DirectX based screen capturer logic

webrtc/modules/desktop_capture/desktop_frame.h

 /*
  *  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.
  */
 
@@ skipping 11 matching lines @@
 
 // DesktopFrame represents a video frame captured from the screen.
 class DesktopFrame {
  public:
   // DesktopFrame objects always hold RGBA data.
   static const int kBytesPerPixel = 4;
 
   virtual ~DesktopFrame();
 
   // Size of the frame.
-  const DesktopSize& size() const { return size_; }
+  virtual const DesktopSize& size() const;

[Sergey Ulanov, 2016/04/08 21:22:26]

Why do you need to make any of these methods virtual?

 
   // Distance in the buffer between two neighboring rows in bytes.
-  int stride() const { return stride_; }
+  virtual int stride() const;
 
   // Data buffer used for the frame.
-  uint8_t* data() const { return data_; }
+  virtual uint8_t* data() const;
 
   // SharedMemory used for the buffer or NULL if memory is allocated on the
   // heap. The result is guaranteed to be deleted only after the frame is
   // deleted (classes that inherit from DesktopFrame must ensure it).
-  SharedMemory* shared_memory() const { return shared_memory_; }
+  virtual SharedMemory* shared_memory() const;
 
   // Indicates region of the screen that has changed since the previous frame.
-  const DesktopRegion& updated_region() const { return updated_region_; }
-  DesktopRegion* mutable_updated_region() { return &updated_region_; }
+  virtual const DesktopRegion& updated_region() const;
+  virtual DesktopRegion* mutable_updated_region();
 
   // DPI of the screen being captured. May be set to zero, e.g. if DPI is
   // unknown.
-  const DesktopVector& dpi() const { return dpi_; }
-  void set_dpi(const DesktopVector& dpi) { dpi_ = dpi; }
+  virtual const DesktopVector& dpi() const;
+  virtual void set_dpi(const DesktopVector& dpi);
 
   // Time taken to capture the frame in milliseconds.
-  int64_t capture_time_ms() const { return capture_time_ms_; }
-  void set_capture_time_ms(int64_t time_ms) { capture_time_ms_ = time_ms; }
+  virtual int64_t capture_time_ms() const;
+  virtual void set_capture_time_ms(int64_t time_ms);
 
   // Optional shape for the frame. Frames may be shaped e.g. if
   // capturing the contents of a shaped window.
-  const DesktopRegion* shape() const { return shape_.get(); }
-  void set_shape(DesktopRegion* shape) { shape_.reset(shape); }
+  virtual const DesktopRegion* shape() const;
+  virtual void set_shape(DesktopRegion* shape);
 
   // Copies pixels from a buffer or another frame. |dest_rect| rect must lay
   // within bounds of this frame.
-  void CopyPixelsFrom(uint8_t* src_buffer, int src_stride,
-                      const DesktopRect& dest_rect);
-  void CopyPixelsFrom(const DesktopFrame& src_frame,
-                      const DesktopVector& src_pos,
-                      const DesktopRect& dest_rect);
+  virtual void CopyPixelsFrom(uint8_t* src_buffer,
+                              int src_stride,
+                              const DesktopRect& dest_rect);
+  virtual void CopyPixelsFrom(const DesktopFrame& src_frame,
+                              const DesktopVector& src_pos,
+                              const DesktopRect& dest_rect);
 
   // A helper to return the data pointer of a frame at the specified position.
-  uint8_t* GetFrameDataAtPos(const DesktopVector& pos) const;
+  virtual uint8_t* GetFrameDataAtPos(const DesktopVector& pos) const;
 
  protected:
   DesktopFrame(DesktopSize size,
                int stride,
                uint8_t* data,
                SharedMemory* shared_memory);
 
+  // TODO(zijiehe): Most of follow variables should belong to an inheritance.
   const DesktopSize size_;
   const int stride_;
 
   // Ownership of the buffers is defined by the classes that inherit from this
   // class. They must guarantee that the buffer is not deleted before the frame
   // is deleted.
+  // Inheritances can set the pointer after construction.
   uint8_t* const data_;
   SharedMemory* const shared_memory_;
 
   DesktopRegion updated_region_;
   DesktopVector dpi_;
   int64_t capture_time_ms_;
   std::unique_ptr<DesktopRegion> shape_;
 
  private:
   RTC_DISALLOW_COPY_AND_ASSIGN(DesktopFrame);
@@ skipping 30 matching lines @@
   ~SharedMemoryDesktopFrame() override;
 
  private:
   RTC_DISALLOW_COPY_AND_ASSIGN(SharedMemoryDesktopFrame);
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_DESKTOP_CAPTURE_DESKTOP_FRAME_H_