-selected": val === selectedValue})}
-      >
-        <input type="radio"
-          name={this.props.name}
-          onChange={_e => this.props.onChange(val)}
-          value={val}
-          checked={val === selectedValue}
-        />
-        {label}
-      </label>;
-    });
-
-    return <fieldset className="maputnik-multibutton" aria-label={this.props["aria-label"]}>
-      {radios}
-    </fieldset>;
+export const InputMultiInput: React.FC<InputMultiInputProps> = (props) => {
+  let options = props.options;
+  if(options.length > 0 && !Array.isArray(options[0])) {
+    options = options.map(v => [v, v]);
   }
-}
+
+  const selectedValue = props.value || options[0][0];
+  const radios = options.map(([val, label])=> {
+    return <label
+      key={val}
+      className={classnames("maputnik-button", "maputnik-radio-as-button", {"maputnik-button-selected": val === selectedValue})}
+    >
+      <input type="radio"
+        name={props.name}
+        onChange={_e => props.onChange(val)}
+        value={val}
+        checked={val === selectedValue}
+      />
+      {label}
+    </label>;
+  });
+
+  return <fieldset className="maputnik-multibutton" aria-label={props["aria-label"]}>
+    {radios}
+  </fieldset>;
+};

src/components/InputNumber.tsx

@@ -1,5 +1,4 @@
-import React, { type BaseSyntheticEvent } from "react";
-import generateUniqueId from "../libs/document-uid";
+import React, { type BaseSyntheticEvent, useRef, useState } from "react";
 
 export type InputNumberProps = {
   value?: number
@@ -14,233 +13,206 @@ export type InputNumberProps = {
   "aria-label"?: string
 };
 
-type InputNumberState = {
-  uuid: number
-  editing: boolean
-  editingRange?: boolean
-  value?: number
-  /**
-   * This is the value that is currently being edited. It can be an invalid value.
-   */
-  dirtyValue?: number | string | undefined
-};
+export const InputNumber: React.FC<InputNumberProps> = (props) => {
+  const { rangeStep = 1 } = props;
 
-export default class InputNumber extends React.Component<InputNumberProps, InputNumberState> {
-  static defaultProps = {
-    rangeStep: 1
-  };
-  _keyboardEvent: boolean = false;
+  const [editing, setEditing] = useState(false);
+  const [editingRange, setEditingRange] = useState(false);
+  const [value, setValue] = useState<number | undefined>(props.value);
+  /** The value currently being edited. It can be an invalid value. */
+  const [dirtyValue, setDirtyValue] = useState<number | string | undefined>(props.value);
 
-  constructor(props: InputNumberProps) {
-    super(props);
-    this.state = {
-      uuid: +generateUniqueId(),
-      editing: false,
-      value: props.value,
-      dirtyValue: props.value,
-    };
+  const keyboardEvent = useRef(false);
+
+  // Replaces getDerivedStateFromProps: while not editing, track the prop.
+  if (!editing && props.value !== value) {
+    setValue(props.value);
+    setDirtyValue(props.value);
   }
 
-  static getDerivedStateFromProps(props: Readonly<InputNumberProps>, state: InputNumberState) {
-    if (!state.editing && props.value !== state.value) {
-      return {
-        value: props.value,
-        dirtyValue: props.value,
-      };
-    }
-    return null;
-  }
-
-  changeValue(newValue: number | string | undefined) {
-    const value = (newValue === "" || newValue === undefined) ?
-      undefined : +newValue;
-
-    const hasChanged = this.props.value !== value;
-    if(this.isValid(value) && hasChanged) {
-      if (this.props.onChange) this.props.onChange(value);
-      this.setState({
-        value: value,
-      });
-    }
-    else if (!this.isValid(value) && hasChanged) {
-      this.setState({
-        value: undefined,
-      });
-    }
-
-    this.setState({
-      dirtyValue: newValue === "" ? undefined : newValue,
-    });
-  }
-
-  isValid(v: number | string | undefined) {
+  function isValid(v: number | string | undefined) {
     if (v === undefined) {
       return true;
     }
 
-    const value = +v;
-    if(isNaN(value)) {
+    const val = +v;
+    if(isNaN(val)) {
       return false;
     }
 
-    if(!isNaN(this.props.min!) && value < this.props.min!) {
+    if(!isNaN(props.min!) && val < props.min!) {
       return false;
     }
 
-    if(!isNaN(this.props.max!) && value > this.props.max!) {
+    if(!isNaN(props.max!) && val > props.max!) {
       return false;
     }
 
     return true;
   }
 
-  resetValue = () => {
-    this.setState({editing: false});
+  function changeValue(newValue: number | string | undefined) {
+    const val = (newValue === "" || newValue === undefined) ?
+      undefined : +newValue;
+
+    const hasChanged = props.value !== val;
+    if(isValid(val) && hasChanged) {
+      if (props.onChange) props.onChange(val);
+      setValue(val);
+    }
+    else if (!isValid(val) && hasChanged) {
+      setValue(undefined);
+    }
+
+    setDirtyValue(newValue === "" ? undefined : newValue);
+  }
+
+  const resetValue = () => {
+    setEditing(false);
     // Reset explicitly to default value if value has been cleared
-    if(!this.state.value) {
+    if(!value) {
       return;
     }
 
     // If set value is invalid fall back to the last valid value from props or at last resort the default value
-    if (!this.isValid(this.state.value)) {
-      if(this.isValid(this.props.value)) {
-        this.changeValue(this.props.value);
-        this.setState({dirtyValue: this.props.value});
+    if (!isValid(value)) {
+      if(isValid(props.value)) {
+        changeValue(props.value);
+        setDirtyValue(props.value);
       } else {
-        this.changeValue(undefined);
-        this.setState({dirtyValue: undefined});
+        changeValue(undefined);
+        setDirtyValue(undefined);
       }
     }
   };
 
-  onChangeRange = (e: BaseSyntheticEvent<Event, HTMLInputElement, HTMLInputElement>) => {
-    let value = parseFloat(e.target.value);
-    const step = this.props.rangeStep;
-    let dirtyValue = value;
+  const onChangeRange = (e: BaseSyntheticEvent<Event, HTMLInputElement, HTMLInputElement>) => {
+    let newValue = parseFloat(e.target.value);
+    const step = rangeStep;
+    let newDirtyValue = newValue;
 
     if(step) {
       // Can't do this with the <input/> range step attribute else we won't be able to set a high precision value via the text input.
-      const snap = value % step;
+      const snap = newValue % step;
 
       // Round up/down to step
-      if (this._keyboardEvent) {
+      if (keyboardEvent.current) {
         // If it's keyboard event we might get a low positive/negative value,
         // for example we might go from 13 to 13.23, however because we know
         // that came from a keyboard event we always want to increase by a
         // single step value.
-        if (value < +this.state.dirtyValue!) {
-          value = this.state.value! - step;
+        if (newValue < +dirtyValue!) {
+          newValue = value! - step;
         }
         else {
-          value = this.state.value! + step;
+          newValue = value! + step;
         }
-        dirtyValue = value;
+        newDirtyValue = newValue;
       }
       else {
         if (snap < step/2) {
-          value = value - snap;
+          newValue = newValue - snap;
         }
         else {
-          value = value + (step - snap);
+          newValue = newValue + (step - snap);
         }
       }
     }
 
-    this._keyboardEvent = false;
+    keyboardEvent.current = false;
 
     // Clamp between min/max
-    value = Math.max(this.props.min!, Math.min(this.props.max!, value));
+    newValue = Math.max(props.min!, Math.min(props.max!, newValue));
 
-    this.setState({value, dirtyValue});
-    if (this.props.onChange) this.props.onChange(value);
+    setValue(newValue);
+    setDirtyValue(newDirtyValue);
+    if (props.onChange) props.onChange(newValue);
   };
 
-  render() {
-    if(
-      Object.prototype.hasOwnProperty.call(this.props, "min") &&
-      Object.prototype.hasOwnProperty.call(this.props, "max") &&
-      this.props.min !== undefined && this.props.max !== undefined &&
-      this.props.allowRange
-    ) {
-      const value = this.state.editing ? this.state.dirtyValue : this.state.value;
-      const defaultValue = this.props.default === undefined ? "" : this.props.default;
-      let inputValue;
-      if (this.state.editingRange) {
-        inputValue = this.state.value;
-      }
-      else {
-        inputValue = value;
-      }
-
-      return <div className="maputnik-number-container">
-        <input
-          className="maputnik-number-range"
-          key="range"
-          type="range"
-          max={this.props.max}
-          min={this.props.min}
-          step="any"
-          spellCheck="false"
-          value={value === undefined ? defaultValue : value}
-          onChange={this.onChangeRange}
-          onKeyDown={() => {
-            this._keyboardEvent = true;
-          }}
-          onPointerDown={() => {
-            this.setState({editing: true, editingRange: true});
-          }}
-          onPointerUp={() => {
-            // Safari doesn't get onBlur event
-            this.setState({editing: false, editingRange: false});
-          }}
-          onBlur={() => {
-            this.setState({
-              editing: false,
-              editingRange: false,
-              dirtyValue: this.state.value,
-            });
-          }}
-          data-wd-key={this.props["data-wd-key"] + "-range"}
-        />
-        <input
-          key="text"
-          type="text"
-          spellCheck="false"
-          className="maputnik-number"
-          placeholder={this.props.default?.toString()}
-          value={inputValue === undefined ? "" : inputValue}
-          onFocus={_e => {
-            this.setState({editing: true});
-          }}
-          onChange={e => {
-            this.changeValue(e.target.value);
-          }}
-          onBlur={_e => {
-            this.setState({editing: false});
-            this.resetValue();
-          }}
-          data-wd-key={this.props["data-wd-key"] + "-text"}
-
-        />
-      </div>;
+  if(
+    Object.prototype.hasOwnProperty.call(props, "min") &&
+    Object.prototype.hasOwnProperty.call(props, "max") &&
+    props.min !== undefined && props.max !== undefined &&
+    props.allowRange
+  ) {
+    const currentValue = editing ? dirtyValue : value;
+    const defaultValue = props.default === undefined ? "" : props.default;
+    let inputValue;
+    if (editingRange) {
+      inputValue = value;
     }
     else {
-      const value = this.state.editing ? this.state.dirtyValue : this.state.value;
+      inputValue = currentValue;
+    }
 
-      return <input
-        aria-label={this.props["aria-label"]}
+    return <div className="maputnik-number-container">
+      <input
+        className="maputnik-number-range"
+        key="range"
+        type="range"
+        max={props.max}
+        min={props.min}
+        step="any"
+        spellCheck="false"
+        value={currentValue === undefined ? defaultValue : currentValue}
+        onChange={onChangeRange}
+        onKeyDown={() => {
+          keyboardEvent.current = true;
+        }}
+        onPointerDown={() => {
+          setEditing(true);
+          setEditingRange(true);
+        }}
+        onPointerUp={() => {
+          // Safari doesn't get onBlur event
+          setEditing(false);
+          setEditingRange(false);
+        }}
+        onBlur={() => {
+          setEditing(false);
+          setEditingRange(false);
+          setDirtyValue(value);
+        }}
+        data-wd-key={props["data-wd-key"] + "-range"}
+      />
+      <input
+        key="text"
+        type="text"
         spellCheck="false"
         className="maputnik-number"
-        placeholder={this.props.default?.toString()}
-        value={value === undefined ? "" : value}
-        onChange={e => this.changeValue(e.target.value)}
-        onFocus={() => {
-          this.setState({editing: true});
+        placeholder={props.default?.toString()}
+        value={inputValue === undefined ? "" : inputValue}
+        onFocus={_e => {
+          setEditing(true);
         }}
-        onBlur={this.resetValue}
-        required={this.props.required}
-        data-wd-key={this.props["data-wd-key"]}
-      />;
-    }
+        onChange={e => {
+          changeValue(e.target.value);
+        }}
+        onBlur={_e => {
+          setEditing(false);
+          resetValue();
+        }}
+        data-wd-key={props["data-wd-key"] + "-text"}
+
+      />
+    </div>;
   }
-}
+  else {
+    const currentValue = editing ? dirtyValue : value;
+
+    return <input
+      aria-label={props["aria-label"]}
+      spellCheck="false"
+      className="maputnik-number"
+      placeholder={props.default?.toString()}
+      value={currentValue === undefined ? "" : currentValue}
+      onChange={e => changeValue(e.target.value)}
+      onFocus={() => {
+        setEditing(true);
+      }}
+      onBlur={resetValue}
+      required={props.required}
+      data-wd-key={props["data-wd-key"]}
+    />;
+  }
+};

src/components/InputSelect.tsx

@@ -10,23 +10,21 @@ export type InputSelectProps = {
   "aria-label"?: string
 };
 
-export default class InputSelect extends React.Component<InputSelectProps> {
-  render() {
-    let options = this.props.options;
-    if(options.length > 0 && !Array.isArray(options[0])) {
-      options = options.map((v) => [v, v]) as [string, any][];
-    }
-
-    return <select
-      className="maputnik-select"
-      data-wd-key={this.props["data-wd-key"]}
-      style={this.props.style}
-      title={this.props.title}
-      value={this.props.value}
-      onChange={e => this.props.onChange(e.target.value)}
-      aria-label={this.props["aria-label"]}
-    >
-      { options.map(([val, label]) => <option key={val} value={val}>{label}</option>) }
-    </select>;
+export const InputSelect: React.FC<InputSelectProps> = (props) => {
+  let options = props.options;
+  if(options.length > 0 && !Array.isArray(options[0])) {
+    options = options.map((v) => [v, v]) as [string, any][];
   }
-}
+
+  return <select
+    className="maputnik-select"
+    data-wd-key={props["data-wd-key"]}
+    style={props.style}
+    title={props.title}
+    value={props.value}
+    onChange={e => props.onChange(e.target.value)}
+    aria-label={props["aria-label"]}
+  >
+    { options.map(([val, label]) => <option key={val} value={val}>{label}</option>) }
+  </select>;
+};

src/components/InputSpec.tsx

@@ -1,14 +1,14 @@
 import React, { type ReactElement } from "react";
 
-import InputColor, { type InputColorProps } from "./InputColor";
-import InputNumber, { type InputNumberProps } from "./InputNumber";
-import InputCheckbox, { type InputCheckboxProps } from "./InputCheckbox";
-import InputString, { type InputStringProps } from "./InputString";
-import InputArray, { type InputArrayProps } from "./InputArray";
-import InputDynamicArray, { type InputDynamicArrayProps } from "./InputDynamicArray";
-import InputFont, { type InputFontProps } from "./InputFont";
-import InputAutocomplete, { type InputAutocompleteProps } from "./InputAutocomplete";
-import InputEnum, { type InputEnumProps } from "./InputEnum";
+import { InputColor, type InputColorProps } from "./InputColor";
+import { InputNumber, type InputNumberProps } from "./InputNumber";
+import { InputCheckbox, type InputCheckboxProps } from "./InputCheckbox";
+import { InputString, type InputStringProps } from "./InputString";
+import { InputArray, type InputArrayProps } from "./InputArray";
+import { InputDynamicArray, type InputDynamicArrayProps } from "./InputDynamicArray";
+import { InputFont, type InputFontProps } from "./InputFont";
+import { InputAutocomplete, type InputAutocompleteProps } from "./InputAutocomplete";
+import { InputEnum, type InputEnumProps } from "./InputEnum";
 import capitalize from "lodash.capitalize";
 
 const iconProperties = ["background-pattern", "fill-pattern", "line-pattern", "fill-extrusion-pattern", "icon-image"];
@@ -38,31 +38,31 @@ export type InputSpecProps = {
 /** Display any field from the Maplibre GL style spec and
  * choose the correct field component based on the @{fieldSpec}
  * to display @{value}. */
-export default class InputSpec extends React.Component<InputSpecProps> {
+export const InputSpec: React.FC<InputSpecProps> = (props) => {
 
-  childNodes() {
+  const childNodes = () => {
     const commonProps = {
-      fieldSpec: this.props.fieldSpec,
-      label: this.props.label,
-      action: this.props.action,
-      style: this.props.style,
-      value: this.props.value,
-      default: this.props.fieldSpec?.default,
-      name: this.props.fieldName,
-      "data-wd-key": "spec-field-input:" + this.props.fieldName,
-      onChange: (newValue: number | undefined | (string | number | undefined)[]) => this.props.onChange!(this.props.fieldName, newValue),
-      "aria-label": this.props["aria-label"],
+      fieldSpec: props.fieldSpec,
+      label: props.label,
+      action: props.action,
+      style: props.style,
+      value: props.value,
+      default: props.fieldSpec?.default,
+      name: props.fieldName,
+      "data-wd-key": "spec-field-input:" + props.fieldName,
+      onChange: (newValue: number | undefined | (string | number | undefined)[]) => props.onChange!(props.fieldName, newValue),
+      "aria-label": props["aria-label"],
     };
-    switch(this.props.fieldSpec?.type) {
+    switch(props.fieldSpec?.type) {
       case "number": return (
         <InputNumber
           {...commonProps as InputNumberProps}
-          min={this.props.fieldSpec.minimum}
-          max={this.props.fieldSpec.maximum}
+          min={props.fieldSpec.minimum}
+          max={props.fieldSpec.maximum}
         />
       );
       case "enum": {
-        const options = Object.keys(this.props.fieldSpec.values || []).map(v => [v, capitalize(v)]);
+        const options = Object.keys(props.fieldSpec.values || []).map(v => [v, capitalize(v)]);
 
         return <InputEnum
           {...commonProps as Omit<InputEnumProps, "options">}
@@ -72,8 +72,8 @@ export default class InputSpec extends React.Component<InputSpecProps> {
       case "resolvedImage":
       case "formatted":
       case "string":
-        if (iconProperties.indexOf(this.props.fieldName!) >= 0) {
-          const options = this.props.fieldSpec.values || [];
+        if (iconProperties.indexOf(props.fieldName!) >= 0) {
+          const options = props.fieldSpec.values || [];
           return <InputAutocomplete
             {...commonProps as Omit<InputAutocompleteProps, "options">}
             options={options.map(f => [f, f])}
@@ -94,61 +94,59 @@ export default class InputSpec extends React.Component<InputSpecProps> {
         />
       );
       case "array":
-        if(this.props.fieldName === "text-font") {
+        if(props.fieldName === "text-font") {
           return <InputFont
             {...commonProps as InputFontProps}
-            fonts={this.props.fieldSpec.values}
+            fonts={props.fieldSpec.values}
           />;
         } else {
-          if (this.props.fieldSpec.length) {
+          if (props.fieldSpec.length) {
             return <InputArray
               {...commonProps as InputArrayProps}
-              type={this.props.fieldSpec.value}
-              length={this.props.fieldSpec.length}
+              type={props.fieldSpec.value}
+              length={props.fieldSpec.length}
             />;
           } else {
             return <InputDynamicArray
               {...commonProps as InputDynamicArrayProps}
-              fieldSpec={this.props.fieldSpec}
-              type={this.props.fieldSpec.value as InputDynamicArrayProps["type"]}
+              fieldSpec={props.fieldSpec}
+              type={props.fieldSpec.value as InputDynamicArrayProps["type"]}
             />;
           }
         }
       case "numberArray": return (
         <InputDynamicArray
           {...commonProps as InputDynamicArrayProps}
-          fieldSpec={this.props.fieldSpec}
+          fieldSpec={props.fieldSpec}
           type="number"
-          value={(Array.isArray(this.props.value) ? this.props.value : [this.props.value]) as (string | number | undefined)[]}
+          value={(Array.isArray(props.value) ? props.value : [props.value]) as (string | number | undefined)[]}
         />
       );
       case "colorArray": return (
         <InputDynamicArray
           {...commonProps as InputDynamicArrayProps}
-          fieldSpec={this.props.fieldSpec}
+          fieldSpec={props.fieldSpec}
           type="color"
-          value={(Array.isArray(this.props.value) ? this.props.value : [this.props.value]) as (string | number | undefined)[]}
+          value={(Array.isArray(props.value) ? props.value : [props.value]) as (string | number | undefined)[]}
         />
       );
       case "padding": return (
         <InputArray
           {...commonProps as InputArrayProps}
           type="number"
-          value={(Array.isArray(this.props.value) ? this.props.value : [this.props.value]) as (string | number | undefined)[]}
+          value={(Array.isArray(props.value) ? props.value : [props.value]) as (string | number | undefined)[]}
           length={4}
         />
       );
       default:
-        console.warn(`No proper field input for ${this.props.fieldName} type: ${this.props.fieldSpec?.type}`);
+        console.warn(`No proper field input for ${props.fieldName} type: ${props.fieldSpec?.type}`);
         return null;
     }
-  }
+  };
 
-  render() {
-    return (
-      <div data-wd-key={"spec-field:"+this.props.fieldName}>
-        {this.childNodes()}
-      </div>
-    );
-  }
-}
+  return (
+    <div data-wd-key={"spec-field:"+props.fieldName}>
+      {childNodes()}
+    </div>
+  );
+};

src/components/InputString.tsx

@@ -1,4 +1,4 @@
-import React from "react";
+import React, { useState } from "react";
 
 export type InputStringProps = {
   "data-wd-key"?: string
@@ -15,85 +15,66 @@ export type InputStringProps = {
   title?: string
 };
 
-type InputStringState = {
-  editing: boolean
-  value?: string
+export const InputString: React.FC<InputStringProps> = (props) => {
+  const { onInput = () => {} } = props;
+  const [editing, setEditing] = useState(false);
+  const [value, setValue] = useState<string | undefined>(props.value);
+
+  // Replaces getDerivedStateFromProps: while the field is not being edited its
+  // value tracks the prop, so an external change to the style is picked up.
+  if (!editing && value !== props.value) {
+    setValue(props.value);
+  }
+
+  let tag;
+  let classes;
+
+  if(props.multi) {
+    tag = "textarea";
+    classes = [
+      "maputnik-string",
+      "maputnik-string--multi"
+    ];
+  }
+  else {
+    tag = "input";
+    classes = [
+      "maputnik-string"
+    ];
+  }
+
+  if(props.disabled) {
+    classes.push("maputnik-string--disabled");
+  }
+
+  return React.createElement(tag, {
+    "aria-label": props["aria-label"],
+    "data-wd-key": props["data-wd-key"],
+    spellCheck: Object.prototype.hasOwnProperty.call(props, "spellCheck") ? props.spellCheck : !(tag === "input"),
+    disabled: props.disabled,
+    className: classes.join(" "),
+    style: props.style,
+    value: value === undefined ? "" : value,
+    placeholder: props.default,
+    title: props.title,
+    onChange: (e: React.BaseSyntheticEvent<Event, HTMLInputElement, HTMLInputElement>) => {
+      setEditing(true);
+      setValue(e.target.value);
+      onInput(e.target.value);
+    },
+    onBlur: () => {
+      // Note: editing is only cleared when the value actually changed; this
+      // mirrors the original and keeps a no-op blur from resyncing the value.
+      if(value !== props.value) {
+        setEditing(false);
+        if (props.onChange) props.onChange(value);
+      }
+    },
+    onKeyDown: (e: React.KeyboardEvent) => {
+      if (e.keyCode === 13 && props.onChange) {
+        props.onChange(value);
+      }
+    },
+    required: props.required,
+  });
 };
-
-export default class InputString extends React.Component<InputStringProps, InputStringState> {
-  static defaultProps = {
-    onInput: () => {},
-  };
-
-  constructor(props: InputStringProps) {
-    super(props);
-    this.state = {
-      editing: false,
-      value: props.value || ""
-    };
-  }
-
-  static getDerivedStateFromProps(props: Readonly<InputStringProps>, state: InputStringState) {
-    if (!state.editing) {
-      return {
-        value: props.value
-      };
-    }
-    return {};
-  }
-
-  render() {
-    let tag;
-    let classes;
-
-    if(this.props.multi) {
-      tag = "textarea";
-      classes = [
-        "maputnik-string",
-        "maputnik-string--multi"
-      ];
-    }
-    else {
-      tag = "input";
-      classes = [
-        "maputnik-string"
-      ];
-    }
-
-    if(this.props.disabled) {
-      classes.push("maputnik-string--disabled");
-    }
-
-    return React.createElement(tag, {
-      "aria-label": this.props["aria-label"],
-      "data-wd-key": this.props["data-wd-key"],
-      spellCheck: Object.prototype.hasOwnProperty.call(this.props, "spellCheck") ? this.props.spellCheck : !(tag === "input"),
-      disabled: this.props.disabled,
-      className: classes.join(" "),
-      style: this.props.style,
-      value: this.state.value === undefined ? "" : this.state.value,
-      placeholder: this.props.default,
-      title: this.props.title,
-      onChange: (e: React.BaseSyntheticEvent<Event, HTMLInputElement, HTMLInputElement>) => {
-        this.setState({
-          editing: true,
-          value: e.target.value
-        }, () => {
-          if (this.props.onInput) this.props.onInput(this.state.value);
-        });
-      },
-      onBlur: () => {
-        if(this.state.value!==this.props.value) {
-          this.setState({editing: false});
-          if (this.props.onChange) this.props.onChange(this.state.value);
-        }
-      },
-      onKeyDown: (e) => {
-        if (e.keyCode === 13 && this.props.onChange) {
-          this.props.onChange(this.state.value);
-        }
-      },
-      required: this.props.required,
-    });
-  }
-}

src/components/InputUrl.tsx

@@ -1,6 +1,6 @@
-import React, { type JSX } from "react";
-import InputString from "./InputString";
-import SmallError from "./SmallError";
+import React, { type JSX, useState } from "react";
+import { InputString } from "./InputString";
+import { SmallError } from "./SmallError";
 import { Trans, type WithTranslation, withTranslation } from "react-i18next";
 import { type TFunction } from "i18next";
 import { ErrorType, validate } from "../libs/urlopen";
@@ -46,50 +46,30 @@ export type FieldUrlProps = {
 
 type InputUrlInternalProps = FieldUrlProps & WithTranslation;
 
-type InputUrlState = {
-  error?: ErrorType
+const InputUrlInternal: React.FC<InputUrlInternalProps> = ({onInput = () => {}, ...props}) => {
+  const [error, setError] = useState<ErrorType | undefined>(() => validate(props.value));
+
+  const handleInput = (url: string) => {
+    setError(validate(url));
+    onInput(url);
+  };
+
+  const handleChange = (url: string) => {
+    setError(validate(url));
+    props.onChange(url);
+  };
+
+  return (
+    <div>
+      <InputString
+        {...props}
+        onInput={handleInput}
+        onChange={handleChange}
+        aria-label={props["aria-label"]}
+      />
+      {errorTypeToJsx(error, props.t)}
+    </div>
+  );
 };
 
-class InputUrlInternal extends React.Component<InputUrlInternalProps, InputUrlState> {
-  static defaultProps = {
-    onInput: () => {},
-  };
-
-  constructor (props: InputUrlInternalProps) {
-    super(props);
-    this.state = {
-      error: validate(props.value),
-    };
-  }
-
-  onInput = (url: string) => {
-    this.setState({
-      error: validate(url),
-    });
-    if (this.props.onInput) this.props.onInput(url);
-  };
-
-  onChange = (url: string) => {
-    this.setState({
-      error: validate(url),
-    });
-    this.props.onChange(url);
-  };
-
-  render () {
-    return (
-      <div>
-        <InputString
-          {...this.props}
-          onInput={this.onInput}
-          onChange={this.onChange}
-          aria-label={this.props["aria-label"]}
-        />
-        {errorTypeToJsx(this.state.error, this.props.t)}
-      </div>
-    );
-  }
-}
-
-const InputUrl = withTranslation()(InputUrlInternal);
-export default InputUrl;
+export const InputUrl = withTranslation()(InputUrlInternal);

src/components/LayerEditor.tsx

@@ -1,4 +1,4 @@
-import React, { type JSX } from "react";
+import React, { type JSX, useState } from "react";
 import { Wrapper, Button, Menu, MenuItem } from "react-aria-menubutton";
 import { Accordion } from "react-accessible-accordion";
 import { MdMoreVert } from "react-icons/md";
@@ -6,18 +6,20 @@ import { IconContext } from "react-icons";
 import { type BackgroundLayerSpecification, type LayerSpecification, type SourceSpecification } from "maplibre-gl";
 import { v8 } from "@maplibre/maplibre-gl-style-spec";
 
-import FieldJson from "./FieldJson";
-import FilterEditor from "./FilterEditor";
-import PropertyGroup from "./PropertyGroup";
-import LayerEditorGroup from "./LayerEditorGroup";
-import FieldType from "./FieldType";
-import FieldId from "./FieldId";
-import FieldMinZoom from "./FieldMinZoom";
-import FieldMaxZoom from "./FieldMaxZoom";
-import FieldComment from "./FieldComment";
-import FieldSource from "./FieldSource";
-import FieldSourceLayer from "./FieldSourceLayer";
-import { changeType, changeProperty } from "../libs/layer";
+import { FieldJson } from "./FieldJson";
+import { FilterEditor } from "./FilterEditor";
+import { PropertyGroup } from "./PropertyGroup";
+import { LayerEditorGroup } from "./LayerEditorGroup";
+import { FieldType } from "./FieldType";
+import { FieldId } from "./FieldId";
+import { FieldMinZoom } from "./FieldMinZoom";
+import { FieldMaxZoom } from "./FieldMaxZoom";
+import { FieldComment } from "./FieldComment";
+import { FieldSource } from "./FieldSource";
+import { FieldSourceLayer } from "./FieldSourceLayer";
+// Aliased: the component defines its own changeProperty, which would otherwise
+// shadow this import (as a class method there was no collision).
+import { changeType, changeProperty as changeLayerProperty } from "../libs/layer";
 import { formatLayerId } from "../libs/format";
 import { type WithTranslation, withTranslation } from "react-i18next";
 import { type TFunction } from "i18next";
@@ -131,67 +133,56 @@ type LayerEditorInternalProps = {
   errors?: MappedError[]
 } & WithTranslation;
 
-type LayerEditorState = {
-  editorGroups: { [keys: string]: boolean }
-};
-
 /** Layer editor supporting multiple types of layers. */
-class LayerEditorInternal extends React.Component<LayerEditorInternalProps, LayerEditorState> {
-  static defaultProps = {
-    onLayerChanged: () => { },
-    onLayerIdChange: () => { },
-    onLayerDestroyed: () => { },
-  };
+const LayerEditorInternal: React.FC<LayerEditorInternalProps> = ({
+  onLayerChanged = () => { },
+  onLayerIdChange = () => { },
+  ...rest
+}) => {
+  const props = { onLayerChanged, onLayerIdChange, ...rest } as LayerEditorInternalProps;
 
-  constructor(props: LayerEditorInternalProps) {
-    super(props);
-
-    const editorGroups: { [keys: string]: boolean } = {};
-    for (const group of layoutGroups(this.props.layer.type, props.t)) {
-      editorGroups[group.title] = true;
+  const [editorGroups, setEditorGroups] = useState<{ [keys: string]: boolean }>(() => {
+    const groups: { [keys: string]: boolean } = {};
+    for (const group of layoutGroups(props.layer.type, props.t)) {
+      groups[group.title] = true;
     }
+    return groups;
+  });
 
-    this.state = { editorGroups };
+  // Replaces getDerivedStateFromProps: groups that appear after mount (because
+  // the layer type changed) start out expanded. Guarded so it only sets state
+  // when a group is genuinely new, otherwise this would loop every render.
+  const newGroups = getLayoutForType(props.layer.type, props.t)
+    .filter(group => !(group.title in editorGroups));
+  if (newGroups.length > 0) {
+    const additionalGroups = { ...editorGroups };
+    for (const group of newGroups) {
+      additionalGroups[group.title] = true;
+    }
+    setEditorGroups(additionalGroups);
   }
 
-  static getDerivedStateFromProps(props: Readonly<LayerEditorInternalProps>, state: LayerEditorState) {
-    const additionalGroups = { ...state.editorGroups };
-
-    for (const group of getLayoutForType(props.layer.type, props.t)) {
-      if (!(group.title in additionalGroups)) {
-        additionalGroups[group.title] = true;
-      }
-    }
-
-    return {
-      editorGroups: additionalGroups
-    };
-  }
-
-
-  changeProperty(group: keyof LayerSpecification | null, property: string, newValue: any) {
-    this.props.onLayerChanged(
-      this.props.layerIndex,
-      changeProperty(this.props.layer, group, property, newValue)
+  function changeProperty(group: keyof LayerSpecification | null, property: string, newValue: any) {
+    props.onLayerChanged(
+      props.layerIndex,
+      changeLayerProperty(props.layer, group, property, newValue)
     );
   }
 
-  onGroupToggle(groupTitle: string, active: boolean) {
+  function onGroupToggle(groupTitle: string, active: boolean) {
     const changedActiveGroups = {
-      ...this.state.editorGroups,
+      ...editorGroups,
       [groupTitle]: active,
     };
-    this.setState({
-      editorGroups: changedActiveGroups
-    });
+    setEditorGroups(changedActiveGroups);
   }
 
-  renderGroupType(type: string, fields?: string[]): JSX.Element {
+  function renderGroupType(type: string, fields?: string[]): JSX.Element {
     let comment = "";
-    if (this.props.layer.metadata) {
-      comment = (this.props.layer.metadata as any)["maputnik:comment"];
+    if (props.layer.metadata) {
+      comment = (props.layer.metadata as any)["maputnik:comment"];
     }
-    const { errors, layerIndex } = this.props;
+    const { errors, layerIndex } = props;
 
     const errorData: MappedLayerErrors = {};
     errors!.forEach(error => {
@@ -207,84 +198,85 @@ class LayerEditorInternal extends React.Component<LayerEditorInternalProps, Laye
     });
 
     let sourceLayerIds;
-    const layer = this.props.layer as Exclude<LayerSpecification, BackgroundLayerSpecification>;
-    if (Object.prototype.hasOwnProperty.call(this.props.sources, layer.source)) {
-      sourceLayerIds = this.props.sources[layer.source].layers;
+    const layer = props.layer as Exclude<LayerSpecification, BackgroundLayerSpecification>;
+    if (Object.prototype.hasOwnProperty.call(props.sources, layer.source)) {
+      sourceLayerIds = props.sources[layer.source].layers;
     }
 
     switch (type) {
       case "layer": return <div>
         <FieldId
-          value={this.props.layer.id}
+          value={props.layer.id}
           wdKey="layer-editor.layer-id"
           error={errorData.id}
-          onChange={newId => this.props.onLayerIdChange(this.props.layerIndex, this.props.layer.id, newId)}
+          onChange={newId => props.onLayerIdChange(props.layerIndex, props.layer.id, newId)}
         />
         <FieldType
           disabled={true}
           error={errorData.type}
-          value={this.props.layer.type}
-          onChange={newType => this.props.onLayerChanged(
-            this.props.layerIndex,
-            changeType(this.props.layer, newType)
+          value={props.layer.type}
+          onChange={newType => props.onLayerChanged(
+            props.layerIndex,
+            changeType(props.layer, newType)
           )}
         />
-        {this.props.layer.type !== "background" && <FieldSource
+        {props.layer.type !== "background" && <FieldSource
+          wdKey="layer-editor.layer-source"
           error={errorData.source}
-          sourceIds={Object.keys(this.props.sources!)}
-          value={this.props.layer.source}
-          onChange={v => this.changeProperty(null, "source", v)}
+          sourceIds={Object.keys(props.sources!)}
+          value={props.layer.source}
+          onChange={v => changeProperty(null, "source", v)}
         />
         }
-        {!NON_SOURCE_LAYERS.includes(this.props.layer.type) &&
+        {!NON_SOURCE_LAYERS.includes(props.layer.type) &&
           <FieldSourceLayer
             error={errorData["source-layer"]}
             sourceLayerIds={sourceLayerIds}
-            value={(this.props.layer as any)["source-layer"]}
-            onChange={v => this.changeProperty(null, "source-layer", v)}
+            value={(props.layer as any)["source-layer"]}
+            onChange={v => changeProperty(null, "source-layer", v)}
           />
         }
         <FieldMinZoom
           error={errorData.minzoom}
-          value={this.props.layer.minzoom}
-          onChange={v => this.changeProperty(null, "minzoom", v)}
+          value={props.layer.minzoom}
+          onChange={v => changeProperty(null, "minzoom", v)}
         />
         <FieldMaxZoom
           error={errorData.maxzoom}
-          value={this.props.layer.maxzoom}
-          onChange={v => this.changeProperty(null, "maxzoom", v)}
+          value={props.layer.maxzoom}
+          onChange={v => changeProperty(null, "maxzoom", v)}
         />
         <FieldComment
           error={errorData.comment}
           value={comment}
-          onChange={v => this.changeProperty("metadata", "maputnik:comment", v == "" ? undefined : v)}
+          onChange={v => changeProperty("metadata", "maputnik:comment", v == "" ? undefined : v)}
         />
       </div>;
       case "filter": return <div>
         <div className="maputnik-filter-editor-wrapper">
           <FilterEditor
             errors={errorData}
-            filter={(this.props.layer as any).filter}
-            properties={this.props.vectorLayers[(this.props.layer as any)["source-layer"]]}
-            onChange={f => this.changeProperty(null, "filter", f)}
+            filter={(props.layer as any).filter}
+            properties={props.vectorLayers[(props.layer as any)["source-layer"]]}
+            onChange={f => changeProperty(null, "filter", f)}
           />
         </div>
       </div>;
       case "properties":
         return <PropertyGroup
           errors={errorData}
-          layer={this.props.layer}
+          layer={props.layer}
           groupFields={fields!}
-          spec={this.props.spec}
-          onChange={this.changeProperty.bind(this)}
+          spec={props.spec}
+          onChange={changeProperty.bind(null)}
         />;
       case "jsoneditor":
         return <FieldJson
           lintType="layer"
-          value={this.props.layer}
+          value={props.layer}
           onChange={(layer: LayerSpecification) => {
-            this.props.onLayerChanged(
-              this.props.layerIndex,
+            props.onLayerChanged(
+              props.layerIndex,
               layer
             );
           }}
@@ -293,131 +285,128 @@ class LayerEditorInternal extends React.Component<LayerEditorInternalProps, Laye
     }
   }
 
-  moveLayer(offset: number) {
-    this.props.onMoveLayer({
-      oldIndex: this.props.layerIndex,
-      newIndex: this.props.layerIndex + offset
+  function moveLayer(offset: number) {
+    props.onMoveLayer({
+      oldIndex: props.layerIndex,
+      newIndex: props.layerIndex + offset
     });
   }
 
-  render() {
-    const t = this.props.t;
+  const t = props.t;
 
-    const groupIds: string[] = [];
-    const layerType = this.props.layer.type;
-    const groups = layoutGroups(layerType, t).filter(group => {
-      return !(layerType === "background" && group.type === "source");
-    }).map(group => {
-      const groupId = group.id;
-      groupIds.push(groupId);
-      return <LayerEditorGroup
-        data-wd-key={group.title}
-        id={groupId}
-        key={groupId}
-        title={group.title}
-        isActive={this.state.editorGroups[group.title]}
-        onActiveToggle={this.onGroupToggle.bind(this, group.title)}
-      >
-        {this.renderGroupType(group.type, group.fields)}
-      </LayerEditorGroup>;
-    });
+  const groupIds: string[] = [];
+  const layerType = props.layer.type;
+  const groups = layoutGroups(layerType, t).filter(group => {
+    return !(layerType === "background" && group.type === "source");
+  }).map(group => {
+    const groupId = group.id;
+    groupIds.push(groupId);
+    return <LayerEditorGroup
+      data-wd-key={group.title}
+      id={groupId}
+      key={groupId}
+      title={group.title}
+      isActive={editorGroups[group.title]}
+      onActiveToggle={onGroupToggle.bind(null, group.title)}
+    >
+      {renderGroupType(group.type, group.fields)}
+    </LayerEditorGroup>;
+  });
 
-    const layout = this.props.layer.layout || {};
+  const layout = props.layer.layout || {};
 
-    const items: {
-      [key: string]: {
-        text: string,
-        handler: () => void,
-        disabled?: boolean,
-        wdKey?: string
-      }
-    } = {
-      delete: {
-        text: t("Delete"),
-        handler: () => this.props.onLayerDestroy(this.props.layerIndex),
-        wdKey: "menu-delete-layer"
-      },
-      duplicate: {
-        text: t("Duplicate"),
-        handler: () => this.props.onLayerCopy(this.props.layerIndex),
-        wdKey: "menu-duplicate-layer"
-      },
-      hide: {
-        text: (layout.visibility === "none") ? t("Show") : t("Hide"),
-        handler: () => this.props.onLayerVisibilityToggle(this.props.layerIndex),
-        wdKey: "menu-hide-layer"
-      },
-      moveLayerUp: {
-        text: t("Move layer up"),
-        disabled: this.props.isFirstLayer,
-        handler: () => this.moveLayer(-1),
-        wdKey: "menu-move-layer-up"
-      },
-      moveLayerDown: {
-        text: t("Move layer down"),
-        disabled: this.props.isLastLayer,
-        handler: () => this.moveLayer(+1),
-        wdKey: "menu-move-layer-down"
-      }
-    };
-
-    function handleSelection(id: string, event: React.SyntheticEvent) {
-      event.stopPropagation();
-      items[id].handler();
+  const items: {
+    [key: string]: {
+      text: string,
+      handler: () => void,
+      disabled?: boolean,
+      wdKey?: string
     }
+  } = {
+    delete: {
+      text: t("Delete"),
+      handler: () => props.onLayerDestroy(props.layerIndex),
+      wdKey: "menu-delete-layer"
+    },
+    duplicate: {
+      text: t("Duplicate"),
+      handler: () => props.onLayerCopy(props.layerIndex),
+      wdKey: "menu-duplicate-layer"
+    },
+    hide: {
+      text: (layout.visibility === "none") ? t("Show") : t("Hide"),
+      handler: () => props.onLayerVisibilityToggle(props.layerIndex),
+      wdKey: "menu-hide-layer"
+    },
+    moveLayerUp: {
+      text: t("Move layer up"),
+      disabled: props.isFirstLayer,
+      handler: () => moveLayer(-1),
+      wdKey: "menu-move-layer-up"
+    },
+    moveLayerDown: {
+      text: t("Move layer down"),
+      disabled: props.isLastLayer,
+      handler: () => moveLayer(+1),
+      wdKey: "menu-move-layer-down"
+    }
+  };
 
-    return <IconContext.Provider value={{ size: "14px", color: "#8e8e8e" }}>
-      <section className="maputnik-layer-editor"
-        role="main"
-        aria-label={t("Layer editor")}
-        data-wd-key="layer-editor"
-      >
-        <header data-wd-key="layer-editor.header">
-          <div className="layer-header">
-            <h2 className="layer-header__title">
-              {t("Layer")}: {formatLayerId(this.props.layer.id)}
-            </h2>
-            <div className="layer-header__info">
-              <Wrapper
-                className='more-menu'
-                onSelection={(id, event) => handleSelection(id as string, event)}
-                closeOnSelection={false}
-              >
-                <Button
-                  id="skip-target-layer-editor"
-                  data-wd-key="skip-target-layer-editor"
-                  className='more-menu__button'
-                  title={"Layer options"}>
-                  <MdMoreVert className="more-menu__button__svg" />
-                </Button>
-                <Menu>
-                  <ul className="more-menu__menu">
-                    {Object.keys(items).map((id) => {
-                      const item = items[id];
-                      return <li key={id}>
-                        <MenuItem value={id} className='more-menu__menu__item' data-wd-key={item.wdKey}>
-                          {item.text}
-                        </MenuItem>
-                      </li>;
-                    })}
-                  </ul>
-                </Menu>
-              </Wrapper>
-            </div>
-          </div>
-
-        </header>
-        <Accordion
-          allowMultipleExpanded={true}
-          allowZeroExpanded={true}
-          preExpanded={groupIds}
-        >
-          {groups}
-        </Accordion>
-      </section>
-    </IconContext.Provider>;
+  function handleSelection(id: string, event: React.SyntheticEvent) {
+    event.stopPropagation();
+    items[id].handler();
   }
-}
 
-const LayerEditor = withTranslation()(LayerEditorInternal);
-export default LayerEditor;
+  return <IconContext.Provider value={{ size: "14px", color: "#8e8e8e" }}>
+    <section className="maputnik-layer-editor"
+      role="main"
+      aria-label={t("Layer editor")}
+      data-wd-key="layer-editor"
+    >
+      <header data-wd-key="layer-editor.header">
+        <div className="layer-header">
+          <h2 className="layer-header__title">
+            {t("Layer")}: {formatLayerId(props.layer.id)}
+          </h2>
+          <div className="layer-header__info">
+            <Wrapper
+              className='more-menu'
+              onSelection={(id, event) => handleSelection(id as string, event)}
+              closeOnSelection={false}
+            >
+              <Button
+                id="skip-target-layer-editor"
+                data-wd-key="skip-target-layer-editor"
+                className='more-menu__button'
+                title={"Layer options"}>
+                <MdMoreVert className="more-menu__button__svg" />
+              </Button>
+              <Menu>
+                <ul className="more-menu__menu">
+                  {Object.keys(items).map((id) => {
+                    const item = items[id];
+                    return <li key={id}>
+                      <MenuItem value={id} className='more-menu__menu__item' data-wd-key={item.wdKey}>
+                        {item.text}
+                      </MenuItem>
+                    </li>;
+                  })}
+                </ul>
+              </Menu>
+            </Wrapper>
+          </div>
+        </div>
+
+      </header>
+      <Accordion
+        allowMultipleExpanded={true}
+        allowZeroExpanded={true}
+        preExpanded={groupIds}
+      >
+        {groups}
+      </Accordion>
+    </section>
+  </IconContext.Provider>;
+};
+
+export const LayerEditor = withTranslation()(LayerEditorInternal);

src/components/LayerEditorGroup.tsx

@@ -18,22 +18,20 @@ type LayerEditorGroupProps = {
 };
 
 
-export default class LayerEditorGroup extends React.Component<LayerEditorGroupProps> {
-  render() {
-    return <AccordionItem uuid={this.props.id}>
-      <AccordionItemHeading className="maputnik-layer-editor-group"
-        data-wd-key={"layer-editor-group:"+this.props["data-wd-key"]}
-        onClick={_e => this.props.onActiveToggle(!this.props.isActive)}
-      >
-        <AccordionItemButton className="maputnik-layer-editor-group__button">
-          <span style={{flexGrow: 1, alignContent: "center"}}>{this.props.title}</span>
-          <MdArrowDropUp size={"2em"} className="maputnik-layer-editor-group__button__icon maputnik-layer-editor-group__button__icon--up"></MdArrowDropUp>
-          <MdArrowDropDown size={"2em"} className="maputnik-layer-editor-group__button__icon maputnik-layer-editor-group__button__icon--down"></MdArrowDropDown>
-        </AccordionItemButton>
-      </AccordionItemHeading>
-      <AccordionItemPanel>
-        {this.props.children}
-      </AccordionItemPanel>
-    </AccordionItem>;
-  }
-}
+export const LayerEditorGroup: React.FC<LayerEditorGroupProps> = (props) => {
+  return <AccordionItem uuid={props.id}>
+    <AccordionItemHeading className="maputnik-layer-editor-group"
+      data-wd-key={"layer-editor-group:"+props["data-wd-key"]}
+      onClick={_e => props.onActiveToggle(!props.isActive)}
+    >
+      <AccordionItemButton className="maputnik-layer-editor-group__button">
+        <span style={{flexGrow: 1, alignContent: "center"}}>{props.title}</span>
+        <MdArrowDropUp size={"2em"} className="maputnik-layer-editor-group__button__icon maputnik-layer-editor-group__button__icon--up"></MdArrowDropUp>
+        <MdArrowDropDown size={"2em"} className="maputnik-layer-editor-group__button__icon maputnik-layer-editor-group__button__icon--down"></MdArrowDropDown>
+      </AccordionItemButton>
+    </AccordionItemHeading>
+    <AccordionItemPanel>
+      {props.children}
+    </AccordionItemPanel>
+  </AccordionItem>;
+};

src/components/LayerList.tsx

@@ -1,4 +1,4 @@
-import React, {type JSX} from "react";
+import React, {type JSX, useEffect, useRef, useState} from "react";
 import classnames from "classnames";
 import lodash from "lodash";
 import {
@@ -14,12 +14,12 @@ import {
   verticalListSortingStrategy,
 } from "@dnd-kit/sortable";
 
-import LayerListGroup from "./LayerListGroup";
-import LayerListItem from "./LayerListItem";
-import ModalAdd from "./modals/ModalAdd";
+import { LayerListGroup } from "./LayerListGroup";
+import { LayerListItem } from "./LayerListItem";
+import { ModalAdd } from "./modals/ModalAdd";
 
 import type {LayerSpecification, SourceSpecification} from "maplibre-gl";
-import generateUniqueId from "../libs/document-uid";
+import { generateUniqueId } from "../libs/document-uid";
 import { findClosestCommonPrefix, layerPrefix } from "../libs/layer";
 import { type WithTranslation, withTranslation } from "react-i18next";
 import { type MappedError, type OnMoveLayerCallback } from "../libs/definitions";
@@ -37,62 +37,98 @@ type LayerListContainerProps = {
 };
 type LayerListContainerInternalProps = LayerListContainerProps & WithTranslation;
 
-type LayerListContainerState = {
-  collapsedGroups: {[ket: string]: boolean}
-  areAllGroupsExpanded: boolean
-  keys: {[key: string]: number}
-  isOpen: {[key: string]: boolean}
-};
+const noopLayerSelect = () => {};
+
+// Replaces the previous `shouldComponentUpdate`. Note the inversion: this
+// returns true when the props are EQUAL (i.e. no re-render is needed), whereas
+// `shouldComponentUpdate` returned true when a re-render WAS needed.
+function arePropsEqual(prevProps: LayerListContainerInternalProps, nextProps: LayerListContainerInternalProps) {
+  // This component tree only requires id and visibility from the layers
+  // objects
+  function getRequiredProps(layer: LayerSpecification) {
+    const out: {id: string, layout?: { visibility: any}} = {
+      id: layer.id,
+    };
+
+    if (layer.layout) {
+      out.layout = {
+        visibility: layer.layout.visibility
+      };
+    }
+    return out;
+  }
+  const layersEqual = lodash.isEqual(
+    nextProps.layers.map(getRequiredProps),
+    prevProps.layers.map(getRequiredProps),
+  );
+
+  function withoutLayers(props: LayerListContainerInternalProps) {
+    const out = {
+      ...props
+    } as LayerListContainerInternalProps & { layers?: any };
+    delete out["layers"];
+    return out;
+  }
+
+  // Compare the props without layers because we've already compared them
+  // efficiently above.
+  const propsEqual = lodash.isEqual(
+    withoutLayers(prevProps),
+    withoutLayers(nextProps)
+  );
+
+  return layersEqual && propsEqual;
+}
 
 // List of collapsible layer editors
-class LayerListContainerInternal extends React.Component<LayerListContainerInternalProps, LayerListContainerState> {
-  static defaultProps = {
-    onLayerSelect: () => {},
-  };
-  selectedItemRef: React.RefObject<any>;
-  scrollContainerRef: React.RefObject<HTMLElement | null>;
+function LayerListContainerInternal({
+  layers: propsLayers,
+  selectedLayerIndex,
+  onLayersChange,
+  onLayerSelect = noopLayerSelect,
+  onLayerDestroy,
+  onLayerCopy,
+  onLayerVisibilityToggle,
+  sources,
+  errors,
+  t,
+}: LayerListContainerInternalProps) {
+  const selectedItemRef = useRef<any>(null);
+  const scrollContainerRef = useRef<HTMLElement | null>(null);
+  const hasMountedRef = useRef(false);
 
-  constructor(props: LayerListContainerInternalProps) {
-    super(props);
-    this.selectedItemRef = React.createRef();
-    this.scrollContainerRef = React.createRef();
-    this.state = {
-      collapsedGroups: {},
-      areAllGroupsExpanded: false,
-      keys: {
-        add: +generateUniqueId(),
-      },
-      isOpen: {
-        add: false,
-      }
-    };
+  const [collapsedGroups, setCollapsedGroups] = useState<{[key: string]: boolean}>({});
+  const [areAllGroupsExpanded, setAreAllGroupsExpanded] = useState(false);
+  const [keys, setKeys] = useState<{[key: string]: number}>(() => ({
+    add: +generateUniqueId(),
+  }));
+  const [isOpen, setIsOpen] = useState<{[key: string]: boolean}>({
+    add: false,
+  });
+
+  function toggleModal(modalName: string) {
+    setKeys(prevKeys => ({
+      ...prevKeys,
+      [modalName]: +generateUniqueId(),
+    }));
+    setIsOpen(prevIsOpen => ({
+      ...prevIsOpen,
+      [modalName]: !prevIsOpen[modalName]
+    }));
   }
 
-  toggleModal(modalName: string) {
-    this.setState({
-      keys: {
-        ...this.state.keys,
-        [modalName]: +generateUniqueId(),
-      },
-      isOpen: {
-        ...this.state.isOpen,
-        [modalName]: !this.state.isOpen[modalName]
-      }
-    });
-  }
-
-  toggleLayers = () => {
+  const toggleLayers = () => {
     let idx = 0;
 
     const newGroups: {[key:string]: boolean} = {};
 
-    this.groupedLayers().forEach(layers => {
+    groupedLayers().forEach(layers => {
       const groupPrefix = layerPrefix(layers[0].id);
       const lookupKey = [groupPrefix, idx].join("-");
 
 
       if (layers.length > 1) {
-        newGroups[lookupKey] = this.state.areAllGroupsExpanded;
+        newGroups[lookupKey] = areAllGroupsExpanded;
       }
 
       layers.forEach((_layer) => {
@@ -100,19 +136,17 @@ class LayerListContainerInternal extends React.Component<LayerListContainerInter
       });
     });
 
-    this.setState({
-      collapsedGroups: newGroups,
-      areAllGroupsExpanded: !this.state.areAllGroupsExpanded
-    });
+    setCollapsedGroups(newGroups);
+    setAreAllGroupsExpanded(!areAllGroupsExpanded);
   };
 
-  groupedLayers(): (LayerSpecification & {key: string})[][] {
+  function groupedLayers(): (LayerSpecification & {key: string})[][] {
     const groups = [];
     const layerIdCount = new Map();
 
-    for (let i = 0; i < this.props.layers.length; i++) {
-      const origLayer = this.props.layers[i];
-      const previousLayer = this.props.layers[i-1];
+    for (let i = 0; i < propsLayers.length; i++) {
+      const origLayer = propsLayers[i];
+      const previousLayer = propsLayers[i-1];
       layerIdCount.set(origLayer.id,
         layerIdCount.has(origLayer.id) ? layerIdCount.get(origLayer.id) + 1 : 0
       );
@@ -130,213 +164,168 @@ class LayerListContainerInternal extends React.Component<LayerListContainerInter
     return groups;
   }
 
-  toggleLayerGroup(groupPrefix: string, idx: number) {
+  function toggleLayerGroup(groupPrefix: string, idx: number) {
     const lookupKey = [groupPrefix, idx].join("-");
-    const newGroups = { ...this.state.collapsedGroups };
-    if(lookupKey in this.state.collapsedGroups) {
-      newGroups[lookupKey] = !this.state.collapsedGroups[lookupKey];
-    } else {
-      newGroups[lookupKey] = false;
-    }
-    this.setState({
-      collapsedGroups: newGroups
+    setCollapsedGroups(prevCollapsedGroups => {
+      const newGroups = { ...prevCollapsedGroups };
+      if(lookupKey in prevCollapsedGroups) {
+        newGroups[lookupKey] = !prevCollapsedGroups[lookupKey];
+      } else {
+        newGroups[lookupKey] = false;
+      }
+      return newGroups;
     });
   }
 
-  isCollapsed(groupPrefix: string, idx: number) {
-    const collapsed = this.state.collapsedGroups[[groupPrefix, idx].join("-")];
+  function isCollapsed(groupPrefix: string, idx: number) {
+    const collapsed = collapsedGroups[[groupPrefix, idx].join("-")];
     return collapsed === undefined ? true : collapsed;
   }
 
-  shouldComponentUpdate (nextProps: LayerListContainerProps, nextState: LayerListContainerState) {
-    // Always update on state change
-    if (this.state !== nextState) {
-      return true;
+  useEffect(() => {
+    // `componentDidUpdate` did not run on mount, so skip the first run here too.
+    if (!hasMountedRef.current) {
+      hasMountedRef.current = true;
+      return;
     }
-
-    // This component tree only requires id and visibility from the layers
-    // objects
-    function getRequiredProps(layer: LayerSpecification) {
-      const out: {id: string, layout?: { visibility: any}} = {
-        id: layer.id,
+    const selectedItemNode = selectedItemRef.current;
+    if (selectedItemNode && selectedItemNode.node) {
+      const target = selectedItemNode.node;
+      const options = {
+        root: scrollContainerRef.current,
+        threshold: 1.0
       };
-
-      if (layer.layout) {
-        out.layout = {
-          visibility: layer.layout.visibility
-        };
-      }
-      return out;
-    }
-    const layersEqual = lodash.isEqual(
-      nextProps.layers.map(getRequiredProps),
-      this.props.layers.map(getRequiredProps),
-    );
-
-    function withoutLayers(props: LayerListContainerProps) {
-      const out = {
-        ...props
-      } as LayerListContainerProps & { layers?: any };
-      delete out["layers"];
-      return out;
-    }
-
-    // Compare the props without layers because we've already compared them
-    // efficiently above.
-    const propsEqual = lodash.isEqual(
-      withoutLayers(this.props),
-      withoutLayers(nextProps)
-    );
-
-    const propsChanged = !(layersEqual && propsEqual);
-    return propsChanged;
-  }
-
-  componentDidUpdate (prevProps: LayerListContainerProps) {
-    if (prevProps.selectedLayerIndex !== this.props.selectedLayerIndex) {
-      const selectedItemNode = this.selectedItemRef.current;
-      if (selectedItemNode && selectedItemNode.node) {
-        const target = selectedItemNode.node;
-        const options = {
-          root: this.scrollContainerRef.current,
-          threshold: 1.0
-        };
-        const observer = new IntersectionObserver(entries => {
-          observer.unobserve(target);
-          if (entries.length > 0 && entries[0].intersectionRatio < 1) {
-            target.scrollIntoView();
-          }
-        }, options);
-
-        observer.observe(target);
-      }
-    }
-  }
-
-  render() {
-
-    const listItems: JSX.Element[] = [];
-    let idx = 0;
-    const layersByGroup = this.groupedLayers();
-    layersByGroup.forEach(layers => {
-      const groupPrefix = layerPrefix(layers[0].id);
-      if(layers.length > 1) {
-        const grp = <LayerListGroup
-          data-wd-key={[groupPrefix, idx].join("-")}
-          aria-controls={layers.map(l => l.key).join(" ")}
-          key={`group-${groupPrefix}-${idx}`}
-          title={groupPrefix}
-          isActive={!this.isCollapsed(groupPrefix, idx) || idx === this.props.selectedLayerIndex}
-          onActiveToggle={this.toggleLayerGroup.bind(this, groupPrefix, idx)}
-        />;
-        listItems.push(grp);
-      }
-
-      layers.forEach((layer, idxInGroup) => {
-        const groupIdx = findClosestCommonPrefix(this.props.layers, idx);
-
-        const layerError = this.props.errors.find(error => {
-          return (
-            error.parsed &&
-            error.parsed.type === "layer" &&
-            error.parsed.data.index == idx
-          );
-        });
-
-        const additionalProps: {ref?: React.RefObject<any>} = {};
-        if (idx === this.props.selectedLayerIndex) {
-          additionalProps.ref = this.selectedItemRef;
+      const observer = new IntersectionObserver(entries => {
+        observer.unobserve(target);
+        if (entries.length > 0 && entries[0].intersectionRatio < 1) {
+          target.scrollIntoView();
         }
+      }, options);
 
-        const listItem = <LayerListItem
-          className={classnames({
-            "maputnik-layer-list-item-collapsed": layers.length > 1 && this.isCollapsed(groupPrefix, groupIdx) && idx !== this.props.selectedLayerIndex,
-            "maputnik-layer-list-item-group-last": idxInGroup == layers.length - 1 && layers.length > 1,
-            "maputnik-layer-list-item--error": !!layerError
-          })}
-          key={layer.key}
-          id={layer.key}
-          layerId={layer.id}
-          layerIndex={idx}
-          layerType={layer.type}
-          visibility={(layer.layout || {}).visibility}
-          isSelected={idx === this.props.selectedLayerIndex}
-          onLayerSelect={this.props.onLayerSelect}
-          onLayerDestroy={this.props.onLayerDestroy?.bind(this)}
-          onLayerCopy={this.props.onLayerCopy.bind(this)}
-          onLayerVisibilityToggle={this.props.onLayerVisibilityToggle.bind(this)}
-          {...additionalProps}
-        />;
-        listItems.push(listItem);
-        idx += 1;
+      observer.observe(target);
+    }
+  }, [selectedLayerIndex]);
+
+  const listItems: JSX.Element[] = [];
+  let idx = 0;
+  const layersByGroup = groupedLayers();
+  layersByGroup.forEach(layers => {
+    const groupPrefix = layerPrefix(layers[0].id);
+    if(layers.length > 1) {
+      const currentIdx = idx;
+      const grp = <LayerListGroup
+        data-wd-key={[groupPrefix, idx].join("-")}
+        aria-controls={layers.map(l => l.key).join(" ")}
+        key={`group-${groupPrefix}-${idx}`}
+        title={groupPrefix}
+        isActive={!isCollapsed(groupPrefix, idx) || idx === selectedLayerIndex}
+        onActiveToggle={() => toggleLayerGroup(groupPrefix, currentIdx)}
+      />;
+      listItems.push(grp);
+    }
+
+    layers.forEach((layer, idxInGroup) => {
+      const groupIdx = findClosestCommonPrefix(propsLayers, idx);
+
+      const layerError = errors.find(error => {
+        return (
+          error.parsed &&
+          error.parsed.type === "layer" &&
+          error.parsed.data.index == idx
+        );
       });
+
+      const additionalProps: {ref?: React.RefObject<any>} = {};
+      if (idx === selectedLayerIndex) {
+        additionalProps.ref = selectedItemRef;
+      }
+
+      const listItem = <LayerListItem
+        className={classnames({
+          "maputnik-layer-list-item-collapsed": layers.length > 1 && isCollapsed(groupPrefix, groupIdx) && idx !== selectedLayerIndex,
+          "maputnik-layer-list-item-group-last": idxInGroup == layers.length - 1 && layers.length > 1,
+          "maputnik-layer-list-item--error": !!layerError
+        })}
+        key={layer.key}
+        id={layer.key}
+        layerId={layer.id}
+        layerIndex={idx}
+        layerType={layer.type}
+        visibility={(layer.layout || {}).visibility}
+        isSelected={idx === selectedLayerIndex}
+        onLayerSelect={onLayerSelect}
+        onLayerDestroy={onLayerDestroy}
+        onLayerCopy={onLayerCopy}
+        onLayerVisibilityToggle={onLayerVisibilityToggle}
+        {...additionalProps}
+      />;
+      listItems.push(listItem);
+      idx += 1;
     });
+  });
 
-    const t = this.props.t;
-
-    return <section
-      className="maputnik-layer-list"
-      data-wd-key="layer-list"
-      role="complementary"
-      aria-label={t("Layers list")}
-      ref={this.scrollContainerRef}
-    >
-      <ModalAdd
-        key={this.state.keys.add}
-        layers={this.props.layers}
-        sources={this.props.sources}
-        isOpen={this.state.isOpen.add}
-        onOpenToggle={this.toggleModal.bind(this, "add")}
-        onLayersChange={this.props.onLayersChange}
-      />
-      <header className="maputnik-layer-list-header" data-wd-key="layer-list.header">
-        <span className="maputnik-layer-list-header-title">{t("Layers")}</span>
-        <span className="maputnik-space" />
-        <div className="maputnik-default-property">
-          <div className="maputnik-multibutton">
-            <button
-              id="skip-target-layer-list"
-              data-wd-key="skip-target-layer-list"
-              onClick={this.toggleLayers}
-              className="maputnik-button">
-              {this.state.areAllGroupsExpanded === true ?
-                t("Collapse")
-                :
-                t("Expand")
-              }
-            </button>
-          </div>
+  return <section
+    className="maputnik-layer-list"
+    data-wd-key="layer-list"
+    role="complementary"
+    aria-label={t("Layers list")}
+    ref={scrollContainerRef}
+  >
+    <ModalAdd
+      key={keys.add}
+      layers={propsLayers}
+      sources={sources}
+      isOpen={isOpen.add}
+      onOpenToggle={() => toggleModal("add")}
+      onLayersChange={onLayersChange}
+    />
+    <header className="maputnik-layer-list-header" data-wd-key="layer-list.header">
+      <span className="maputnik-layer-list-header-title">{t("Layers")}</span>
+      <span className="maputnik-space" />
+      <div className="maputnik-default-property">
+        <div className="maputnik-multibutton">
+          <button
+            id="skip-target-layer-list"
+            data-wd-key="skip-target-layer-list"
+            onClick={toggleLayers}
+            className="maputnik-button">
+            {areAllGroupsExpanded === true ?
+              t("Collapse")
+              :
+              t("Expand")
+            }
+          </button>
         </div>
-        <div className="maputnik-default-property">
-          <div className="maputnik-multibutton">
-            <button
-              onClick={this.toggleModal.bind(this, "add")}
-              data-wd-key="layer-list:add-layer"
-              className="maputnik-button maputnik-button-selected">
-              {t("Add Layer")}
-            </button>
-          </div>
-        </div>
-      </header>
-      <div
-        role="navigation"
-        aria-label={t("Layers list")}
-      >
-        <ul className="maputnik-layer-list-container">
-          {listItems}
-        </ul>
       </div>
-    </section>;
-  }
+      <div className="maputnik-default-property">
+        <div className="maputnik-multibutton">
+          <button
+            onClick={() => toggleModal("add")}
+            data-wd-key="layer-list:add-layer"
+            className="maputnik-button maputnik-button-selected">
+            {t("Add Layer")}
+          </button>
+        </div>
+      </div>
+    </header>
+    <div
+      role="navigation"
+      aria-label={t("Layers list")}
+    >
+      <ul className="maputnik-layer-list-container">
+        {listItems}
+      </ul>
+    </div>
+  </section>;
 }
 
-const LayerListContainer = withTranslation()(LayerListContainerInternal);
+const LayerListContainer = withTranslation()(React.memo(LayerListContainerInternal, arePropsEqual));
 
 type LayerListProps = LayerListContainerProps & {
   onMoveLayer: OnMoveLayerCallback
 };
 
-const LayerList: React.FC<LayerListProps> = (props) => {
+export const LayerList: React.FC<LayerListProps> = (props) => {
   const sensors = useSensors(useSensor(PointerSensor, { activationConstraint: { distance: 5 } }));
 
   const handleDragEnd = (event: DragEndEvent) => {
@@ -361,5 +350,3 @@ const LayerList: React.FC<LayerListProps> = (props) => {
     </DndContext>
   );
 };
-
-export default LayerList;

src/components/LayerListGroup.tsx

@@ -1,5 +1,5 @@
 import React from "react";
-import Collapser from "./Collapser";
+import { Collapser } from "./Collapser";
 
 type LayerListGroupProps = {
   title: string
@@ -9,26 +9,24 @@ type LayerListGroupProps = {
   "aria-controls"?: string
 };
 
-export default class LayerListGroup extends React.Component<LayerListGroupProps> {
-  render() {
-    return <li className="maputnik-layer-list-group">
-      <div className="maputnik-layer-list-group-header"
-        data-wd-key={"layer-list-group:"+this.props["data-wd-key"]}
-        onClick={_e => this.props.onActiveToggle(!this.props.isActive)}
+export const LayerListGroup: React.FC<LayerListGroupProps> = (props) => {
+  return <li className="maputnik-layer-list-group">
+    <div className="maputnik-layer-list-group-header"
+      data-wd-key={"layer-list-group:"+props["data-wd-key"]}
+      onClick={_e => props.onActiveToggle(!props.isActive)}
+    >
+      <button
+        className="maputnik-layer-list-group-title"
+        aria-controls={props["aria-controls"]}
+        aria-expanded={props.isActive}
       >
-        <button
-          className="maputnik-layer-list-group-title"
-          aria-controls={this.props["aria-controls"]}
-          aria-expanded={this.props.isActive}
-        >
-          {this.props.title}
-        </button>
-        <span className="maputnik-space" />
-        <Collapser
-          style={{ height: 14, width: 14 }}
-          isCollapsed={this.props.isActive}
-        />
-      </div>
-    </li>;
-  }
-}
+        {props.title}
+      </button>
+      <span className="maputnik-space" />
+      <Collapser
+        style={{ height: 14, width: 14 }}
+        isCollapsed={props.isActive}
+      />
+    </div>
+  </li>;
+};

src/components/LayerListItem.tsx

@@ -5,7 +5,7 @@ import { IconContext } from "react-icons";
 import { useSortable } from "@dnd-kit/sortable";
 import { CSS } from "@dnd-kit/utilities";
 
-import IconLayer from "./IconLayer";
+import { IconLayer } from "./IconLayer";
 import type { VisibilitySpecification } from "maplibre-gl";
 
 
@@ -38,9 +38,9 @@ type IconActionProps = {
   classBlockModifier?: string
 };
 
-class IconAction extends React.Component<IconActionProps> {
-  renderIcon() {
-    switch (this.props.action) {
+const IconAction: React.FC<IconActionProps> = (props) => {
+  function renderIcon() {
+    switch (props.action) {
       case "duplicate": return <MdContentCopy />;
       case "show": return <MdVisibility />;
       case "hide": return <MdVisibilityOff />;
@@ -48,30 +48,28 @@ class IconAction extends React.Component<IconActionProps> {
     }
   }
 
-  render() {
-    const { classBlockName, classBlockModifier } = this.props;
+  const { classBlockName, classBlockModifier } = props;
 
-    let classAdditions = "";
-    if (classBlockName) {
-      classAdditions = `maputnik-layer-list-icon-action__${classBlockName}`;
+  let classAdditions = "";
+  if (classBlockName) {
+    classAdditions = `maputnik-layer-list-icon-action__${classBlockName}`;
 
-      if (classBlockModifier) {
-        classAdditions += ` maputnik-layer-list-icon-action__${classBlockName}--${classBlockModifier}`;
-      }
+    if (classBlockModifier) {
+      classAdditions += ` maputnik-layer-list-icon-action__${classBlockName}--${classBlockModifier}`;
     }
-
-    return <button
-      tabIndex={-1}
-      title={this.props.action}
-      className={`maputnik-layer-list-icon-action ${classAdditions}`}
-      data-wd-key={this.props.wdKey}
-      onClick={this.props.onClick}
-      aria-hidden="true"
-    >
-      {this.renderIcon()}
-    </button>;
   }
-}
+
+  return <button
+    tabIndex={-1}
+    title={props.action}
+    className={`maputnik-layer-list-icon-action ${classAdditions}`}
+    data-wd-key={props.wdKey}
+    onClick={props.onClick}
+    aria-hidden="true"
+  >
+    {renderIcon()}
+  </button>;
+};
 
 type LayerListItemProps = {
   id?: string
@@ -87,7 +85,7 @@ type LayerListItemProps = {
   onLayerVisibilityToggle?(...args: unknown[]): unknown
 };
 
-const LayerListItem = React.forwardRef<HTMLLIElement, LayerListItemProps>((props, ref) => {
+export const LayerListItem = React.forwardRef<HTMLLIElement, LayerListItemProps>((props, ref) => {
   const {
     isSelected = false,
     visibility = "visible",
@@ -162,5 +160,3 @@ const LayerListItem = React.forwardRef<HTMLLIElement, LayerListItemProps>((props
     </li>
   </IconContext.Provider>;
 });
-
-export default LayerListItem;

src/components/MapMaplibreGl.tsx

@@ -1,12 +1,12 @@
-import React from "react";
+import React, {useCallback, useEffect, useReducer, useRef} from "react";
 import {createRoot} from "react-dom/client";
 import MapLibreGl, {type LayerSpecification, type LngLat, type Map, type MapOptions, type SourceSpecification, type StyleSpecification} from "maplibre-gl";
 import MaplibreInspect from "@maplibre/maplibre-gl-inspect";
 import colors from "@maplibre/maplibre-gl-inspect/lib/colors";
-import MapMaplibreGlLayerPopup from "./MapMaplibreGlLayerPopup";
-import MapMaplibreGlFeaturePropertyPopup, { type InspectFeature } from "./MapMaplibreGlFeaturePropertyPopup";
+import { FeatureLayerPopup as MapMaplibreGlLayerPopup } from "./MapMaplibreGlLayerPopup";
+import { FeaturePropertyPopup as MapMaplibreGlFeaturePropertyPopup, type InspectFeature } from "./MapMaplibreGlFeaturePropertyPopup";
 import Color from "color";
-import ZoomControl from "../libs/zoomcontrol";
+import { ZoomControl } from "../libs/zoomcontrol";
 import { type HighlightedLayer, colorHighlightedLayer } from "../libs/highlight";
 import "maplibre-gl/dist/maplibre-gl.css";
 import "../maplibregl.css";
@@ -71,199 +71,65 @@ type MapMaplibreGlInternalProps = {
   onChange(value: {center: LngLat, zoom: number, _from: "map" | "app"}): unknown
 } & WithTranslation;
 
-type MapMaplibreGlState = {
-  map: Map | null;
-  inspect: MaplibreInspect | null;
-  geocoder: MaplibreGeocoder | null;
-  zoomControl: ZoomControl | null;
-  zoom?: number;
-};
-
-class MapMaplibreGlInternal extends React.Component<MapMaplibreGlInternalProps, MapMaplibreGlState> {
-  static defaultProps = {
-    onMapLoaded: () => {},
-    onDataChange: () => {},
-    onLayerSelect: () => {},
-    onChange: () => {},
-    options: {} as MapOptions,
-  };
-  container: HTMLDivElement | null = null;
-
-  constructor(props: MapMaplibreGlInternalProps) {
-    super(props);
-    this.state = {
-      map: null,
-      inspect: null,
-      geocoder: null,
-      zoomControl: null,
-    };
-    i18next.on("languageChanged", () => {
-      this.forceUpdate();
-    });
+/**
+ * Replacement for the previous `shouldComponentUpdate`. `React.memo` expects the
+ * inverse: `true` means "props are equal, skip the render", whereas
+ * `shouldComponentUpdate` returned `true` when it *should* re-render.
+ * As before, if the props cannot be serialized we treat them as equal and skip
+ * the render ("no biggie, carry on").
+ */
+function arePropsEqual(prevProps: MapMaplibreGlInternalProps, nextProps: MapMaplibreGlInternalProps) {
+  let should = false;
+  try {
+    should = JSON.stringify(prevProps) !== JSON.stringify(nextProps);
+  } catch(_e) {
+    // no biggie, carry on
   }
+  return !should;
+}
 
+const MapMaplibreGlInternal = ({
+  onDataChange = () => {},
+  onLayerSelect = () => {},
+  onChange = () => {},
+  options = {},
+  mapStyle,
+  mapView,
+  inspectModeEnabled,
+  highlightedLayer,
+  replaceAccessTokens,
+  t,
+}: MapMaplibreGlInternalProps) => {
+  const container = useRef<HTMLDivElement | null>(null);
 
-  shouldComponentUpdate(nextProps: MapMaplibreGlInternalProps, nextState: MapMaplibreGlState) {
-    let should = false;
-    try {
-      should = JSON.stringify(this.props) !== JSON.stringify(nextProps) || JSON.stringify(this.state) !== JSON.stringify(nextState);
-    } catch(_e) {
-      // no biggie, carry on
-    }
-    return should;
-  }
+  // These used to live in `this.state`, but were never able to trigger a
+  // re-render: `shouldComponentUpdate` stringified the state, which throws for
+  // the (circular) maplibre `Map`, so the comparison was swallowed and the
+  // component only ever re-rendered on prop changes. They are imperative
+  // handles, so they are refs here and mutating them does not re-render.
+  const map = useRef<Map | null>(null);
+  const inspect = useRef<MaplibreInspect | null>(null);
+  const geocoder = useRef<MaplibreGeocoder | null>(null);
+  const zoomControl = useRef<ZoomControl | null>(null);
+  const zoom = useRef<number | undefined>(undefined);
 
-  componentDidUpdate() {
-    const map = this.state.map;
+  // `componentDidUpdate` did not run on mount, so neither may the effect below.
+  const hasMounted = useRef(false);
 
-    const styleWithTokens = this.props.replaceAccessTokens(this.props.mapStyle);
-    if (map) {
-      // Maplibre GL now does diffing natively so we don't need to calculate
-      // the necessary operations ourselves!
-      // We also need to update the style for inspect to work properly
-      map.setStyle(styleWithTokens, {diff: true});
-      map.showTileBoundaries = this.props.options?.showTileBoundaries!;
-      map.showCollisionBoxes = this.props.options?.showCollisionBoxes!;
-      map.showOverdrawInspector = this.props.options?.showOverdrawInspector!;
+  const [, forceUpdate] = useReducer((tick: number) => tick + 1, 0);
 
-      // set the map view when the prop was updated from outside
-      if (this.props.mapView._from === "app") {
-        map.jumpTo(this.props.mapView);
-      }
-    }
+  // The maplibre event handlers/callbacks below are registered once (on mount)
+  // but read `this.props` at call time in the class version, so they must not
+  // close over the props of the first render.
+  const latestProps = useRef({onDataChange, onLayerSelect, onChange, mapStyle, inspectModeEnabled, highlightedLayer, t});
+  latestProps.current = {onDataChange, onLayerSelect, onChange, mapStyle, inspectModeEnabled, highlightedLayer, t};
 
-    if(this.state.inspect && this.props.inspectModeEnabled !== this.state.inspect._showInspectMap) {
-      this.state.inspect.toggleInspector();
-    }
-    if (this.state.inspect && this.props.inspectModeEnabled) {
-      this.state.inspect.setOriginalStyle(styleWithTokens);
-      // In case the sources are the same, there's a need to refresh the style
-      setTimeout(() => {
-        this.state.inspect!.render();
-      }, 500);
-    }
+  const onLayerSelectById = useCallback((id: string) => {
+    const index = latestProps.current.mapStyle.layers.findIndex(layer => layer.id === id);
+    latestProps.current.onLayerSelect(index);
+  }, []);
 
-  }
-
-  componentDidMount() {
-    const mapOpts = {
-      ...this.props.options,
-      container: this.container!,
-      style: this.props.mapStyle,
-      hash: true,
-      maxZoom: 24,
-      // make root relative urls in stylefiles work as maplibre gl js does
-      // not support this for everything:
-      // https://github.com/maplibre/maplibre-gl-js/issues/6818
-      transformRequest: (url) => {
-        if (url.startsWith("/")) {
-          url = `${window.location.origin}${url}`;
-        }
-        return { url };
-      },
-      // setting to always load glyphs of CJK fonts from server
-      // https://maplibre.org/maplibre-gl-js/docs/examples/local-ideographs/
-      localIdeographFontFamily: false
-    } satisfies MapOptions;
-
-    const protocol = new Protocol({metadata: true});
-    MapLibreGl.addProtocol("pmtiles",protocol.tile);
-    const map = new MapLibreGl.Map(mapOpts);
-
-    const mapViewChange = () => {
-      const center = map.getCenter();
-      const zoom = map.getZoom();
-      this.props.onChange({center, zoom, _from: "map"});
-    };
-    mapViewChange();
-
-    map.showTileBoundaries = mapOpts.showTileBoundaries!;
-    map.showCollisionBoxes = mapOpts.showCollisionBoxes!;
-    map.showOverdrawInspector = mapOpts.showOverdrawInspector!;
-
-    const geocoder = this.initGeocoder(map);
-
-    const zoomControl = new ZoomControl();
-    map.addControl(zoomControl, "top-right");
-
-    const nav = new MapLibreGl.NavigationControl({visualizePitch:true});
-    map.addControl(nav, "top-right");
-
-    const tmpNode = document.createElement("div");
-    const root = createRoot(tmpNode);
-
-    const inspectPopup = new MapLibreGl.Popup({
-      closeOnClick: false
-    });
-
-    const inspect = new MaplibreInspect({
-      popup: inspectPopup,
-      showMapPopup: true,
-      showMapPopupOnHover: false,
-      showInspectMapPopupOnHover: true,
-      showInspectButton: false,
-      blockHoverPopupOnClick: true,
-      assignLayerColor: (layerId: string, alpha: number) => {
-        return Color(colors.brightColor(layerId, alpha)).desaturate(0.5).string();
-      },
-      buildInspectStyle: (originalMapStyle: StyleSpecification, coloredLayers: HighlightedLayer[]) => buildInspectStyle(originalMapStyle, coloredLayers, this.props.highlightedLayer),
-      renderPopup: (features: InspectFeature[]) => {
-        if(this.props.inspectModeEnabled) {
-          inspectPopup.once("open", () => {
-            root.render(<MapMaplibreGlFeaturePropertyPopup features={features} />);
-          });
-          return tmpNode;
-        } else {
-          inspectPopup.once("open", () => {
-            root.render(<MapMaplibreGlLayerPopup
-              features={features}
-              onLayerSelect={this.onLayerSelectById}
-              zoom={this.state.zoom}
-            />,);
-          });
-          return tmpNode;
-        }
-      }
-    });
-    map.addControl(inspect);
-
-    map.on("style.load", () => {
-      this.setState({
-        map,
-        inspect,
-        geocoder,
-        zoomControl,
-        zoom: map.getZoom()
-      });
-    });
-
-    map.on("data", e => {
-      if(e.dataType !== "tile") return;
-      this.props.onDataChange!({
-        map: this.state.map
-      });
-    });
-
-    map.on("error", e => {
-      console.log("ERROR", e);
-    });
-
-    map.on("zoom", _e => {
-      this.setState({
-        zoom: map.getZoom()
-      });
-    });
-
-    map.on("dragend", mapViewChange);
-    map.on("zoomend", mapViewChange);
-  }
-
-  onLayerSelectById = (id: string) => {
-    const index = this.props.mapStyle.layers.findIndex(layer => layer.id === id);
-    this.props.onLayerSelect(index);
-  };
-
-  initGeocoder(map: Map) {
+  const initGeocoder = useCallback((mapInstance: Map) => {
     const geocoderConfig = {
       forwardGeocode: async (config: MaplibreGeocoderApiConfig) => {
         const features = [];
@@ -300,27 +166,190 @@ class MapMaplibreGlInternal extends React.Component<MapMaplibreGlInternalProps,
         };
       },
     } as unknown as MaplibreGeocoderApi;
-    const geocoder = new MaplibreGeocoder(geocoderConfig, {
-      placeholder: this.props.t("Search"),
+    const geocoderInstance = new MaplibreGeocoder(geocoderConfig, {
+      placeholder: latestProps.current.t("Search"),
       maplibregl: MapLibreGl,
     });
-    map.addControl(geocoder, "top-left");
-    return geocoder;
-  }
+    mapInstance.addControl(geocoderInstance, "top-left");
+    return geocoderInstance;
+  }, []);
 
-  render() {
-    const t = this.props.t;
-    this.state.geocoder?.setPlaceholder(t("Search"));
-    this.state.zoomControl?.setLabel(t("Zoom:"));
-    return <div
-      className="maputnik-map__map"
-      role="region"
-      aria-label={t("Map view")}
-      ref={x => {this.container = x;}}
-      data-wd-key="maplibre:map"
-    ></div>;
-  }
-}
+  // Was the `i18next.on("languageChanged", () => this.forceUpdate())` in the
+  // constructor. `forceUpdate` bypassed `shouldComponentUpdate`; a state update
+  // likewise bypasses `React.memo`.
+  useEffect(() => {
+    const onLanguageChanged = () => {
+      forceUpdate();
+    };
+    i18next.on("languageChanged", onLanguageChanged);
+    return () => {
+      i18next.off("languageChanged", onLanguageChanged);
+    };
+  }, []);
 
-const MapMaplibreGl = withTranslation()(MapMaplibreGlInternal);
-export default MapMaplibreGl;
+  // componentDidMount
+  useEffect(() => {
+    const mapOpts = {
+      ...options,
+      container: container.current!,
+      style: mapStyle,
+      hash: true,
+      maxZoom: 24,
+      // make root relative urls in stylefiles work as maplibre gl js does
+      // not support this for everything:
+      // https://github.com/maplibre/maplibre-gl-js/issues/6818
+      transformRequest: (url) => {
+        if (url.startsWith("/")) {
+          url = `${window.location.origin}${url}`;
+        }
+        return { url };
+      },
+      // setting to always load glyphs of CJK fonts from server
+      // https://maplibre.org/maplibre-gl-js/docs/examples/local-ideographs/
+      localIdeographFontFamily: false
+    } satisfies MapOptions;
+
+    const protocol = new Protocol({metadata: true});
+    MapLibreGl.addProtocol("pmtiles",protocol.tile);
+    const mapInstance = new MapLibreGl.Map(mapOpts);
+
+    const mapViewChange = () => {
+      const center = mapInstance.getCenter();
+      const currentZoom = mapInstance.getZoom();
+      latestProps.current.onChange({center, zoom: currentZoom, _from: "map"});
+    };
+    mapViewChange();
+
+    mapInstance.showTileBoundaries = mapOpts.showTileBoundaries!;
+    mapInstance.showCollisionBoxes = mapOpts.showCollisionBoxes!;
+    mapInstance.showOverdrawInspector = mapOpts.showOverdrawInspector!;
+
+    const geocoderInstance = initGeocoder(mapInstance);
+
+    const zoomControlInstance = new ZoomControl();
+    mapInstance.addControl(zoomControlInstance, "top-right");
+
+    const nav = new MapLibreGl.NavigationControl({visualizePitch:true});
+    mapInstance.addControl(nav, "top-right");
+
+    const tmpNode = document.createElement("div");
+    const root = createRoot(tmpNode);
+
+    const inspectPopup = new MapLibreGl.Popup({
+      closeOnClick: false
+    });
+
+    const inspectInstance = new MaplibreInspect({
+      popup: inspectPopup,
+      showMapPopup: true,
+      showMapPopupOnHover: false,
+      showInspectMapPopupOnHover: true,
+      showInspectButton: false,
+      blockHoverPopupOnClick: true,
+      assignLayerColor: (layerId: string, alpha: number) => {
+        return Color(colors.brightColor(layerId, alpha)).desaturate(0.5).string();
+      },
+      buildInspectStyle: (originalMapStyle: StyleSpecification, coloredLayers: HighlightedLayer[]) => buildInspectStyle(originalMapStyle, coloredLayers, latestProps.current.highlightedLayer),
+      renderPopup: (features: InspectFeature[]) => {
+        if(latestProps.current.inspectModeEnabled) {
+          inspectPopup.once("open", () => {
+            root.render(<MapMaplibreGlFeaturePropertyPopup features={features} />);
+          });
+          return tmpNode;
+        } else {
+          inspectPopup.once("open", () => {
+            root.render(<MapMaplibreGlLayerPopup
+              features={features}
+              onLayerSelect={onLayerSelectById}
+              zoom={zoom.current}
+            />,);
+          });
+          return tmpNode;
+        }
+      }
+    });
+    mapInstance.addControl(inspectInstance);
+
+    mapInstance.on("style.load", () => {
+      map.current = mapInstance;
+      inspect.current = inspectInstance;
+      geocoder.current = geocoderInstance;
+      zoomControl.current = zoomControlInstance;
+      zoom.current = mapInstance.getZoom();
+    });
+
+    mapInstance.on("data", e => {
+      if(e.dataType !== "tile") return;
+      latestProps.current.onDataChange!({
+        map: map.current
+      });
+    });
+
+    mapInstance.on("error", e => {
+      console.log("ERROR", e);
+    });
+
+    mapInstance.on("zoom", _e => {
+      zoom.current = mapInstance.getZoom();
+    });
+
+    mapInstance.on("dragend", mapViewChange);
+    mapInstance.on("zoomend", mapViewChange);
+    // Mount only, exactly like componentDidMount: the map is created from the
+    // props of the first render and kept up to date imperatively below (the
+    // handlers read `latestProps`, so no prop belongs in the dependencies). The
+    // class had no componentWillUnmount, so there is no teardown here either.
+    // eslint-disable-next-line react-hooks/exhaustive-deps -- mount-only: adding mapStyle/options would re-create the map
+  }, [initGeocoder, onLayerSelectById]);
+
+  // componentDidUpdate. It had no `prevProps` guards, so it ran after *every*
+  // re-render; the equivalent is an effect without a dependency array. Since the
+  // component only re-renders when `arePropsEqual` reports a prop change (or on
+  // a language change, as before), this runs exactly as often as it used to.
+  useEffect(() => {
+    if (!hasMounted.current) {
+      // componentDidUpdate does not run on mount.
+      hasMounted.current = true;
+      return;
+    }
+
+    const styleWithTokens = replaceAccessTokens(mapStyle);
+    if (map.current) {
+      // Maplibre GL now does diffing natively so we don't need to calculate
+      // the necessary operations ourselves!
+      // We also need to update the style for inspect to work properly
+      map.current.setStyle(styleWithTokens, {diff: true});
+      map.current.showTileBoundaries = options?.showTileBoundaries!;
+      map.current.showCollisionBoxes = options?.showCollisionBoxes!;
+      map.current.showOverdrawInspector = options?.showOverdrawInspector!;
+
+      // set the map view when the prop was updated from outside
+      if (mapView._from === "app") {
+        map.current.jumpTo(mapView);
+      }
+    }
+
+    if(inspect.current && inspectModeEnabled !== inspect.current._showInspectMap) {
+      inspect.current.toggleInspector();
+    }
+    if (inspect.current && inspectModeEnabled) {
+      inspect.current.setOriginalStyle(styleWithTokens);
+      // In case the sources are the same, there's a need to refresh the style
+      setTimeout(() => {
+        inspect.current!.render();
+      }, 500);
+    }
+  });
+
+  geocoder.current?.setPlaceholder(t("Search"));
+  zoomControl.current?.setLabel(t("Zoom:"));
+  return <div
+    className="maputnik-map__map"
+    role="region"
+    aria-label={t("Map view")}
+    ref={container}
+    data-wd-key="maplibre:map"
+  ></div>;
+};
+
+export const MapMaplibreGl = withTranslation()(React.memo(MapMaplibreGlInternal, arePropsEqual));

src/components/MapMaplibreGlFeaturePropertyPopup.tsx

@@ -63,18 +63,13 @@ type FeaturePropertyPopupProps = {
   features: InspectFeature[]
 };
 
-class FeaturePropertyPopup extends React.Component<FeaturePropertyPopupProps> {
-  render() {
-    const features = removeDuplicatedFeatures(this.props.features);
-    return <div className="maputnik-feature-property-popup" dir="ltr" data-wd-key="feature-property-popup">
-      <table className="maputnik-popup-table">
-        <tbody>
-          {features.map(renderFeature)}
-        </tbody>
-      </table>
-    </div>;
-  }
-}
-
-
-export default FeaturePropertyPopup;
+export const FeaturePropertyPopup: React.FC<FeaturePropertyPopupProps> = (props) => {
+  const features = removeDuplicatedFeatures(props.features);
+  return <div className="maputnik-feature-property-popup" dir="ltr" data-wd-key="feature-property-popup">
+    <table className="maputnik-popup-table">
+      <tbody>
+        {features.map(renderFeature)}
+      </tbody>
+    </table>
+  </div>;
+};

src/components/MapMaplibreGlLayerPopup.tsx

@@ -1,5 +1,5 @@
 import React from "react";
-import IconLayer from "./IconLayer";
+import { IconLayer } from "./IconLayer";
 import type {InspectFeature} from "./MapMaplibreGlFeaturePropertyPopup";
 
 function groupFeaturesBySourceLayer(features: InspectFeature[]) {
@@ -32,8 +32,8 @@ type FeatureLayerPopupProps = {
   zoom?: number
 };
 
-class FeatureLayerPopup extends React.Component<FeatureLayerPopupProps> {
-  _getFeatureColor(feature: InspectFeature, _zoom?: number) {
+export const FeatureLayerPopup: React.FC<FeatureLayerPopupProps> = (props) => {
+  function _getFeatureColor(feature: InspectFeature, _zoom?: number) {
     // Guard because openlayers won't have this
     if (!feature.layer.paint) {
       return;
@@ -65,50 +65,45 @@ class FeatureLayerPopup extends React.Component<FeatureLayerPopupProps> {
     }
   }
 
-  render() {
-    const sources = groupFeaturesBySourceLayer(this.props.features);
+  const sources = groupFeaturesBySourceLayer(props.features);
 
-    const items = Object.keys(sources).map(vectorLayerId => {
-      const layers = sources[vectorLayerId].map((feature: InspectFeature, idx: number) => {
-        const featureColor = this._getFeatureColor(feature, this.props.zoom);
+  const items = Object.keys(sources).map(vectorLayerId => {
+    const layers = sources[vectorLayerId].map((feature: InspectFeature, idx: number) => {
+      const featureColor = _getFeatureColor(feature, props.zoom);
 
-        return <div
-          key={idx}
-          className="maputnik-popup-layer"
+      return <div
+        key={idx}
+        className="maputnik-popup-layer"
+      >
+        <div
+          className="maputnik-popup-layer__swatch"
+          style={{background: featureColor}}
+        ></div>
+        <label
+          className="maputnik-popup-layer__label"
+          onClick={() => {
+            props.onLayerSelect(feature.layer.id);
+          }}
         >
-          <div
-            className="maputnik-popup-layer__swatch"
-            style={{background: featureColor}}
-          ></div>
-          <label
-            className="maputnik-popup-layer__label"
-            onClick={() => {
-              this.props.onLayerSelect(feature.layer.id);
-            }}
-          >
-            {feature.layer.type &&
-              <IconLayer type={feature.layer.type} style={{
-                width: 14,
-                height: 14,
-                paddingRight: 3
-              }}/>
-            }
-            {feature.layer.id}
-            {feature.counter && <span> × {feature.counter}</span>}
-          </label>
-        </div>;
-      });
-      return <div key={vectorLayerId}>
-        <div className="maputnik-popup-layer-id">{vectorLayerId}</div>
-        {layers}
+          {feature.layer.type &&
+            <IconLayer type={feature.layer.type} style={{
+              width: 14,
+              height: 14,
+              paddingRight: 3
+            }}/>
+          }
+          {feature.layer.id}
+          {feature.counter && <span> × {feature.counter}</span>}
+        </label>
       </div>;
     });
-
-    return <div className="maputnik-feature-layer-popup" data-wd-key="feature-layer-popup" dir="ltr">
-      {items}
+    return <div key={vectorLayerId}>
+      <div className="maputnik-popup-layer-id">{vectorLayerId}</div>
+      {layers}
     </div>;
-  }
-}
+  });
 
-
-export default FeatureLayerPopup;
+  return <div className="maputnik-feature-layer-popup" data-wd-key="feature-layer-popup" dir="ltr">
+    {items}
+  </div>;
+};

src/components/MapOpenLayers.tsx

@@ -1,8 +1,8 @@
-import React from "react";
+import {useCallback, useEffect, useMemo, useRef, useState} from "react";
 import {throttle} from "lodash";
 import { type WithTranslation, withTranslation } from "react-i18next";
 
-import MapMaplibreGlLayerPopup from "./MapMaplibreGlLayerPopup";
+import { FeatureLayerPopup as MapMaplibreGlLayerPopup } from "./MapMaplibreGlLayerPopup";
 
 import "ol/ol.css";
 //@ts-ignore
@@ -35,56 +35,52 @@ type MapOpenLayersInternalProps = {
   onChange(...args: unknown[]): unknown
 } & WithTranslation;
 
-type MapOpenLayersState = {
-  zoom: string
-  rotation: string
-  cursor: string[]
-  center: string[]
-  selectedFeatures?: any[]
-};
+const MapOpenLayersInternal = ({
+  onLayerSelect = () => {},
+  mapStyle,
+  style,
+  debugToolbox,
+  replaceAccessTokens,
+  onChange,
+  t,
+}: MapOpenLayersInternalProps) => {
+  const [zoom, setZoom] = useState("0");
+  const [rotation, setRotation] = useState("0");
+  const [cursor, setCursor] = useState<string[]>([]);
+  const [center, setCenter] = useState<string[]>([]);
+  // Never assigned in the class version either, kept for the popup below.
+  const [selectedFeatures] = useState<any[] | undefined>(undefined);
 
-class MapOpenLayersInternal extends React.Component<MapOpenLayersInternalProps, MapOpenLayersState> {
-  static defaultProps = {
-    onMapLoaded: () => {},
-    onDataChange: () => {},
-    onLayerSelect: () => {},
-  };
-  updateStyle: any;
-  map: any;
-  container: HTMLDivElement | null = null;
-  overlay: Overlay | undefined;
-  popupContainer: HTMLElement | null = null;
+  // Imperative handles: they were plain instance fields, so they are refs and
+  // mutating them must not re-render.
+  const map = useRef<Map | null>(null);
+  const container = useRef<HTMLDivElement | null>(null);
+  const overlay = useRef<Overlay | undefined>(undefined);
+  const popupContainer = useRef<HTMLDivElement | null>(null);
 
-  constructor(props: MapOpenLayersInternalProps) {
-    super(props);
-    this.state = {
-      zoom: "0",
-      rotation: "0",
-      cursor: [] as string[],
-      center: [],
-    };
-    this.updateStyle = throttle(this._updateStyle.bind(this), 200);
-  }
+  // componentDidUpdate did not run on mount, and componentDidMount already
+  // applies the initial style, so the style effect below must skip the mount.
+  const hasMounted = useRef(false);
 
-  _updateStyle(newMapStyle: StyleSpecification) {
-    if(!this.map) return;
+  // The openlayers event handlers are registered on mount but read `this.props`
+  // at call time in the class version.
+  const latestProps = useRef({mapStyle, replaceAccessTokens, onChange});
+  latestProps.current = {mapStyle, replaceAccessTokens, onChange};
+
+  // Was `this.updateStyle = throttle(this._updateStyle.bind(this), 200)` in the
+  // constructor: created once per instance, so it is memoized once here.
+  const updateStyle = useMemo(() => throttle((newMapStyle: StyleSpecification) => {
+    if(!map.current) return;
 
     // See <https://github.com/openlayers/ol-mapbox-style/issues/215#issuecomment-493198815>
-    this.map.getLayers().clear();
-    apply(this.map, newMapStyle);
-  }
+    map.current.getLayers().clear();
+    apply(map.current, newMapStyle);
+  }, 200), []);
 
-  componentDidUpdate(prevProps: MapOpenLayersInternalProps) {
-    if (this.props.mapStyle !== prevProps.mapStyle) {
-      this.updateStyle(
-        this.props.replaceAccessTokens(this.props.mapStyle)
-      );
-    }
-  }
-
-  componentDidMount() {
-    this.overlay = new Overlay({
-      element: this.popupContainer!,
+  // componentDidMount
+  useEffect(() => {
+    overlay.current = new Overlay({
+      element: popupContainer.current!,
       autoPan: {
         animation: {
           duration: 250
@@ -92,117 +88,131 @@ class MapOpenLayersInternal extends React.Component<MapOpenLayersInternalProps,
       },
     });
 
-    const map = new Map({
-      target: this.container!,
-      overlays: [this.overlay],
+    const mapInstance = new Map({
+      target: container.current!,
+      overlays: [overlay.current],
       view: new View({
         zoom: 1,
         center: [180, -90],
       })
     });
 
-    map.on("pointermove", (evt) => {
+    mapInstance.on("pointermove", (evt) => {
       const coords = toLonLat(evt.coordinate);
-      this.setState({
-        cursor: [
-          coords[0].toFixed(2),
-          coords[1].toFixed(2)
-        ]
-      });
+      setCursor([
+        coords[0].toFixed(2),
+        coords[1].toFixed(2)
+      ]);
     });
 
     const onMoveEnd = () => {
-      const zoom = map.getView().getZoom();
-      const center = toLonLat(map.getView().getCenter()!);
+      const currentZoom = mapInstance.getView().getZoom();
+      const currentCenter = toLonLat(mapInstance.getView().getCenter()!);
 
-      this.props.onChange({
-        zoom,
+      latestProps.current.onChange({
+        zoom: currentZoom,
         center: {
-          lng: center[0],
-          lat: center[1],
+          lng: currentCenter[0],
+          lat: currentCenter[1],
         },
       });
     };
 
     onMoveEnd();
-    map.on("moveend", onMoveEnd);
+    mapInstance.on("moveend", onMoveEnd);
 
-    map.on("postrender", (_e) => {
-      const center = toLonLat(map.getView().getCenter()!);
-      this.setState({
-        center: [
-          center[0].toFixed(2),
-          center[1].toFixed(2),
-        ],
-        rotation: map.getView().getRotation().toFixed(2),
-        zoom: map.getView().getZoom()!.toFixed(2)
-      });
+    mapInstance.on("postrender", (_e) => {
+      const currentCenter = toLonLat(mapInstance.getView().getCenter()!);
+      setCenter([
+        currentCenter[0].toFixed(2),
+        currentCenter[1].toFixed(2),
+      ]);
+      setRotation(mapInstance.getView().getRotation().toFixed(2));
+      setZoom(mapInstance.getView().getZoom()!.toFixed(2));
     });
 
 
 
-    this.map = map;
-    this.updateStyle(
-      this.props.replaceAccessTokens(this.props.mapStyle)
+    map.current = mapInstance;
+    updateStyle(
+      latestProps.current.replaceAccessTokens(latestProps.current.mapStyle) as StyleSpecification
     );
-  }
+    // Mount only, like componentDidMount. The class had no componentWillUnmount,
+    // so there is no teardown here either. The props read above are read from
+    // latestProps/the first render on purpose, so they are not dependencies.
+  }, [updateStyle]);
 
-  closeOverlay = (e: any) => {
+  // componentDidUpdate: `if (this.props.mapStyle !== prevProps.mapStyle)`.
+  useEffect(() => {
+    if (!hasMounted.current) {
+      // componentDidUpdate does not run on mount; componentDidMount already
+      // applied the initial style, and applying it twice would push a second
+      // (throttled) clear + apply through ol-mapbox-style.
+      hasMounted.current = true;
+      return;
+    }
+    updateStyle(
+      replaceAccessTokens(mapStyle) as StyleSpecification
+    );
+    // `replaceAccessTokens` is deliberately *not* a dependency: the parent
+    // re-creates it on every render, so depending on it would re-apply the style
+    // on every render instead of only when `mapStyle` changes, which is exactly
+    // what the `this.props.mapStyle !== prevProps.mapStyle` guard checked.
+    // eslint-disable-next-line react-hooks/exhaustive-deps -- see above: replaceAccessTokens is a new identity each render
+  }, [mapStyle, updateStyle]);
+
+  const closeOverlay = useCallback((e: any) => {
     e.target.blur();
-    this.overlay!.setPosition(undefined);
-  };
+    overlay.current!.setPosition(undefined);
+  }, []);
 
-  render() {
-    const t = this.props.t;
-    return <div className="maputnik-ol-container">
-      <div
-        ref={x => {this.popupContainer = x;}}
-        style={{background: "black"}}
-        className="maputnik-popup"
+  return <div className="maputnik-ol-container">
+    <div
+      ref={popupContainer}
+      style={{background: "black"}}
+      className="maputnik-popup"
+    >
+      <button
+        className="maplibregl-popup-close-button"
+        onClick={closeOverlay}
+        aria-label={t("Close popup")}
       >
-        <button
-          className="maplibregl-popup-close-button"
-          onClick={this.closeOverlay}
-          aria-label={t("Close popup")}
-        >
-          ×
-        </button>
-        <MapMaplibreGlLayerPopup
-          features={this.state.selectedFeatures || []}
-          onLayerSelect={this.props.onLayerSelect}
-        />
-      </div>
-      <div className="maputnik-ol-zoom">
-        {t("Zoom:")} {this.state.zoom}
-      </div>
-      {this.props.debugToolbox &&
-        <div className="maputnik-ol-debug">
-          <div>
-            <label>{t("cursor:")} </label>
-            <span>{renderCoords(this.state.cursor)}</span>
-          </div>
-          <div>
-            <label>{t("center:")} </label>
-            <span>{renderCoords(this.state.center)}</span>
-          </div>
-          <div>
-            <label>{t("rotation:")} </label>
-            <span>{this.state.rotation}</span>
-          </div>
+        ×
+      </button>
+      <MapMaplibreGlLayerPopup
+        features={selectedFeatures || []}
+        onLayerSelect={onLayerSelect}
+      />
+    </div>
+    <div className="maputnik-ol-zoom">
+      {t("Zoom:")} {zoom}
+    </div>
+    {debugToolbox &&
+      <div className="maputnik-ol-debug">
+        <div>
+          <label>{t("cursor:")} </label>
+          <span>{renderCoords(cursor)}</span>
+        </div>
+        <div>
+          <label>{t("center:")} </label>
+          <span>{renderCoords(center)}</span>
+        </div>
+        <div>
+          <label>{t("rotation:")} </label>
+          <span>{rotation}</span>
         </div>
-      }
-      <div
-        className="maputnik-ol"
-        ref={x => {this.container = x;}}
-        role="region"
-        aria-label={t("Map view")}
-        style={{
-          ...this.props.style,
-        }}>
       </div>
-    </div>;
-  }
-}
+    }
+    <div
+      className="maputnik-ol"
+      ref={container}
+      role="region"
+      aria-label={t("Map view")}
+      style={{
+        ...style,
+      }}>
+    </div>
+  </div>;
+};
 
-const MapOpenLayers = withTranslation()(MapOpenLayersInternal);
-export default MapOpenLayers;
+export const MapOpenLayers = withTranslation()(MapOpenLayersInternal);

src/components/PropertyGroup.tsx

@@ -1,6 +1,6 @@
 import React from "react";
 
-import FieldFunction from "./FieldFunction";
+import { FieldFunction } from "./FieldFunction";
 import type {LayerSpecification} from "maplibre-gl";
 import { type MappedLayerErrors } from "../libs/definitions";
 
@@ -40,37 +40,35 @@ type PropertyGroupProps = {
   errors?: MappedLayerErrors
 };
 
-export default class PropertyGroup extends React.Component<PropertyGroupProps> {
-  onPropertyChange = (property: string, newValue: any) => {
-    const group = getGroupName(this.props.spec, this.props.layer.type, property);
-    this.props.onChange(group ,property, newValue);
+export const PropertyGroup: React.FC<PropertyGroupProps> = (props) => {
+  const onPropertyChange = (property: string, newValue: any) => {
+    const group = getGroupName(props.spec, props.layer.type, property);
+    props.onChange(group ,property, newValue);
   };
 
-  render() {
-    const {errors} = this.props;
-    const fields = this.props.groupFields.map(fieldName => {
-      const fieldSpec = getFieldSpec(this.props.spec, this.props.layer.type, fieldName);
+  const {errors} = props;
+  const fields = props.groupFields.map(fieldName => {
+    const fieldSpec = getFieldSpec(props.spec, props.layer.type, fieldName);
 
-      const paint = this.props.layer.paint || {};
-      const layout = this.props.layer.layout || {};
-      const fieldValue = fieldName in paint
-        ? paint[fieldName as keyof typeof paint]
-        : layout[fieldName as keyof typeof layout];
-      const fieldType = fieldName in paint ? "paint" : "layout";
+    const paint = props.layer.paint || {};
+    const layout = props.layer.layout || {};
+    const fieldValue = fieldName in paint
+      ? paint[fieldName as keyof typeof paint]
+      : layout[fieldName as keyof typeof layout];
+    const fieldType = fieldName in paint ? "paint" : "layout";
 
-      return <FieldFunction
-        errors={errors}
-        onChange={this.onPropertyChange}
-        key={fieldName}
-        fieldName={fieldName}
-        value={fieldValue}
-        fieldType={fieldType}
-        fieldSpec={fieldSpec}
-      />;
-    });
+    return <FieldFunction
+      errors={errors}
+      onChange={onPropertyChange}
+      key={fieldName}
+      fieldName={fieldName}
+      value={fieldValue}
+      fieldType={fieldType}
+      fieldSpec={fieldSpec}
+    />;
+  });
 
-    return <div className="maputnik-property-group">
-      {fields}
-    </div>;
-  }
-}
+  return <div className="maputnik-property-group">
+    {fields}
+  </div>;
+};

src/components/ScrollContainer.tsx

@@ -4,10 +4,8 @@ type ScrollContainerProps = {
   children?: React.ReactNode
 };
 
-export default class ScrollContainer extends React.Component<ScrollContainerProps> {
-  render() {
-    return <div className="maputnik-scroll-container">
-      {this.props.children}
-    </div>;
-  }
-}
+export const ScrollContainer: React.FC<ScrollContainerProps> = (props) => {
+  return <div className="maputnik-scroll-container">
+    {props.children}
+  </div>;
+};

src/components/SingleFilterEditor.tsx

@@ -1,9 +1,9 @@
 import React from "react";
 
 import {otherFilterOps} from "../libs/filterops";
-import InputString from "./InputString";
-import InputAutocomplete from "./InputAutocomplete";
-import InputSelect from "./InputSelect";
+import { InputString } from "./InputString";
+import { InputAutocomplete } from "./InputAutocomplete";
+import { InputSelect } from "./InputSelect";
 
 function tryParseInt(v: string | number) {
   if (v === "") return v;
@@ -40,53 +40,50 @@ type SingleFilterEditorProps = {
   properties?: {[key: string]: string}
 };
 
-export default class SingleFilterEditor extends React.Component<SingleFilterEditorProps> {
-  static defaultProps = {
-    properties: {},
-  };
-
-  onFilterPartChanged(filterOp: string, propertyName: string, filterArgs: string[]) {
+export const SingleFilterEditor: React.FC<SingleFilterEditorProps> = ({
+  properties = {},
+  ...props
+}) => {
+  function onFilterPartChanged(filterOp: string, propertyName: string, filterArgs: string[]) {
     let newFilter = [filterOp, propertyName, ...filterArgs.map(parseFilter)];
     if(filterOp === "has" || filterOp === "!has") {
       newFilter = [filterOp, propertyName];
     } else if(filterArgs.length === 0) {
       newFilter = [filterOp, propertyName, ""];
     }
-    this.props.onChange(newFilter);
+    props.onChange(newFilter);
   }
 
-  render() {
-    const f = this.props.filter;
-    const filterOp = f[0];
-    const propertyName = f[1];
-    const filterArgs = f.slice(2);
+  const f = props.filter;
+  const filterOp = f[0];
+  const propertyName = f[1];
+  const filterArgs = f.slice(2);
 
-    return <div className="maputnik-filter-editor-single">
-      <div className="maputnik-filter-editor-property">
-        <InputAutocomplete
-          aria-label="key"
-          value={propertyName}
-          options={Object.keys(this.props.properties!).map(propName => [propName, propName])}
-          onChange={(newPropertyName: string) => this.onFilterPartChanged(filterOp, newPropertyName, filterArgs)}
-        />
-      </div>
-      <div className="maputnik-filter-editor-operator">
-        <InputSelect
-          aria-label="function"
-          value={filterOp}
-          onChange={(newFilterOp: string) => this.onFilterPartChanged(newFilterOp, propertyName, filterArgs)}
-          options={otherFilterOps}
-        />
-      </div>
-      {filterArgs.length > 0 &&
-      <div className="maputnik-filter-editor-args">
-        <InputString
-          aria-label="value"
-          value={filterArgs.join(",")}
-          onChange={(v: string) => this.onFilterPartChanged(filterOp, propertyName, v.split(","))}
-        />
-      </div>
-      }
-    </div>;
-  }
-}
+  return <div className="maputnik-filter-editor-single">
+    <div className="maputnik-filter-editor-property">
+      <InputAutocomplete
+        aria-label="key"
+        value={propertyName}
+        options={Object.keys(properties).map(propName => [propName, propName])}
+        onChange={(newPropertyName: string) => onFilterPartChanged(filterOp, newPropertyName, filterArgs)}
+      />
+    </div>
+    <div className="maputnik-filter-editor-operator">
+      <InputSelect
+        aria-label="function"
+        value={filterOp}
+        onChange={(newFilterOp: string) => onFilterPartChanged(newFilterOp, propertyName, filterArgs)}
+        options={otherFilterOps}
+      />
+    </div>
+    {filterArgs.length > 0 &&
+    <div className="maputnik-filter-editor-args">
+      <InputString
+        aria-label="value"
+        value={filterArgs.join(",")}
+        onChange={(v: string) => onFilterPartChanged(filterOp, propertyName, v.split(","))}
+      />
+    </div>
+    }
+  </div>;
+};

src/components/SmallError.tsx

@@ -7,16 +7,13 @@ type SmallErrorInternalProps = {
   children?: React.ReactNode
 } & WithTranslation;
 
-class SmallErrorInternal extends React.Component<SmallErrorInternalProps> {
-  render () {
-    const t = this.props.t;
-    return (
-      <div className="SmallError">
-        {t("Error:")} {this.props.children}
-      </div>
-    );
-  }
-}
+const SmallErrorInternal: React.FC<SmallErrorInternalProps> = (props) => {
+  const t = props.t;
+  return (
+    <div className="SmallError">
+      {t("Error:")} {props.children}
+    </div>
+  );
+};
 
-const SmallError = withTranslation()(SmallErrorInternal);
-export default SmallError;
+export const SmallError = withTranslation()(SmallErrorInternal);

src/components/SpecProperty.tsx

@@ -0,0 +1,44 @@
+import React from "react";
+
+import { FieldSpec, type FieldSpecProps } from "./FieldSpec";
+import { FunctionInputButtons as FunctionButtons } from "./FunctionButtons";
+
+import { labelFromFieldName } from "../libs/label-from-field-name";
+
+
+type SpecPropertyProps = FieldSpecProps & {
+  fieldName?: string
+  fieldType?: string
+  fieldSpec?: any
+  value?: any
+  errors?: {[key: string]: {message: string}}
+  onZoomClick(): void
+  onDataClick(): void
+  onExpressionClick?(): void
+  onElevationClick?(): void
+};
+
+
+export const SpecProperty: React.FC<SpecPropertyProps> = (props) => {
+  const {errors = {}, fieldName, fieldType} = props;
+
+  const functionBtn = <FunctionButtons
+    fieldSpec={props.fieldSpec}
+    onZoomClick={props.onZoomClick}
+    onDataClick={props.onDataClick}
+    onExpressionClick={props.onExpressionClick}
+    onElevationClick={props.onElevationClick}
+  />;
+
+  const error = errors[fieldType+"."+fieldName as any] as any;
+
+  const propsWithDefaults = {...props, errors};
+
+  return <FieldSpec
+    {...propsWithDefaults}
+    error={error}
+    fieldSpec={props.fieldSpec}
+    label={labelFromFieldName(props.fieldName || "")}
+    action={functionBtn}
+  />;
+};

src/components/ZoomProperty.tsx

@@ -0,0 +1,246 @@
+import React, { useRef } from "react";
+import { PiListPlusBold } from "react-icons/pi";
+import { TbMathFunction } from "react-icons/tb";
+import latest from "@maplibre/maplibre-gl-style-spec/dist/latest.json";
+import { type WithTranslation, withTranslation } from "react-i18next";
+
+import { InputButton } from "./InputButton";
+import { InputSpec } from "./InputSpec";
+import { InputNumber } from "./InputNumber";
+import { InputSelect } from "./InputSelect";
+import { Block } from "./Block";
+
+import { DeleteStopButton } from "./DeleteStopButton";
+import { labelFromFieldName } from "../libs/label-from-field-name";
+
+import { generateUniqueId as docUid } from "../libs/document-uid";
+import { sortNumerically } from "../libs/sort-numerically";
+import { type MappedLayerErrors } from "../libs/definitions";
+
+
+/**
+ * We cache a reference for each stop by its index.
+ *
+ * When the stops are reordered the references are also updated (see this.orderStops) this allows React to use the same key for the element and keep keyboard focus.
+ */
+function setStopRefs(props: ZoomPropertyInternalProps, state: ZoomPropertyState) {
+  // This is initialised below only if required to improved performance.
+  let newRefs: {[key: number]: string} = {};
+
+  if(props.value && (props.value as ZoomWithStops).stops) {
+    (props.value as ZoomWithStops).stops.forEach((_val, idx: number) => {
+      if(Object.prototype.hasOwnProperty.call(!state.refs, idx)) {
+        if(!newRefs) {
+          newRefs = {...state};
+        }
+        newRefs[idx] = docUid("stop-");
+      } else {
+        newRefs[idx] = state.refs[idx];
+      }
+    });
+  }
+  return newRefs;
+}
+
+type ZoomWithStops = {
+  stops: [number | undefined, number][]
+  base?: number
+};
+
+
+type ZoomPropertyInternalProps = {
+  onChange?(...args: unknown[]): unknown
+  onChangeToDataFunction?(...args: unknown[]): unknown
+  onDeleteStop?(...args: unknown[]): unknown
+  onAddStop?(...args: unknown[]): unknown
+  onExpressionClick?(...args: unknown[]): unknown
+  fieldType?: string
+  fieldName: string
+  fieldSpec?: {
+    "property-type"?: string
+    "function-type"?: string
+  }
+  errors?: MappedLayerErrors
+  value?: ZoomWithStops
+} & WithTranslation;
+
+type ZoomPropertyState = {
+  refs: {[key: number]: string}
+};
+
+const ZoomPropertyInternal: React.FC<ZoomPropertyInternalProps> = ({ errors = {}, ...rest }) => {
+  const props = { errors, ...rest } as ZoomPropertyInternalProps;
+
+  // The stop refs never reach the rendered output (the row key is derived from
+  // the stop itself), so they live in a ref rather than state: keeping them in
+  // state would mean setting state during render on every pass.
+  const refs = useRef<{[key: number]: string}>({});
+  refs.current = setStopRefs(props, { refs: refs.current });
+
+  // Order the stops altering the refs to reflect their new position.
+  function orderStopsByZoom(stops: ZoomWithStops["stops"]) {
+    const mappedWithRef = stops
+      .map((stop, idx) => {
+        return {
+          ref: refs.current[idx],
+          data: stop
+        };
+      })
+    // Sort by zoom
+      .sort((a, b) => sortNumerically(a.data[0]!, b.data[0]!));
+
+    // Fetch the new position of the stops
+    const newRefs: {[key:number]: string} = {};
+    mappedWithRef
+      .forEach((stop, idx) =>{
+        newRefs[idx] = stop.ref;
+      });
+
+    refs.current = newRefs;
+
+    return mappedWithRef.map((item) => item.data);
+  }
+
+  function changeZoomStop(changeIdx: number, stopData: number | undefined, value: number) {
+    const stops = (props.value as ZoomWithStops).stops.slice(0);
+    stops[changeIdx] = [stopData, value];
+
+    const orderedStops = orderStopsByZoom(stops);
+
+    const changedValue = {
+      ...props.value as ZoomWithStops,
+      stops: orderedStops
+    };
+    props.onChange!(props.fieldName, changedValue);
+  }
+
+  function changeBase(newValue: number | undefined) {
+    const changedValue = {
+      ...props.value,
+      base: newValue
+    };
+
+    if (changedValue.base === undefined) {
+      delete changedValue["base"];
+    }
+    props.onChange!(props.fieldName, changedValue);
+  }
+
+  const changeDataType = (type: string) => {
+    if (type !== "interpolate" && props.onChangeToDataFunction) {
+      props.onChangeToDataFunction(type);
+    }
+  };
+
+  function getDataFunctionTypes(fieldSpec: {
+    "property-type"?: string
+    "function-type"?: string
+  }) {
+    if (fieldSpec["property-type"] === "data-driven") {
+      return ["interpolate", "categorical", "interval", "exponential", "identity"];
+    }
+    else {
+      return ["interpolate"];
+    }
+  }
+
+  const t = props.t;
+  const zoomFields = props.value?.stops.map((stop, idx) => {
+    const zoomLevel = stop[0];
+    const value = stop[1];
+    const deleteStopBtn = <DeleteStopButton onClick={props.onDeleteStop?.bind(null, idx)} />;
+    return <tr
+      key={`${stop[0]}-${stop[1]}`}
+    >
+      <td>
+        <InputNumber
+          aria-label={t("Zoom")}
+          value={zoomLevel}
+          onChange={changedStop => changeZoomStop(idx, changedStop, value)}
+          min={0}
+          max={22}
+        />
+      </td>
+      <td>
+        <InputSpec
+          aria-label={t("Output value")}
+          fieldName={props.fieldName}
+          fieldSpec={props.fieldSpec as any}
+          value={value}
+          onChange={(_, newValue) => changeZoomStop(idx, zoomLevel, newValue as number)}
+        />
+      </td>
+      <td>
+        {deleteStopBtn}
+      </td>
+    </tr>;
+  });
+
+  // return <div className="maputnik-zoom-spec-property">
+  return <div className="maputnik-data-spec-block">
+    <fieldset className="maputnik-data-spec-property">
+      <legend>{labelFromFieldName(props.fieldName)}</legend>
+      <div className="maputnik-data-fieldset-inner">
+        <Block
+          label={t("Function")}
+          data-wd-key="function-type"
+        >
+          <div className="maputnik-data-spec-property-input">
+            <InputSelect
+              value={"interpolate"}
+              onChange={(propVal: string) => changeDataType(propVal)}
+              title={t("Select a type of data scale (default is 'categorical').")}
+              options={getDataFunctionTypes(props.fieldSpec!)}
+            />
+          </div>
+        </Block>
+        <Block
+          label={t("Base")}
+          data-wd-key="function-base"
+        >
+          <div className="maputnik-data-spec-property-input">
+            <InputSpec
+              fieldName={"base"}
+              fieldSpec={latest.function.base as typeof latest.function.base & { type: "number" }}
+              value={props.value?.base}
+              onChange={(_, newValue) => changeBase(newValue as number | undefined)}
+            />
+          </div>
+        </Block>
+        <div className="maputnik-function-stop">
+          <table className="maputnik-function-stop-table maputnik-function-stop-table--zoom">
+            <caption>{t("Stops")}</caption>
+            <thead>
+              <tr>
+                <th>{t("Zoom")}</th>
+                <th rowSpan={2}>{t("Output value")}</th>
+              </tr>
+            </thead>
+            <tbody>
+              {zoomFields}
+            </tbody>
+          </table>
+        </div>
+        <div className="maputnik-toolbox">
+          <InputButton
+            className="maputnik-add-stop"
+            onClick={props.onAddStop?.bind(null)}
+          >
+            <PiListPlusBold style={{ verticalAlign: "text-bottom" }} />
+            {t("Add stop")}
+          </InputButton>
+          <InputButton
+            className="maputnik-add-stop"
+            data-wd-key="convert-to-expression"
+            onClick={props.onExpressionClick?.bind(null)}
+          >
+            <TbMathFunction style={{ verticalAlign: "text-bottom" }} />
+            {t("Convert to expression")}
+          </InputButton>
+        </div>
+      </div>
+    </fieldset>
+  </div>;
+};
+
+export const ZoomProperty = withTranslation()(ZoomPropertyInternal);

src/components/_DataProperty.tsx

@@ -1,384 +0,0 @@
-import React from "react";
-import {PiListPlusBold} from "react-icons/pi";
-import {TbMathFunction} from "react-icons/tb";
-import latest from "@maplibre/maplibre-gl-style-spec/dist/latest.json";
-
-import InputButton from "./InputButton";
-import InputSpec from "./InputSpec";
-import InputNumber from "./InputNumber";
-import InputString from "./InputString";
-import InputSelect from "./InputSelect";
-import Block from "./Block";
-import docUid from "../libs/document-uid";
-import sortNumerically from "../libs/sort-numerically";
-import {findDefaultFromSpec} from "../libs/spec-helper";
-import { type WithTranslation, withTranslation } from "react-i18next";
-
-import labelFromFieldName from "../libs/label-from-field-name";
-import DeleteStopButton from "./_DeleteStopButton";
-import { type MappedLayerErrors } from "../libs/definitions";
-
-
-
-function setStopRefs(props: DataPropertyInternalProps, state: DataPropertyState) {
-  // This is initialised below only if required to improved performance.
-  let newRefs: {[key: number]: string} | undefined;
-
-  if(props.value && props.value.stops) {
-    props.value.stops.forEach((_val, idx) => {
-      if(!Object.prototype.hasOwnProperty.call(state.refs, idx)) {
-        if(!newRefs) {
-          newRefs = {...state};
-        }
-        newRefs[idx] = docUid("stop-");
-      }
-    });
-  }
-
-  return newRefs;
-}
-
-type DataPropertyInternalProps = {
-  onChange?(fieldName: string, value: any): unknown
-  onDeleteStop?(...args: unknown[]): unknown
-  onAddStop?(...args: unknown[]): unknown
-  onExpressionClick?(...args: unknown[]): unknown
-  onChangeToZoomFunction?(...args: unknown[]): unknown
-  fieldName: string
-  fieldType?: string
-  fieldSpec?: object
-  value?: DataPropertyValue
-  errors?: MappedLayerErrors
-} & WithTranslation;
-
-type DataPropertyState = {
-  refs: {[key: number]: string}
-};
-
-type DataPropertyValue = {
-  default?: any
-  property?: string
-  base?: number
-  type?: string
-  stops: Stop[]
-};
-
-export type Stop = [{
-  zoom: number
-  value: number
-}, number];
-
-class DataPropertyInternal extends React.Component<DataPropertyInternalProps, DataPropertyState> {
-  state = {
-    refs: {} as {[key: number]: string}
-  };
-
-  componentDidMount() {
-    const newRefs = setStopRefs(this.props, this.state);
-
-    if(newRefs) {
-      this.setState({
-        refs: newRefs
-      });
-    }
-  }
-
-  static getDerivedStateFromProps(props: Readonly<DataPropertyInternalProps>, state: DataPropertyState) {
-    const newRefs = setStopRefs(props, state);
-    if(newRefs) {
-      return {
-        refs: newRefs
-      };
-    }
-    return null;
-  }
-
-  getFieldFunctionType(fieldSpec: any) {
-    if (fieldSpec.expression.interpolated) {
-      return "exponential";
-    }
-    if (fieldSpec.type === "number") {
-      return "interval";
-    }
-    return "categorical";
-  }
-
-  getDataFunctionTypes(fieldSpec: any) {
-    if (fieldSpec.expression.interpolated) {
-      return ["interpolate", "categorical", "interval", "exponential", "identity"];
-    }
-    else {
-      return ["categorical", "interval", "identity"];
-    }
-  }
-
-  // Order the stops altering the refs to reflect their new position.
-  orderStopsByZoom(stops: Stop[]) {
-    const mappedWithRef = stops
-      .map((stop, idx) => {
-        return {
-          ref: this.state.refs[idx],
-          data: stop
-        };
-      })
-    // Sort by zoom
-      .sort((a, b) => sortNumerically(a.data[0].zoom, b.data[0].zoom));
-
-    // Fetch the new position of the stops
-    const newRefs = {} as {[key: number]: string};
-    mappedWithRef
-      .forEach((stop, idx) =>{
-        newRefs[idx] = stop.ref;
-      });
-
-    this.setState({
-      refs: newRefs
-    });
-
-    return mappedWithRef.map((item) => item.data);
-  }
-
-  onChange = (fieldName: string, value: any) => {
-    if (value.type === "identity") {
-      value = {
-        type: value.type,
-        property: value.property,
-      };
-    }
-    else {
-      const stopValue = value.type === "categorical" ? "" : 0;
-      value = {
-        property: "",
-        type: value.type,
-        // Default props if they don't already exist.
-        stops: [
-          [{zoom: 6, value: stopValue}, findDefaultFromSpec(this.props.fieldSpec as any)],
-          [{zoom: 10, value: stopValue}, findDefaultFromSpec(this.props.fieldSpec as any)]
-        ],
-        ...value,
-      };
-    }
-    this.props.onChange!(fieldName, value);
-  };
-
-  changeStop(changeIdx: number, stopData: { zoom: number | undefined, value: number }, value: number) {
-    const stops = this.props.value?.stops.slice(0) || [];
-    // const changedStop = stopData.zoom === undefined ? stopData.value : stopData
-    stops[changeIdx] = [
-      {
-        value: stopData.value,
-        zoom: (stopData.zoom === undefined) ? 0 : stopData.zoom,
-      },
-      value
-    ];
-
-    const orderedStops = this.orderStopsByZoom(stops);
-
-    const changedValue = {
-      ...this.props.value,
-      stops: orderedStops,
-    };
-    this.onChange(this.props.fieldName, changedValue);
-  }
-
-  changeBase(newValue: number | undefined) {
-    const changedValue = {
-      ...this.props.value,
-      base: newValue
-    };
-
-    if (changedValue.base === undefined) {
-      delete changedValue["base"];
-    }
-    this.props.onChange!(this.props.fieldName, changedValue);
-  }
-
-  changeDataType(propVal: string) {
-    if (propVal === "interpolate" && this.props.onChangeToZoomFunction) {
-      this.props.onChangeToZoomFunction();
-    }
-    else {
-      this.onChange(this.props.fieldName, {
-        ...this.props.value,
-        type: propVal,
-      });
-    }
-  }
-
-  changeDataProperty(propName: "property" | "default", propVal: any) {
-    if (propVal) {
-      this.props.value![propName] = propVal;
-    }
-    else {
-      delete this.props.value![propName];
-    }
-    this.onChange(this.props.fieldName, this.props.value);
-  }
-
-  render() {
-    const t = this.props.t;
-
-    if (typeof this.props.value?.type === "undefined") {
-      this.props.value!.type = this.getFieldFunctionType(this.props.fieldSpec);
-    }
-
-    let dataFields;
-    if (this.props.value?.stops) {
-      dataFields = this.props.value.stops.map((stop, idx) => {
-        const zoomLevel = typeof stop[0] === "object" ? stop[0].zoom : undefined;
-        const key  = this.state.refs[idx];
-        const dataLevel = typeof stop[0] === "object" ? stop[0].value : stop[0];
-        const value = stop[1];
-        const deleteStopBtn = <DeleteStopButton onClick={this.props.onDeleteStop?.bind(this, idx)} />;
-
-        const dataProps = {
-          "aria-label": t("Input value"),
-          label: t("Data value"),
-          value: dataLevel as any,
-          onChange: (newData: string | number | undefined) => this.changeStop(idx, { zoom: zoomLevel, value: newData as number }, value)
-        };
-
-        let dataInput;
-        if(this.props.value?.type === "categorical") {
-          dataInput = <InputString {...dataProps} />;
-        }
-        else {
-          dataInput = <InputNumber {...dataProps} />;
-        }
-
-        let zoomInput = null;
-        if(zoomLevel !== undefined) {
-          zoomInput = <div>
-            <InputNumber
-              aria-label="Zoom"
-              value={zoomLevel}
-              onChange={newZoom => this.changeStop(idx, {zoom: newZoom, value: dataLevel}, value)}
-              min={0}
-              max={22}
-            />
-          </div>;
-        }
-
-        return <tr key={key}>
-          <td>
-            {zoomInput}
-          </td>
-          <td>
-            {dataInput}
-          </td>
-          <td>
-            <InputSpec
-              aria-label={t("Output value")}
-              fieldName={this.props.fieldName}
-              fieldSpec={this.props.fieldSpec}
-              value={value}
-              onChange={(_, newValue) => this.changeStop(idx, {zoom: zoomLevel, value: dataLevel}, newValue as number)}
-            />
-          </td>
-          <td>
-            {deleteStopBtn}
-          </td>
-        </tr>;
-      });
-    }
-
-    return <div className="maputnik-data-spec-block">
-      <fieldset className="maputnik-data-spec-property">
-        <legend>{labelFromFieldName(this.props.fieldName)}</legend>
-        <div className="maputnik-data-fieldset-inner">
-          <Block
-            label={t("Function")}
-            key="function"
-          >
-            <div className="maputnik-data-spec-property-input">
-              <InputSelect
-                value={this.props.value!.type}
-                onChange={(propVal: string) => this.changeDataType(propVal)}
-                title={t("Select a type of data scale (default is 'categorical').")}
-                options={this.getDataFunctionTypes(this.props.fieldSpec)}
-              />
-            </div>
-          </Block>
-          {this.props.value?.type !== "identity" &&
-            <Block
-              label={t("Base")}
-              key="base"
-            >
-              <div className="maputnik-data-spec-property-input">
-                <InputSpec
-                  fieldName={"base"}
-                  fieldSpec={latest.function.base as typeof latest.function.base & { type: "number" }}
-                  value={this.props.value?.base}
-                  onChange={(_, newValue) => this.changeBase(newValue as number)}
-                />
-              </div>
-            </Block>
-          }
-          <Block
-            label={"Property"}
-            key="property"
-          >
-            <div className="maputnik-data-spec-property-input">
-              <InputString
-                value={this.props.value?.property}
-                title={t("Input a data property to base styles off of.")}
-                onChange={propVal => this.changeDataProperty("property", propVal)}
-              />
-            </div>
-          </Block>
-          {dataFields &&
-            <Block
-              label={t("Default")}
-              key="default"
-            >
-              <InputSpec
-                fieldName={this.props.fieldName}
-                fieldSpec={this.props.fieldSpec}
-                value={this.props.value?.default}
-                onChange={(_, propVal) => this.changeDataProperty("default", propVal)}
-              />
-            </Block>
-          }
-          {dataFields &&
-            <div className="maputnik-function-stop">
-              <table className="maputnik-function-stop-table">
-                <caption>{t("Stops")}</caption>
-                <thead>
-                  <tr>
-                    <th>{t("Zoom")}</th>
-                    <th>{t("Input value")}</th>
-                    <th rowSpan={2}>{t("Output value")}</th>
-                  </tr>
-                </thead>
-                <tbody>
-                  {dataFields}
-                </tbody>
-              </table>
-            </div>
-          }
-          <div className="maputnik-toolbox">
-            {dataFields &&
-              <InputButton
-                className="maputnik-add-stop"
-                onClick={this.props.onAddStop?.bind(this)}
-              >
-                <PiListPlusBold style={{ verticalAlign: "text-bottom" }} />
-                {t("Add stop")}
-              </InputButton>
-            }
-            <InputButton
-              className="maputnik-add-stop"
-              onClick={this.props.onExpressionClick?.bind(this)}
-            >
-              <TbMathFunction style={{ verticalAlign: "text-bottom" }} />
-              {t("Convert to expression")}
-            </InputButton>
-          </div>
-        </div>
-      </fieldset>
-    </div>;
-  }
-}
-
-const DataProperty = withTranslation()(DataPropertyInternal);
-export default DataProperty;

src/components/_DeleteStopButton.tsx

@@ -1,27 +0,0 @@
-import React from "react";
-
-import InputButton from "./InputButton";
-import {MdDelete} from "react-icons/md";
-import { type WithTranslation, withTranslation } from "react-i18next";
-
-
-type DeleteStopButtonInternalProps = {
-  onClick?(...args: unknown[]): unknown
-} & WithTranslation;
-
-
-class DeleteStopButtonInternal extends React.Component<DeleteStopButtonInternalProps> {
-  render() {
-    const t = this.props.t;
-    return <InputButton
-      className="maputnik-delete-stop"
-      onClick={this.props.onClick}
-      title={t("Remove zoom level from stop")}
-    >
-      <MdDelete />
-    </InputButton>;
-  }
-}
-
-const DeleteStopButton = withTranslation()(DeleteStopButtonInternal);
-export default DeleteStopButton;

src/components/_ExpressionProperty.tsx

@@ -1,94 +0,0 @@
-import React from "react";
-import {MdDelete, MdUndo} from "react-icons/md";
-import { type WithTranslation, withTranslation } from "react-i18next";
-
-import Block from "./Block";
-import InputButton from "./InputButton";
-import labelFromFieldName from "../libs/label-from-field-name";
-import FieldJson from "./FieldJson";
-import type { StylePropertySpecification } from "maplibre-gl";
-import { type MappedLayerErrors } from "../libs/definitions";
-
-
-type ExpressionPropertyInternalProps = {
-  fieldName: string
-  fieldType?: string
-  fieldSpec?: StylePropertySpecification
-  value?: any
-  errors?: MappedLayerErrors
-  onDelete?(...args: unknown[]): unknown
-  onChange(value: object): void
-  onUndo?(...args: unknown[]): unknown
-  canUndo?(...args: unknown[]): unknown
-  onFocus?(...args: unknown[]): unknown
-  onBlur?(...args: unknown[]): unknown
-} & WithTranslation;
-
-class ExpressionPropertyInternal extends React.Component<ExpressionPropertyInternalProps> {
-  static defaultProps = {
-    errors: {},
-    onFocus: () => {},
-    onBlur: () => {},
-  };
-
-  constructor(props: ExpressionPropertyInternalProps) {
-    super(props);
-    this.state = {
-      jsonError: false,
-    };
-  }
-
-  render() {
-    const {t, value, canUndo} = this.props;
-    const undoDisabled = canUndo ? !canUndo() : true;
-
-    const deleteStopBtn = (
-      <>
-        {this.props.onUndo &&
-          <InputButton
-            key="undo_action"
-            onClick={this.props.onUndo}
-            disabled={undoDisabled}
-            className="maputnik-delete-stop"
-            title={t("Revert from expression")}
-          >
-            <MdUndo />
-          </InputButton>
-        }
-        <InputButton
-          key="delete_action"
-          onClick={this.props.onDelete}
-          className="maputnik-delete-stop"
-          title={t("Delete expression")}
-        >
-          <MdDelete />
-        </InputButton>
-      </>
-    );
-    let error = undefined;
-    if (this.props.errors) {
-      const fieldKey = this.props.fieldType ? this.props.fieldType + "." + this.props.fieldName : this.props.fieldName;
-      error = this.props.errors[fieldKey];
-    }
-    return <Block
-      fieldSpec={this.props.fieldSpec}
-      label={t(labelFromFieldName(this.props.fieldName))}
-      action={deleteStopBtn}
-      wideMode={true}
-      error={error}
-    >
-      <FieldJson
-        lintType="expression"
-        spec={this.props.fieldSpec}
-        className="maputnik-expression-editor"
-        onFocus={this.props.onFocus}
-        onBlur={this.props.onBlur}
-        value={value}
-        onChange={this.props.onChange}
-      />
-    </Block>;
-  }
-}
-
-const ExpressionProperty = withTranslation()(ExpressionPropertyInternal);
-export default ExpressionProperty;

src/components/_FunctionButtons.tsx

@@ -1,71 +0,0 @@
-import React from "react";
-
-import InputButton from "./InputButton";
-import {MdFunctions, MdInsertChart} from "react-icons/md";
-import { TbMathFunction } from "react-icons/tb";
-import { type WithTranslation, withTranslation } from "react-i18next";
-
-type FunctionInputButtonsInternalProps = {
-  fieldSpec?: any
-  onZoomClick?(): void
-  onDataClick?(): void
-  onExpressionClick?(): void
-  onElevationClick?(): void
-} & WithTranslation;
-
-class FunctionInputButtonsInternal extends React.Component<FunctionInputButtonsInternalProps> {
-  render() {
-    const t = this.props.t;
-
-    if (this.props.fieldSpec.expression?.parameters.includes("zoom")) {
-      const expressionInputButton = (
-        <InputButton
-          className="maputnik-make-zoom-function"
-          onClick={this.props.onExpressionClick}
-          title={t("Convert to expression")}
-        >
-          <TbMathFunction />
-        </InputButton>
-      );
-
-      const makeZoomInputButton = <InputButton
-        className="maputnik-make-zoom-function"
-        onClick={this.props.onZoomClick}
-        title={t("Convert property into a zoom function")}
-      >
-        <MdFunctions />
-      </InputButton>;
-
-      let makeDataInputButton;
-      if (this.props.fieldSpec["property-type"] === "data-driven") {
-        makeDataInputButton = <InputButton
-          className="maputnik-make-data-function"
-          onClick={this.props.onDataClick}
-          title={t("Convert property to data function")}
-        >
-          <MdInsertChart />
-        </InputButton>;
-      }
-      return <div>
-        {expressionInputButton}
-        {makeDataInputButton}
-        {makeZoomInputButton}
-      </div>;
-    } else if (this.props.fieldSpec.expression?.parameters.includes("elevation")) {
-      const inputElevationButton = <InputButton
-        className="maputnik-make-elevation-function"
-        onClick={this.props.onElevationClick}
-        title={t("Convert property into a elevation function")}
-        data-wd-key='make-elevation-function'
-      >
-        <MdFunctions />
-      </InputButton>;
-      return <div>{inputElevationButton}</div>;
-    } else {
-      return <div></div>;
-    }
-  }
-}
-
-const FunctionInputButtons = withTranslation()(FunctionInputButtonsInternal);
-export default FunctionInputButtons;

src/components/_SpecProperty.tsx

@@ -1,48 +0,0 @@
-import React from "react";
-
-import FieldSpec, {type FieldSpecProps} from "./FieldSpec";
-import FunctionButtons from "./_FunctionButtons";
-
-import labelFromFieldName from "../libs/label-from-field-name";
-
-
-type SpecPropertyProps = FieldSpecProps & {
-  fieldName?: string
-  fieldType?: string
-  fieldSpec?: any
-  value?: any
-  errors?: {[key: string]: {message: string}}
-  onZoomClick(): void
-  onDataClick(): void
-  onExpressionClick?(): void
-  onElevationClick?(): void
-};
-
-
-export default class SpecProperty extends React.Component<SpecPropertyProps> {
-  static defaultProps = {
-    errors: {},
-  };
-
-  render() {
-    const {errors, fieldName, fieldType} = this.props;
-
-    const functionBtn = <FunctionButtons
-      fieldSpec={this.props.fieldSpec}
-      onZoomClick={this.props.onZoomClick}
-      onDataClick={this.props.onDataClick}
-      onExpressionClick={this.props.onExpressionClick}
-      onElevationClick={this.props.onElevationClick}
-    />;
-
-    const error = errors![fieldType+"."+fieldName as any] as any;
-
-    return <FieldSpec
-      {...this.props}
-      error={error}
-      fieldSpec={this.props.fieldSpec}
-      label={labelFromFieldName(this.props.fieldName || "")}
-      action={functionBtn}
-    />;
-  }
-}