fuchsia: Remove dead code / break dependencies (flutter#19396)

The fuchsia code around metrics and sizing was just sending this
information through a side-channel, when the engine already had the
information available. So, delete all of it to make future CLs simpler.

Additionally, the SceneUpdateContext has many unneccesary dependencies
re: metrics and PaintTasks. Break those to make future CLs simpler.

Tested: Ran all unittests and ran workstation on Fuchsia
BUG: 53062, 53063

Author: arbreng

flow/layers/child_scene_layer.cc

@@ -4,8 +4,6 @@
 
 #include "flutter/flow/layers/child_scene_layer.h"
 
-#include "flutter/flow/view_holder.h"
-
 namespace flutter {
 
 ChildSceneLayer::ChildSceneLayer(zx_koid_t layer_id,
@@ -19,11 +17,9 @@ ChildSceneLayer::ChildSceneLayer(zx_koid_t layer_id,
 
 void ChildSceneLayer::Preroll(PrerollContext* context, const SkMatrix& matrix) {
   TRACE_EVENT0("flutter", "ChildSceneLayer::Preroll");
-  set_needs_system_composite(true);
-
-  CheckForChildLayerBelow(context);
 
   context->child_scene_layer_exists_below = true;
+  CheckForChildLayerBelow(context);
 
   // An alpha "hole punch" is required if the frame behind us is not opaque.
   if (!context->is_opaque) {
@@ -49,15 +45,7 @@ void ChildSceneLayer::Paint(PaintContext& context) const {
 void ChildSceneLayer::UpdateScene(SceneUpdateContext& context) {
   TRACE_EVENT0("flutter", "ChildSceneLayer::UpdateScene");
   FML_DCHECK(needs_system_composite());
-
-  Layer::UpdateScene(context);
-
-  auto* view_holder = ViewHolder::FromId(layer_id_);
-  FML_DCHECK(view_holder);
-
-  view_holder->UpdateScene(context, offset_, size_,
-                           SkScalarRoundToInt(context.alphaf() * 255),
-                           hit_testable_);
+  context.UpdateView(layer_id_, offset_, size_, hit_testable_);
 }
 
 }  // namespace flutter

flow/layers/container_layer.cc

@@ -4,6 +4,8 @@
 
 #include "flutter/flow/layers/container_layer.h"
 
+#include <optional>
+
 namespace flutter {
 
 ContainerLayer::ContainerLayer() {}
@@ -30,6 +32,9 @@ void ContainerLayer::PrerollChildren(PrerollContext* context,
                                      const SkMatrix& child_matrix,
                                      SkRect* child_paint_bounds) {
 #if defined(LEGACY_FUCHSIA_EMBEDDER)
+  // If there is embedded Fuchsia content in the scene (a ChildSceneLayer),
+  // Layers that appear above the embedded content will be turned into their own
+  // Scenic layers.
   child_layer_exists_below_ = context->child_scene_layer_exists_below;
   context->child_scene_layer_exists_below = false;
 #endif
@@ -98,63 +103,20 @@ void ContainerLayer::UpdateScene(SceneUpdateContext& context) {
 }
 
 void ContainerLayer::UpdateSceneChildren(SceneUpdateContext& context) {
-  auto update_scene_layers = [&] {
-    // Paint all of the layers which need to be drawn into the container.
-    // These may be flattened down to a containing Scenic Frame.
-    for (auto& layer : layers_) {
-      if (layer->needs_system_composite()) {
-        layer->UpdateScene(context);
-      }
-    }
-  };
-
   FML_DCHECK(needs_system_composite());
 
-  // If there is embedded Fuchsia content in the scene (a ChildSceneLayer),
-  // PhysicalShapeLayers that appear above the embedded content will be turned
-  // into their own Scenic layers.
+  std::optional<SceneUpdateContext::Frame> frame;
   if (child_layer_exists_below_) {
-    float global_scenic_elevation =
-        context.GetGlobalElevationForNextScenicLayer();
-    float local_scenic_elevation =
-        global_scenic_elevation - context.scenic_elevation();
-    float z_translation = -local_scenic_elevation;
-
-    // Retained rendering: speedup by reusing a retained entity node if
-    // possible. When an entity node is reused, no paint layer is added to the
-    // frame so we won't call PhysicalShapeLayer::Paint.
-    LayerRasterCacheKey key(unique_id(), context.Matrix());
-    if (context.HasRetainedNode(key)) {
-      TRACE_EVENT_INSTANT0("flutter", "retained layer cache hit");
-      scenic::EntityNode* retained_node = context.GetRetainedNode(key);
-      FML_DCHECK(context.top_entity());
-      FML_DCHECK(retained_node->session() == context.session());
-
-      // Re-adjust the elevation.
-      retained_node->SetTranslation(0.f, 0.f, z_translation);
-
-      context.top_entity()->entity_node().AddChild(*retained_node);
-      return;
-    }
-
-    TRACE_EVENT_INSTANT0("flutter", "cache miss, creating");
-    // If we can't find an existing retained surface, create one.
-    SceneUpdateContext::Frame frame(
+    frame.emplace(
         context, SkRRect::MakeRect(paint_bounds()), SK_ColorTRANSPARENT,
-        SkScalarRoundToInt(context.alphaf() * 255),
-        "flutter::PhysicalShapeLayer", z_translation, this);
-
-    frame.AddPaintLayer(this);
-
-    // Node: UpdateSceneChildren needs to be called here so that |frame| is
-    // still in scope (and therefore alive) while UpdateSceneChildren is being
-    // called.
-    float scenic_elevation = context.scenic_elevation();
-    context.set_scenic_elevation(scenic_elevation + local_scenic_elevation);
-    update_scene_layers();
-    context.set_scenic_elevation(scenic_elevation);
-  } else {
-    update_scene_layers();
+        SkScalarRoundToInt(context.alphaf() * 255), "flutter::ContainerLayer");
+    frame->AddPaintLayer(this);
+  }
+
+  for (auto& layer : layers_) {
+    if (layer->needs_system_composite()) {
+      layer->UpdateScene(context);
+    }
   }
 }
 

flow/layers/fuchsia_layer_unittests.cc

@@ -238,57 +238,17 @@ class MockSession : public fuchsia::ui::scenic::testing::Session_TestBase {
   fuchsia::ui::scenic::SessionListenerPtr listener_;
 };
 
-class MockSurfaceProducerSurface
-    : public SceneUpdateContext::SurfaceProducerSurface {
+class MockSessionWrapper : public flutter::SessionWrapper {
  public:
-  MockSurfaceProducerSurface(scenic::Session* session, const SkISize& size)
-      : image_(session, 0, 0, {}), size_(size) {}
+  MockSessionWrapper(fuchsia::ui::scenic::SessionPtr session_ptr)
+      : session_(std::move(session_ptr)) {}
+  ~MockSessionWrapper() override = default;
 
-  size_t AdvanceAndGetAge() override { return 0; }
-
-  bool FlushSessionAcquireAndReleaseEvents() override { return false; }
-
-  bool IsValid() const override { return false; }
-
-  SkISize GetSize() const override { return size_; }
-
-  void SignalWritesFinished(
-      const std::function<void(void)>& on_writes_committed) override {}
-
-  scenic::Image* GetImage() override { return &image_; };
-
-  sk_sp<SkSurface> GetSkiaSurface() const override { return nullptr; };
+  scenic::Session* get() override { return &session_; }
+  void Present() override { session_.Flush(); }
 
  private:
-  scenic::Image image_;
-  SkISize size_;
-};
-
-class MockSurfaceProducer : public SceneUpdateContext::SurfaceProducer {
- public:
-  MockSurfaceProducer(scenic::Session* session) : session_(session) {}
-  std::unique_ptr<SceneUpdateContext::SurfaceProducerSurface> ProduceSurface(
-      const SkISize& size,
-      const LayerRasterCacheKey& layer_key,
-      std::unique_ptr<scenic::EntityNode> entity_node) override {
-    return std::make_unique<MockSurfaceProducerSurface>(session_, size);
-  }
-
-  // Query a retained entity node (owned by a retained surface) for retained
-  // rendering.
-  bool HasRetainedNode(const LayerRasterCacheKey& key) const override {
-    return false;
-  }
-
-  scenic::EntityNode* GetRetainedNode(const LayerRasterCacheKey& key) override {
-    return nullptr;
-  }
-
-  void SubmitSurface(std::unique_ptr<SceneUpdateContext::SurfaceProducerSurface>
-                         surface) override {}
-
- private:
-  scenic::Session* session_;
+  scenic::Session session_;
 };
 
 struct TestContext {
@@ -297,12 +257,11 @@ struct TestContext {
   fml::RefPtr<fml::TaskRunner> task_runner;
 
   // Session.
-  MockSession mock_session;
   fidl::InterfaceRequest<fuchsia::ui::scenic::SessionListener> listener_request;
-  std::unique_ptr<scenic::Session> session;
+  MockSession mock_session;
+  std::unique_ptr<MockSessionWrapper> mock_session_wrapper;
 
   // SceneUpdateContext.
-  std::unique_ptr<MockSurfaceProducer> mock_surface_producer;
   std::unique_ptr<SceneUpdateContext> scene_update_context;
 
   // PrerollContext.
@@ -324,15 +283,13 @@ std::unique_ptr<TestContext> InitTest() {
   fuchsia::ui::scenic::SessionListenerPtr listener;
   context->listener_request = listener.NewRequest();
   context->mock_session.Bind(session_ptr.NewRequest(), std::move(listener));
-  context->session = std::make_unique<scenic::Session>(std::move(session_ptr));
+  context->mock_session_wrapper =
+      std::make_unique<MockSessionWrapper>(std::move(session_ptr));
 
   // Init SceneUpdateContext.
-  context->mock_surface_producer =
-      std::make_unique<MockSurfaceProducer>(context->session.get());
   context->scene_update_context = std::make_unique<SceneUpdateContext>(
-      context->session.get(), context->mock_surface_producer.get());
-  context->scene_update_context->set_metrics(
-      fidl::MakeOptional(fuchsia::ui::gfx::Metrics{1.f, 1.f, 1.f}));
+      "fuchsia_layer_unittest", fuchsia::ui::views::ViewToken(),
+      scenic::ViewRefPair::New(), *(context->mock_session_wrapper));
 
   // Init PrerollContext.
   context->preroll_context = std::unique_ptr<PrerollContext>(new PrerollContext{
@@ -348,7 +305,6 @@ std::unique_ptr<TestContext> InitTest() {
       context->unused_texture_registry,  // texture registry (not
                                          // supported)
       false,                             // checkerboard_offscreen_layers
-      100.f,                             // maximum depth allowed for rendering
       1.f                                // ratio between logical and physical
   });
 
@@ -602,7 +558,7 @@ TEST_F(FuchsiaLayerTest, DISABLED_PhysicalShapeLayersAndChildSceneLayers) {
   // against the list above.
   root->UpdateScene(*(test_context->scene_update_context));
 
-  test_context->session->Flush();
+  test_context->mock_session_wrapper->Present();
 
   // Run loop until idle, so that the Session receives and processes
   // its method calls.
@@ -784,7 +740,7 @@ TEST_F(FuchsiaLayerTest, DISABLED_OpacityAndTransformLayer) {
   // commands against the list above.
   root->UpdateScene(*(test_context->scene_update_context));
 
-  test_context->session->Flush();
+  test_context->mock_session_wrapper->Present();
 
   // Run loop until idle, so that the Session receives and processes
   // its method calls.

flow/layers/layer.cc

@@ -58,49 +58,24 @@ Layer::AutoPrerollSaveLayerState::~AutoPrerollSaveLayerState() {
 #if defined(LEGACY_FUCHSIA_EMBEDDER)
 
 void Layer::CheckForChildLayerBelow(PrerollContext* context) {
+  // If there is embedded Fuchsia content in the scene (a ChildSceneLayer),
+  // PhysicalShapeLayers that appear above the embedded content will be turned
+  // into their own Scenic layers.
   child_layer_exists_below_ = context->child_scene_layer_exists_below;
   if (child_layer_exists_below_) {
     set_needs_system_composite(true);
   }
 }
 
 void Layer::UpdateScene(SceneUpdateContext& context) {
-  // If there is embedded Fuchsia content in the scene (a ChildSceneLayer),
-  // PhysicalShapeLayers that appear above the embedded content will be turned
-  // into their own Scenic layers.
-  if (child_layer_exists_below_) {
-    float global_scenic_elevation =
-        context.GetGlobalElevationForNextScenicLayer();
-    float local_scenic_elevation =
-        global_scenic_elevation - context.scenic_elevation();
-    float z_translation = -local_scenic_elevation;
-
-    // Retained rendering: speedup by reusing a retained entity node if
-    // possible. When an entity node is reused, no paint layer is added to the
-    // frame so we won't call PhysicalShapeLayer::Paint.
-    LayerRasterCacheKey key(unique_id(), context.Matrix());
-    if (context.HasRetainedNode(key)) {
-      TRACE_EVENT_INSTANT0("flutter", "retained layer cache hit");
-      scenic::EntityNode* retained_node = context.GetRetainedNode(key);
-      FML_DCHECK(context.top_entity());
-      FML_DCHECK(retained_node->session() == context.session());
-
-      // Re-adjust the elevation.
-      retained_node->SetTranslation(0.f, 0.f, z_translation);
-
-      context.top_entity()->entity_node().AddChild(*retained_node);
-      return;
-    }
-
-    TRACE_EVENT_INSTANT0("flutter", "cache miss, creating");
-    // If we can't find an existing retained surface, create one.
-    SceneUpdateContext::Frame frame(
-        context, SkRRect::MakeRect(paint_bounds()), SK_ColorTRANSPARENT,
-        SkScalarRoundToInt(context.alphaf() * 255),
-        "flutter::PhysicalShapeLayer", z_translation, this);
-
-    frame.AddPaintLayer(this);
-  }
+  FML_DCHECK(needs_system_composite());
+  FML_DCHECK(child_layer_exists_below_);
+
+  SceneUpdateContext::Frame frame(
+      context, SkRRect::MakeRect(paint_bounds()), SK_ColorTRANSPARENT,
+      SkScalarRoundToInt(context.alphaf() * 255), "flutter::Layer");
+
+  frame.AddPaintLayer(this);
 }
 
 #endif

flow/layers/layer.h

@@ -56,14 +56,10 @@ struct PrerollContext {
   const Stopwatch& ui_time;
   TextureRegistry& texture_registry;
   const bool checkerboard_offscreen_layers;
-
-  // These allow us to make use of the scene metrics during Preroll.
-  float frame_physical_depth;
-  float frame_device_pixel_ratio;
+  const float frame_device_pixel_ratio;
 
   // These allow us to track properties like elevation, opacity, and the
   // prescence of a platform view during Preroll.
-  float total_elevation = 0.0f;
   bool has_platform_view = false;
   bool is_opaque = true;
 #if defined(LEGACY_FUCHSIA_EMBEDDER)
@@ -128,10 +124,7 @@ class Layer {
     TextureRegistry& texture_registry;
     const RasterCache* raster_cache;
     const bool checkerboard_offscreen_layers;
-
-    // These allow us to make use of the scene metrics during Paint.
-    float frame_physical_depth;
-    float frame_device_pixel_ratio;
+    const float frame_device_pixel_ratio;
   };
 
   // Calls SkCanvas::saveLayer and restores the layer upon destruction. Also