chromium/src/third_party/blink/renderer/platform/graphics/paint/subsequence_recorder.h

// Copyright 2015 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 THIRD_PARTY_BLINK_RENDERER_PLATFORM_GRAPHICS_PAINT_SUBSEQUENCE_RECORDER_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_GRAPHICS_PAINT_SUBSEQUENCE_RECORDER_H_

#include "base/macros.h"
#include "third_party/blink/renderer/platform/graphics/graphics_context.h"
#include "third_party/blink/renderer/platform/graphics/paint/display_item.h"
#include "third_party/blink/renderer/platform/graphics/paint/paint_controller.h"
#include "third_party/blink/renderer/platform/wtf/allocator/allocator.h"

namespace blink {

class GraphicsContext;
class PaintController;

// SubsequenceRecorder records BeginSubsequenceDisplayItem and
// EndSubsequenceDisplayItem sentinels at either end of a continguous sequence
// of DisplayItems, and supports caching via a CachedDisplayItem with the
// CachedSubsequence DisplayItem type.
//
// Also note that UseCachedSubsequenceIfPossible is not sufficient to determine
// whether a CachedSubsequence can be used. In particular, the client is
// responsible for checking that none of the DisplayItemClients that contribute
// to the subsequence have been invalidated.
//
class SubsequenceRecorder final {
  STACK_ALLOCATED();

 public:
  static bool UseCachedSubsequenceIfPossible(GraphicsContext& context,
                                             const DisplayItemClient& client) {
    return context.GetPaintController().UseCachedSubsequenceIfPossible(client);
  }

  SubsequenceRecorder(GraphicsContext& context, const DisplayItemClient& client)
      : paint_controller_(context.GetPaintController()),
        client_(client),
        start_(0) {
    start_ = paint_controller_.BeginSubsequence();
  }

  ~SubsequenceRecorder() { paint_controller_.EndSubsequence(client_, start_); }

 private:
  PaintController& paint_controller_;
  const DisplayItemClient& client_;
  wtf_size_t start_;

  DISALLOW_COPY_AND_ASSIGN(SubsequenceRecorder);
};

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_PLATFORM_GRAPHICS_PAINT_SUBSEQUENCE_RECORDER_H_