text: /*
   *  Copyright (c) 2013 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_CAPTURER_HELPER_H_
  #define MODULES_DESKTOP_CAPTURE_SCREEN_CAPTURER_HELPER_H_
  
  #include <memory>
  
  #include "modules/desktop_capture/desktop_geometry.h"
  #include "modules/desktop_capture/desktop_region.h"
  #include "rtc_base/synchronization/mutex.h"
  #include "rtc_base/thread_annotations.h"
  
  namespace webrtc {
  
  // ScreenCapturerHelper is intended to be used by an implementation of the
  // ScreenCapturer interface. It maintains a thread-safe invalid region, and
  // the size of the most recently captured screen, on behalf of the
  // ScreenCapturer that owns it.
  class ScreenCapturerHelper {
   public:
    ScreenCapturerHelper() = default;
    ~ScreenCapturerHelper() = default;
  
    ScreenCapturerHelper(const ScreenCapturerHelper&) = delete;
    ScreenCapturerHelper& operator=(const ScreenCapturerHelper&) = delete;
  
    // Clear out the invalid region.
    void ClearInvalidRegion();
  
    // Invalidate the specified region.
    void InvalidateRegion(const DesktopRegion& invalid_region);
  
    // Invalidate the entire screen, of a given size.
    void InvalidateScreen(const DesktopSize& size);
  
    // Copies current invalid region to `invalid_region` clears invalid region
    // storage for the next frame.
    void TakeInvalidRegion(DesktopRegion* invalid_region);
  
    // Access the size of the most recently captured screen.
    const DesktopSize& size_most_recent() const;
    void set_size_most_recent(const DesktopSize& 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 TakeInvalidRegion()
    // 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 void ExpandToGrid(const DesktopRegion& region,
                             int log_grid_size,
                             DesktopRegion* result);
  
   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.
    DesktopRegion invalid_region_ RTC_GUARDED_BY(invalid_region_mutex_);
  
    // A lock protecting `invalid_region_` across threads.
    Mutex invalid_region_mutex_;
  
    // The size of the most recently captured screen.
    DesktopSize 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_ = 0;
  };
  
  }  // namespace webrtc
  
  #endif  // MODULES_DESKTOP_CAPTURE_SCREEN_CAPTURER_HELPER_H_
  