Clip tile layers by extent

rendering/cases/layer-tile-2layers-extentclip/main.js

@@ -1,47 +0,0 @@
-import Map from '../../../src/ol/Map.js';
-import View from '../../../src/ol/View.js';
-import TileLayer from '../../../src/ol/layer/Tile.js';
-import {fromLonLat} from '../../../src/ol/proj';
-import XYZ from '../../../src/ol/source/XYZ';
-import {getSize} from '../../../src/ol/extent';
-
-const center = fromLonLat([8.6, 50.1]);
-
-const map = new Map({
-  target: 'map',
-  view: new View({
-    center: center,
-    zoom: 3
-  })
-});
-
-const layerExtent = centerExtent();
-
-map.addLayer(
-  new TileLayer({
-    source: new XYZ({
-      url: '/data/tiles/satellite/{z}/{x}/{y}.jpg'
-    }),
-    extent: layerExtent
-  }),
-);
-
-map.addLayer(
-  new TileLayer({
-    source: new XYZ({
-      url: '/data/tiles/stamen-labels/{z}/{x}/{y}.png'
-    }),
-    extent: layerExtent
-  })
-);
-
-render();
-
-function centerExtent() {
-  const c = map.getView().calculateExtent([256, 256]);
-  const qw = getSize(c)[0] / 4;
-  const qh = getSize(c)[1] / 4;
-  return [c[0] + qw, c[1] + qh, c[2] - qw, c[3] - qh];
-}
-
-

rendering/cases/layer-tile-extent/main.js

@@ -0,0 +1,40 @@
+/**
+ * Tile layers get clipped to their extent.
+ */
+
+import Map from '../../../src/ol/Map.js';
+import View from '../../../src/ol/View.js';
+import TileLayer from '../../../src/ol/layer/Tile.js';
+import {fromLonLat} from '../../../src/ol/proj';
+import {transformExtent} from '../../../src/ol/proj.js';
+import XYZ from '../../../src/ol/source/XYZ';
+
+const center = fromLonLat([7, 50]);
+const extent = transformExtent([2, 47, 10, 53], 'EPSG:4326', 'EPSG:3857');
+
+new Map({
+  target: 'map',
+  view: new View({
+    center: center,
+    zoom: 3
+  }),
+  layers: [
+    new TileLayer({
+      source: new XYZ({
+        url: '/data/tiles/satellite/{z}/{x}/{y}.jpg',
+        maxZoom: 3
+      }),
+      extent: extent
+    }),
+    new TileLayer({
+      source: new XYZ({
+        url: '/data/tiles/stamen-labels/{z}/{x}/{y}.png',
+        minZoom: 3,
+        maxZoom: 5
+      }),
+      extent: extent
+    })
+  ]
+});
+
+render();

src/ol/renderer/canvas/Layer.js

@@ -85,6 +85,39 @@ class CanvasLayerRenderer extends LayerRenderer {
     rotateAtOffset(context, rotation, halfWidth, halfHeight);
   }
 
+  /**
+   * @param {CanvasRenderingContext2D} context Context.
+   * @param {import("../../PluggableMap.js").FrameState} frameState Frame state.
+   * @param {import("../../extent.js").Extent} extent Clip extent.
+   * @protected
+   */
+  clipUnrotated(context, frameState, extent) {
+    const topLeft = getTopLeft(extent);
+    const topRight = getTopRight(extent);
+    const bottomRight = getBottomRight(extent);
+    const bottomLeft = getBottomLeft(extent);
+
+    applyTransform(frameState.coordinateToPixelTransform, topLeft);
+    applyTransform(frameState.coordinateToPixelTransform, topRight);
+    applyTransform(frameState.coordinateToPixelTransform, bottomRight);
+    applyTransform(frameState.coordinateToPixelTransform, bottomLeft);
+
+    const inverted = invertTransform(this.pixelTransform_.slice());
+
+    applyTransform(inverted, topLeft);
+    applyTransform(inverted, topRight);
+    applyTransform(inverted, bottomRight);
+    applyTransform(inverted, bottomLeft);
+
+    context.save();
+    context.beginPath();
+    context.moveTo(Math.round(topLeft[0]), Math.round(topLeft[1]));
+    context.lineTo(Math.round(topRight[0]), Math.round(topRight[1]));
+    context.lineTo(Math.round(bottomRight[0]), Math.round(bottomRight[1]));
+    context.lineTo(Math.round(bottomLeft[0]), Math.round(bottomLeft[1]));
+    context.clip();
+  }
+
   /**
    * @param {import("../../render/EventType.js").default} type Event type.
    * @param {CanvasRenderingContext2D} context Context.

src/ol/renderer/canvas/TileLayer.js

@@ -143,12 +143,10 @@ class CanvasTileLayerRenderer extends CanvasLayerRenderer {
     const tileResolution = tileGrid.getResolution(z);
     let extent = frameState.extent;
 
-    if (layerState.extent !== undefined) {
+    if (layerState.extent) {
       extent = getIntersection(extent, layerState.extent);
     }
 
-    // TODO: clip by layer extent
-
     const tilePixelRatio = tileSource.getTilePixelRatio(pixelRatio);
 
     // desired dimensions of the canvas in pixels
@@ -235,6 +233,10 @@ class CanvasTileLayerRenderer extends CanvasLayerRenderer {
       context.clearRect(0, 0, width, height);
     }
 
+    if (layerState.extent) {
+      this.clipUnrotated(context, frameState, layerState.extent);
+    }
+
     this.preRender(context, frameState, pixelTransform);
 
     this.renderedTiles.length = 0;
@@ -285,6 +287,10 @@ class CanvasTileLayerRenderer extends CanvasLayerRenderer {
 
     this.postRender(context, frameState, pixelTransform);
 
+    if (layerState.extent) {
+      context.restore();
+    }
+
     const opacity = layerState.opacity;
     if (opacity !== canvas.style.opacity) {
       canvas.style.opacity = opacity;