Improve Aura overdraw by changing hole calculation

ui/gfx/compositor/layer.h

 // Copyright (c) 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 UI_GFX_COMPOSITOR_LAYER_H_
 #define UI_GFX_COMPOSITOR_LAYER_H_
 #pragma once
 
 #include <string>
 #include <vector>
@@ skipping 167 matching lines @@
   // TODO(vollick): Eventually, if a non-leaf node has an opacity of less than
   // 1.0, we'll render to a separate texture, and then apply the alpha.
   // Currently, we multiply our opacity by all our ancestor's opacities and
   // use the combined result, but this is only temporary.
   float GetCombinedOpacity() const;
 
   // Called during the Draw() pass to freshen the Layer's contents from the
   // delegate.
   void UpdateLayerCanvas();
 
+  // Resets |hole_rect_| to the empty rect for all layers below and
+  // including this one.
+  void ClearHoleRects();
+
+  // Does a preorder traversal of layers starting with this layer. Omits layers
+  // which cannot punch a hole in  another layer such as non visible layers

[sky, 2011/10/24 15:44:52]

'in  another' -> 'in another'

+  // and layers which don't fill their bounds opaquely.
+  void GeneratePreorderTraversal(std::vector<ui::Layer*>* layer_traversal);
+
   // A hole in a layer is an area in the layer that does not get drawn
   // because this area is covered up with another layer which is known to be
   // opaque.
   // This method computes the dimension of the hole (if there is one)
   // based on whether one of its child nodes is always opaque.
   // Note: For simplicity's sake, currently a hole is only created if the child
   // view has no transform with respect to its parent.
   void RecomputeHole();
 
-  // Returns true if the layer paints every pixel (fills_bounds_opaquely)
-  // and the alpha of the layer is 1.0f.
-  bool IsCompletelyOpaque() const;
+  void set_hole_rect(const gfx::Rect& hole_rect) {
+    hole_rect_ = hole_rect;
+  }
 
   // Determines the regions that don't intersect |rect| and places the
   // result in |sides|.
   //
   //  rect_____________________________
   //  |xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx|
   //  |xxxxxxxxxxxxx top xxxxxxxxxxxxxx|
   //  |________________________________|
   //  |xxxxx|                    |xxxxx|
   //  |xxxxx|region_to_punch_out |xxxxx|
   //  |left |                    |right|
   //  |_____|____________________|_____|
   //  |xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx|
   //  |xxxxxxxxxx bottom xxxxxxxxxxxxxx|
   //  |________________________________|
   static void PunchHole(const gfx::Rect& rect,
                         const gfx::Rect& region_to_punch_out,
                         std::vector<gfx::Rect>* sides);
 
+  // Drops texture just for this layer.
+  void DropTexture();
+
   // Drop all textures for layers below and including this one. Called when
   // the layer is removed from a hierarchy. Textures will be re-generated if
   // the layer is subsequently re-attached and needs to be drawn.
   void DropTextures();
 
   bool ConvertPointForAncestor(const Layer* ancestor, gfx::Point* point) const;
   bool ConvertPointFromAncestor(const Layer* ancestor, gfx::Point* point) const;
 
   bool GetTransformRelativeTo(const Layer* ancestor,
                               Transform* transform) const;
@@ skipping 50 matching lines @@
   LayerDelegate* delegate_;
 
   scoped_ptr<LayerAnimator> animator_;
 
   DISALLOW_COPY_AND_ASSIGN(Layer);
 };
 
 }  // namespace ui
 
 #endif  // UI_GFX_COMPOSITOR_LAYER_H_