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.
  41   void EnterLayer(const LayerIteratorPosition<LayerType>& layer_iterator);
  42   // Called at the end of each step in the LayerIterator's front-to-back
  43   // traversal.
  44   void LeaveLayer(const LayerIteratorPosition<LayerType>& layer_iterator);
  45
  46   // Returns true if the given rect in content space for a layer is fully
  47   // occluded in either screen space or the layer's target surface.
  48   // |render_target| is the contributing layer's render target, and
  49   // |draw_transform|, |transformsToTargetKnown| and |clippedRectInTarget| are
  50   // relative to that.
  51   bool Occluded(const LayerType* render_target,
  52                 gfx::Rect content_rect,
  53                 const gfx::Transform& draw_transform,
  54                 bool impl_draw_transform_is_unknown,
  55                 bool is_clipped,
  56                 gfx::Rect clip_rect_in_target,
  57                 bool* has_occlusion_from_outside_target_surface) const;
  58
  59   // Gives an unoccluded sub-rect of |content_rect| in the content space of a
  60   // layer. Used when considering occlusion for a layer that paints/draws
  61   // something. |render_target| is the contributing layer's render target, and
  62   // |draw_transform|, |transformsToTargetKnown| and |clippedRectInTarget| are
  63   // relative to that.
  64   gfx::Rect UnoccludedContentRect(
  65       const LayerType* render_target,
  66       gfx::Rect content_rect,
  67       const gfx::Transform& draw_transform,
  68       bool impl_draw_transform_is_unknown,
  69       bool is_clipped,
  70       gfx::Rect clip_rect_in_target,
  71       bool* has_occlusion_from_outside_target_surface) const;
  72
  73   // Gives an unoccluded sub-rect of |content_rect| in the content space of the
  74   // render_target owned by the layer. Used when considering occlusion for a
  75   // contributing surface that is rendering into another target.
  76   gfx::Rect UnoccludedContributingSurfaceContentRect(
  77       const LayerType* layer,
  78       bool for_replica,
  79       gfx::Rect content_rect,
  80       bool* has_occlusion_from_outside_target_surface) const;
  81
  82   // Report operations for recording overdraw metrics.
  83   OverdrawMetrics* overdraw_metrics() const {
  84     return overdraw_metrics_.get();
  85   }
  86
  87   // Gives the region of the screen that is not occluded by something opaque.
  88   Region ComputeVisibleRegionInScreen() const {
  89     DCHECK(!stack_.back().target->parent());
  90     return SubtractRegions(screen_space_clip_rect_,
  91                            stack_.back().occlusion_from_inside_target);
  92   }
  93
  94   void set_minimum_tracking_size(gfx::Size size) {
  95     minimum_tracking_size_ = size;
  96   }
  97
  98   // The following is used for visualization purposes.
  99   void set_occluding_screen_space_rects_container(
 100       std::vector<gfx::Rect>* rects) {
 101     occluding_screen_space_rects_ = rects;
 102   }
 103   void set_non_occluding_screen_space_rects_container(
 104       std::vector<gfx::Rect>* rects) {
 105     non_occluding_screen_space_rects_ = rects;
 106   }
 107
 108  protected:
 109   struct StackObject {
 110     StackObject() : target(0) {}
 111     explicit StackObject(const LayerType* target) : target(target) {}
 112     const LayerType* target;
 113     Region occlusion_from_outside_target;
 114     Region occlusion_from_inside_target;
 115   };
 116
 117   // The stack holds occluded regions for subtrees in the
 118   // RenderSurfaceImpl-Layer tree, so that when we leave a subtree we may apply
 119   // a mask to it, but not to the parts outside the subtree.
 120   // - The first time we see a new subtree under a target, we add that target to
 121   // the top of the stack. This can happen as a layer representing itself, or as
 122   // a target surface.
 123   // - When we visit a target surface, we apply its mask to its subtree, which
 124   // is at the top of the stack.
 125   // - When we visit a layer representing itself, we add its occlusion to the
 126   // current subtree, which is at the top of the stack.
 127   // - When we visit a layer representing a contributing surface, the current
 128   // target will never be the top of the stack since we just came from the
 129   // contributing surface.
 130   // We merge the occlusion at the top of the stack with the new current
 131   // subtree. This new target is pushed onto the stack if not already there.
 132   std::vector<StackObject> stack_;
 133
 134  private:
 135   // Called when visiting a layer representing itself. If the target was not
 136   // already current, then this indicates we have entered a new surface subtree.
 137   void EnterRenderTarget(const LayerType* new_target);
 138
 139   // Called when visiting a layer representing a target surface. This indicates
 140   // we have visited all the layers within the surface, and we may perform any
 141   // surface-wide operations.
 142   void FinishedRenderTarget(const LayerType* finished_target);
 143
 144   // Called when visiting a layer representing a contributing surface. This
 145   // indicates that we are leaving our current surface, and entering the new
 146   // one. We then perform any operations required for merging results from the
 147   // child subtree into its parent.
 148   void LeaveToRenderTarget(const LayerType* new_target);
 149
 150   // Add the layer's occlusion to the tracked state.
 151   void MarkOccludedBehindLayer(const LayerType* layer);
 152
 153   gfx::Rect screen_space_clip_rect_;
 154   scoped_ptr<class OverdrawMetrics> overdraw_metrics_;
 155   gfx::Size minimum_tracking_size_;
 156
 157   // This is used for visualizing the occlusion tracking process.
 158   std::vector<gfx::Rect>* occluding_screen_space_rects_;
 159   std::vector<gfx::Rect>* non_occluding_screen_space_rects_;
 160
 161   DISALLOW_COPY_AND_ASSIGN(OcclusionTrackerBase);
 162 };
 163
 164 typedef OcclusionTrackerBase<Layer, RenderSurface> OcclusionTracker;
 165 typedef OcclusionTrackerBase<LayerImpl, RenderSurfaceImpl> OcclusionTrackerImpl;
 166 #if !defined(COMPILER_MSVC)
 167 extern template class OcclusionTrackerBase<Layer, RenderSurface>;
 168 extern template class OcclusionTrackerBase<LayerImpl, RenderSurfaceImpl>;
 169 #endif
 170
 171 }  // namespace cc
 172
 173 #endif  // CC_TREES_OCCLUSION_TRACKER_H_