Trigger a rendering when a data source becomes ready

CHANGES.md

@@ -7,6 +7,7 @@
 ##### Fixes :wrench:
 
 - Fixed a bug that Label position height may not be correctly updated when its HeightReference is relative. [#11929](https://github.com/CesiumGS/cesium/pull/11929)
+- Fixed a bug where a data source was not automatically rendered after is was added in request render mode. [#11934](https://github.com/CesiumGS/cesium/pull/11934)
 
 ### 1.116 - 2024-04-01
 

packages/engine/Source/DataSources/DataSourceDisplay.js

@@ -325,6 +325,11 @@ DataSourceDisplay.prototype.update = function (time) {
     result = visualizers[x].update(time) && result;
   }
 
+  // Request a rendering of the scene when the data source
+  // becomes 'ready' for the first time
+  if (!this._ready && result) {
+    this._scene.requestRender();
+  }
   this._ready = result;
 
   return result;

packages/engine/Specs/DataSources/DataSourceDisplaySpec.js

@@ -351,6 +351,45 @@ describe(
       });
     });
 
+    it("triggers a rendering when the data source becomes ready", function () {
+      scene.requestRenderMode = true;
+      scene.maximumRenderTimeChange = undefined;
+
+      // When the scene is constructed, then a listener that will be added via
+      // RequestScheduler.requestCompletedEvent.addEventListener
+      // that requests a single render (by putting a call to scene.requestRender()
+      // into the scene._frameState.afterRender list). The requestCompletedEvent
+      // is triggered when the request for the terrain heights completes that
+      // is initiated via GroundPolylinePrimitive.initializeTerrainHeights()
+      // in beforeAll of this suite.
+      // Consume this render request here
+      scene.renderForSpecs();
+
+      const source = new MockDataSource();
+      display = new DataSourceDisplay({
+        scene: scene,
+        dataSourceCollection: dataSourceCollection,
+        visualizersCallback: visualizersCallback,
+      });
+      expect(display.ready).toBe(false);
+
+      return dataSourceCollection.add(source).then(function () {
+        // When the source becomes ready, a render should
+        // be requested
+        display.update(Iso8601.MINIMUM_VALUE);
+        expect(display.ready).toBe(true);
+        expect(scene._renderRequested).toBe(true);
+
+        scene.renderForSpecs();
+
+        // The source should remain ready during subsequent updates,
+        // and no further renders should be requested
+        display.update(Iso8601.MINIMUM_VALUE);
+        expect(display.ready).toBe(true);
+        expect(scene._renderRequested).toBe(false);
+      });
+    });
+
     it("constructor throws if scene undefined", function () {
       expect(function () {
         return new DataSourceDisplay({