Switch over to using SkRegions to calculate dirty areas.

remoting/host/differ.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 REMOTING_HOST_DIFFER_H_
 #define REMOTING_HOST_DIFFER_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
-#include "remoting/base/types.h"
-#include "ui/gfx/rect.h"
+#include "third_party/skia/include/core/SkRegion.h"
 
 namespace remoting {
 
 typedef uint8 DiffInfo;
 
 // Size (in pixels) of each square block used for diffing.
 // This must be a multiple of sizeof(uint64).
 static const int kBlockSize = 32;
 
+// TODO(dmaclach): Simplify differ now that we are working with SkRegions.
+// diff_info_ should no longer be needed, as we can put our data directly into
+// the region that we are calculating.
 class Differ {
  public:
   // Create a differ that operates on bitmaps with the specified width, height
   // and bytes_per_pixel.
   Differ(int width, int height, int bytes_per_pixel, int stride);
   ~Differ();
 
   int width() { return width_; }
   int height() { return height_; }
   int bytes_per_pixel() { return bytes_per_pixel_; }
   int bytes_per_row() { return bytes_per_row_; }
 
-  // Given the previous and current screen buffer, calculate the set of
-  // rectangles that enclose all the changed pixels in the new screen.
-  void CalcDirtyRects(const void* prev_buffer, const void* curr_buffer,
-                      InvalidRects* rects);
+  // Given the previous and current screen buffer, calculate the dirty region
+  // that encloses all of the changed pixels in the new screen.
+  void CalcDirtyRegion(const void* prev_buffer, const void* curr_buffer,
+                       SkRegion* region);
+
+ private:
+  // Allow tests to access our private parts.
+  friend class DifferTest;
 
   // Identify all of the blocks that contain changed pixels.
   void MarkDirtyBlocks(const void* prev_buffer, const void* curr_buffer);
 
   // After the dirty blocks have been identified, this routine merges adjacent
-  // blocks into larger rectangular units.
-  // The goal is to minimize the number of rects that cover the dirty blocks,
-  // although it is not required to calc the absolute minimum of rects.
-  void MergeBlocks(InvalidRects* rects);
-
-  // Allow tests to access our private parts.
-  friend class DifferTest;
-
- private:
+  // blocks into a region.
+  // The goal is to minimize the region that covers the dirty blocks.
+  void MergeBlocks(SkRegion* region);

[Wez, 2011/08/08 20:49:34]

You decided not to optimize out these steps in this CL?

[dmac, 2011/08/10 20:30:36]

Added todo at the top of this file, and have now logged a bug to track it as
well.

 
   // Check for diffs in upper-left portion of the block. The size of the portion
   // to check is specified by the |width| and |height| values.
   // Note that if we force the capturer to always return images whose width and
   // height are multiples of kBlockSize, then this will never be called.
   DiffInfo DiffPartialBlock(const uint8* prev_buffer, const uint8* curr_buffer,
                             int stride, int width, int height);
 
   // Dimensions of screen.
   int width_;
@@ skipping 13 matching lines @@
   int diff_info_width_;
   int diff_info_height_;
   int diff_info_size_;
 
   DISALLOW_COPY_AND_ASSIGN(Differ);
 };
 
 }  // namespace remoting
 
 #endif  // REMOTING_HOST_DIFFER_H_