Support multiple sources for layers

test/rendering/cases/webgl-tile-multisource/main.js

@@ -0,0 +1,58 @@
+import Map from '../../../../src/ol/Map.js';
+import TileGrid from '../../../../src/ol/tilegrid/TileGrid.js';
+import TileLayer from '../../../../src/ol/layer/WebGLTile.js';
+import View from '../../../../src/ol/View.js';
+import XYZ from '../../../../src/ol/source/XYZ.js';
+import {createXYZ} from '../../../../src/ol/tilegrid.js';
+import {get} from '../../../../src/ol/proj.js';
+import {sourcesFromTileGrid} from '../../../../src/ol/source.js';
+
+const resolutions = createXYZ({maxZoom: 1}).getResolutions();
+const tilePyramid = new TileGrid({
+  extent: get('EPSG:3857').getExtent(),
+  resolutions: [resolutions[1]],
+  tileSizes: [[256, 512]],
+});
+
+new Map({
+  target: 'map',
+  layers: [
+    new TileLayer({
+      sources: sourcesFromTileGrid(tilePyramid, (tileCoord) => {
+        let source;
+        switch (tileCoord.toString()) {
+          case '0,1,0':
+            source = new XYZ({
+              url: '/data/tiles/osm/{z}/{x}/{y}.png',
+              tileGrid: new TileGrid({
+                resolutions,
+                minZoom: tileCoord[0],
+                maxZoom: tileCoord[0] + 1,
+                extent: tilePyramid.getTileCoordExtent(tileCoord),
+                origin: [-20037508.342789244, 20037508.342789244],
+              }),
+            });
+            break;
+          default:
+            source = new XYZ({
+              url: '/data/tiles/satellite/{z}/{x}/{y}.jpg',
+              tileGrid: new TileGrid({
+                resolutions,
+                minZoom: tileCoord[0],
+                maxZoom: tileCoord[0] + 1,
+                extent: tilePyramid.getTileCoordExtent(tileCoord),
+                origin: [-20037508.342789244, 20037508.342789244],
+              }),
+            });
+        }
+        return source;
+      }),
+    }),
+  ],
+  view: new View({
+    center: [0, 0],
+    zoom: 1,
+  }),
+});
+
+render();