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      1 // Copyright 2011 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef CC_TREES_DAMAGE_TRACKER_H_
      6 #define CC_TREES_DAMAGE_TRACKER_H_
      7 
      8 #include <vector>
      9 #include "base/containers/hash_tables.h"
     10 #include "base/memory/scoped_ptr.h"
     11 #include "cc/base/cc_export.h"
     12 #include "cc/layers/layer_lists.h"
     13 #include "ui/gfx/rect_f.h"
     14 
     15 class SkImageFilter;
     16 
     17 namespace gfx {
     18 class Rect;
     19 }
     20 
     21 namespace cc {
     22 
     23 class FilterOperations;
     24 class LayerImpl;
     25 class RenderSurfaceImpl;
     26 
     27 // Computes the region where pixels have actually changed on a
     28 // RenderSurfaceImpl. This region is used to scissor what is actually drawn to
     29 // the screen to save GPU computation and bandwidth.
     30 class CC_EXPORT DamageTracker {
     31  public:
     32   static scoped_ptr<DamageTracker> Create();
     33   ~DamageTracker();
     34 
     35   void DidDrawDamagedArea() { current_damage_rect_ = gfx::RectF(); }
     36   void AddDamageNextUpdate(gfx::RectF dmg) { current_damage_rect_.Union(dmg); }
     37   void UpdateDamageTrackingState(
     38       const LayerImplList& layer_list,
     39       int target_surface_layer_id,
     40       bool target_surface_property_changed_only_from_descendant,
     41       gfx::Rect target_surface_content_rect,
     42       LayerImpl* target_surface_mask_layer,
     43       const FilterOperations& filters,
     44       SkImageFilter* filter);
     45 
     46   gfx::RectF current_damage_rect() { return current_damage_rect_; }
     47 
     48  private:
     49   DamageTracker();
     50 
     51   gfx::RectF TrackDamageFromActiveLayers(
     52       const LayerImplList& layer_list,
     53       int target_surface_layer_id);
     54   gfx::RectF TrackDamageFromSurfaceMask(LayerImpl* target_surface_mask_layer);
     55   gfx::RectF TrackDamageFromLeftoverRects();
     56 
     57   gfx::RectF RemoveRectFromCurrentFrame(int layer_id, bool* layer_is_new);
     58   void SaveRectForNextFrame(int layer_id, const gfx::RectF& target_space_rect);
     59 
     60   // These helper functions are used only in TrackDamageFromActiveLayers().
     61   void ExtendDamageForLayer(LayerImpl* layer, gfx::RectF* target_damage_rect);
     62   void ExtendDamageForRenderSurface(LayerImpl* layer,
     63                                     gfx::RectF* target_damage_rect);
     64 
     65   // To correctly track exposed regions, two hashtables of rects are maintained.
     66   // The "current" map is used to compute exposed regions of the current frame,
     67   // while the "next" map is used to collect layer rects that are used in the
     68   // next frame.
     69   typedef base::hash_map<int, gfx::RectF> RectMap;
     70   scoped_ptr<RectMap> current_rect_history_;
     71   scoped_ptr<RectMap> next_rect_history_;
     72 
     73   gfx::RectF current_damage_rect_;
     74 
     75   DISALLOW_COPY_AND_ASSIGN(DamageTracker);
     76 };
     77 
     78 }  // namespace cc
     79 
     80 #endif  // CC_TREES_DAMAGE_TRACKER_H_
     81