cc: Remove vectors from tiling eviction tile iterator.

cc/layers/picture_layer_impl.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_LAYERS_PICTURE_LAYER_IMPL_H_
 #define CC_LAYERS_PICTURE_LAYER_IMPL_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 59 matching lines @@
     LayerEvictionTileIterator(PictureLayerImpl* layer,
                               TreePriority tree_priority);
     ~LayerEvictionTileIterator();
 
     Tile* operator*();
     const Tile* operator*() const;
     LayerEvictionTileIterator& operator++();
     operator bool() const;
 
    private:
+    struct TilingIterationRange {
+      int start_index;
+      int one_past_end_index;
+    };
+
+    void ConstructRanges();
+    bool CurrentTilingIndexInRange();
     void AdvanceToNextIterator();
-    bool IsCorrectType(
-        PictureLayerTiling::TilingEvictionTileIterator* it) const;
+    bool AdvanceTiling();
+    bool AdvanceRange();
+    bool AdvanceStage();
 
-    std::vector<PictureLayerTiling::TilingEvictionTileIterator> iterators_;
-    size_t iterator_index_;
+    PictureLayerTiling::TilingEvictionTileIterator iterator_;
+    int tiling_index_;
     TilePriority::PriorityBin iteration_stage_;
+    TilingIterationRange ranges_[5];

[reveman, 2014/07/29 16:50:49]

Some enums representing each stage and each range might help make the code a bit
easier to read.

[vmpstr, 2014/07/29 17:08:49]

Ok, I will do this.

+    int range_index_;
     bool required_for_activation_;
+    TreePriority tree_priority_;
 
     PictureLayerImpl* layer_;
   };

[reveman, 2014/07/29 16:50:49]

If I understand this iterator correctly. This is what it does: it iterates
through all tiles, for each tiling of each range of each stage.

Seems like what we really have here is a number of iterators baked into one.
Would it be possible to separate this into different iterators. I think that
might make it easier to understand and reduce the complexity of the code a bit.
We'd have a StageIterator and a RangeIterator. Wdyt?

[vmpstr, 2014/07/29 17:08:49]

That's kind of what we have with AdvanceTiling/AdvanceRange/AdvanceStage.. Those
are the operator++ of the iterators you propose. Are you suggesting making this
an explicit separate class? My initial thought is that it's a bit of an
overkill, but I can try and see if it makes it better. Let me know if that's
what you meant.

[reveman, 2014/07/29 18:04:32]

Yea, that's what I was thinking. Maybe the RangeIterator should be a
TilingSet::EvictionTileIterator that takes a range.

 
   static scoped_ptr<PictureLayerImpl> Create(LayerTreeImpl* tree_impl, int id) {
     return make_scoped_ptr(new PictureLayerImpl(tree_impl, id));
   }
   virtual ~PictureLayerImpl();
 
   // LayerImpl overrides.
   virtual const char* LayerTypeAsString() const OVERRIDE;
   virtual scoped_ptr<LayerImpl> CreateLayerImpl(LayerTreeImpl* tree_impl)
       OVERRIDE;
@@ skipping 116 matching lines @@
   gfx::Size viewport_size_for_tile_priority_;
   gfx::Transform screen_space_transform_for_tile_priority_;
 
   friend class PictureLayer;
   DISALLOW_COPY_AND_ASSIGN(PictureLayerImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_PICTURE_LAYER_IMPL_H_