cc/output/software_output_device.h

// Copyright 2012 The Chromium 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 CC_OUTPUT_SOFTWARE_OUTPUT_DEVICE_H_
#define CC_OUTPUT_SOFTWARE_OUTPUT_DEVICE_H_

#include <memory>

#include "base/macros.h"
#include "cc/base/cc_export.h"
#include "third_party/skia/include/core/SkSurface.h"
#include "ui/gfx/geometry/rect.h"
#include "ui/gfx/geometry/size.h"
#include "ui/gfx/geometry/vector2d.h"

class SkCanvas;

namespace gfx {
class VSyncProvider;
}

namespace cc {

// This is a "tear-off" class providing software drawing support to
// OutputSurface, such as to a platform-provided window framebuffer.
class CC_EXPORT SoftwareOutputDevice {
 public:
  SoftwareOutputDevice();
  virtual ~SoftwareOutputDevice();

  // Discards any pre-existing backing buffers and allocates memory for a
  // software device of |size|. This must be called before the
  // |SoftwareOutputDevice| can be used in other ways.
  virtual void Resize(const gfx::Size& pixel_size, float scale_factor);

  // Called on BeginDrawingFrame. The compositor will draw into the returned
  // SkCanvas. The |SoftwareOutputDevice| implementation needs to provide a
  // valid SkCanvas of at least size |damage_rect|. This class retains ownership
  // of the SkCanvas.
  virtual SkCanvas* BeginPaint(const gfx::Rect& damage_rect);

  // Called on FinishDrawingFrame. The compositor will no longer mutate the the
  // SkCanvas instance returned by |BeginPaint| and should discard any reference
  // that it holds to it.
  virtual void EndPaint();

  // Discard the backing buffer in the surface provided by this instance.
  virtual void DiscardBackbuffer() {}

  // Ensures that there is a backing buffer available on this instance.
  virtual void EnsureBackbuffer() {}

  // VSyncProvider used to update the timer used to schedule draws with the
  // hardware vsync. Return NULL if a provider doesn't exist.
  virtual gfx::VSyncProvider* GetVSyncProvider();

 protected:
  gfx::Size viewport_pixel_size_;
  gfx::Rect damage_rect_;
  sk_sp<SkSurface> surface_;
  std::unique_ptr<gfx::VSyncProvider> vsync_provider_;

 private:
  DISALLOW_COPY_AND_ASSIGN(SoftwareOutputDevice);
};

}  // namespace cc

#endif  // CC_OUTPUT_SOFTWARE_OUTPUT_DEVICE_H_