From 1a6c8c8362a0f8f3939e08734cacd3196d8b2799 Mon Sep 17 00:00:00 2001
From: Yegor Jbanov <yjbanov@google.com>
Date: Wed, 27 Jan 2021 13:53:37 -0800
Subject: [PATCH] [canvaskit] remove the DOM node of unrendered platform view

---
 .../src/engine/canvaskit/embedded_views.dart  | 24 ++++--
 .../test/canvaskit/embedded_views_test.dart   | 82 ++++++++++++++++++-
 2 files changed, 100 insertions(+), 6 deletions(-)

diff --git a/lib/web_ui/lib/src/engine/canvaskit/embedded_views.dart b/lib/web_ui/lib/src/engine/canvaskit/embedded_views.dart
index 90b047214086f..aa9055f9318ac 100644
--- a/lib/web_ui/lib/src/engine/canvaskit/embedded_views.dart
+++ b/lib/web_ui/lib/src/engine/canvaskit/embedded_views.dart
@@ -359,14 +359,17 @@ class HtmlViewEmbedder {
     final Set<int> unusedViews = Set<int>.from(_activeCompositionOrder);
     _activeCompositionOrder.clear();
 
+    List<int>? debugInvalidViewIds;
     for (int i = 0; i < _compositionOrder.length; i++) {
       int viewId = _compositionOrder[i];
 
-      assert(
-        _views.containsKey(viewId),
-        'Cannot render platform view $viewId. '
-        'It has not been created, or it has been deleted.',
-      );
+      if (assertionsEnabled) {
+        if (!_views.containsKey(viewId)) {
+          debugInvalidViewIds ??= <int>[];
+          debugInvalidViewIds.add(viewId);
+          continue;
+        }
+      }
 
       unusedViews.remove(viewId);
       html.Element platformViewRoot = _rootViews[viewId]!;
@@ -381,6 +384,16 @@ class HtmlViewEmbedder {
 
     for (final int unusedViewId in unusedViews) {
       _releaseOverlay(unusedViewId);
+      _rootViews[unusedViewId]?.remove();
+    }
+
+    if (assertionsEnabled) {
+      if (debugInvalidViewIds != null && debugInvalidViewIds.isNotEmpty) {
+        throw AssertionError(
+          'Cannot render platform views: ${debugInvalidViewIds.join(', ')}. '
+          'These views have not been created, or they have been deleted.',
+        );
+      }
     }
   }
 
@@ -476,6 +489,7 @@ class OverlayCache {
     for (final Surface overlay in _cache) {
       overlay.dispose();
     }
+    _cache.clear();
   }
 }
 
diff --git a/lib/web_ui/test/canvaskit/embedded_views_test.dart b/lib/web_ui/test/canvaskit/embedded_views_test.dart
index a1dc4f99f1695..4788d61c5cead 100644
--- a/lib/web_ui/test/canvaskit/embedded_views_test.dart
+++ b/lib/web_ui/test/canvaskit/embedded_views_test.dart
@@ -287,9 +287,79 @@ void testMain() {
       } on AssertionError catch (error) {
         expect(
           error.toString(),
-          'Assertion failed: "Cannot render platform view 0. It has not been created, or it has been deleted."',
+          'Assertion failed: "Cannot render platform views: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9. These views have not been created, or they have been deleted."',
         );
       }
+
+      // Frame 7:
+      //   Render: a platform view after error.
+      //   Expect: success. Just checking the system is not left in a corrupted state.
+      await _createPlatformView(0, 'test-platform-view');
+      renderTestScene(viewCount: 0);
+    });
+
+    test('embeds and disposes of a platform view', () async {
+      ui.platformViewRegistry.registerViewFactory(
+        'test-platform-view',
+        (viewId) => html.DivElement()..id = 'view-0',
+      );
+      await _createPlatformView(0, 'test-platform-view');
+
+      final EnginePlatformDispatcher dispatcher =
+          ui.window.platformDispatcher as EnginePlatformDispatcher;
+
+      LayerSceneBuilder sb = LayerSceneBuilder();
+      sb.pushOffset(0, 0);
+      sb.addPlatformView(0, width: 10, height: 10);
+      dispatcher.rasterizer!.draw(sb.build().layerTree);
+
+      expect(
+        domRenderer.sceneElement!.querySelectorAll('#view-0'),
+        hasLength(1),
+      );
+
+      await _disposePlatformView(0);
+
+      sb = LayerSceneBuilder();
+      sb.pushOffset(0, 0);
+      dispatcher.rasterizer!.draw(sb.build().layerTree);
+
+      expect(
+        domRenderer.sceneElement!.querySelectorAll('#view-0'),
+        hasLength(0),
+      );
+    });
+
+    test('removed the DOM node of an unrendered platform view', () async {
+      ui.platformViewRegistry.registerViewFactory(
+        'test-platform-view',
+        (viewId) => html.DivElement()..id = 'view-0',
+      );
+      await _createPlatformView(0, 'test-platform-view');
+
+      final EnginePlatformDispatcher dispatcher =
+          ui.window.platformDispatcher as EnginePlatformDispatcher;
+
+      LayerSceneBuilder sb = LayerSceneBuilder();
+      sb.pushOffset(0, 0);
+      sb.addPlatformView(0, width: 10, height: 10);
+      dispatcher.rasterizer!.draw(sb.build().layerTree);
+
+      expect(
+        domRenderer.sceneElement!.querySelectorAll('#view-0'),
+        hasLength(1),
+      );
+
+      // Render a frame without a platform view, but also without disposing of
+      // the platform view.
+      sb = LayerSceneBuilder();
+      sb.pushOffset(0, 0);
+      dispatcher.rasterizer!.draw(sb.build().layerTree);
+
+      expect(
+        domRenderer.sceneElement!.querySelectorAll('#view-0'),
+        hasLength(0),
+      );
     });
     // TODO: https://github.com/flutter/flutter/issues/60040
   }, skip: isIosSafari);
@@ -311,3 +381,13 @@ Future<void> _createPlatformView(int id, String viewType) {
   );
   return completer.future;
 }
+
+Future<void> _disposePlatformView(int id) {
+  final completer = Completer<void>();
+  window.sendPlatformMessage(
+    'flutter/platform_views',
+    codec.encodeMethodCall(MethodCall('dispose', id)),
+    (dynamic _) => completer.complete(),
+  );
+  return completer.future;
+}