Improve Aura overdraw by changing hole calculation

ui/gfx/compositor/layer.h

Index: ui/gfx/compositor/layer.h
diff --git a/ui/gfx/compositor/layer.h b/ui/gfx/compositor/layer.h
index 7abb0f3ad8f5cb44bdfe1a0ffcbaeacdfcf7f1df..78c57641a7b88df9eff4c89c1e97e564a5c07405 100644
--- a/ui/gfx/compositor/layer.h
+++ b/ui/gfx/compositor/layer.h
@@ -26,6 +26,20 @@
 
 class SkCanvas;
 
+namespace {

[sky, 2011/10/25 21:44:09]

Move this to the private section of Layer.

+
+// contains info for a layer with respect to the root layer.

[sky, 2011/10/25 21:44:09]

Contains

+struct LayerProperties {
+ public:

[sky, 2011/10/25 21:44:09]

don't use a public section with structs.

+  ui::Layer* layer;
+  ui::Transform transform_relative_to_root;
+  float combined_opacity;
+
+  // Copy and assignment are allowed.

[sky, 2011/10/25 21:44:09]

Remove this comment. Generally when we use structs in the code we want
copy/assignment, so you would only comment if you didn't want them.

+};
+
+} // namespace
+
 namespace ui {
 
 class Animation;
@@ -201,18 +215,31 @@ class COMPOSITOR_EXPORT Layer :
   // delegate.
   void UpdateLayerCanvas();
 
+  // Called to indicate that a layer's properties have changed and that the
+  // holes for the layers must be recomputed.
+  void SetNeedsToRecomputeHole();
+
+  // 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
+  // and layers which don't fill their bounds opaquely.
+  void GeneratePreorderTraversal(std::vector<LayerProperties>* layer_traversal,
+      const ui::Transform& current_transform, float current_opacity);

[sky, 2011/10/25 21:44:09]

When you wrap, you want each argument on its own line. Also, the style guide
says out params should be last.
And I think this method should be renamed to something like GetLayerProperties

+
   // 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.
+  // Note: This method should only be called from the root.
   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|.
@@ -232,6 +259,9 @@ class COMPOSITOR_EXPORT Layer :
                         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.
@@ -292,6 +322,8 @@ class COMPOSITOR_EXPORT Layer :
 
   gfx::Rect hole_rect_;
 
+  bool recompute_hole_;
+
   gfx::Rect invalid_rect_;
 
   // If true the layer is always up to date.