[web:multiview] Make CanvasKitRenderer listen for view creation/disposal events

lib/web_ui/lib/src/engine/canvaskit/embedded_views.dart

@@ -657,8 +657,8 @@ class HtmlViewEmbedder {
     element.remove();
   }
 
-  /// Clears the state of this view embedder. Used in tests.
-  void debugClear() {
+  /// Disposes the state of this view embedder.
+  void dispose() {
     final Set<int> allViews = PlatformViewManager.instance.debugClear();
     disposeViews(allViews);
     _context = EmbedderFrameContext();

lib/web_ui/lib/src/engine/canvaskit/rasterizer.dart

@@ -43,8 +43,8 @@ class Rasterizer {
     final CkPictureRecorder pictureRecorder = CkPictureRecorder();
     pictureRecorder.beginRecording(ui.Offset.zero & _currentFrameSize);
     pictureRecorder.recordingCanvas!.clear(const ui.Color(0x00000000));
-    final Frame compositorFrame = context.acquireFrame(
-        pictureRecorder.recordingCanvas!, viewEmbedder);
+    final Frame compositorFrame =
+        context.acquireFrame(pictureRecorder.recordingCanvas!, viewEmbedder);
 
     compositorFrame.raster(layerTree, ignoreRasterCache: true);
 
@@ -54,4 +54,10 @@ class Rasterizer {
 
     viewEmbedder.submitFrame();
   }
+
+  /// Disposes of this rasterizer.
+  void dispose() {
+    viewEmbedder.dispose();
+    renderCanvasFactory.dispose();
+  }
 }

lib/web_ui/lib/src/engine/canvaskit/render_canvas_factory.dart

@@ -9,7 +9,7 @@ import '../../engine.dart';
 class RenderCanvasFactory {
   RenderCanvasFactory() {
     assert(() {
-      registerHotRestartListener(debugClear);
+      registerHotRestartListener(dispose);
       return true;
     }());
   }
@@ -102,8 +102,8 @@ class RenderCanvasFactory {
     return false;
   }
 
-  /// Dispose all canvases created by this factory. Used in tests.
-  void debugClear() {
+  /// Dispose all canvases created by this factory.
+  void dispose() {
     for (final RenderCanvas canvas in _cache) {
       canvas.dispose();
     }

lib/web_ui/lib/src/engine/canvaskit/renderer.dart

@@ -55,6 +55,11 @@ class CanvasKitRenderer implements Renderer {
   /// is supported.
   final Surface pictureToImageSurface = Surface();
 
+  // Listens for view creation events from the view manager.
+  StreamSubscription<int>? _onViewCreatedListener;
+  // Listens for view disposal events from the view manager.
+  StreamSubscription<int>? _onViewDisposedListener;
+
   @override
   Future<void> initialize() async {
     _initialized ??= () async {
@@ -64,6 +69,20 @@ class CanvasKitRenderer implements Renderer {
         canvasKit = await downloadCanvasKit();
         windowFlutterCanvasKit = canvasKit;
       }
+      // Views may have been registered before this renderer was initialized.
+      // Create rasterizers for them and then start listening for new view
+      // creation/disposal events.
+      final FlutterViewManager viewManager =
+          EnginePlatformDispatcher.instance.viewManager;
+      if (_onViewCreatedListener == null) {
+        for (final EngineFlutterView view in viewManager.views) {
+          _onViewCreated(view.viewId);
+        }
+      }
+      _onViewCreatedListener ??=
+          viewManager.onViewCreated.listen(_onViewCreated);
+      _onViewDisposedListener ??=
+          viewManager.onViewDisposed.listen(_onViewDisposed);
       _instance = this;
     }();
     return _initialized;
@@ -394,37 +413,44 @@ class CanvasKitRenderer implements Renderer {
     frameTimingsOnBuildFinish();
     frameTimingsOnRasterStart();
 
-    // TODO(harryterkelsen): Use `FlutterViewManager.onViewsChanged` to manage
-    // the lifecycle of Rasterizers,
-    // https://github.com/flutter/flutter/issues/137073.
-    final Rasterizer rasterizer =
-        _getRasterizerForView(view as EngineFlutterView);
+    assert(_rasterizers.containsKey(view.viewId),
+        "Unable to render to a view which hasn't been registered");
+    final Rasterizer rasterizer = _rasterizers[view.viewId]!;
 
     rasterizer.draw((scene as LayerScene).layerTree);
     frameTimingsOnRasterFinish();
   }
 
-  final Map<EngineFlutterView, Rasterizer> _rasterizers =
-      <EngineFlutterView, Rasterizer>{};
+  // Map from view id to the associated Rasterizer for that view.
+  final Map<int, Rasterizer> _rasterizers = <int, Rasterizer>{};
 
-  Rasterizer _getRasterizerForView(EngineFlutterView view) {
-    return _rasterizers.putIfAbsent(view, () {
-      return Rasterizer(view);
-    });
+  void _onViewCreated(int viewId) {
+    final EngineFlutterView view =
+        EnginePlatformDispatcher.instance.viewManager[viewId]!;
+    _rasterizers[view.viewId] = Rasterizer(view);
+  }
+
+  void _onViewDisposed(int viewId) {
+    // The view has already been disposed.
+    if (!_rasterizers.containsKey(viewId)) {
+      return;
+    }
+    final Rasterizer rasterizer = _rasterizers.remove(viewId)!;
+    rasterizer.dispose();
   }
 
-  /// Returns the [Rasterizer] that has been created for the given [view].
-  /// Used in tests.
-  Rasterizer debugGetRasterizerForView(EngineFlutterView view) {
-    return _getRasterizerForView(view);
+  Rasterizer? debugGetRasterizerForView(EngineFlutterView view) {
+    return _rasterizers[view.viewId];
   }
 
-  /// Resets the state of the renderer. Used in tests.
-  void debugClear() {
+  /// Disposes this renderer.
+  void dispose() {
+    _onViewCreatedListener?.cancel();
+    _onViewDisposedListener?.cancel();
     for (final Rasterizer rasterizer in _rasterizers.values) {
-      rasterizer.renderCanvasFactory.debugClear();
-      rasterizer.viewEmbedder.debugClear();
+      rasterizer.dispose();
     }
+    _rasterizers.clear();
   }
 
   @override

lib/web_ui/lib/src/engine/view_embedder/flutter_view_manager.dart

@@ -15,12 +15,18 @@ class FlutterViewManager {
   // A map of (optional) JsFlutterViewOptions, indexed by their viewId.
   final Map<int, JsFlutterViewOptions> _jsViewOptions =
       <int, JsFlutterViewOptions>{};
-  // The controller of the [onViewsChanged] stream.
-  final StreamController<void> _onViewsChangedController =
-      StreamController<void>.broadcast();
+  // The controller of the [onViewCreated] stream.
+  final StreamController<int> _onViewCreatedController =
+      StreamController<int>.broadcast(sync: true);
+  // The controller of the [onViewDisposed] stream.
+  final StreamController<int> _onViewDisposedController =
+      StreamController<int>.broadcast(sync: true);
 
-  /// A stream of `void` events that will fire when a view is registered/unregistered.
-  Stream<void> get onViewsChanged => _onViewsChangedController.stream;
+  /// A stream of viewIds that will fire when a view is created.
+  Stream<int> get onViewCreated => _onViewCreatedController.stream;
+
+  /// A stream of viewIds that will fire when a view is disposed.
+  Stream<int> get onViewDisposed => _onViewDisposedController.stream;
 
   /// Exposes all the [EngineFlutterView]s registered so far.
   Iterable<EngineFlutterView> get views => _viewData.values;
@@ -33,7 +39,8 @@ class FlutterViewManager {
   EngineFlutterView createAndRegisterView(
     JsFlutterViewOptions jsViewOptions,
   ) {
-    final EngineFlutterView view = EngineFlutterView(_dispatcher, jsViewOptions.hostElement);
+    final EngineFlutterView view =
+        EngineFlutterView(_dispatcher, jsViewOptions.hostElement);
     registerView(view, jsViewOptions: jsViewOptions);
     return view;
   }
@@ -53,7 +60,7 @@ class FlutterViewManager {
     if (jsViewOptions != null) {
       _jsViewOptions[viewId] = jsViewOptions;
     }
-    _onViewsChangedController.add(null);
+    _onViewCreatedController.add(viewId);
 
     return view;
   }
@@ -74,7 +81,7 @@ class FlutterViewManager {
   JsFlutterViewOptions? unregisterView(int viewId) {
     _viewData.remove(viewId); // .dispose();
     final JsFlutterViewOptions? jsViewOptions = _jsViewOptions.remove(viewId);
-    _onViewsChangedController.add(null);
+    _onViewDisposedController.add(viewId);
     return jsViewOptions;
   }
 
@@ -91,7 +98,8 @@ class FlutterViewManager {
     // inside the loop.
     _viewData.keys.toList().forEach(disposeAndUnregisterView);
     // Let listeners receive the unregistration events from the loop above, then
-    // close the stream.
-    _onViewsChangedController.close();
+    // close the streams.
+    _onViewCreatedController.close();
+    _onViewDisposedController.close();
   }
 }

lib/web_ui/test/canvaskit/common.dart

@@ -22,10 +22,6 @@ void setUpCanvasKitTest() {
     setUpTestViewDimensions: false,
   );
 
-  tearDown(() {
-    CanvasKitRenderer.instance.debugClear();
-  });
-
   setUp(() => renderer.fontCollection.fontFallbackManager!.downloadQueue
       .fallbackFontUrlPrefixOverride = 'assets/fallback_fonts/');
   tearDown(() => renderer.fontCollection.fontFallbackManager!.downloadQueue

lib/web_ui/test/canvaskit/embedded_views_test.dart

@@ -61,6 +61,8 @@ void testMain() {
           reason: 'The slot reenables pointer events.');
       expect(contentsHost.getAttribute('slot'), slot.getAttribute('name'),
           reason: 'The contents and slot are correctly related.');
+
+      await disposePlatformView(0);
     });
 
     test('clips platform views with RRects', () async {
@@ -101,6 +103,8 @@ void testMain() {
         sceneHost.querySelectorAll('flt-clip').single.style.height,
         '100%',
       );
+
+      await disposePlatformView(0);
     });
 
     test('correctly transforms platform views', () async {
@@ -131,6 +135,8 @@ void testMain() {
         // 503 (5 * 100 + 3).
         'matrix3d(5, 0, 0, 0, 0, 5, 0, 0, 0, 0, 5, 0, 515, 515, 0, 1)',
       );
+
+      await disposePlatformView(0);
     });
 
     test('correctly offsets platform views', () async {
@@ -157,6 +163,8 @@ void testMain() {
       expect(slotRect.top, 4);
       expect(slotRect.right, 8);
       expect(slotRect.bottom, 10);
+
+      await disposePlatformView(0);
     });
 
     // Returns the list of CSS transforms applied to the ancestor chain of
@@ -189,8 +197,7 @@ void testMain() {
       CanvasKitRenderer.instance.renderScene(sb.build(), implicitView);
 
       // Transformations happen on the slot element.
-      DomElement slotHost =
-          sceneHost.querySelector('flt-platform-view-slot')!;
+      DomElement slotHost = sceneHost.querySelector('flt-platform-view-slot')!;
 
       expect(
         getTransformChain(slotHost),
@@ -220,6 +227,8 @@ void testMain() {
           'matrix(1, 0, 0, 1, 3, 3)',
         ],
       );
+
+      await disposePlatformView(0);
     });
 
     test('converts device pixels to logical pixels (no clips)', () async {
@@ -245,6 +254,8 @@ void testMain() {
         getTransformChain(slotHost),
         <String>['matrix(0.25, 0, 0, 0.25, 1.5, 1.5)'],
       );
+
+      await disposePlatformView(0);
     });
 
     test('converts device pixels to logical pixels (with clips)', () async {
@@ -276,6 +287,8 @@ void testMain() {
           'matrix(0.25, 0, 0, 0.25, 0.75, 0.75)',
         ],
       );
+
+      await disposePlatformView(0);
     });
 
     test('renders overlays on top of platform views', () async {
@@ -428,6 +441,10 @@ void testMain() {
       await createPlatformView(0, 'test-platform-view');
       renderTestScene(viewCount: 0);
       _expectSceneMatches(<_EmbeddedViewMarker>[_overlay]);
+
+      for (int i = 0; i < 16; i++) {
+        await disposePlatformView(i);
+      }
       // TODO(yjbanov): skipped due to https://github.com/flutter/flutter/issues/73867
     }, skip: isSafari);
 
@@ -561,6 +578,10 @@ void testMain() {
         _overlay,
       ]);
 
+      for (int i = 0; i < 20; i++) {
+        await disposePlatformView(i);
+      }
+
       // TODO(yjbanov): skipped due to https://github.com/flutter/flutter/issues/73867
     }, skip: isSafari);
 
@@ -641,6 +662,8 @@ void testMain() {
 
       implicitView.debugPhysicalSizeOverride = null;
       implicitView.debugForceResize();
+
+      await disposePlatformView(0);
       // ImageDecoder is not supported in Safari or Firefox.
     }, skip: isSafari || isFirefox);
 
@@ -695,6 +718,9 @@ void testMain() {
         platformViewsHost.querySelectorAll('flt-platform-view'),
         hasLength(2),
       );
+
+      await disposePlatformView(0);
+      await disposePlatformView(1);
     });
 
     test(
@@ -729,6 +755,8 @@ void testMain() {
       await Future<void>.delayed(Duration.zero);
       renderTestScene();
       expect(skPathDefs.childNodes, hasLength(1));
+
+      await disposePlatformView(0);
     });
 
     test('does not crash when a prerolled platform view is not composited',
@@ -749,6 +777,8 @@ void testMain() {
       _expectSceneMatches(<_EmbeddedViewMarker>[
         _overlay,
       ]);
+
+      await disposePlatformView(0);
     });
 
     test('does not create overlays for invisible platform views', () async {
@@ -951,6 +981,9 @@ void testMain() {
         _platformView,
         _overlay,
       ]);
+      for (int i = 0; i < 7; i++) {
+        await disposePlatformView(i);
+      }
     });
   });
 }