cc/trees/occlusion_tracker.h

   1 // Copyright 2012 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_OCCLUSION_TRACKER_H_
   6 #define CC_TREES_OCCLUSION_TRACKER_H_
   7
   8 #include <vector>
   9
  10 #include "base/basictypes.h"
  11 #include "cc/base/cc_export.h"
  12 #include "cc/base/region.h"
  13 #include "cc/layers/layer_iterator.h"
  14 #include "ui/gfx/rect.h"
  15
  16 namespace cc {
  17 class OverdrawMetrics;
  18 class LayerImpl;
  19 class RenderSurfaceImpl;
  20 class Layer;
  21 class RenderSurface;
  22
  23 // This class is used to track occlusion of layers while traversing them in a
  24 // front-to-back order. As each layer is visited, one of the methods in this
  25 // class is called to notify it about the current target surface. Then,
  26 // occlusion in the content space of the current layer may be queried, via
  27 // methods such as Occluded() and UnoccludedContentRect(). If the current layer
  28 // owns a RenderSurfaceImpl, then occlusion on that RenderSurfaceImpl may also
  29 // be queried via surfaceOccluded() and surfaceUnoccludedContentRect(). Finally,
  30 // once finished with the layer, occlusion behind the layer should be marked by
  31 // calling MarkOccludedBehindLayer().
  32 template <typename LayerType, typename RenderSurfaceType>
  33 class CC_EXPORT OcclusionTrackerBase {
  34  public:
  35   OcclusionTrackerBase(gfx::Rect screen_space_clip_rect,
  36                        bool record_metrics_for_frame);
  37   ~OcclusionTrackerBase();
  38
  39   // Called at the beginning of each step in the LayerIterator's front-to-back
  40   // traversal. If |prevent_occlusion| is true, the layer will be considered
  41   // unoccluded.
  42   void EnterLayer(const LayerIteratorPosition<LayerType>& layer_iterator,
  43                   bool prevent_occlusion);
  44   // Called at the end of each step in the LayerIterator's front-to-back
  45   // traversal.
  46   void LeaveLayer(const LayerIteratorPosition<LayerType>& layer_iterator);
  47
  48   // Returns true if the given rect in content space for a layer is fully
  49   // occluded in either screen space or the layer's target surface.
  50   // |render_target| is the contributing layer's render target, and
  51   // |draw_transform| and |impl_draw_transform_is_unknown| are relative to that.
  52   bool Occluded(const LayerType* render_target,
  53                 gfx::Rect content_rect,
  54                 const gfx::Transform& draw_transform,
  55                 bool impl_draw_transform_is_unknown) const;
  56
  57   // Gives an unoccluded sub-rect of |content_rect| in the content space of a
  58   // layer. Used when considering occlusion for a layer that paints/draws
  59   // something. |render_target| is the contributing layer's render target, and
  60   // |draw_transform| and |impl_draw_transform_is_unknown| are relative to that.
  61   gfx::Rect UnoccludedContentRect(
  62       const LayerType* render_target,
  63       gfx::Rect content_rect,
  64       const gfx::Transform& draw_transform,
  65       bool impl_draw_transform_is_unknown) const;
  66
  67   // Gives an unoccluded sub-rect of |content_rect| in the content space of the
  68   // render_target owned by the layer. Used when considering occlusion for a
  69   // contributing surface that is rendering into another target.
  70   gfx::Rect UnoccludedContributingSurfaceContentRect(
  71       const LayerType* layer,
  72       bool for_replica,
  73       gfx::Rect content_rect) const;
  74
  75   // Report operations for recording overdraw metrics.
  76   OverdrawMetrics* overdraw_metrics() const {
  77     return overdraw_metrics_.get();
  78   }
  79
  80   // Gives the region of the screen that is not occluded by something opaque.
  81   Region ComputeVisibleRegionInScreen() const {
  82     DCHECK(!stack_.back().target->parent());
  83     return SubtractRegions(screen_space_clip_rect_,
  84                            stack_.back().occlusion_from_inside_target);
  85   }
  86
  87   void set_minimum_tracking_size(gfx::Size size) {
  88     minimum_tracking_size_ = size;
  89   }
  90
  91   // The following is used for visualization purposes.
  92   void set_occluding_screen_space_rects_container(
  93       std::vector<gfx::Rect>* rects) {
  94     occluding_screen_space_rects_ = rects;
  95   }
  96   void set_non_occluding_screen_space_rects_container(
  97       std::vector<gfx::Rect>* rects) {
  98     non_occluding_screen_space_rects_ = rects;
  99   }
 100
 101  protected:
 102   struct StackObject {
 103     StackObject() : target(0) {}
 104     explicit StackObject(const LayerType* target) : target(target) {}
 105     const LayerType* target;
 106     Region occlusion_from_outside_target;
 107     Region occlusion_from_inside_target;
 108   };
 109
 110   // The stack holds occluded regions for subtrees in the
 111   // RenderSurfaceImpl-Layer tree, so that when we leave a subtree we may apply
 112   // a mask to it, but not to the parts outside the subtree.
 113   // - The first time we see a new subtree under a target, we add that target to
 114   // the top of the stack. This can happen as a layer representing itself, or as
 115   // a target surface.
 116   // - When we visit a target surface, we apply its mask to its subtree, which
 117   // is at the top of the stack.
 118   // - When we visit a layer representing itself, we add its occlusion to the
 119   // current subtree, which is at the top of the stack.
 120   // - When we visit a layer representing a contributing surface, the current
 121   // target will never be the top of the stack since we just came from the
 122   // contributing surface.
 123   // We merge the occlusion at the top of the stack with the new current
 124   // subtree. This new target is pushed onto the stack if not already there.
 125   std::vector<StackObject> stack_;
 126
 127  private:
 128   // Called when visiting a layer representing itself. If the target was not
 129   // already current, then this indicates we have entered a new surface subtree.
 130   void EnterRenderTarget(const LayerType* new_target);
 131
 132   // Called when visiting a layer representing a target surface. This indicates
 133   // we have visited all the layers within the surface, and we may perform any
 134   // surface-wide operations.
 135   void FinishedRenderTarget(const LayerType* finished_target);
 136
 137   // Called when visiting a layer representing a contributing surface. This
 138   // indicates that we are leaving our current surface, and entering the new
 139   // one. We then perform any operations required for merging results from the
 140   // child subtree into its parent.
 141   void LeaveToRenderTarget(const LayerType* new_target);
 142
 143   // Add the layer's occlusion to the tracked state.
 144   void MarkOccludedBehindLayer(const LayerType* layer);
 145
 146   gfx::Rect screen_space_clip_rect_;
 147   scoped_ptr<class OverdrawMetrics> overdraw_metrics_;
 148   gfx::Size minimum_tracking_size_;
 149   bool prevent_occlusion_;
 150
 151   // This is used for visualizing the occlusion tracking process.
 152   std::vector<gfx::Rect>* occluding_screen_space_rects_;
 153   std::vector<gfx::Rect>* non_occluding_screen_space_rects_;
 154
 155   DISALLOW_COPY_AND_ASSIGN(OcclusionTrackerBase);
 156 };
 157
 158 typedef OcclusionTrackerBase<Layer, RenderSurface> OcclusionTracker;
 159 typedef OcclusionTrackerBase<LayerImpl, RenderSurfaceImpl> OcclusionTrackerImpl;
 160 #if !defined(COMPILER_MSVC)
 161 extern template class OcclusionTrackerBase<Layer, RenderSurface>;
 162 extern template class OcclusionTrackerBase<LayerImpl, RenderSurfaceImpl>;
 163 #endif
 164
 165 }  // namespace cc
 166
 167 #endif  // CC_TREES_OCCLUSION_TRACKER_H_