gecko-dev/gfx/layers/CanvasRenderer.h

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef GFX_CANVASRENDERER_H
#define GFX_CANVASRENDERER_H

#include <stdint.h>          // for uint32_t
#include "GLContextTypes.h"  // for GLContext
#include "gfxContext.h"      // for gfxContext, etc
#include "gfxTypes.h"
#include "gfxPlatform.h"          // for gfxImageFormat
#include "mozilla/Assertions.h"   // for MOZ_ASSERT, etc
#include "mozilla/Preferences.h"  // for Preferences
#include "mozilla/RefPtr.h"       // for RefPtr
#include "mozilla/gfx/2D.h"       // for DrawTarget
#include "mozilla/mozalloc.h"     // for operator delete, etc
#include "nsISupportsImpl.h"      // for MOZ_COUNT_CTOR, etc

namespace mozilla {
namespace layers {

class AsyncCanvasRenderer;
class ClientCanvasRenderer;
class CopyableCanvasRenderer;
class PersistentBufferProvider;
class WebRenderCanvasRendererAsync;

struct CanvasInitializeData final {
  CanvasInitializeData();
  ~CanvasInitializeData();

  // One of these three must be specified for Canvas2D, but never more than one
  RefPtr<PersistentBufferProvider>
      mBufferProvider;  // A BufferProvider for the Canvas contents
  RefPtr<mozilla::gl::GLContext> mGLContext;  // or this, for GL.
  RefPtr<AsyncCanvasRenderer> mRenderer;      // or this, for OffscreenCanvas

  typedef void (*TransactionCallback)(void* closureData);
  TransactionCallback mPreTransCallback = nullptr;
  void* mPreTransCallbackData = nullptr;
  TransactionCallback mDidTransCallback = nullptr;
  void* mDidTransCallbackData = nullptr;

  // The size of the canvas content
  gfx::IntSize mSize = {0, 0};

  // Whether the canvas drawingbuffer has an alpha channel.
  bool mHasAlpha = false;

  // Whether mGLContext contains data that is alpha-premultiplied.
  bool mIsGLAlphaPremult = true;
};

// Based class which used for canvas rendering. There are many derived classes
// for different purposes. such as:
//
// CopyableCanvasRenderer provides a utility which readback canvas content to a
// SourceSurface. BasicCanvasLayer uses CopyableCanvasRenderer.
//
// ShareableCanvasRenderer provides IPC capabilities that allow sending canvas
// content over IPC. This is pure virtual class because the IPC handling is
// different in different LayerManager. So that we have following classes
// inherite ShareableCanvasRenderer.
//
// ClientCanvasRenderer inherites ShareableCanvasRenderer and be used in
// ClientCanvasLayer.
// WebRenderCanvasRenderer inherites ShareableCanvasRenderer and provides all
// functionality that WebRender uses.
// WebRenderCanvasRendererAsync inherites WebRenderCanvasRenderer and be used in
// layers-free mode of WebRender.
//
// class diagram shows below:
//
//                       +--------------+
//                       |CanvasRenderer|
//                       +-------+------+
//                               ^
//                               |
//                   +----------------------+
//                   |CopyableCanvasRenderer|
//                   +----------------------+
//                               ^
//                               |
//                   +-----------+-----------+
//                   |ShareableCanvasRenderer|
//                   +-----+-----------------+
//                         ^      ^
//           +-------------+      +-------+
//           |                            |
// +--------------------+       +---------+-------------+
// |ClientCanvasRenderer|       |WebRenderCanvasRenderer|
// +--------------------+       +-----------+-----------+
//                                          ^
//                                          |
//                           +-------------+--------------+
//                           |WebRenderCanvasRendererAsync|
//                           +----------------------------+
class CanvasRenderer {
 public:
  CanvasRenderer();
  virtual ~CanvasRenderer();

 public:
  virtual void Initialize(const CanvasInitializeData& aData);
  virtual bool IsDataValid(const CanvasInitializeData& aData) { return true; }

  virtual void ClearCachedResources() {}
  virtual void Destroy() {}

  const gfx::IntSize& GetSize() const { return mSize; }

  void SetDirty() { mDirty = true; }
  void ResetDirty() { mDirty = false; }
  bool IsDirty() const { return mDirty; }

  virtual CopyableCanvasRenderer* AsCopyableCanvasRenderer() { return nullptr; }
  virtual ClientCanvasRenderer* AsClientCanvasRenderer() { return nullptr; }
  virtual WebRenderCanvasRendererAsync* AsWebRenderCanvasRendererAsync() {
    return nullptr;
  }

 protected:
  void FirePreTransactionCallback() {
    if (mPreTransCallback) {
      mPreTransCallback(mPreTransCallbackData);
    }
  }

  void FireDidTransactionCallback() {
    if (mDidTransCallback) {
      mDidTransCallback(mDidTransCallbackData);
    }
  }

  typedef void (*TransactionCallback)(void* closureData);
  TransactionCallback mPreTransCallback;
  void* mPreTransCallbackData;
  TransactionCallback mDidTransCallback;
  void* mDidTransCallbackData;
  gfx::IntSize mSize;

 private:
  /**
   * Set to true in Updated(), cleared during a transaction.
   */
  bool mDirty;
};

}  // namespace layers
}  // namespace mozilla

#endif