[WebRTC] A real ScreenCapturer test

webrtc/modules/desktop_capture/color.h

+/*
+ *  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 WEBRTC_MODULES_DESKTOP_CAPTURE_COLOR_H_
+#define WEBRTC_MODULES_DESKTOP_CAPTURE_COLOR_H_
+
+#include <stdint.h>
+
+#include "webrtc/modules/desktop_capture/desktop_frame.h"
+
+namespace webrtc {
+
+// A four-byte structure to store a color in BGRA format. This structure also
+// provides functions to compare with uint8_t array, say, DesktopFrame::data().
+// It always uses BGRA order for internal storage to match DesktopFrame::data().
+//
+// This struct is for testing purpose only, and should not be used in production
+// logic.
+struct Color final {

[Sergey Ulanov, 2016/09/02 19:35:00]

Maybe call this RgbColor to avoid confusion as WebRTC uses YUV in many places.

[Hzj_jie, 2016/09/02 21:46:09]

RgbaColor may be better.

+  // Creates a color with BGRA channels.
+  Color(uint8_t blue, uint8_t green, uint8_t red, uint8_t alpha);
+
+  // Creates a color with BGR channels, and set alpha channel to 255 (opaque).
+  Color(uint8_t blue, uint8_t green, uint8_t red);
+
+  // Returns true if |bgra| four-byte in BGRA order represents a same color as
+  // |this|.
+  bool operator==(const uint8_t* const bgra) const;

[Sergey Ulanov, 2016/09/02 19:35:00]

Style guide requires overloaded operators behavior to be obvious:
https://google.github.io/styleguide/cppguide.html#Operator_Overloading
IMO this operator doesn't fit that requirement because it's comparing Color with
uint8_t pointer. Maybe just add another constructor that creates Color from
uint8_t array and use it when you need it?

[Hzj_jie, 2016/09/02 21:46:09]

Done.

+
+  // Returns true if |bgra| four-byte in BGRA order represents a different color
+  // as |this|.
+  bool operator!=(const uint8_t* const bgra) const;

[Sergey Ulanov, 2016/09/02 19:35:00]

I don't think you need the second const here. We normally don't use const for
parameters themselves i.e. foo(int i) instead of foo(const int i).

[Hzj_jie, 2016/09/02 21:46:09]

Done.

+
+  // Returns true if |this| and |right| is the same color.
+  bool operator==(const Color& right) const;
+
+  // Returns true if |this| and |right| are different colors.
+  bool operator!=(const Color& right) const;
+
+  uint8_t blue;
+  uint8_t green;
+  uint8_t red;
+  uint8_t alpha;
+};
+static_assert(
+    DesktopFrame::kBytesPerPixel == sizeof(uint32_t),

[Sergey Ulanov, 2016/09/02 19:35:00]

What about sizeof(Color)?

[Hzj_jie, 2016/09/02 21:46:09]

It used to be sizeof(Color), but Jamie has a different opinion. (This class used
to be able to memcpy & memcmp with uint8_t*.)

But since we are 2:1 now, I am happy to change it into sizeof(Color). :)

+    "A pixel in DesktopFrame should be safe to represent by a uint32_t");
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_DESKTOP_CAPTURE_COLOR_H_