remoting/host: Rename Capturer to VideoFrameCapturer.

remoting/host/video_frame_capturer_linux.cc

Index: remoting/host/video_frame_capturer_linux.cc
diff --git a/remoting/host/video_frame_capturer_linux.cc b/remoting/host/video_frame_capturer_linux.cc
new file mode 100644
index 0000000000000000000000000000000000000000..68196f23e4310835952fd1e776cf57507ff3473c
--- /dev/null
+++ b/remoting/host/video_frame_capturer_linux.cc
@@ -0,0 +1,638 @@
+// 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.
+
+#include "remoting/host/video_frame_capturer.h"
+
+#include <X11/Xlib.h>
+#include <X11/Xutil.h>
+#include <X11/extensions/Xdamage.h>
+#include <X11/extensions/Xfixes.h>
+
+#include <set>
+
+#include "base/basictypes.h"
+#include "base/logging.h"
+#include "base/memory/scoped_ptr.h"
+#include "remoting/base/capture_data.h"
+#include "remoting/host/video_frame_capturer_helper.h"

[Wez, 2012/07/12 15:59:22]

nit: move this below differ.h

+#include "remoting/host/differ.h"
+#include "remoting/host/x_server_pixel_buffer.h"
+#include "remoting/proto/control.pb.h"
+
+namespace remoting {
+
+namespace {
+
+static const int kBytesPerPixel = 4;
+
+// Default to false, since many systems have broken XDamage support - see
+// http://crbug.com/73423.
+static bool g_should_use_x_damage = false;
+
+static bool ShouldUseXDamage() {
+  return g_should_use_x_damage;
+}
+
+// A class representing a full-frame pixel buffer
+class VideoFrameBuffer {
+ public:
+  VideoFrameBuffer() : bytes_per_row_(0), needs_update_(true) {
+    size_.set(0, 0);
+  }
+
+  void Update(Display* display, Window root_window) {
+    if (needs_update_) {
+      needs_update_ = false;
+      XWindowAttributes root_attr;
+      XGetWindowAttributes(display, root_window, &root_attr);
+      if (root_attr.width != size_.width() ||
+          root_attr.height != size_.height()) {
+        size_.set(root_attr.width, root_attr.height);
+        bytes_per_row_ = size_.width() * kBytesPerPixel;
+        size_t buffer_size = size_.width() * size_.height() * kBytesPerPixel;
+        ptr_.reset(new uint8[buffer_size]);
+      }
+    }
+  }
+
+  SkISize size() const { return size_; }
+  int bytes_per_row() const { return bytes_per_row_; }
+  uint8* ptr() const { return ptr_.get(); }
+
+  void set_needs_update() { needs_update_ = true; }
+
+ private:
+  SkISize size_;
+  int bytes_per_row_;
+  scoped_array<uint8> ptr_;
+  bool needs_update_;
+
+  DISALLOW_COPY_AND_ASSIGN(VideoFrameBuffer);
+};
+
+// A class to perform video frame capturing for Linux.
+class VideoFrameCapturerLinux : public VideoFrameCapturer {
+ public:
+  VideoFrameCapturerLinux();
+  virtual ~VideoFrameCapturerLinux();
+
+  bool Init();  // TODO(ajwong): Do we really want this to be synchronous?
+
+  // Capturer interface.
+  virtual void Start(const CursorShapeChangedCallback& callback) OVERRIDE;
+  virtual void Stop() OVERRIDE;
+  virtual void ScreenConfigurationChanged() OVERRIDE;
+  virtual media::VideoFrame::Format pixel_format() const OVERRIDE;
+  virtual void ClearInvalidRegion() OVERRIDE;
+  virtual void InvalidateRegion(const SkRegion& invalid_region) OVERRIDE;
+  virtual void InvalidateScreen(const SkISize& size) OVERRIDE;
+  virtual void InvalidateFullScreen() OVERRIDE;
+  virtual void CaptureInvalidRegion(
+      const CaptureCompletedCallback& callback) OVERRIDE;
+  virtual const SkISize& size_most_recent() const OVERRIDE;
+
+ private:
+  void InitXDamage();
+
+  // Read and handle all currently-pending XEvents.
+  // In the DAMAGE case, process the XDamage events and store the resulting
+  // damage rectangles in the VideoFrameCapturerHelper.
+  // In all cases, call ScreenConfigurationChanged() in response to any
+  // ConfigNotify events.
+  void ProcessPendingXEvents();
+
+  // Capture screen pixels, and return the data in a new CaptureData object,
+  // to be freed by the caller.
+  // In the DAMAGE case, the VideoFrameCapturerHelper already holds the list of
+  // invalid rectangles from ProcessPendingXEvents().
+  // In the non-DAMAGE case, this captures the whole screen, then calculates
+  // some invalid rectangles that include any differences between this and the
+  // previous capture.
+  CaptureData* CaptureFrame();
+
+  // Capture the cursor image and call the CursorShapeChangedCallback if it
+  // has been set (using SetCursorShapeChangedCallback).
+  void CaptureCursor();
+
+  // Synchronize the current buffer with |last_buffer_|, by copying pixels from
+  // the area of |last_invalid_rects|.
+  // Note this only works on the assumption that kNumBuffers == 2, as
+  // |last_invalid_rects| holds the differences from the previous buffer and
+  // the one prior to that (which will then be the current buffer).
+  void SynchronizeFrame();
+
+  void DeinitXlib();
+
+  // Capture a rectangle from |x_server_pixel_buffer_|, and copy the data into
+  // |capture_data|.
+  void CaptureRect(const SkIRect& rect, CaptureData* capture_data);
+
+  // We expose two forms of blitting to handle variations in the pixel format.
+  // In FastBlit, the operation is effectively a memcpy.
+  void FastBlit(uint8* image, const SkIRect& rect, CaptureData* capture_data);
+  void SlowBlit(uint8* image, const SkIRect& rect, CaptureData* capture_data);
+
+  // X11 graphics context.
+  Display* display_;
+  GC gc_;
+  Window root_window_;
+
+  // XFixes.
+  bool has_xfixes_;
+  int xfixes_event_base_;
+  int xfixes_error_base_;
+
+  // XDamage information.
+  bool use_damage_;
+  Damage damage_handle_;
+  int damage_event_base_;
+  int damage_error_base_;
+  XserverRegion damage_region_;
+
+  // Access to the X Server's pixel buffer.
+  XServerPixelBuffer x_server_pixel_buffer_;
+
+  // A thread-safe list of invalid rectangles, and the size of the most
+  // recently captured screen.
+  VideoFrameCapturerHelper helper_;
+
+  // Callback notified whenever the cursor shape is changed.
+  CursorShapeChangedCallback cursor_shape_changed_callback_;
+
+  // Capture state.
+  static const int kNumBuffers = 2;
+  VideoFrameBuffer buffers_[kNumBuffers];
+  int current_buffer_;
+
+  // Format of pixels returned in buffer.
+  media::VideoFrame::Format pixel_format_;
+
+  // Invalid region from the previous capture. This is used to synchronize the
+  // current with the last buffer used.
+  SkRegion last_invalid_region_;
+
+  // Last capture buffer used.
+  uint8* last_buffer_;
+
+  // |Differ| for use when polling for changes.
+  scoped_ptr<Differ> differ_;
+
+  DISALLOW_COPY_AND_ASSIGN(VideoFrameCapturerLinux);
+};
+
+VideoFrameCapturerLinux::VideoFrameCapturerLinux()
+    : display_(NULL),
+      gc_(NULL),
+      root_window_(BadValue),
+      has_xfixes_(false),
+      xfixes_event_base_(-1),
+      xfixes_error_base_(-1),
+      use_damage_(false),
+      damage_handle_(0),
+      damage_event_base_(-1),
+      damage_error_base_(-1),
+      damage_region_(0),
+      current_buffer_(0),
+      pixel_format_(media::VideoFrame::RGB32),
+      last_buffer_(NULL) {
+  helper_.SetLogGridSize(4);
+}
+
+VideoFrameCapturerLinux::~VideoFrameCapturerLinux() {
+  DeinitXlib();
+}
+
+bool VideoFrameCapturerLinux::Init() {
+  // TODO(ajwong): We should specify the display string we are attaching to
+  // in the constructor.
+  display_ = XOpenDisplay(NULL);
+  if (!display_) {
+    LOG(ERROR) << "Unable to open display";
+    return false;
+  }
+
+  x_server_pixel_buffer_.Init(display_);
+
+  root_window_ = RootWindow(display_, DefaultScreen(display_));
+  if (root_window_ == BadValue) {
+    LOG(ERROR) << "Unable to get the root window";
+    DeinitXlib();
+    return false;
+  }
+
+  gc_ = XCreateGC(display_, root_window_, 0, NULL);
+  if (gc_ == NULL) {
+    LOG(ERROR) << "Unable to get graphics context";
+    DeinitXlib();
+    return false;
+  }
+
+  // Check for XFixes extension. This is required for cursor shape
+  // notifications, and for our use of XDamage.
+  if (XFixesQueryExtension(display_, &xfixes_event_base_,
+                           &xfixes_error_base_)) {
+    has_xfixes_ = true;
+  } else {
+    LOG(INFO) << "X server does not support XFixes.";
+  }
+
+  if (ShouldUseXDamage()) {
+    InitXDamage();
+  }
+
+  // Register for changes to the dimensions of the root window.
+  XSelectInput(display_, root_window_, StructureNotifyMask);
+
+  if (has_xfixes_) {
+    // Register for changes to the cursor shape.
+    XFixesSelectCursorInput(display_, root_window_,
+                            XFixesDisplayCursorNotifyMask);
+  }
+
+  return true;
+}
+
+void VideoFrameCapturerLinux::InitXDamage() {
+  // Our use of XDamage requires XFixes.
+  if (!has_xfixes_) {
+    return;
+  }
+
+  // Check for XDamage extension.
+  if (!XDamageQueryExtension(display_, &damage_event_base_,
+                             &damage_error_base_)) {
+    LOG(INFO) << "X server does not support XDamage.";
+    return;
+  }
+
+  // TODO(lambroslambrou): Disable DAMAGE in situations where it is known
+  // to fail, such as when Desktop Effects are enabled, with graphics
+  // drivers (nVidia, ATI) that fail to report DAMAGE notifications
+  // properly.
+
+  // Request notifications every time the screen becomes damaged.
+  damage_handle_ = XDamageCreate(display_, root_window_,
+                                 XDamageReportNonEmpty);
+  if (!damage_handle_) {
+    LOG(ERROR) << "Unable to initialize XDamage.";
+    return;
+  }
+
+  // Create an XFixes server-side region to collate damage into.
+  damage_region_ = XFixesCreateRegion(display_, 0, 0);
+  if (!damage_region_) {
+    XDamageDestroy(display_, damage_handle_);
+    LOG(ERROR) << "Unable to create XFixes region.";
+    return;
+  }
+
+  use_damage_ = true;
+  LOG(INFO) << "Using XDamage extension.";
+}
+
+void VideoFrameCapturerLinux::Start(
+    const CursorShapeChangedCallback& callback) {
+  cursor_shape_changed_callback_ = callback;
+}
+
+void VideoFrameCapturerLinux::Stop() {
+}
+
+void VideoFrameCapturerLinux::ScreenConfigurationChanged() {
+  last_buffer_ = NULL;
+  for (int i = 0; i < kNumBuffers; ++i) {
+    buffers_[i].set_needs_update();
+  }
+  helper_.ClearInvalidRegion();
+  x_server_pixel_buffer_.Init(display_);
+}
+
+media::VideoFrame::Format VideoFrameCapturerLinux::pixel_format() const {
+  return pixel_format_;
+}
+
+void VideoFrameCapturerLinux::ClearInvalidRegion() {
+  helper_.ClearInvalidRegion();
+}
+
+void VideoFrameCapturerLinux::InvalidateRegion(const SkRegion& invalid_region) {
+  helper_.InvalidateRegion(invalid_region);
+}
+
+void VideoFrameCapturerLinux::InvalidateScreen(const SkISize& size) {
+  helper_.InvalidateScreen(size);
+}
+
+void VideoFrameCapturerLinux::InvalidateFullScreen() {
+  helper_.InvalidateFullScreen();
+  last_buffer_ = NULL;
+}
+
+void VideoFrameCapturerLinux::CaptureInvalidRegion(
+    const CaptureCompletedCallback& callback) {
+  // Process XEvents for XDamage and cursor shape tracking.
+  ProcessPendingXEvents();
+
+  // Resize the current buffer if there was a recent change of
+  // screen-resolution.
+  VideoFrameBuffer &current = buffers_[current_buffer_];
+  current.Update(display_, root_window_);
+  // Also refresh the Differ helper used by CaptureFrame(), if needed.
+  if (!use_damage_ && !last_buffer_) {
+    differ_.reset(new Differ(current.size().width(), current.size().height(),
+                             kBytesPerPixel, current.bytes_per_row()));
+  }
+
+  scoped_refptr<CaptureData> capture_data(CaptureFrame());
+
+  current_buffer_ = (current_buffer_ + 1) % kNumBuffers;
+
+  callback.Run(capture_data);
+}
+
+void VideoFrameCapturerLinux::ProcessPendingXEvents() {
+  // Find the number of events that are outstanding "now."  We don't just loop
+  // on XPending because we want to guarantee this terminates.
+  int events_to_process = XPending(display_);
+  XEvent e;
+
+  for (int i = 0; i < events_to_process; i++) {
+    XNextEvent(display_, &e);
+    if (use_damage_ && (e.type == damage_event_base_ + XDamageNotify)) {
+      XDamageNotifyEvent* event = reinterpret_cast<XDamageNotifyEvent*>(&e);
+      DCHECK(event->level == XDamageReportNonEmpty);
+    } else if (e.type == ConfigureNotify) {
+      ScreenConfigurationChanged();
+    } else if (has_xfixes_ &&
+               e.type == xfixes_event_base_ + XFixesCursorNotify) {
+      XFixesCursorNotifyEvent* cne;
+      cne = reinterpret_cast<XFixesCursorNotifyEvent*>(&e);
+      if (cne->subtype == XFixesDisplayCursorNotify) {
+        CaptureCursor();
+      }
+    } else {
+      LOG(WARNING) << "Got unknown event type: " << e.type;
+    }
+  }
+}
+
+void VideoFrameCapturerLinux::CaptureCursor() {
+  DCHECK(has_xfixes_);
+  if (cursor_shape_changed_callback_.is_null())
+    return;
+
+  XFixesCursorImage* img = XFixesGetCursorImage(display_);
+  if (!img) {
+    return;
+  }
+
+  int width = img->width;
+  int height = img->height;
+  int total_bytes = width * height * kBytesPerPixel;
+
+  scoped_ptr<protocol::CursorShapeInfo> cursor_proto(
+      new protocol::CursorShapeInfo());
+  cursor_proto->set_width(width);
+  cursor_proto->set_height(height);
+  cursor_proto->set_hotspot_x(img->xhot);
+  cursor_proto->set_hotspot_y(img->yhot);
+
+  cursor_proto->mutable_data()->resize(total_bytes);
+  uint8* proto_data = const_cast<uint8*>(reinterpret_cast<const uint8*>(
+      cursor_proto->mutable_data()->data()));
+
+  // Xlib stores 32-bit data in longs, even if longs are 64-bits long.
+  unsigned long* src = img->pixels;
+  uint32* dst = reinterpret_cast<uint32*>(proto_data);
+  uint32* dst_end = dst + (width * height);
+  while (dst < dst_end) {
+    *dst++ = static_cast<uint32>(*src++);
+  }
+  XFree(img);
+
+  cursor_shape_changed_callback_.Run(cursor_proto.Pass());
+}
+
+CaptureData* VideoFrameCapturerLinux::CaptureFrame() {
+  VideoFrameBuffer& buffer = buffers_[current_buffer_];
+  DataPlanes planes;
+  planes.data[0] = buffer.ptr();
+  planes.strides[0] = buffer.bytes_per_row();
+
+  CaptureData* capture_data = new CaptureData(planes, buffer.size(),
+                                              media::VideoFrame::RGB32);
+
+  // Pass the screen size to the helper, so it can clip the invalid region if it
+  // expands that region to a grid.
+  helper_.set_size_most_recent(capture_data->size());
+
+  // In the DAMAGE case, ensure the frame is up-to-date with the previous frame
+  // if any.  If there isn't a previous frame, that means a screen-resolution
+  // change occurred, and |invalid_rects| will be updated to include the whole
+  // screen.
+  if (use_damage_ && last_buffer_)
+    SynchronizeFrame();
+
+  SkRegion invalid_region;
+
+  x_server_pixel_buffer_.Synchronize();
+  if (use_damage_ && last_buffer_) {
+    // Atomically fetch and clear the damage region.
+    XDamageSubtract(display_, damage_handle_, None, damage_region_);
+    int nRects = 0;
+    XRectangle bounds;
+    XRectangle* rects = XFixesFetchRegionAndBounds(display_, damage_region_,
+                                                   &nRects, &bounds);
+    for (int i=0; i<nRects; ++i) {
+      invalid_region.op(SkIRect::MakeXYWH(rects[i].x, rects[i].y,
+                                          rects[i].width, rects[i].height),
+                        SkRegion::kUnion_Op);
+    }
+    XFree(rects);
+    helper_.InvalidateRegion(invalid_region);
+
+    // Capture the damaged portions of the desktop.
+    helper_.SwapInvalidRegion(&invalid_region);
+    for (SkRegion::Iterator it(invalid_region); !it.done(); it.next()) {
+      CaptureRect(it.rect(), capture_data);
+    }
+  } else {
+    // Doing full-screen polling, or this is the first capture after a
+    // screen-resolution change.  In either case, need a full-screen capture.
+    SkIRect screen_rect = SkIRect::MakeWH(buffer.size().width(),
+                                          buffer.size().height());
+    CaptureRect(screen_rect, capture_data);
+
+    if (last_buffer_) {
+      // Full-screen polling, so calculate the invalid rects here, based on the
+      // changed pixels between current and previous buffers.
+      DCHECK(differ_ != NULL);
+      differ_->CalcDirtyRegion(last_buffer_, buffer.ptr(), &invalid_region);
+    } else {
+      // No previous buffer, so always invalidate the whole screen, whether
+      // or not DAMAGE is being used.  DAMAGE doesn't necessarily send a
+      // full-screen notification after a screen-resolution change, so
+      // this is done here.
+      invalid_region.op(screen_rect, SkRegion::kUnion_Op);
+    }
+  }
+
+  capture_data->mutable_dirty_region() = invalid_region;
+  last_invalid_region_ = invalid_region;
+  last_buffer_ = buffer.ptr();
+  return capture_data;
+}
+
+void VideoFrameCapturerLinux::SynchronizeFrame() {
+  // Synchronize the current buffer with the previous one since we do not
+  // capture the entire desktop. Note that encoder may be reading from the
+  // previous buffer at this time so thread access complaints are false
+  // positives.
+
+  // TODO(hclam): We can reduce the amount of copying here by subtracting
+  // |capturer_helper_|s region from |last_invalid_region_|.
+  // http://crbug.com/92354
+  DCHECK(last_buffer_);
+  VideoFrameBuffer& buffer = buffers_[current_buffer_];
+  for (SkRegion::Iterator it(last_invalid_region_); !it.done(); it.next()) {
+    const SkIRect& r = it.rect();
+    int offset = r.fTop * buffer.bytes_per_row() + r.fLeft * kBytesPerPixel;
+    for (int i = 0; i < r.height(); ++i) {
+      memcpy(buffer.ptr() + offset, last_buffer_ + offset,
+             r.width() * kBytesPerPixel);
+      offset += buffer.size().width() * kBytesPerPixel;
+    }
+  }
+}
+
+void VideoFrameCapturerLinux::DeinitXlib() {
+  if (gc_) {
+    XFreeGC(display_, gc_);
+    gc_ = NULL;
+  }
+
+  x_server_pixel_buffer_.Release();
+
+  if (display_) {
+    if (damage_handle_)
+      XDamageDestroy(display_, damage_handle_);
+    if (damage_region_)
+      XFixesDestroyRegion(display_, damage_region_);
+    XCloseDisplay(display_);
+    display_ = NULL;
+    damage_handle_ = 0;
+    damage_region_ = 0;
+  }
+}
+
+void VideoFrameCapturerLinux::CaptureRect(const SkIRect& rect,
+                                          CaptureData* capture_data) {
+  uint8* image = x_server_pixel_buffer_.CaptureRect(rect);
+  int depth = x_server_pixel_buffer_.GetDepth();
+  int bpp = x_server_pixel_buffer_.GetBitsPerPixel();
+  bool is_rgb = x_server_pixel_buffer_.IsRgb();
+  if ((depth == 24 || depth == 32) && bpp == 32 && is_rgb) {
+    DVLOG(3) << "Fast blitting";
+    FastBlit(image, rect, capture_data);
+  } else {
+    DVLOG(3) << "Slow blitting";
+    SlowBlit(image, rect, capture_data);
+  }
+}
+
+void VideoFrameCapturerLinux::FastBlit(uint8* image, const SkIRect& rect,
+                                       CaptureData* capture_data) {
+  uint8* src_pos = image;
+  int src_stride = x_server_pixel_buffer_.GetStride();
+  int dst_x = rect.fLeft, dst_y = rect.fTop;
+
+  DataPlanes planes = capture_data->data_planes();
+  uint8* dst_buffer = planes.data[0];
+
+  const int dst_stride = planes.strides[0];
+
+  uint8* dst_pos = dst_buffer + dst_stride * dst_y;
+  dst_pos += dst_x * kBytesPerPixel;
+
+  int height = rect.height(), row_bytes = rect.width() * kBytesPerPixel;
+  for (int y = 0; y < height; ++y) {
+    memcpy(dst_pos, src_pos, row_bytes);
+    src_pos += src_stride;
+    dst_pos += dst_stride;
+  }
+}
+
+void VideoFrameCapturerLinux::SlowBlit(uint8* image, const SkIRect& rect,
+                                       CaptureData* capture_data) {
+  DataPlanes planes = capture_data->data_planes();
+  uint8* dst_buffer = planes.data[0];
+  const int dst_stride = planes.strides[0];
+  int src_stride = x_server_pixel_buffer_.GetStride();
+  int dst_x = rect.fLeft, dst_y = rect.fTop;
+  int width = rect.width(), height = rect.height();
+
+  unsigned int red_mask = x_server_pixel_buffer_.GetRedMask();
+  unsigned int blue_mask = x_server_pixel_buffer_.GetBlueMask();
+  unsigned int green_mask = x_server_pixel_buffer_.GetGreenMask();
+  unsigned int red_shift = x_server_pixel_buffer_.GetRedShift();
+  unsigned int blue_shift = x_server_pixel_buffer_.GetBlueShift();
+  unsigned int green_shift = x_server_pixel_buffer_.GetGreenShift();
+
+  unsigned int max_red = red_mask >> red_shift;
+  unsigned int max_blue = blue_mask >> blue_shift;
+  unsigned int max_green = green_mask >> green_shift;
+
+  unsigned int bits_per_pixel = x_server_pixel_buffer_.GetBitsPerPixel();
+
+  uint8* dst_pos = dst_buffer + dst_stride * dst_y;
+  uint8* src_pos = image;
+  dst_pos += dst_x * kBytesPerPixel;
+  // TODO(hclam): Optimize, perhaps using MMX code or by converting to
+  // YUV directly
+  for (int y = 0; y < height; y++) {
+    uint32_t* dst_pos_32 = reinterpret_cast<uint32_t*>(dst_pos);
+    uint32_t* src_pos_32 = reinterpret_cast<uint32_t*>(src_pos);
+    uint16_t* src_pos_16 = reinterpret_cast<uint16_t*>(src_pos);
+    for (int x = 0; x < width; x++) {
+      // Dereference through an appropriately-aligned pointer.
+      uint32_t pixel;
+      if (bits_per_pixel == 32)
+        pixel = src_pos_32[x];
+      else if (bits_per_pixel == 16)
+        pixel = src_pos_16[x];
+      else
+        pixel = src_pos[x];
+      uint32_t r = (((pixel & red_mask) >> red_shift) * 255) / max_red;
+      uint32_t b = (((pixel & blue_mask) >> blue_shift) * 255) / max_blue;
+      uint32_t g = (((pixel & green_mask) >> green_shift) * 255) / max_green;
+      // Write as 32-bit RGB.
+      dst_pos_32[x] = r << 16 | g << 8 | b;
+    }
+    dst_pos += dst_stride;
+    src_pos += src_stride;
+  }
+}
+
+const SkISize& VideoFrameCapturerLinux::size_most_recent() const {
+  return helper_.size_most_recent();
+}
+
+}  // namespace
+
+// static
+VideoFrameCapturer* VideoFrameCapturer::Create() {
+  VideoFrameCapturerLinux* capturer = new VideoFrameCapturerLinux();
+  if (!capturer->Init()) {
+    delete capturer;
+    capturer = NULL;
+  }
+  return capturer;
+}
+
+// static
+void VideoFrameCapturer::EnableXDamage(bool enable) {
+  g_should_use_x_damage = enable;
+}
+
+}  // namespace remoting