mbcorona · Aug 7, 2026 · Jul 27, 2026 · Aug 4, 2026 · Aug 5, 2026 · Aug 6, 2026
diff --git a/engine/src/flutter/lib/web_ui/lib/src/engine/platform_views/embedder.dart b/engine/src/flutter/lib/web_ui/lib/src/engine/platform_views/embedder.dart
@@ -517,23 +517,38 @@ class PlatformViewEmbedder {
       canvas.displayCanvas!.setIsOverlay(needsOverlayPositioning);
     }
 
+    // Platform views which were disposed while they were still being
+    // composited. They are left out of the DOM.
+    final missingViewIds = <int>{};
+
     // At this point, the DOM contains the static elements and the elements from
     // the previous composition which need to move. We iterate over the static
     // elements and insert the elements which come before them into the DOM.
     var staticElementIndex = 0;
     var nextCompositionIndex = 0;
     while (staticElementIndex < staticElements.length) {
       final int staticElementIndexInActiveComposition = staticElements[staticElementIndex];
-      final DomElement staticDomElement = _getElement(
+      final DomElement? staticDomElement = _getElement(
         _activeComposition.entities[staticElementIndexInActiveComposition],
       );
+      if (staticDomElement == null) {
+        // This view is not in the DOM, so it can't position other elements.
+        // Use the next static element instead.
+        staticElementIndex++;
+        continue;
+      }
       // Go through next composition elements until we reach the static element.
       while (indexMap[nextCompositionIndex] != staticElementIndexInActiveComposition) {
         final CompositionEntity nextEntity = composition.entities[nextCompositionIndex];
         if (nextEntity is CompositionCanvas) {
           updateCompositionCanvasWithDisplay(nextEntity, nextCompositionIndex);
         }
-        sceneHost.insertBefore(_getElement(nextEntity), staticDomElement);
+        final DomElement? nextDomElement = _getElement(nextEntity);
+        if (nextDomElement != null) {
+          sceneHost.insertBefore(nextDomElement, staticDomElement);
+        } else if (nextEntity is CompositionPlatformView) {
+          missingViewIds.add(nextEntity.viewId);
+        }
         nextCompositionIndex++;
       }
       if (composition.entities[nextCompositionIndex] is CompositionCanvas) {
@@ -554,15 +569,35 @@ class PlatformViewEmbedder {
       if (nextEntity is CompositionCanvas) {
         updateCompositionCanvasWithDisplay(nextEntity, nextCompositionIndex);
       }
-      sceneHost.append(_getElement(nextEntity));
+      final DomElement? nextDomElement = _getElement(nextEntity);
+      if (nextDomElement != null) {
+        sceneHost.append(nextDomElement);
+      } else if (nextEntity is CompositionPlatformView) {
+        missingViewIds.add(nextEntity.viewId);
+      }
       nextCompositionIndex++;
     }
+
+    if (missingViewIds.isNotEmpty) {
+      // Drop the skipped views, so the next frame doesn't expect them to be
+      // in the DOM.
+      composition.entities.removeWhere(
+        (CompositionEntity entity) =>
+            entity is CompositionPlatformView && missingViewIds.contains(entity.viewId),
+      );
+      printWarning(
+        'Cannot render platform views: ${missingViewIds.join(', ')}. '
+        'These views were disposed while they were being composited.',
+      );
+    }
   }
 
-  DomElement _getElement(CompositionEntity entity) {
+  /// Returns the DOM element for [entity], or null if the platform view no
+  /// longer has a clip chain because it was disposed.
+  DomElement? _getElement(CompositionEntity entity) {
     return switch (entity) {
       CompositionCanvas() => entity.displayCanvas!.hostElement,
-      CompositionPlatformView() => _viewClipChains[entity.viewId]!.root,
+      CompositionPlatformView() => _viewClipChains[entity.viewId]?.root,
     };
   }
 

diff --git a/engine/src/flutter/lib/web_ui/test/ui/platform_view_test.dart b/engine/src/flutter/lib/web_ui/test/ui/platform_view_test.dart
@@ -824,6 +824,59 @@ Future<void> testMain() async {
     expect(platformViewsHost.querySelector('flt-platform-view'), isNull);
   });
 
+  test('does not crash when a platform view is disposed mid-frame', () async {
+    await createPlatformView(0, platformViewType);
+    await createPlatformView(1, platformViewType);
+
+    final sb = ui.SceneBuilder()
+      ..pushOffset(0, 0)
+      ..addPlatformView(0, width: 10, height: 10)
+      ..addPlatformView(1, width: 10, height: 10)
+      ..pop();
+    await renderScene(sb.build());
+    _expectSceneMatches(<_EmbeddedViewMarker>[_platformView, _platformView]);
+
+    // Build the next frame by hand so that a platform view can be disposed
+    // after the composition was created, but before the frame is submitted.
+    final ViewRasterizer rasterizer = renderer.rasterizers[implicitView.viewId]!;
+    final PlatformViewEmbedder embedder = rasterizer.viewEmbedder;
+    final rootLayer = RootLayer();
+    // The views are composited in the opposite order, so the DOM needs to be
+    // updated for this composition.
+    rootLayer.children.add(PlatformViewLayer(1, ui.Offset.zero, 10, 10));
+    rootLayer.children.add(PlatformViewLayer(0, ui.Offset.zero, 10, 10));
+
+    embedder.frameSize = rasterizer.currentFrameSize;
+    final Frame frame = rasterizer.context.acquireFrame(embedder);
+    frame.raster(LayerTree(rootLayer), rasterizer.currentFrameSize, null);
+
+    // View 0 is disposed while it is still part of the composition which is
+    // about to be submitted.
+    embedder.disposeView(0);
+
+    final warnings = <String>[];
+    final void Function(String) originalPrintWarning = printWarning;
+    printWarning = (String warning) => warnings.add(warning);
+    try {
+      await expectLater(embedder.submitFrame(null), completes);
+    } finally {
+      printWarning = originalPrintWarning;
+    }
+
+    // The disposed view is left out of the composition.
+    _expectSceneMatches(<_EmbeddedViewMarker>[_platformView]);
+    expect(embedder.debugActiveComposition.entities, hasLength(1));
+    expect(
+      warnings,
+      contains(
+        contains(
+          'Cannot render platform views: 0. '
+          'These views were disposed while they were being composited.',
+        ),
+      ),
+    );
+  });
+
   test('preserves the DOM node of an unrendered platform view', () async {
     await createPlatformView(1, platformViewType);