Keeping track of descendants that draw content instead of recalcualting

cc/layers/layer.h

 // Copyright 2010 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_LAYERS_LAYER_H_
 #define CC_LAYERS_LAYER_H_
 
 #include <set>
 #include <string>
 
@@ skipping 334 matching lines @@
 
   bool has_mask() const { return !!mask_layer_.get(); }
   bool has_replica() const { return !!replica_layer_.get(); }
   bool replica_has_mask() const {
     return replica_layer_.get() &&
            (mask_layer_.get() || replica_layer_->mask_layer_.get());
   }
 
   // These methods typically need to be overwritten by derived classes.
   virtual bool DrawsContent() const;
+  virtual int NumDescendantsThatDrawContent() const;
   virtual void SavePaintProperties();
   // Returns true iff any resources were updated that need to be committed.
   virtual bool Update(ResourceUpdateQueue* queue,
                       const OcclusionTracker<Layer>* occlusion);
   virtual bool NeedMoreUpdates();
   virtual void SetIsMask(bool is_mask) {}
   virtual void ReduceMemoryUsage() {}
   virtual void OnOutputSurfaceCreated() {}
   virtual bool IsSuitableForGpuRasterization() const;
 
@@ skipping 88 matching lines @@
   }
   void reset_needs_push_properties_for_testing() {
     needs_push_properties_ = false;
   }
 
   virtual void RunMicroBenchmark(MicroBenchmark* benchmark);
 
   void Set3dSortingContextId(int id);
   int sorting_context_id() const { return sorting_context_id_; }
 
+  // Called when our number of Drawable Descendants changes

[danakj, 2014/07/14 15:49:23]

nit: s/D/d/g and add a .

[awoloszyn, 2014/07/14 19:38:33]

Done.

+  void AddDrawableDescendants(int num);

[danakj, 2014/07/14 15:49:23]

Can these all be protected?

[awoloszyn, 2014/07/14 19:38:33]

Done.

+  void RemoveDrawableDescendants(int num);
+
+  void SetDrawsContent(bool draws_content);
+
  protected:
   friend class LayerImpl;
   friend class TreeSynchronizer;
   virtual ~Layer();
 
   Layer();
 
   // These SetNeeds functions are in order of severity of update:
   //
   // Called when this layer has been modified in some way, but isn't sure
   // that it needs a commit yet.  It needs CalcDrawProperties and UpdateLayers
   // before it knows whether or not a commit is required.
   void SetNeedsUpdate();
   // Called when a property has been modified in a way that the layer
   // knows immediately that a commit is required.  This implies SetNeedsUpdate
   // as well as SetNeedsPushProperties to push that property.
   void SetNeedsCommit();
   // Called when there's been a change in layer structure.  Implies both
   // SetNeedsUpdate and SetNeedsCommit, but not SetNeedsPushProperties.
   void SetNeedsFullTreeSync();
 
   // Called when the next commit should wait until the pending tree is activated
   // before finishing the commit and unblocking the main thread. Used to ensure
   // unused resources on the impl thread are returned before commit completes.
   void SetNextCommitWaitsForActivation();
 
+  // Will relcalculate whether or not we draw content and set draws_content_
+  // appropriately.
+  virtual void UpdateDrawsContent(bool draws_content);
   void AddDependentNeedsPushProperties();
   void RemoveDependentNeedsPushProperties();
   bool parent_should_know_need_push_properties() const {
     return needs_push_properties() || descendant_needs_push_properties();
   }
 
   bool IsPropertyChangeAllowed() const;
 
   // If this layer has a scroll parent, it removes |this| from its list of
   // scroll children.
@@ skipping 73 matching lines @@
   scoped_refptr<LayerAnimationController> layer_animation_controller_;
 
   // Layer properties.
   gfx::Size bounds_;
 
   gfx::Vector2d scroll_offset_;
   // This variable indicates which ancestor layer (if any) whose size,
   // transformed relative to this layer, defines the maximum scroll offset for
   // this layer.
   int scroll_clip_layer_id_;
+  int num_descendants_that_draw_content_;
   bool should_scroll_on_main_thread_ : 1;
   bool have_wheel_event_handlers_ : 1;
   bool have_scroll_event_handlers_ : 1;
   bool user_scrollable_horizontal_ : 1;
   bool user_scrollable_vertical_ : 1;
   bool is_root_for_isolated_group_ : 1;
   bool is_container_for_fixed_position_layers_ : 1;
   bool is_drawable_ : 1;
+  bool draws_content_ : 1;
   bool hide_layer_and_subtree_ : 1;
   bool masks_to_bounds_ : 1;
   bool contents_opaque_ : 1;
   bool double_sided_ : 1;
   bool should_flatten_transform_ : 1;
   bool use_parent_backface_visibility_ : 1;
   bool draw_checkerboard_for_missing_tiles_ : 1;
   bool force_render_surface_ : 1;
   bool transform_is_invertible_ : 1;
   Region non_fast_scrollable_region_;
@@ skipping 29 matching lines @@
   DrawProperties<Layer> draw_properties_;
 
   PaintProperties paint_properties_;
 
   DISALLOW_COPY_AND_ASSIGN(Layer);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_LAYER_H_