[web] Add canUpdateAsMatch to PersistedPlatformView. (flutter/engine#21313)

engine/src/flutter/lib/web_ui/dev/driver_manager.dart

@@ -5,7 +5,6 @@
 // @dart = 2.6
 import 'dart:io' as io;
 
-import 'package:meta/meta.dart';
 import 'package:path/path.dart' as pathlib;
 import 'package:web_driver_installer/chrome_driver_installer.dart';
 import 'package:web_driver_installer/firefox_driver_installer.dart';
@@ -184,14 +183,12 @@ class SafariDriverManager extends DriverManager {
 /// tests.
 abstract class DriverManager {
   /// Installation directory for browser's driver.
-  @protected
   final io.Directory _browserDriverDir;
 
   /// This is the parent directory for all drivers.
   ///
   /// This directory is saved to [temporaryDirectories] and deleted before
   /// tests shutdown.
-  @protected
   final io.Directory _drivers;
 
   DriverManager(String browser)
@@ -223,7 +220,6 @@ abstract class DriverManager {
 
   Future<void> _verifyDriverForLUCI();
 
-  @protected
   Future<void> _startDriver();
 
   static DriverManager chooseDriver(String browser) {

engine/src/flutter/lib/web_ui/lib/src/engine/history.dart

@@ -88,16 +88,13 @@ abstract class BrowserHistory {
   ///
   /// Subclasses should send appropriate system messages to update the flutter
   /// applications accordingly.
-  @protected
   void onPopState(covariant html.PopStateEvent event);
 
   /// Sets up any prerequisites to use this browser history class.
-  @protected
   Future<void> setup() => Future<void>.value();
 
   /// Restore any modifications to the html browser history during the lifetime
   /// of this class.
-  @protected
   Future<void> tearDown() => Future<void>.value();
 }
 

engine/src/flutter/lib/web_ui/lib/src/engine/html/platform_view.dart

@@ -75,6 +75,16 @@ class PersistedPlatformView extends PersistedLeafSurface {
     }
   }
 
+  // Platform Views can only be updated if their viewId matches.
+  @override
+  bool canUpdateAsMatch(PersistedSurface oldSurface) {
+    if (super.canUpdateAsMatch(oldSurface)) {
+      // super checks the runtimeType of the surface, so we can just cast...
+      return viewId == ((oldSurface as PersistedPlatformView).viewId);
+    }
+    return false;
+  }
+
   @override
   double matchForUpdate(PersistedPlatformView existingSurface) {
     return existingSurface.viewId == viewId ? 0.0 : 1.0;
@@ -82,11 +92,10 @@ class PersistedPlatformView extends PersistedLeafSurface {
 
   @override
   void update(PersistedPlatformView oldSurface) {
+    assert(viewId == oldSurface.viewId, 'PersistedPlatformView with different viewId should never be updated. Check the canUpdateAsMatch method.',);
     super.update(oldSurface);
-    if (viewId != oldSurface.viewId) {
-      // The content of the surface has to be rebuild if the viewId is changed.
-      build();
-    } else if (dx != oldSurface.dx ||
+    // Only update if the view has been resized
+    if (dx != oldSurface.dx ||
         dy != oldSurface.dy ||
         width != oldSurface.width ||
         height != oldSurface.height) {

engine/src/flutter/lib/web_ui/lib/src/engine/html/surface.dart

@@ -275,7 +275,6 @@ abstract class PersistedSurface implements ui.EngineLayer {
   /// retain came in.
   @mustCallSuper
   @visibleForTesting
-  @protected
   void revive() {
     assert(debugAssertSurfaceState(this, PersistedSurfaceState.released));
     state = PersistedSurfaceState.created;
@@ -304,6 +303,7 @@ abstract class PersistedSurface implements ui.EngineLayer {
   html.Element? rootElement;
 
   /// Whether this surface can update an existing [oldSurface].
+  @mustCallSuper
   bool canUpdateAsMatch(PersistedSurface oldSurface) {
     return oldSurface.isActive && runtimeType == oldSurface.runtimeType;
   }
@@ -342,7 +342,6 @@ abstract class PersistedSurface implements ui.EngineLayer {
   ///
   /// This is called when we failed to locate an existing DOM element to reuse,
   /// such as on the very first frame.
-  @protected
   @mustCallSuper
   void build() {
     if (rootElement != null) {
@@ -371,7 +370,6 @@ abstract class PersistedSurface implements ui.EngineLayer {
   /// frame, we reuse old ones as much as possible. This method should only be
   /// called when [isTotalMatchFor] returns true for the [oldSurface]. Otherwise
   /// adopting the [oldSurface]'s elements could lead to correctness issues.
-  @protected
   @mustCallSuper
   void adoptElements(covariant PersistedSurface oldSurface) {
     assert(oldSurface.rootElement != null);
@@ -399,7 +397,6 @@ abstract class PersistedSurface implements ui.EngineLayer {
   ///
   /// Attempts to reuse [oldSurface]'s DOM element, if possible. Otherwise,
   /// creates a new element by calling [build].
-  @protected
   @mustCallSuper
   void update(covariant PersistedSurface oldSurface) {
     assert(oldSurface != null); // ignore: unnecessary_null_comparison
@@ -424,7 +421,6 @@ abstract class PersistedSurface implements ui.EngineLayer {
   ///
   /// This is also different from [build], which constructs a brand new surface
   /// sub-tree.
-  @protected
   @mustCallSuper
   void retain() {
     assert(rootElement != null);
@@ -448,7 +444,6 @@ abstract class PersistedSurface implements ui.EngineLayer {
   ///
   /// This method may be overridden by concrete implementations, for example, to
   /// recycle the resources owned by this surface.
-  @protected
   @mustCallSuper
   void discard() {
     assert(debugAssertSurfaceState(this, PersistedSurfaceState.active));
@@ -471,7 +466,6 @@ abstract class PersistedSurface implements ui.EngineLayer {
     state = PersistedSurfaceState.released;
   }
 
-  @protected
   @mustCallSuper
   void debugValidate(List<String> validationErrors) {
     if (rootElement == null) {
@@ -541,7 +535,6 @@ abstract class PersistedSurface implements ui.EngineLayer {
   /// clip behaviors.
   ///
   /// This method is called by the [preroll] method.
-  @protected
   void recomputeTransformAndClip() {
     _transform = parent!._transform;
     _localClipBounds = null;
@@ -578,7 +571,6 @@ abstract class PersistedSurface implements ui.EngineLayer {
     }
   }
 
-  @protected
   @mustCallSuper
   void debugPrintAttributes(StringBuffer buffer) {
     if (rootElement != null) {
@@ -586,7 +578,6 @@ abstract class PersistedSurface implements ui.EngineLayer {
     }
   }
 
-  @protected
   @mustCallSuper
   void debugPrintChildren(StringBuffer buffer, int indent) {}
 
@@ -1155,7 +1146,6 @@ abstract class PersistedContainerSurface extends PersistedSurface {
   }
 
   @override
-  @protected
   @mustCallSuper
   void debugValidate(List<String> validationErrors) {
     super.debugValidate(validationErrors);

engine/src/flutter/lib/web_ui/test/engine/surface/platform_view_test.dart

@@ -0,0 +1,88 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// @dart = 2.6
+import 'dart:async';
+import 'dart:html' as html;
+
+import 'package:ui/src/engine.dart';
+import 'package:ui/ui.dart';
+
+import 'package:test/bootstrap/browser.dart';
+import 'package:test/test.dart';
+
+import '../../matchers.dart';
+
+const MethodCodec codec = StandardMethodCodec();
+final EngineWindow window = EngineWindow();
+
+void main() {
+  internalBootstrapBrowserTest(() => testMain);
+}
+
+void testMain() {
+  PersistedPlatformView view;
+
+  group('PersistedPlatformView', () {
+    setUp(() async {
+      platformViewRegistry.registerViewFactory(
+        'test-0',
+        (viewId) => html.DivElement(),
+      );
+      platformViewRegistry.registerViewFactory(
+        'test-1',
+        (viewId) => html.DivElement(),
+      );
+      // Ensure the views are created...
+      await Future.wait([
+        _createPlatformView(0, 'test-0'),
+        _createPlatformView(1, 'test-1'),
+      ]);
+      view = PersistedPlatformView(0, 0, 0, 100, 100)..build();
+    });
+
+    group('update', () {
+      test('throws assertion error if called with different viewIds', () {
+        final differentView = PersistedPlatformView(1, 1, 1, 100, 100)..build();
+        expect(() {
+          view.update(differentView);
+        }, throwsAssertionError);
+      });
+    });
+
+    group('canUpdateAsMatch', () {
+      test('returns true when viewId is the same', () {
+        final sameView = PersistedPlatformView(0, 1, 1, 100, 100)..build();
+        expect(view.canUpdateAsMatch(sameView), isTrue);
+      });
+
+      test('returns false when viewId is different', () {
+        final differentView = PersistedPlatformView(1, 1, 1, 100, 100)..build();
+        expect(view.canUpdateAsMatch(differentView), isFalse);
+      });
+
+      test('returns false when other view is not a PlatformView', () {
+        final anyView = PersistedOpacity(null, 1, Offset(0, 0))..build();
+        expect(view.canUpdateAsMatch(anyView), isFalse);
+      });
+    });
+  });
+}
+
+// Sends a platform message to create a Platform View with the given id and viewType.
+Future<void> _createPlatformView(int id, String viewType) {
+  final completer = Completer<void>();
+  window.sendPlatformMessage(
+    'flutter/platform_views',
+    codec.encodeMethodCall(MethodCall(
+      'create',
+      <String, dynamic>{
+        'id': id,
+        'viewType': viewType,
+      },
+    )),
+    (dynamic _) => completer.complete(),
+  );
+  return completer.future;
+}