Do nothing if the params didn't change when compositing iOS platform views. (#8999)

flow/embedded_views.h

@@ -18,6 +18,10 @@ class EmbeddedViewParams {
  public:
   SkPoint offsetPixels;
   SkSize sizePoints;
+
+  bool operator==(const EmbeddedViewParams& other) const {
+    return offsetPixels == other.offsetPixels && sizePoints == other.sizePoints;
+  }
 };
 
 // This is only used on iOS when running in a non headless mode,

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

@@ -187,7 +187,14 @@ SkCanvas* FlutterPlatformViewsController::CompositeEmbeddedView(
     const flutter::EmbeddedViewParams& params) {
   // TODO(amirh): assert that this is running on the platform thread once we support the iOS
   // embedded views thread configuration.
-  // TODO(amirh): do nothing if the params didn't change.
+
+  // Do nothing if the params didn't change.
+  if (current_composition_params_.count(view_id) == 1 &&
+      current_composition_params_[view_id] == params) {
+    return picture_recorders_[view_id]->getRecordingCanvas();
+  }
+  current_composition_params_[view_id] = params;
+
   CGFloat screenScale = [[UIScreen mainScreen] scale];
   CGRect rect =
       CGRectMake(params.offsetPixels.x() / screenScale, params.offsetPixels.y() / screenScale,
@@ -209,6 +216,7 @@ void FlutterPlatformViewsController::Reset() {
   composition_order_.clear();
   active_composition_order_.clear();
   picture_recorders_.clear();
+  current_composition_params_.clear();
 }
 
 bool FlutterPlatformViewsController::SubmitFrame(bool gl_rendering,
@@ -288,6 +296,7 @@ void FlutterPlatformViewsController::DisposeViews() {
     views_.erase(viewId);
     touch_interceptors_.erase(viewId);
     overlays_.erase(viewId);
+    current_composition_params_.erase(viewId);
   }
   views_to_dispose_.clear();
 }

shell/platform/darwin/ios/framework/Source/FlutterPlatformViews_Internal.h

@@ -88,6 +88,8 @@ class FlutterPlatformViewsController {
   std::map<std::string, fml::scoped_nsobject<NSObject<FlutterPlatformViewFactory>>> factories_;
   std::map<int64_t, fml::scoped_nsobject<NSObject<FlutterPlatformView>>> views_;
   std::map<int64_t, fml::scoped_nsobject<FlutterTouchInterceptingView>> touch_interceptors_;
+  // Mapping a platform view ID to its latest composition params.
+  std::map<int64_t, EmbeddedViewParams> current_composition_params_;
   std::map<int64_t, std::unique_ptr<FlutterPlatformViewLayer>> overlays_;
   // The GrContext that is currently used by all of the overlay surfaces.
   // We track this to know when the GrContext for the Flutter app has changed