modules/desktop_capture/linux/screen_capturer_x11.h

/*
 *  Copyright 2018 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */

#ifndef MODULES_DESKTOP_CAPTURE_LINUX_SCREEN_CAPTURER_X11_H_
#define MODULES_DESKTOP_CAPTURE_LINUX_SCREEN_CAPTURER_X11_H_

#include <X11/X.h>
#include <X11/Xlib.h>
#include <X11/extensions/Xdamage.h>
#include <X11/extensions/Xfixes.h>
#include <memory>

#include "modules/desktop_capture/desktop_capture_options.h"
#include "modules/desktop_capture/desktop_capturer.h"
#include "modules/desktop_capture/desktop_frame.h"
#include "modules/desktop_capture/desktop_region.h"
#include "modules/desktop_capture/linux/shared_x_display.h"
#include "modules/desktop_capture/linux/x_atom_cache.h"
#include "modules/desktop_capture/linux/x_server_pixel_buffer.h"
#include "modules/desktop_capture/screen_capture_frame_queue.h"
#include "modules/desktop_capture/screen_capturer_helper.h"
#include "modules/desktop_capture/shared_desktop_frame.h"
#include "rtc_base/constructor_magic.h"

namespace webrtc {

// A class to perform video frame capturing for Linux on X11.
//
// If XDamage is used, this class sets DesktopFrame::updated_region() according
// to the areas reported by XDamage. Otherwise this class does not detect
// DesktopFrame::updated_region(), the field is always set to the entire frame
// rectangle. ScreenCapturerDifferWrapper should be used if that functionality
// is necessary.
class ScreenCapturerX11 : public DesktopCapturer,
                          public SharedXDisplay::XEventHandler {
 public:
  ScreenCapturerX11();
  ~ScreenCapturerX11() override;

  static std::unique_ptr<DesktopCapturer> CreateRawScreenCapturer(
      const DesktopCaptureOptions& options);

  // TODO(ajwong): Do we really want this to be synchronous?
  bool Init(const DesktopCaptureOptions& options);

  // DesktopCapturer interface.
  void Start(Callback* delegate) override;
  void CaptureFrame() override;
  bool GetSourceList(SourceList* sources) override;
  bool SelectSource(SourceId id) override;

 private:
  Display* display() { return options_.x_display()->display(); }

  // SharedXDisplay::XEventHandler interface.
  bool HandleXEvent(const XEvent& event) override;

  void InitXDamage();

  // Capture screen pixels to the current buffer in the queue. In the DAMAGE
  // case, the ScreenCapturerHelper already holds the list of invalid rectangles
  // from HandleXEvent(). 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.
  std::unique_ptr<DesktopFrame> CaptureScreen();

  // Called when the screen configuration is changed.
  void ScreenConfigurationChanged();

  // 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();

  DesktopCaptureOptions options_;

  Callback* callback_ = nullptr;

  // X11 graphics context.
  GC gc_ = nullptr;
  Window root_window_ = BadValue;

  // XFixes.
  bool has_xfixes_ = false;
  int xfixes_event_base_ = -1;
  int xfixes_error_base_ = -1;

  // XDamage information.
  bool use_damage_ = false;
  Damage damage_handle_ = 0;
  int damage_event_base_ = -1;
  int damage_error_base_ = -1;
  XserverRegion damage_region_ = 0;

  // 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.
  ScreenCapturerHelper helper_;

  // Queue of the frames buffers.
  ScreenCaptureFrameQueue<SharedDesktopFrame> queue_;

  // Invalid region from the previous capture. This is used to synchronize the
  // current with the last buffer used.
  DesktopRegion last_invalid_region_;

  std::unique_ptr<XAtomCache> atom_cache_;

  RTC_DISALLOW_COPY_AND_ASSIGN(ScreenCapturerX11);
};

}  // namespace webrtc

#endif  // MODULES_DESKTOP_CAPTURE_LINUX_SCREEN_CAPTURER_X11_H_