revert canvaskit changes + use js interop instead of platform messages

Author: mdebbar

lib/web_ui/lib/src/engine.dart

@@ -162,6 +162,9 @@ void webOnlyInitializeEngine() {
   // initialize framework bindings.
   domRenderer;
 
+  // Calling this getter to force the [WebExperiments] instance to be created.
+  webExperiments;
+
   bool waitingForAnimation = false;
   ui.webOnlyScheduleFrameCallback = () {
     // We're asked to schedule a frame and call `frameHandler` when the frame

lib/web_ui/lib/src/engine/compositor/initialization.dart

@@ -6,7 +6,8 @@
 part of engine;
 
 /// EXPERIMENTAL: Enable the Skia-based rendering backend.
-bool get experimentalUseSkia => webExperiments.useSkia;
+const bool experimentalUseSkia =
+    bool.fromEnvironment('FLUTTER_WEB_USE_SKIA', defaultValue: false);
 
 /// The URL to use when downloading the CanvasKit script and associated wasm.
 ///

lib/web_ui/lib/src/engine/web_experiments.dart

@@ -5,51 +5,39 @@
 // @dart = 2.6
 part of engine;
 
-const MethodCodec codec = JSONMethodCodec();
-
 final WebExperiments webExperiments = WebExperiments._();
 
 /// A bag of all experiment flags in the web engine.
 ///
 /// This class also handles platform messages that can be sent to enable/disable
 /// certain experiments at runtime without the need to access engine internals.
 class WebExperiments {
-  WebExperiments._();
-
-  /// Experiment flag for using the Skia-based rendering backend.
-  bool get useSkia => _useSkia ?? false;
-  set useSkia(bool enabled) {
-    _useSkia = enabled;
+  WebExperiments._() {
+    js.context['_flutter_internal_update_experiment'] = updateExperiment;
   }
-  bool _useSkia = const bool.fromEnvironment('FLUTTER_WEB_USE_SKIA');
 
   /// Experiment flag for using canvas-based text measurement.
   bool get useCanvasText => _useCanvasText ?? false;
   set useCanvasText(bool enabled) {
     _useCanvasText = enabled;
   }
-  bool _useCanvasText =
-      const bool.fromEnvironment('FLUTTER_WEB_USE_EXPERIMENTAL_CANVAS_TEXT');
+
+  bool _useCanvasText = const bool.fromEnvironment(
+    'FLUTTER_WEB_USE_EXPERIMENTAL_CANVAS_TEXT',
+    defaultValue: null,
+  );
 
   /// Reset all experimental flags to their default values.
   void reset() {
-    _useSkia = null;
     _useCanvasText = null;
   }
 
-  /// Handles the platform message used to enable/disable web experiments in the
-  /// web engine.
-  void enableWebExperiments(Map<String, dynamic> message) {
-    for (final String name in message.keys) {
-      final bool enabled = message[name];
-      switch (name) {
-        case 'useSkia':
-          _useSkia = enabled;
-          break;
-        case 'useCanvasText':
-          _useCanvasText = enabled;
-          break;
-      }
+  /// Used to enable/disable experimental flags in the web engine.
+  void updateExperiment(String name, bool enabled) {
+    switch (name) {
+      case 'useCanvasText':
+        _useCanvasText = enabled;
+        break;
     }
   }
 }

lib/web_ui/lib/src/engine/window.dart

@@ -210,16 +210,6 @@ class EngineWindow extends ui.Window {
             break;
         }
         return;
-
-      case 'flutter/experiments':
-        const MethodCodec codec = JSONMethodCodec();
-        final MethodCall decoded = codec.decodeMethodCall(data);
-        final Map<String, dynamic> arguments = decoded.arguments;
-        switch (decoded.method) {
-          case 'enableWebExperiments':
-            webExperiments.enableWebExperiments(arguments);
-            return;
-        }
     }
 
     if (pluginMessageCallHandler != null) {

lib/web_ui/test/engine/web_experiments_test.dart

@@ -3,6 +3,9 @@
 // found in the LICENSE file.
 
 // @dart = 2.6
+import 'dart:html' as html;
+import 'dart:js_util' as js_util;
+
 import 'package:test/test.dart';
 import 'package:ui/src/engine.dart';
 
@@ -12,63 +15,55 @@ void main() {
   });
 
   test('default web experiment values', () {
-    expect(webExperiments.useSkia, false);
     expect(webExperiments.useCanvasText, false);
   });
 
   test('can turn on/off web experiments', () {
-    webExperiments.enableWebExperiments(<String, bool>{
-      'useSkia': true,
-    });
-    expect(webExperiments.useSkia, true);
-    expect(webExperiments.useCanvasText, false);
-
-    webExperiments.enableWebExperiments(<String, bool>{
-      'useSkia': false,
-      'useCanvasText': true,
-    });
-    expect(webExperiments.useSkia, false);
+    webExperiments.updateExperiment('useCanvasText', true);
     expect(webExperiments.useCanvasText, true);
 
-    webExperiments.enableWebExperiments(<String, bool>{
-      'useSkia': true,
-      'useCanvasText': null,
-    });
-    expect(webExperiments.useSkia, true);
-    // Goes back to default value.
+    webExperiments.updateExperiment('useCanvasText', false);
     expect(webExperiments.useCanvasText, false);
 
-    webExperiments.enableWebExperiments(<String, bool>{
-      'useSkia': null,
-    });
+    webExperiments.updateExperiment('useCanvasText', null);
     // Goes back to default value.
-    expect(webExperiments.useSkia, false);
+    expect(webExperiments.useCanvasText, false);
+  });
+
+  test('ignores unknown experiments', () {
+    expect(webExperiments.useCanvasText, false);
+    webExperiments.updateExperiment('foobarbazqux', true);
+    expect(webExperiments.useCanvasText, false);
+    webExperiments.updateExperiment('foobarbazqux', false);
     expect(webExperiments.useCanvasText, false);
   });
 
   test('can reset web experiments', () {
-    webExperiments.enableWebExperiments(<String, bool>{
-      'useSkia': true,
-      'useCanvasText': false,
-    });
+    webExperiments.updateExperiment('useCanvasText', true);
     webExperiments.reset();
-    expect(webExperiments.useSkia, false);
     expect(webExperiments.useCanvasText, false);
 
-    webExperiments.enableWebExperiments(<String, bool>{
-      'useSkia': false,
-      'useCanvasText': true,
-    });
+    webExperiments.updateExperiment('useCanvasText', true);
+    webExperiments.updateExperiment('foobarbazqux', true);
     webExperiments.reset();
-    expect(webExperiments.useSkia, false);
     expect(webExperiments.useCanvasText, false);
+  });
 
-    webExperiments.enableWebExperiments(<String, bool>{
-      'useSkia': true,
-      'useCanvasText': true,
-    });
-    webExperiments.reset();
-    expect(webExperiments.useSkia, false);
+  test('js interop also works', () {
+    expect(webExperiments.useCanvasText, false);
+
+    js_util.callMethod(
+      html.window,
+      '_flutter_internal_update_experiment',
+      <dynamic>['useCanvasText', true],
+    );
+    expect(webExperiments.useCanvasText, true);
+
+    js_util.callMethod(
+      html.window,
+      '_flutter_internal_update_experiment',
+      <dynamic>['useCanvasText', null],
+    );
     expect(webExperiments.useCanvasText, false);
   });
 }