[iOS] Fix jitter keyboard animation by updating metrics value in onFrameRasterized callback.

shell/common/shell.cc

@@ -1510,6 +1510,14 @@ void Shell::OnFrameRasterized(const FrameTiming& timing) {
         },
         fml::TimeDelta::FromMilliseconds(kBatchTimeInMilliseconds));
   }
+
+  {
+    std::scoped_lock<std::mutex> lock(on_frame_rasterized_callbacks_mutex_);
+    for (auto callback : on_frame_rasterized_callbacks_) {
+      callback();
+    }
+    on_frame_rasterized_callbacks_.clear();
+  }
 }
 
 fml::Milliseconds Shell::GetFrameBudget() {
@@ -1749,6 +1757,11 @@ void Shell::RegisterImageDecoder(ImageGeneratorFactory factory,
       });
 }
 
+void Shell::AddOnFrameRasterizedCallback(const fml::closure& callback) {
+  std::scoped_lock<std::mutex> lock(on_frame_rasterized_callbacks_mutex_);
+  on_frame_rasterized_callbacks_.push_back(callback);
+}
+
 bool Shell::OnServiceProtocolGetSkSLs(
     const ServiceProtocol::Handler::ServiceProtocolMap& params,
     rapidjson::Document* response) {

shell/common/shell.h

@@ -397,6 +397,8 @@ class Shell final : public PlatformView::Delegate,
   /// @see        `CreateCompatibleGenerator`
   void RegisterImageDecoder(ImageGeneratorFactory factory, int32_t priority);
 
+  void AddOnFrameRasterizedCallback(const fml::closure& callback);
+
   // |Engine::Delegate|
   const std::shared_ptr<PlatformMessageHandler>& GetPlatformMessageHandler()
       const override;
@@ -474,6 +476,9 @@ class Shell final : public PlatformView::Delegate,
   // Used to communicate the right frame bounds via service protocol.
   double device_pixel_ratio_ = 0.0;
 
+  std::mutex on_frame_rasterized_callbacks_mutex_;
+  std::vector<fml::closure> on_frame_rasterized_callbacks_;
+
   // How many frames have been timed since last report.
   size_t UnreportedFramesCount() const;
 

shell/platform/darwin/ios/framework/Source/FlutterViewController.mm

@@ -1609,15 +1609,16 @@ - (void)setupKeyboardAnimationVsyncClient {
         flutterViewController.get()->_viewportMetrics.physical_view_inset_bottom =
             flutterViewController.get()
                 .keyboardAnimationView.layer.presentationLayer.frame.origin.y;
-        [flutterViewController updateViewportMetrics];
+        [flutterViewController keyboardAnimationUpdateViewportMetricsInFrameRasterizedCallback];
       }
     } else {
-      fml::TimeDelta timeElapsed = recorder.get()->GetVsyncTargetTime() -
+      fml::TimeDelta frameInterval = recorder->GetVsyncTargetTime() - recorder->GetVsyncStartTime();
+      fml::TimeDelta timeElapsed = recorder.get()->GetVsyncTargetTime() + frameInterval -
                                    flutterViewController.get().keyboardAnimationStartTime;
 
       flutterViewController.get()->_viewportMetrics.physical_view_inset_bottom =
           [[flutterViewController keyboardSpringAnimation] curveFunction:timeElapsed.ToSecondsF()];
-      [flutterViewController updateViewportMetrics];
+      [flutterViewController keyboardAnimationUpdateViewportMetricsInFrameRasterizedCallback];
     }
   };
   flutter::Shell& shell = [_engine.get() shell];
@@ -1630,6 +1631,26 @@ - (void)setupKeyboardAnimationVsyncClient {
   [_keyboardAnimationVSyncClient await];
 }
 
+- (void)keyboardAnimationUpdateViewportMetricsInFrameRasterizedCallback {
+  fml::closure platformTask = [weakSelf = [self getWeakPtr]] {
+    if (!weakSelf) {
+      return;
+    }
+    fml::scoped_nsobject<FlutterViewController> flutterViewController(
+        [(FlutterViewController*)weakSelf.get() retain]);
+    if (!flutterViewController) {
+      return;
+    }
+    [flutterViewController updateViewportMetrics];
+  };
+
+  flutter::Shell& shell = [_engine.get() shell];
+  fml::closure onFrameRasterizedCallback = [&shell, platformTask] {
+    shell.GetTaskRunners().GetPlatformTaskRunner()->PostTask(platformTask);
+  };
+  shell.AddOnFrameRasterizedCallback(onFrameRasterizedCallback);
+}
+
 - (void)invalidateKeyboardAnimationVSyncClient {
   [_keyboardAnimationVSyncClient invalidate];
   [_keyboardAnimationVSyncClient release];