Re-land "Custom compositor layers must take into account the device p…

…ixel ratio."

This reverts commit 6c2381d and applies iOS fixes.

flow/embedded_views.h

@@ -208,7 +208,9 @@ class ExternalViewEmbedder {
   // sets the stage for the next pre-roll.
   virtual void CancelFrame() = 0;
 
-  virtual void BeginFrame(SkISize frame_size, GrContext* context) = 0;
+  virtual void BeginFrame(SkISize frame_size,
+                          GrContext* context,
+                          double device_pixel_ratio) = 0;
 
   virtual void PrerollCompositeEmbeddedView(
       int view_id,

flow/layers/layer_tree.h

@@ -71,8 +71,15 @@ class LayerTree {
     checkerboard_offscreen_layers_ = checkerboard;
   }
 
+  void set_device_pixel_ratio(double device_pixel_ratio) {
+    device_pixel_ratio_ = device_pixel_ratio;
+  }
+
+  double device_pixel_ratio() const { return device_pixel_ratio_; }
+
  private:
   SkISize frame_size_ = SkISize::MakeEmpty();  // Physical pixels.
+  double device_pixel_ratio_ = 1.0;
   std::shared_ptr<Layer> root_layer_;
   fml::TimePoint build_start_;
   fml::TimePoint build_finish_;

shell/common/engine.cc

@@ -438,6 +438,7 @@ void Engine::Render(std::unique_ptr<flutter::LayerTree> layer_tree) {
     return;
 
   layer_tree->set_frame_size(frame_size);
+  layer_tree->set_device_pixel_ratio(viewport_metrics_.device_pixel_ratio);
   animator_->Render(std::move(layer_tree));
 }
 

shell/common/rasterizer.cc

@@ -230,7 +230,8 @@ RasterStatus Rasterizer::DrawToSurface(flutter::LayerTree& layer_tree) {
 
   if (external_view_embedder != nullptr) {
     external_view_embedder->BeginFrame(layer_tree.frame_size(),
-                                       surface_->GetContext());
+                                       surface_->GetContext(),
+                                       layer_tree.device_pixel_ratio());
     embedder_root_surface = external_view_embedder->GetRootSurface();
   }
 

shell/platform/darwin/ios/ios_surface_gl.h

@@ -60,7 +60,7 @@ class IOSSurfaceGL final : public IOSSurface,
   void CancelFrame() override;
 
   // |ExternalViewEmbedder|
-  void BeginFrame(SkISize frame_size, GrContext* context) override;
+  void BeginFrame(SkISize frame_size, GrContext* context, double device_pixel_ratio) override;
 
   // |ExternalViewEmbedder|
   void PrerollCompositeEmbeddedView(int view_id,

shell/platform/darwin/ios/ios_surface_gl.mm

@@ -100,7 +100,7 @@
 }
 
 // |ExternalViewEmbedder|
-void IOSSurfaceGL::BeginFrame(SkISize frame_size, GrContext* context) {
+void IOSSurfaceGL::BeginFrame(SkISize frame_size, GrContext* context, double device_pixel_ratio) {
   FlutterPlatformViewsController* platform_views_controller = GetPlatformViewsController();
   FML_CHECK(platform_views_controller != nullptr);
   platform_views_controller->SetFrameSize(frame_size);

shell/platform/darwin/ios/ios_surface_metal.h

@@ -48,7 +48,7 @@ class IOSSurfaceMetal final : public IOSSurface,
   void CancelFrame() override;
 
   // |ExternalViewEmbedder|
-  void BeginFrame(SkISize frame_size, GrContext* context) override;
+  void BeginFrame(SkISize frame_size, GrContext* context, double device_pixel_ratio) override;
 
   // |ExternalViewEmbedder|
   void PrerollCompositeEmbeddedView(int view_id,

shell/platform/darwin/ios/ios_surface_metal.mm

@@ -61,7 +61,9 @@
   [CATransaction commit];
 }
 
-void IOSSurfaceMetal::BeginFrame(SkISize frame_size, GrContext* context) {
+void IOSSurfaceMetal::BeginFrame(SkISize frame_size,
+                                 GrContext* context,
+                                 double device_pixel_ratio) {
   FlutterPlatformViewsController* platform_views_controller = GetPlatformViewsController();
   FML_CHECK(platform_views_controller != nullptr);
   platform_views_controller->SetFrameSize(frame_size);

shell/platform/darwin/ios/ios_surface_software.h

@@ -52,7 +52,7 @@ class IOSSurfaceSoftware final : public IOSSurface,
   void CancelFrame() override;
 
   // |ExternalViewEmbedder|
-  void BeginFrame(SkISize frame_size, GrContext* context) override;
+  void BeginFrame(SkISize frame_size, GrContext* context, double device_pixel_ratio) override;
 
   // |ExternalViewEmbedder|
   void PrerollCompositeEmbeddedView(int view_id,

shell/platform/darwin/ios/ios_surface_software.mm

@@ -150,7 +150,9 @@
 }
 
 // |ExternalViewEmbedder|
-void IOSSurfaceSoftware::BeginFrame(SkISize frame_size, GrContext* context) {
+void IOSSurfaceSoftware::BeginFrame(SkISize frame_size,
+                                    GrContext* context,
+                                    double device_pixel_ratio) {
   FlutterPlatformViewsController* platform_views_controller = GetPlatformViewsController();
   FML_CHECK(platform_views_controller != nullptr);
   platform_views_controller->SetFrameSize(frame_size);

shell/platform/embedder/embedder.cc

@@ -984,6 +984,12 @@ FlutterEngineResult FlutterEngineSendWindowMetricsEvent(
   metrics.physical_height = SAFE_ACCESS(flutter_metrics, height, 0.0);
   metrics.device_pixel_ratio = SAFE_ACCESS(flutter_metrics, pixel_ratio, 1.0);
 
+  if (metrics.device_pixel_ratio <= 0.0) {
+    FML_LOG(ERROR) << "Device pixel ratio invalid: "
+                   << metrics.device_pixel_ratio;
+    return LOG_EMBEDDER_ERROR(kInvalidArguments);
+  }
+
   return reinterpret_cast<flutter::EmbedderEngine*>(engine)->SetViewportMetrics(
              std::move(metrics))
              ? kSuccess

shell/platform/embedder/embedder_external_view_embedder.cc

@@ -67,9 +67,12 @@ static SkISize TransformedSurfaceSize(const SkISize& size,
 
 // |ExternalViewEmbedder|
 void EmbedderExternalViewEmbedder::BeginFrame(SkISize frame_size,
-                                              GrContext* context) {
+                                              GrContext* context,
+                                              double device_pixel_ratio) {
   Reset();
+
   pending_frame_size_ = frame_size;
+  pending_device_pixel_ratio_ = device_pixel_ratio;
   pending_surface_transformation_ = GetSurfaceTransformation();
 
   const auto surface_size = TransformedSurfaceSize(
@@ -155,7 +158,8 @@ SkCanvas* EmbedderExternalViewEmbedder::CompositeEmbeddedView(int view_id) {
 static FlutterLayer MakeBackingStoreLayer(
     const SkISize& frame_size,
     const FlutterBackingStore* store,
-    const SkMatrix& surface_transformation) {
+    const SkMatrix& surface_transformation,
+    double device_pixel_ratio) {
   FlutterLayer layer = {};
 
   layer.struct_size = sizeof(layer);
@@ -166,7 +170,9 @@ static FlutterLayer MakeBackingStoreLayer(
       SkRect::MakeWH(frame_size.width(), frame_size.height());
 
   const auto transformed_layer_bounds =
-      surface_transformation.mapRect(layer_bounds);
+      SkMatrix::Concat(surface_transformation,
+                       SkMatrix::MakeScale(device_pixel_ratio))
+          .mapRect(layer_bounds);
 
   layer.offset.x = transformed_layer_bounds.x();
   layer.offset.y = transformed_layer_bounds.y();
@@ -190,7 +196,8 @@ static FlutterPlatformView MakePlatformView(
 static FlutterLayer MakePlatformViewLayer(
     const EmbeddedViewParams& params,
     const FlutterPlatformView& platform_view,
-    const SkMatrix& surface_transformation) {
+    const SkMatrix& surface_transformation,
+    double device_pixel_ratio) {
   FlutterLayer layer = {};
 
   layer.struct_size = sizeof(layer);
@@ -204,7 +211,9 @@ static FlutterLayer MakePlatformViewLayer(
   );
 
   const auto transformed_layer_bounds =
-      surface_transformation.mapRect(layer_bounds);
+      SkMatrix::Concat(surface_transformation,
+                       SkMatrix::MakeScale(device_pixel_ratio))
+          .mapRect(layer_bounds);
 
   layer.offset.x = transformed_layer_bounds.x();
   layer.offset.y = transformed_layer_bounds.y();
@@ -235,8 +244,11 @@ bool EmbedderExternalViewEmbedder::SubmitFrame(GrContext* context) {
   {
     // The root surface is expressed as a layer.
     presented_layers.push_back(MakeBackingStoreLayer(
-        pending_frame_size_, root_render_target_->GetBackingStore(),
-        pending_surface_transformation_));
+        pending_frame_size_,                     // frame size
+        root_render_target_->GetBackingStore(),  // backing store
+        pending_surface_transformation_,         // surface transformation
+        pending_device_pixel_ratio_              // device pixel ratio
+        ));
   }
 
   const auto surface_size = TransformedSurfaceSize(
@@ -262,9 +274,12 @@ bool EmbedderExternalViewEmbedder::SubmitFrame(GrContext* context) {
     // The layers presented to the embedder will contain a back pointer to this
     // struct. It is safe to deallocate when the embedder callback is done.
     presented_platform_views[view_id] = MakePlatformView(view_id);
-    presented_layers.push_back(
-        MakePlatformViewLayer(params, presented_platform_views.at(view_id),
-                              pending_surface_transformation_));
+    presented_layers.push_back(MakePlatformViewLayer(
+        params,                                // embedded view params
+        presented_platform_views.at(view_id),  // platform view
+        pending_surface_transformation_,       // surface transformation
+        pending_device_pixel_ratio_            // device pixel ratio
+        ));
 
     if (!pending_canvas_spies_.at(view_id)->DidDrawIntoCanvas()) {
       // Nothing was drawn into the overlay canvas, we don't need to composite
@@ -312,8 +327,11 @@ bool EmbedderExternalViewEmbedder::SubmitFrame(GrContext* context) {
     // Indicate a layer for the backing store containing contents rendered by
     // Flutter.
     presented_layers.push_back(MakeBackingStoreLayer(
-        pending_frame_size_, render_target->GetBackingStore(),
-        pending_surface_transformation_));
+        pending_frame_size_,               // frame size
+        render_target->GetBackingStore(),  // backing store
+        pending_surface_transformation_,   // surface transformation
+        pending_device_pixel_ratio_        // device pixel ratio
+        ));
   }
 
   {

shell/platform/embedder/embedder_external_view_embedder.h

@@ -73,7 +73,9 @@ class EmbedderExternalViewEmbedder final : public ExternalViewEmbedder {
   void CancelFrame() override;
 
   // |ExternalViewEmbedder|
-  void BeginFrame(SkISize frame_size, GrContext* context) override;
+  void BeginFrame(SkISize frame_size,
+                  GrContext* context,
+                  double device_pixel_ratio) override;
 
   // |ExternalViewEmbedder|
   void PrerollCompositeEmbeddedView(
@@ -127,6 +129,7 @@ class EmbedderExternalViewEmbedder final : public ExternalViewEmbedder {
                                       RegistryKey::Equal>;
 
   SkISize pending_frame_size_ = SkISize::Make(0, 0);
+  double pending_device_pixel_ratio_ = 1.0;
   SkMatrix pending_surface_transformation_;
   std::map<ViewIdentifier, std::unique_ptr<SkPictureRecorder>>
       pending_recorders_;

shell/platform/embedder/fixtures/main.dart

@@ -430,3 +430,16 @@ void verify_b141980393() {
   };
   window.scheduleFrame();
 }
+
+@pragma('vm:entry-point')
+void can_display_platform_view_with_pixel_ratio() {
+  window.onBeginFrame = (Duration duration) {
+    SceneBuilder builder = SceneBuilder();
+    builder.pushOffset(0.0, 20.0);
+    builder.addPlatformView(42, width: 400.0, height: 280.0);
+    builder.addPicture(Offset(0.0, 0.0), CreateSimplePicture());
+    builder.pop();
+    window.render(builder.build());
+  };
+  window.scheduleFrame();
+}