shell/platform/fuchsia/flutter/gfx_external_view_embedder.h

// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef FLUTTER_SHELL_PLATFORM_FUCHSIA_FLUTTER_GFX_EXTERNAL_VIEW_EMBEDDER_H_
#define FLUTTER_SHELL_PLATFORM_FUCHSIA_FLUTTER_GFX_EXTERNAL_VIEW_EMBEDDER_H_

#include <fuchsia/ui/views/cpp/fidl.h>
#include <lib/ui/scenic/cpp/id.h>
#include <lib/ui/scenic/cpp/resources.h>
#include <lib/ui/scenic/cpp/view_ref_pair.h>

#include <cstdint>  // For uint32_t & uint64_t
#include <memory>
#include <string>
#include <unordered_map>
#include <vector>

#include "flutter/flow/embedded_views.h"
#include "flutter/fml/logging.h"
#include "flutter/fml/macros.h"
#include "flutter/shell/common/canvas_spy.h"
#include "third_party/skia/include/core/SkCanvas.h"
#include "third_party/skia/include/core/SkPictureRecorder.h"
#include "third_party/skia/include/core/SkPoint.h"
#include "third_party/skia/include/core/SkRect.h"
#include "third_party/skia/include/core/SkSize.h"
#include "third_party/skia/include/gpu/GrDirectContext.h"

#include "gfx_session_connection.h"
#include "surface_producer.h"

namespace flutter_runner {

using ViewCallback = std::function<void()>;
using GfxViewIdCallback = std::function<void(scenic::ResourceId)>;

// This struct represents a transformed clip rect.
struct TransformedClip {
  SkMatrix transform = SkMatrix::I();
  SkRect rect = SkRect::MakeEmpty();

  bool operator==(const TransformedClip& other) const {
    return transform == other.transform && rect == other.rect;
  }
};

// This struct represents all the mutators that can be applied to a
// PlatformView, unpacked from the `MutatorStack`.
struct ViewMutators {
  std::vector<TransformedClip> clips;
  SkMatrix total_transform = SkMatrix::I();
  SkMatrix transform = SkMatrix::I();
  SkScalar opacity = 1.f;

  bool operator==(const ViewMutators& other) const {
    return clips == other.clips && total_transform == other.total_transform &&
           transform == other.transform && opacity == other.opacity;
  }
};

// This class orchestrates interaction with the Scenic compositor on Fuchsia. It
// ensures that flutter content and platform view content are both rendered
// correctly in a unified scene.
class GfxExternalViewEmbedder final : public flutter::ExternalViewEmbedder {
 public:
  // Layer separation is as infinitesimal as possible without introducing
  // Z-fighting.
  constexpr static float kScenicZElevationBetweenLayers = 0.0001f;
  constexpr static float kScenicZElevationForPlatformView = 100.f;
  constexpr static float kScenicElevationForInputInterceptor = 500.f;
  constexpr static SkAlpha kBackgroundLayerOpacity = SK_AlphaOPAQUE;
  constexpr static SkAlpha kOverlayLayerOpacity = SK_AlphaOPAQUE - 1;

  GfxExternalViewEmbedder(std::string debug_label,
                          fuchsia::ui::views::ViewToken view_token,
                          scenic::ViewRefPair view_ref_pair,
                          GfxSessionConnection& session,
                          SurfaceProducer& surface_producer,
                          bool intercept_all_input = false);
  ~GfxExternalViewEmbedder();

  // |ExternalViewEmbedder|
  SkCanvas* GetRootCanvas() override;

  // |ExternalViewEmbedder|
  std::vector<SkCanvas*> GetCurrentCanvases() override;

  // |ExternalViewEmbedder|
  void PrerollCompositeEmbeddedView(
      int view_id,
      std::unique_ptr<flutter::EmbeddedViewParams> params) override;

  // |ExternalViewEmbedder|
  SkCanvas* CompositeEmbeddedView(int view_id) override;

  // |ExternalViewEmbedder|
  flutter::PostPrerollResult PostPrerollAction(
      fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) override;

  // |ExternalViewEmbedder|
  void BeginFrame(
      SkISize frame_size,
      GrDirectContext* context,
      double device_pixel_ratio,
      fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) override;

  // |ExternalViewEmbedder|
  void EndFrame(
      bool should_resubmit_frame,
      fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) override;

  // |ExternalViewEmbedder|
  void SubmitFrame(GrDirectContext* context,
                   std::unique_ptr<flutter::SurfaceFrame> frame) override;

  // |ExternalViewEmbedder|
  void CancelFrame() override { Reset(); }

  // |ExternalViewEmbedder|
  bool SupportsDynamicThreadMerging() override { return false; }

  // View manipulation.
  // |SetViewProperties| doesn't manipulate the view directly -- it sets pending
  // properties for the next |UpdateView| call.
  void EnableWireframe(bool enable);
  void CreateView(int64_t view_id,
                  ViewCallback on_view_created,
                  GfxViewIdCallback on_view_bound);
  void DestroyView(int64_t view_id, GfxViewIdCallback on_view_unbound);
  void SetViewProperties(int64_t view_id,
                         const SkRect& occlusion_hint,
                         bool hit_testable,
                         bool focusable);

 private:
  void Reset();  // Reset state for a new frame.

  struct EmbedderLayer {
    EmbedderLayer(const SkISize& frame_size,
                  std::optional<flutter::EmbeddedViewParams> view_params)
        : embedded_view_params(std::move(view_params)),
          recorder(std::make_unique<SkPictureRecorder>()),
          canvas_spy(std::make_unique<flutter::CanvasSpy>(
              recorder->beginRecording(frame_size.width(),
                                       frame_size.height()))),
          surface_size(frame_size) {}

    std::optional<flutter::EmbeddedViewParams> embedded_view_params;
    std::unique_ptr<SkPictureRecorder> recorder;
    std::unique_ptr<flutter::CanvasSpy> canvas_spy;
    SkISize surface_size;
  };
  using EmbedderLayerId = std::optional<uint32_t>;
  constexpr static EmbedderLayerId kRootLayerId = EmbedderLayerId{};

  struct ScenicView {
    std::vector<scenic::EntityNode> clip_nodes;
    scenic::OpacityNodeHACK opacity_node;
    scenic::EntityNode transform_node;
    scenic::ViewHolder view_holder;

    ViewMutators mutators;
    float elevation = 0.f;

    SkSize size = SkSize::MakeEmpty();
    SkRect occlusion_hint = SkRect::MakeEmpty();
    SkRect pending_occlusion_hint = SkRect::MakeEmpty();
    bool hit_testable = true;
    bool pending_hit_testable = true;
    bool focusable = true;
    bool pending_focusable = true;
  };

  struct ScenicLayer {
    scenic::ShapeNode shape_node;
    scenic::Material material;
  };

  GfxSessionConnection& session_;
  SurfaceProducer& surface_producer_;

  scenic::View root_view_;
  scenic::EntityNode metrics_node_;
  scenic::EntityNode layer_tree_node_;
  std::optional<scenic::ShapeNode> input_interceptor_node_;

  std::unordered_map<uint64_t, scenic::Rectangle> scenic_interceptor_rects_;
  std::unordered_map<uint64_t, std::vector<scenic::Rectangle>> scenic_rects_;
  std::unordered_map<int64_t, ScenicView> scenic_views_;
  std::vector<ScenicLayer> scenic_layers_;

  std::unordered_map<EmbedderLayerId, EmbedderLayer> frame_layers_;
  std::vector<EmbedderLayerId> frame_composition_order_;
  SkISize frame_size_ = SkISize::Make(0, 0);
  float frame_dpr_ = 1.f;

  FML_DISALLOW_COPY_AND_ASSIGN(GfxExternalViewEmbedder);
};

}  // namespace flutter_runner

#endif  // FLUTTER_SHELL_PLATFORM_FUCHSIA_FLUTTER_GFX_EXTERNAL_VIEW_EMBEDDER_H_