cc/trees/damage_tracker.h

// Copyright 2011 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_TREES_DAMAGE_TRACKER_H_
#define CC_TREES_DAMAGE_TRACKER_H_

#include <vector>
#include "base/memory/scoped_ptr.h"
#include "cc/base/cc_export.h"
#include "cc/layers/layer_lists.h"
#include "ui/gfx/geometry/rect.h"

class SkImageFilter;

namespace gfx {
class Rect;
}

namespace cc {

class FilterOperations;
class LayerImpl;
class RenderSurfaceImpl;

// Computes the region where pixels have actually changed on a
// RenderSurfaceImpl. This region is used to scissor what is actually drawn to
// the screen to save GPU computation and bandwidth.
class CC_EXPORT DamageTracker {
 public:
  static scoped_ptr<DamageTracker> Create();
  ~DamageTracker();

  void DidDrawDamagedArea() { current_damage_rect_ = gfx::Rect(); }
  void AddDamageNextUpdate(const gfx::Rect& dmg) {
    current_damage_rect_.Union(dmg);
  }
  void UpdateDamageTrackingState(
      const LayerImplList& layer_list,
      int target_surface_layer_id,
      bool target_surface_property_changed_only_from_descendant,
      const gfx::Rect& target_surface_content_rect,
      LayerImpl* target_surface_mask_layer,
      const FilterOperations& filters);

  gfx::Rect current_damage_rect() { return current_damage_rect_; }

 private:
  DamageTracker();

  gfx::Rect TrackDamageFromActiveLayers(const LayerImplList& layer_list,
                                        int target_surface_layer_id);
  gfx::Rect TrackDamageFromSurfaceMask(LayerImpl* target_surface_mask_layer);
  gfx::Rect TrackDamageFromLeftoverRects();

  void PrepareRectHistoryForUpdate();

  // These helper functions are used only in TrackDamageFromActiveLayers().
  void ExtendDamageForLayer(LayerImpl* layer, gfx::Rect* target_damage_rect);
  void ExtendDamageForRenderSurface(LayerImpl* layer,
                                    gfx::Rect* target_damage_rect);

  struct RectMapData {
    RectMapData() : layer_id_(0), mailboxId_(0) {}
    explicit RectMapData(int layer_id) : layer_id_(layer_id), mailboxId_(0) {}
    void Update(const gfx::Rect& rect, unsigned int mailboxId) {
      mailboxId_ = mailboxId;
      rect_ = rect;
    }

    bool operator < (const RectMapData& other) const {
      return layer_id_ < other.layer_id_;
    }

    int layer_id_;
    unsigned int mailboxId_;
    gfx::Rect rect_;
  };
  typedef std::vector<RectMapData> SortedRectMap;

  RectMapData& RectDataForLayer(int layer_id, bool* layer_is_new);

  SortedRectMap rect_history_;

  unsigned int mailboxId_;
  gfx::Rect current_damage_rect_;

  DISALLOW_COPY_AND_ASSIGN(DamageTracker);
};

}  // namespace cc

#endif  // CC_TREES_DAMAGE_TRACKER_H_