content/renderer/paint_aggregator.h

// Copyright (c) 2009 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 CONTENT_RENDERER_PAINT_AGGREGATOR_H_
#define CONTENT_RENDERER_PAINT_AGGREGATOR_H_
#pragma once

#include <vector>

#include "base/basictypes.h"
#include "ui/gfx/rect.h"

// This class is responsible for aggregating multiple invalidation and scroll
// commands to produce a scroll and repaint sequence.
class PaintAggregator {
 public:
  // This structure describes an aggregation of InvalidateRect and ScrollRect
  // calls.  If |scroll_rect| is non-empty, then that rect should be scrolled
  // by the amount specified by |scroll_delta|.  If |paint_rects| is non-empty,
  // then those rects should be repainted.  If |scroll_rect| and |paint_rects|
  // are non-empty, then scrolling should be performed before repainting.
  // |scroll_delta| can only specify scrolling in one direction (i.e., the x
  // and y members cannot both be non-zero).
  struct PendingUpdate {
    PendingUpdate();
    ~PendingUpdate();

    // Returns the rect damaged by scrolling within |scroll_rect| by
    // |scroll_delta|.  This rect must be repainted.
    gfx::Rect GetScrollDamage() const;

    // Returns the smallest rect containing all paint rects.
    gfx::Rect GetPaintBounds() const;

    gfx::Point scroll_delta;
    gfx::Rect scroll_rect;
    std::vector<gfx::Rect> paint_rects;
  };

  // There is a PendingUpdate if InvalidateRect or ScrollRect were called and
  // ClearPendingUpdate was not called.
  bool HasPendingUpdate() const;
  void ClearPendingUpdate();

  // Fills |update| and clears the pending update.
  void PopPendingUpdate(PendingUpdate* update);

  // The given rect should be repainted.
  void InvalidateRect(const gfx::Rect& rect);

  // The given rect should be scrolled by the given amounts.
  void ScrollRect(int dx, int dy, const gfx::Rect& clip_rect);

 private:
  gfx::Rect ScrollPaintRect(const gfx::Rect& paint_rect, int dx, int dy) const;
  bool ShouldInvalidateScrollRect(const gfx::Rect& rect) const;
  void InvalidateScrollRect();
  void CombinePaintRects();

  PendingUpdate update_;
};

#endif  // CONTENT_RENDERER_PAINT_AGGREGATOR_H_