cc: Added a spiral difference iterator to tiling data.

cc/base/tiling_data.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_BASE_TILING_DATA_H_
 #define CC_BASE_TILING_DATA_H_
 
 #include <utility>
 
 #include "base/basictypes.h"
@@ skipping 106 matching lines @@
     int consider_left_;
     int consider_top_;
     int consider_right_;
     int consider_bottom_;
     int ignore_left_;
     int ignore_top_;
     int ignore_right_;
     int ignore_bottom_;
   };
 
+  // Iterate through all indices whose bounds + border intersect with
+  // |consider| but which also do not intersect with |ignore|. The iterator
+  // order is a counterclockwise spiral around the given center.
+  class CC_EXPORT SpiralDifferenceIterator : public BaseIterator {
+   public:
+    SpiralDifferenceIterator(const TilingData* tiling_data,
+                             const gfx::Rect& consider_rect,
+                             const gfx::Rect& ignore_rect,
+                             const gfx::Rect& center_rect);
+    SpiralDifferenceIterator& operator++();
+
+   private:
+    bool in_consider_rect() const {
+      return index_x_ >= consider_left_ && index_x_ <= consider_right_ &&
+             index_y_ >= consider_top_ && index_y_ <= consider_bottom_;
+    }
+    bool in_ignore_rect() const {
+      return index_x_ >= ignore_left_ && index_x_ <= ignore_right_ &&
+             index_y_ >= ignore_top_ && index_y_ <= ignore_bottom_;
+    }
+    bool valid_column() const {
+      return index_x_ >= consider_left_ && index_x_ <= consider_right_;
+    }
+    bool valid_row() const {
+      return index_y_ >= consider_top_ && index_y_ <= consider_bottom_;
+    }
+
+    int current_step_count() const {
+      return (direction_ == UP || direction_ == DOWN) ? vertical_step_count_
+                                                      : horizontal_step_count_;
+    }
+
+    bool needs_direction_switch() const;
+    void switch_direction();
+
+    int consider_left_;
+    int consider_top_;
+    int consider_right_;
+    int consider_bottom_;
+    int ignore_left_;
+    int ignore_top_;
+    int ignore_right_;
+    int ignore_bottom_;
+
+    enum Direction { UP, LEFT, DOWN, RIGHT };
+
+    Direction direction_;
+    int delta_x_;
+    int delta_y_;
+    int current_step_;
+    int horizontal_step_count_;
+    int vertical_step_count_;
+  };
+
  private:
+  std::pair<int, int> UnclampedFirstBorderTileIndexFromSrcCoord(int x,
+                                                                int y) const;
+  std::pair<int, int> UnclampedLastBorderTileIndexFromSrcCoord(int x,
+                                                               int y) const;
+
   void AssertTile(int i, int j) const {
     DCHECK_GE(i,  0);
     DCHECK_LT(i, num_tiles_x_);
     DCHECK_GE(j, 0);
     DCHECK_LT(j, num_tiles_y_);
   }
 
   void RecomputeNumTiles();
 
   gfx::Size max_texture_size_;
   gfx::Size total_size_;
   int border_texels_;
 
   // These are computed values.
   int num_tiles_x_;
   int num_tiles_y_;
 };
 
 }  // namespace cc
 
 #endif  // CC_BASE_TILING_DATA_H_