Web

Author: dkwingsmt

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

@@ -102,6 +102,30 @@ void debugResetEngineInitializationState() {
   _initializationState = DebugEngineInitializationState.uninitialized;
 }
 
+void renderFrame(int timeInMicroseconds) {
+  frameTimingsOnVsync();
+
+  // In Flutter terminology "building a frame" consists of "beginning
+  // frame" and "drawing frame".
+  //
+  // We do not call `frameTimingsOnBuildFinish` from here because
+  // part of the rasterization process, particularly in the HTML
+  // renderer, takes place in the `SceneBuilder.build()`.
+  frameTimingsOnBuildStart();
+  if (EnginePlatformDispatcher.instance.onBeginFrame != null) {
+    EnginePlatformDispatcher.instance.invokeOnBeginFrame(
+        Duration(microseconds: timeInMicroseconds));
+  }
+
+  if (EnginePlatformDispatcher.instance.onDrawFrame != null) {
+    // TODO(yjbanov): technically Flutter flushes microtasks between
+    //                onBeginFrame and onDrawFrame. We don't, which hasn't
+    //                been an issue yet, but eventually we'll have to
+    //                implement it properly.
+    EnginePlatformDispatcher.instance.invokeOnDrawFrame();
+  }
+}
+
 /// Initializes non-UI engine services.
 ///
 /// Does not put any UI onto the page. It is therefore safe to call this
@@ -158,8 +182,6 @@ Future<void> initializeEngineServices({
     if (!waitingForAnimation) {
       waitingForAnimation = true;
       domWindow.requestAnimationFrame((JSNumber highResTime) {
-        frameTimingsOnVsync();
-
         // Reset immediately, because `frameHandler` can schedule more frames.
         waitingForAnimation = false;
 
@@ -170,29 +192,14 @@ Future<void> initializeEngineServices({
         // microsecond precision, and only then convert to `int`.
         final int highResTimeMicroseconds =
             (1000 * highResTime.toDartDouble).toInt();
-
-        // In Flutter terminology "building a frame" consists of "beginning
-        // frame" and "drawing frame".
-        //
-        // We do not call `frameTimingsOnBuildFinish` from here because
-        // part of the rasterization process, particularly in the HTML
-        // renderer, takes place in the `SceneBuilder.build()`.
-        frameTimingsOnBuildStart();
-        if (EnginePlatformDispatcher.instance.onBeginFrame != null) {
-          EnginePlatformDispatcher.instance.invokeOnBeginFrame(
-              Duration(microseconds: highResTimeMicroseconds));
-        }
-
-        if (EnginePlatformDispatcher.instance.onDrawFrame != null) {
-          // TODO(yjbanov): technically Flutter flushes microtasks between
-          //                onBeginFrame and onDrawFrame. We don't, which hasn't
-          //                been an issue yet, but eventually we'll have to
-          //                implement it properly.
-          EnginePlatformDispatcher.instance.invokeOnDrawFrame();
-        }
+        renderFrame(highResTimeMicroseconds);
       });
     }
   };
+  warmUpFrameCallback = () {
+    // TODO(dkwingsmt): Can we give it some time value?
+    renderFrame(0);
+  };
 
   assetManager ??= ui_web.AssetManager(assetBase: configuration.assetBase);
   _setAssetManager(assetManager);

lib/web_ui/lib/src/engine/platform_dispatcher.dart

@@ -17,6 +17,13 @@ import '../engine.dart';
 /// This may be overridden in tests, for example, to pump fake frames.
 ui.VoidCallback? scheduleFrameCallback;
 
+/// Requests that the framework tries to render a frame immediately.
+///
+/// Since this will probably call [PlatformWindow.render] outside of an
+/// animation frame, the render will not be actually presented, but just to warm
+/// up the framework.
+ui.VoidCallback? warmUpFrameCallback;
+
 /// Signature of functions added as a listener to high contrast changes
 typedef HighContrastListener = void Function(bool enabled);
 typedef _KeyDataResponseCallback = void Function(bool handled);
@@ -773,8 +780,10 @@ class EnginePlatformDispatcher extends ui.PlatformDispatcher {
 
   @override
   void forceSyncFrame() {
-    // TODO(dkwingsmt): Call beginFrame and drawFrame, since the framework
-    // will no longer call them once it switches to forceSyncFrame.
+    if (warmUpFrameCallback == null) {
+      throw Exception('warmUpFrameCallback must be initialized first.');
+    }
+    warmUpFrameCallback!();
   }
 
   /// Updates the application's rendering on the GPU with the newly provided