cc: Do GatherPixelRefs from skia at record time

cc/resources/picture.h

 // Copyright 2012 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_RESOURCES_PICTURE_H_
 #define CC_RESOURCES_PICTURE_H_
 
 #include <list>
 #include <vector>
 
@@ skipping 42 matching lines @@
   void Raster(SkCanvas* canvas,
               gfx::Rect content_rect,
               float contents_scale,
               bool enable_lcd_text);
 
   void GatherPixelRefs(
       const gfx::Rect& layer_rect,
       std::list<skia::LazyPixelRef*>& pixel_ref_list);
 
  private:
+  struct PositionPixelRefs {
+    gfx::Rect rect;
+    std::list<skia::LazyPixelRef*> pixel_refs;
+  };
+  typedef std::vector<PositionPixelRefs> PositionPixelRefsVector;

[reveman, 2013/04/16 18:38:35]

how about using:
base::hash_map<std::pair<int, int>,
               std::list<skia::LazyPixelRef*> > PixelRefMap;

that would give us the pixel refs for a tile in constant time on the cc thread.

[enne (OOO), 2013/04/16 22:03:36]

For a recorded tile, you mean?  I think the original code is good, since a given
"get me the pixel refs for this rect" call doesn't seem like it should pick up
every image in the whole recorded tile.  (Unless that's what you're suggesting,
and I'm misunderstanding?)

[reveman, 2013/04/17 00:25:28]

we're trying to get the pixel refs for a playback tile in close to constant time
on cc thread. guaranteeing constant time for this seem hard but I think having
it not depend on SkPicture size (neither bytes or area) or number of pixel refs
in the recording is good enough.

the performance of using a vector would depend on SkPicture size (area).

+
   explicit Picture(gfx::Rect layer_rect);
   // This constructor assumes SkPicture is already ref'd and transfers
   // ownership to this picture.
   Picture(const skia::RefPtr<SkPicture>&,
           gfx::Rect layer_rect,
-          gfx::Rect opaque_rect);
+          gfx::Rect opaque_rect,
+          const PositionPixelRefsVector& lazy_pixel_refs);
   ~Picture();
 
+  void GatherPixelRefsFromSkia(
+      const gfx::Rect& layer_rect,
+      std::list<skia::LazyPixelRef*>& pixel_ref_list);
+  void GatherAllPixelRefs();
+
   gfx::Rect layer_rect_;
   gfx::Rect opaque_rect_;
   skia::RefPtr<SkPicture> picture_;
 
   typedef std::vector<scoped_refptr<Picture> > PictureVector;
   PictureVector clones_;
 
+  PositionPixelRefsVector lazy_pixel_refs_;

[enne (OOO), 2013/04/16 22:03:36]

These are safe to store using raw pointers because the SkPicture and any clones
have refcounted pointers to them?

+
   friend class base::RefCountedThreadSafe<Picture>;
   DISALLOW_COPY_AND_ASSIGN(Picture);
 };
 
 }  // namespace cc
 
 #endif  // CC_RESOURCES_PICTURE_H_