examples/ui/lib/host_canvas_cycler.h

// Copyright 2017 The Fuchsia 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 LIB_UI_SCENIC_SKIA_HOST_CANVAS_CYCLER_H_
#define LIB_UI_SCENIC_SKIA_HOST_CANVAS_CYCLER_H_

#include "examples/ui/lib/host_surfaces.h"
#include "third_party/skia/include/core/SkCanvas.h"

namespace scenic {
namespace skia {

// Creates a node which presents double-buffered content drawn to a Skia canvas
// using software rendering.
class HostCanvasCycler : public EntityNode {
 public:
  HostCanvasCycler(Session* session);
  ~HostCanvasCycler();

  HostCanvasCycler(const HostCanvasCycler&) = delete;
  HostCanvasCycler& operator=(const HostCanvasCycler&) = delete;

  // Acquires a canvas for rendering.
  // At most one canvas can be acquired at a time.
  // The client is responsible for clearing the canvas.
  SkCanvas* AcquireCanvas(float logical_width, float logical_height,
                          float scale_x, float scale_y);

  // Releases the canvas most recently acquired using |AcquireCanvas()|.
  // Sets the content node's texture to be backed by the canvas.
  void ReleaseAndSwapCanvas();

 private:
  static constexpr uint32_t kNumBuffers = 2u;

  ShapeNode content_node_;
  Material content_material_;
  HostSkSurfacePool surface_pool_;
  sk_sp<SkSurface> acquired_surface_;
  bool reconfigured_ = false;
  uint32_t surface_index_ = 0u;
  float logical_width_ = 0.f;
  float logical_height_ = 0.f;
};

}  // namespace skia
}  // namespace scenic

#endif  // LIB_UI_SCENIC_SKIA_HOST_CANVAS_CYCLER_H_