Warn once when suspicious coordinate are used

src/ol/View.js

@@ -10,6 +10,7 @@ import {DEFAULT_TILE_SIZE} from './tilegrid/common.js';
 import {
   METERS_PER_UNIT,
   createProjection,
+  disableCoordinateWarning,
   fromUserCoordinate,
   fromUserExtent,
   getUserProjection,
@@ -241,7 +242,7 @@ const DEFAULT_MIN_ZOOM = 0;
  * A View has a `projection`. The projection determines the
  * coordinate system of the center, and its units determine the units of the
  * resolution (projection units per pixel). The default projection is
- * Spherical Mercator (EPSG:3857).
+ * Web Mercator (EPSG:3857).
  *
  * ### The view states
  *
@@ -406,6 +407,9 @@ class View extends BaseObject {
     if (options.extent) {
       options.extent = fromUserExtent(options.extent, this.projection_);
     }
+    if (options.projection) {
+      disableCoordinateWarning();
+    }
 
     this.applyOptions_(options);
   }

src/ol/proj.js

@@ -73,8 +73,8 @@ import {
 } from './proj/transforms.js';
 import {applyTransform, getWidth} from './extent.js';
 import {clamp, modulo} from './math.js';
+import {equals, getWorldsAway} from './coordinate.js';
 import {getDistance} from './sphere.js';
-import {getWorldsAway} from './coordinate.js';
 
 /**
  * A projection as {@link module:ol/proj/Projection}, SRS identifier
@@ -97,6 +97,16 @@ export {METERS_PER_UNIT};
 
 export {Projection};
 
+let showCoordinateWarning = true;
+
+/**
+ * @param {boolean} [opt_disable = true] Disable console info about `useGeographic()`
+ */
+export function disableCoordinateWarning(opt_disable) {
+  const hide = opt_disable === undefined ? true : opt_disable;
+  showCoordinateWarning = !hide;
+}
+
 /**
  * @param {Array<number>} input Input coordinate array.
  * @param {Array<number>} [opt_output] Output array of coordinate values.
@@ -386,6 +396,7 @@ export function addCoordinateTransforms(source, destination, forward, inverse) {
  * @api
  */
 export function fromLonLat(coordinate, opt_projection) {
+  disableCoordinateWarning();
   return transform(
     coordinate,
     'EPSG:4326',
@@ -598,6 +609,20 @@ export function toUserCoordinate(coordinate, sourceProjection) {
  */
 export function fromUserCoordinate(coordinate, destProjection) {
   if (!userProjection) {
+    if (
+      showCoordinateWarning &&
+      !equals(coordinate, [0, 0]) &&
+      coordinate[0] >= -180 &&
+      coordinate[0] <= 180 &&
+      coordinate[1] >= -90 &&
+      coordinate[1] <= 90
+    ) {
+      showCoordinateWarning = false;
+      // eslint-disable-next-line no-console
+      console.warn(
+        'Call useGeographic() ol/proj once to work with [longitude, latitude] coordinates.'
+      );
+    }
     return coordinate;
   }
   return transform(coordinate, userProjection, destProjection);

test/node/ol/proj.test.js

@@ -1,5 +1,6 @@
 import Projection from '../../../src/ol/proj/Projection.js';
 import Units from '../../../src/ol/proj/Units.js';
+import View from '../../../src/ol/View.js';
 import expect from '../expect.js';
 import proj4 from 'proj4';
 import {HALF_SIZE} from '../../../src/ol/proj/epsg3857.js';
@@ -8,6 +9,7 @@ import {
   addCommon,
   clearAllProjections,
   clearUserProjection,
+  disableCoordinateWarning,
   equivalent,
   fromLonLat,
   fromUserCoordinate,
@@ -890,4 +892,43 @@ describe('ol/proj.js', function () {
       );
     });
   });
+
+  describe('Console info about `setUserProjection`', function () {
+    let originalConsole, callCount;
+    beforeEach(function () {
+      disableCoordinateWarning(false);
+      originalConsole = console;
+      callCount = 0;
+      global.console = {
+        ...console,
+        warn: () => ++callCount,
+      };
+    });
+    afterEach(function () {
+      global.console = originalConsole;
+      clearUserProjection();
+    });
+    it('is shown once when suspicious coordinates are used', function () {
+      const view = new View({
+        center: [16, 48],
+      });
+      view.setCenter([15, 47]);
+      expect(callCount).to.be(1);
+    });
+    it('is not shown when fromLonLat() is used', function () {
+      const view = new View({
+        center: fromLonLat([16, 48]),
+      });
+      view.setCenter(fromLonLat([15, 47]));
+      expect(callCount).to.be(0);
+    });
+    it('is not shown when useGeographic() is used', function () {
+      useGeographic();
+      const view = new View({
+        center: [16, 48],
+      });
+      view.setCenter([15, 47]);
+      expect(callCount).to.be(0);
+    });
+  });
 });