text: /*
   *  Copyright (c) 2016 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_SCREEN_DRAWER_H_
  #define MODULES_DESKTOP_CAPTURE_SCREEN_DRAWER_H_
  
  #include "modules/desktop_capture/desktop_capture_types.h"
  #include "modules/desktop_capture/desktop_geometry.h"
  #include "modules/desktop_capture/rgba_color.h"
  
  namespace webrtc {
  
  // A cross-process lock to ensure only one ScreenDrawer can be used at a certain
  // time.
  class ScreenDrawerLock {
   public:
    virtual ~ScreenDrawerLock();
  
    static std::unique_ptr<ScreenDrawerLock> Create();
  
   protected:
    ScreenDrawerLock();
  };
  
  // A set of basic platform dependent functions to draw various shapes on the
  // screen.
  class ScreenDrawer {
   public:
    // Creates a ScreenDrawer for the current platform, returns nullptr if no
    // ScreenDrawer implementation available.
    // If the implementation cannot guarantee two ScreenDrawer instances won't
    // impact each other, this function may block current thread until another
    // ScreenDrawer has been destroyed.
    static std::unique_ptr<ScreenDrawer> Create();
  
    ScreenDrawer();
    virtual ~ScreenDrawer();
  
    // Returns the region inside which DrawRectangle() function are expected to
    // work, in capturer coordinates (assuming ScreenCapturer::SelectScreen has
    // not been called). This region may exclude regions of the screen reserved by
    // the OS for things like menu bars or app launchers. The DesktopRect is in
    // system coordinate, i.e. the primary monitor always starts from (0, 0).
    virtual DesktopRect DrawableRegion() = 0;
  
    // Draws a rectangle to cover |rect| with |color|. Note, rect.bottom() and
    // rect.right() two lines are not included. The part of |rect| which is out of
    // DrawableRegion() will be ignored.
    virtual void DrawRectangle(DesktopRect rect, RgbaColor color) = 0;
  
    // Clears all content on the screen by filling the area with black.
    virtual void Clear() = 0;
  
    // Blocks current thread until OS finishes previous DrawRectangle() actions.
    // ScreenCapturer should be able to capture the changes after this function
    // finish.
    virtual void WaitForPendingDraws() = 0;
  
    // Returns true if incomplete shapes previous actions required may be drawn on
    // the screen after a WaitForPendingDraws() call. i.e. Though the complete
    // shapes will eventually be drawn on the screen, due to some OS limitations,
    // these shapes may be partially appeared sometimes.
    virtual bool MayDrawIncompleteShapes() = 0;
  
    // Returns the id of the drawer window. This function returns kNullWindowId if
    // the implementation does not draw on a window of the system.
    virtual WindowId window_id() const = 0;
  };
  
  }  // namespace webrtc
  
  #endif  // MODULES_DESKTOP_CAPTURE_SCREEN_DRAWER_H_
  