remoting/host: Rename Capturer to VideoFrameCapturer.

remoting/host/video_frame_capturer_helper.h

+// Copyright (c) 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 REMOTING_HOST_VIDEO_FRAME_CAPTURER_HELPER_H_
+#define REMOTING_HOST_VIDEO_FRAME_CAPTURER_HELPER_H_
+#pragma once
+
+#include "base/memory/scoped_ptr.h"
+#include "base/synchronization/lock.h"
+#include "third_party/skia/include/core/SkRegion.h"
+
+namespace remoting {
+
+// VideoFrameCapturerHelper is intended to be used by an implementation of the
+// VideoFrameCapturer interface. It maintains a thread-safe invalid region, and
+// the size of the most recently captured screen, on behalf of the
+// VideoFrameCapturer that owns it.
+class VideoFrameCapturerHelper {
+ public:
+  VideoFrameCapturerHelper();
+  ~VideoFrameCapturerHelper();
+
+  // Clear out the invalid region.
+  void ClearInvalidRegion();
+
+  // Invalidate the specified region.
+  void InvalidateRegion(const SkRegion& invalid_region);
+
+  // Invalidate the entire screen, of a given size.
+  void InvalidateScreen(const SkISize& size);
+
+  // Invalidate the entire screen, using the size of the most recently
+  // captured screen.
+  void InvalidateFullScreen();
+
+  // Swap the given region with the stored invalid region.
+  void SwapInvalidRegion(SkRegion* invalid_region);
+
+  // Access the size of the most recently captured screen.
+  const SkISize& size_most_recent() const;
+  void set_size_most_recent(const SkISize& size);
+
+  // Lossy compression can result in color values leaking between pixels in one
+  // block. If part of a block changes, then unchanged parts of that block can
+  // be changed in the compressed output. So we need to re-render an entire
+  // block whenever part of the block changes.
+  //
+  // If |log_grid_size| is >= 1, then this function makes SwapInvalidRegion
+  // produce an invalid region expanded so that its vertices lie on a grid of
+  // size 2 ^ |log_grid_size|. The expanded region is then clipped to the size
+  // of the most recently captured screen, as previously set by
+  // set_size_most_recent().
+  // If |log_grid_size| is <= 0, then the invalid region is not expanded.
+  void SetLogGridSize(int log_grid_size);
+
+  // Expands a region so that its vertices all lie on a grid.
+  // The grid size must be >= 2, so |log_grid_size| must be >= 1.
+  static scoped_ptr<SkRegion> ExpandToGrid(const SkRegion& region,
+                                           int log_grid_size);
+
+ private:
+  // A region that has been manually invalidated (through InvalidateRegion).
+  // These will be returned as dirty_region in the capture data during the next
+  // capture.
+  SkRegion invalid_region_;
+
+  // A lock protecting |invalid_region_| across threads.
+  base::Lock invalid_region_lock_;
+
+  // The size of the most recently captured screen.
+  SkISize size_most_recent_;
+
+  // The log (base 2) of the size of the grid to which the invalid region is
+  // expanded.
+  // If the value is <= 0, then the invalid region is not expanded to a grid.
+  int log_grid_size_;
+
+  DISALLOW_COPY_AND_ASSIGN(VideoFrameCapturerHelper);
+};
+
+}  // namespace remoting
+
+#endif  // REMOTING_HOST_VIDEO_FRAME_CAPTURER_HELPER_H_