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Allow embedder controlled composition of Flutter layers. (flutter-team-archive/engine#10195)
This patch allows embedders to split the Flutter layer tree into multiple chunks. These chunks are meant to be composed one on top of another. This gives embedders a chance to interleave their own contents between these chunks. The Flutter embedder API already provides hooks for the specification of textures for the Flutter engine to compose within its own hierarchy (for camera feeds, video, etc..). However, not all embedders can render the contents of such sources into textures the Flutter engine can accept. Moreover, this composition model may have overheads that are non-trivial for certain use cases. In such cases, the embedder may choose to specify multiple render target for Flutter to render into instead of just one. The use of this API allows embedders to perform composition very similar to the iOS embedder. This composition model is used on that platform for the embedding of UIKit view such and web view and map views within the Flutter hierarchy. However, do note that iOS also has threading configurations that are currently not available to custom embedders. The embedder API updates in this patch are ABI stable and existing embedders will continue to work are normal. For embedders that want to enable this composition mode, the API is designed to make it easy to opt into the same in an incremental manner. Rendering of contents into the “root” rendering surface remains unchanged. However, now the application can push “platform views” via a scene builder. These platform views need to handled by a FlutterCompositor specified in a new field at the end of the FlutterProjectArgs struct. When a new platform view in introduced within the layer tree, the compositor will ask the embedder to create a new render target for that platform view. Render targets can currently be OpenGL framebuffers, OpenGL textures or software buffers. The type of the render target returned by the embedder must be compatible with the root render surface. That is, if the root render surface is an OpenGL framebuffer, the render target for each platform view must either be a texture or a framebuffer in the same OpenGL context. New render target types as well as root renderers for newer APIs like Metal & Vulkan can and will be added in the future. The addition of these APIs will be done in an ABI & API stable manner. As Flutter renders frames, it gives the embedder a callback with information about the position of the various platform views in the effective hierarchy. The embedder is then meant to put the contents of the render targets that it setup and had previously given to the engine onto the screen (of course interleaving the contents of the platform views). Unit-tests have been added that test not only the structure and properties of layer hierarchy given to the compositor, but also the contents of the texels rendered by a test compositor using both the OpenGL and software rendering backends. Fixes b/132812775 Fixes #35410
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Lines changed: 2942 additions & 209 deletions

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‎engine/src/flutter/ci/licenses_golden/licenses_flutter‎

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@@ -521,6 +521,8 @@ FILE: ../../../flutter/shell/gpu/gpu_surface_metal.h
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FILE: ../../../flutter/shell/gpu/gpu_surface_metal.mm
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FILE: ../../../flutter/shell/gpu/gpu_surface_software.cc
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FILE: ../../../flutter/shell/gpu/gpu_surface_software.h
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FILE: ../../../flutter/shell/gpu/gpu_surface_software_delegate.cc
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FILE: ../../../flutter/shell/gpu/gpu_surface_software_delegate.h
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FILE: ../../../flutter/shell/gpu/gpu_surface_vulkan.cc
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FILE: ../../../flutter/shell/gpu/gpu_surface_vulkan.h
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FILE: ../../../flutter/shell/platform/android/AndroidManifest.xml
@@ -810,9 +812,13 @@ FILE: ../../../flutter/shell/platform/embedder/embedder_engine.cc
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FILE: ../../../flutter/shell/platform/embedder/embedder_engine.h
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FILE: ../../../flutter/shell/platform/embedder/embedder_external_texture_gl.cc
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FILE: ../../../flutter/shell/platform/embedder/embedder_external_texture_gl.h
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FILE: ../../../flutter/shell/platform/embedder/embedder_external_view_embedder.cc
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FILE: ../../../flutter/shell/platform/embedder/embedder_external_view_embedder.h
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FILE: ../../../flutter/shell/platform/embedder/embedder_include.c
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FILE: ../../../flutter/shell/platform/embedder/embedder_platform_message_response.cc
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FILE: ../../../flutter/shell/platform/embedder/embedder_platform_message_response.h
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FILE: ../../../flutter/shell/platform/embedder/embedder_render_target.cc
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FILE: ../../../flutter/shell/platform/embedder/embedder_render_target.h
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FILE: ../../../flutter/shell/platform/embedder/embedder_safe_access.h
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FILE: ../../../flutter/shell/platform/embedder/embedder_surface.cc
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FILE: ../../../flutter/shell/platform/embedder/embedder_surface.h
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FILE: ../../../flutter/shell/platform/embedder/embedder_task_runner.h
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FILE: ../../../flutter/shell/platform/embedder/embedder_thread_host.cc
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FILE: ../../../flutter/shell/platform/embedder/embedder_thread_host.h
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FILE: ../../../flutter/shell/platform/embedder/fixtures/compositor.png
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FILE: ../../../flutter/shell/platform/embedder/fixtures/main.dart
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FILE: ../../../flutter/shell/platform/embedder/platform_view_embedder.cc
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FILE: ../../../flutter/shell/platform/embedder/platform_view_embedder.h

‎engine/src/flutter/flow/embedded_views.h‎

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#include "third_party/skia/include/core/SkRRect.h"
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#include "third_party/skia/include/core/SkRect.h"
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#include "third_party/skia/include/core/SkSize.h"
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#include "third_party/skia/include/core/SkSurface.h"
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namespace flutter {
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@@ -194,11 +195,19 @@ class ExternalViewEmbedder {
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public:
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ExternalViewEmbedder() = default;
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virtual ~ExternalViewEmbedder() = default;
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// Usually, the root surface is not owned by the view embedder. However, if
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// the view embedder wants to provide a surface to the rasterizer, it may
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// return one here. This surface takes priority over the surface materialized
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// from the on-screen render target.
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virtual sk_sp<SkSurface> GetRootSurface() = 0;
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// Call this in-lieu of |SubmitFrame| to clear pre-roll state and
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// sets the stage for the next pre-roll.
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virtual void CancelFrame() = 0;
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virtual void BeginFrame(SkISize frame_size) = 0;
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virtual void BeginFrame(SkISize frame_size, GrContext* context) = 0;
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virtual void PrerollCompositeEmbeddedView(
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int view_id,
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virtual bool SubmitFrame(GrContext* context);
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virtual ~ExternalViewEmbedder() = default;
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FML_DISALLOW_COPY_AND_ASSIGN(ExternalViewEmbedder);
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}; // ExternalViewEmbedder

‎engine/src/flutter/fml/closure.h‎

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#include <functional>
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#include "flutter/fml/macros.h"
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namespace fml {
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using closure = std::function<void()>;
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//------------------------------------------------------------------------------
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/// @brief Wraps a closure that is invoked in the destructor unless
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/// released by the caller.
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///
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/// This is especially useful in dealing with APIs that return a
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/// resource by accepting ownership of a sub-resource and a closure
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/// that releases that resource. When such APIs are chained, each
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/// link in the chain must check that the next member in the chain
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/// has accepted the resource. If not, it must invoke the closure
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/// eagerly. Not doing this results in a resource leak in the
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/// erroneous case. Using this wrapper, the closure can be released
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/// once the next call in the chain has successfully accepted
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/// ownership of the resource. If not, the closure gets invoked
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/// automatically at the end of the scope. This covers the cases
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/// where there are early returns as well.
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///
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class ScopedCleanupClosure {
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public:
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ScopedCleanupClosure(fml::closure closure) : closure_(closure) {}
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~ScopedCleanupClosure() {
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if (closure_) {
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closure_();
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}
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}
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fml::closure Release() {
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fml::closure closure = closure_;
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closure_ = nullptr;
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return closure;
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}
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private:
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fml::closure closure_;
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FML_DISALLOW_COPY_AND_ASSIGN(ScopedCleanupClosure);
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};
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} // namespace fml
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#endif // FLUTTER_FML_CLOSURE_H_

‎engine/src/flutter/fml/mapping.cc‎

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// NonOwnedMapping
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NonOwnedMapping::NonOwnedMapping(const uint8_t* data,
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size_t size,
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ReleaseProc release_proc)
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: data_(data), size_(size), release_proc_(release_proc) {}
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NonOwnedMapping::~NonOwnedMapping() {
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if (release_proc_) {
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release_proc_(data_, size_);
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}
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}
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size_t NonOwnedMapping::GetSize() const {
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}

‎engine/src/flutter/fml/mapping.h‎

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class NonOwnedMapping final : public Mapping {
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NonOwnedMapping(const uint8_t* data, size_t size)
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: data_(data), size_(size) {}
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using ReleaseProc = std::function<void(const uint8_t* data, size_t size)>;
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NonOwnedMapping(const uint8_t* data,
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size_t size,
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ReleaseProc release_proc = nullptr);
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~NonOwnedMapping() override;
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size_t GetSize() const override;
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const uint8_t* const data_;
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const size_t size_;
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const ReleaseProc release_proc_;
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FML_DISALLOW_COPY_AND_ASSIGN(NonOwnedMapping);
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};

‎engine/src/flutter/lib/ui/painting/image_decoder_unittests.cc‎

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TestIOManager(fml::RefPtr<fml::TaskRunner> task_runner,
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bool has_gpu_context = true)
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: gl_context_(has_gpu_context ? gl_surface_.CreateContext() : nullptr),
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: gl_context_(has_gpu_context ? gl_surface_.CreateGrContext() : nullptr),
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weak_gl_context_factory_(
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has_gpu_context ? std::make_unique<fml::WeakPtrFactory<GrContext>>(
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gl_context_.get())

‎engine/src/flutter/shell/common/rasterizer.cc‎

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compositor_context_->ui_time().SetLapTime(layer_tree.build_time());
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auto* canvas = frame->SkiaCanvas();
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auto* external_view_embedder = surface_->GetExternalViewEmbedder();
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sk_sp<SkSurface> embedder_root_surface;
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if (external_view_embedder != nullptr) {
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external_view_embedder->BeginFrame(layer_tree.frame_size());
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external_view_embedder->BeginFrame(layer_tree.frame_size(),
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surface_->GetContext());
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embedder_root_surface = external_view_embedder->GetRootSurface();
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// If the external view embedder has specified an optional root surface, the
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// root surface transformation is set by the embedder instead of
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// having to apply it here.
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SkMatrix root_surface_transformation =
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embedder_root_surface ? SkMatrix{} : surface_->GetRootTransformation();
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auto root_surface_canvas = embedder_root_surface
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? embedder_root_surface->getCanvas()
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: frame->SkiaCanvas();
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surface_->GetContext(), canvas, external_view_embedder,
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surface_->GetRootTransformation(), true, gpu_thread_merger_);
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surface_->GetContext(), // skia GrContext
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root_surface_canvas, // root surface canvas
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external_view_embedder, // external view embedder
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root_surface_transformation, // root surface transformation
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true, // instrumentation enabled
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gpu_thread_merger_ // thread merger
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);
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external_view_embedder->SubmitFrame(surface_->GetContext());
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}
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FireNextFrameCallbackIfPresent();
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if (surface_->GetContext()) {
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surface_->GetContext()->performDeferredCleanup(kSkiaCleanupExpiration);
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}
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‎engine/src/flutter/shell/common/shell_test.cc‎

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// |PlatformView|
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std::unique_ptr<Surface> ShellTestPlatformView::CreateRenderingSurface() {
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return std::make_unique<GPUSurfaceGL>(this, true);
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}
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// |GPUSurfaceGLDelegate|
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};
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// |GPUSurfaceGLDelegate|
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ExternalViewEmbedder* ShellTestPlatformView::GetExternalViewEmbedder() {
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return nullptr;
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}
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} // namespace testing
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} // namespace flutter

‎engine/src/flutter/shell/common/shell_test.h‎

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// |GPUSurfaceGLDelegate|
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GLProcResolver GetGLProcResolver() const override;
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// |GPUSurfaceGLDelegate|
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ExternalViewEmbedder* GetExternalViewEmbedder() override;
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FML_DISALLOW_COPY_AND_ASSIGN(ShellTestPlatformView);
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};
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‎engine/src/flutter/shell/gpu/BUILD.gn‎

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sources = [
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"$gpu_dir/gpu_surface_software.cc",
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"$gpu_dir/gpu_surface_software.h",
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"$gpu_dir/gpu_surface_software_delegate.cc",
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"$gpu_dir/gpu_surface_software_delegate.h",
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]
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deps = gpu_common_deps

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