Use RgbaColor in DesktopFrameGenerator and add RgbaColorTest

This change uses RgbaColor in DesktopFrameGenerator instead of raw uint32_t to
avoid potential endian issues.

BUG=633802

Review-Url: https://codereview.webrtc.org/2334853002
Cr-Commit-Position: refs/heads/master@{#14337}

webrtc/modules/BUILD.gn

@@ -521,6 +521,7 @@ if (rtc_include_tests) {
         "desktop_capture/mouse_cursor_monitor_unittest.cc",
         "desktop_capture/rgba_color.cc",
         "desktop_capture/rgba_color.h",
+        "desktop_capture/rgba_color_unittest.cc",
         "desktop_capture/screen_capturer_differ_wrapper_unittest.cc",
         "desktop_capture/screen_capturer_helper_unittest.cc",
         "desktop_capture/screen_capturer_mac_unittest.cc",

webrtc/modules/desktop_capture/desktop_frame_generator.cc

@@ -17,6 +17,7 @@
 
 #include "webrtc/base/random.h"
 #include "webrtc/base/timeutils.h"
+#include "webrtc/modules/desktop_capture/rgba_color.h"
 
 namespace webrtc {
 
@@ -60,11 +61,12 @@ void SetUpdatedRegion(DesktopFrame* frame,
 }
 
 // Paints pixels in |rect| of |frame| to |color|.
-void PaintRect(DesktopFrame* frame, DesktopRect rect, uint32_t color) {
+void PaintRect(DesktopFrame* frame, DesktopRect rect, RgbaColor rgba_color) {
   static_assert(DesktopFrame::kBytesPerPixel == sizeof(uint32_t),
                 "kBytesPerPixel should be 4.");
   RTC_DCHECK(frame->size().width() >= rect.right() &&
              frame->size().height() >= rect.bottom());
+  uint32_t color = rgba_color.ToUInt32();
   uint8_t* row = frame->GetFrameDataAtPos(rect.top_left());
   for (int i = 0; i < rect.height(); i++) {
     uint32_t* column = reinterpret_cast<uint32_t*>(row);
@@ -76,10 +78,12 @@ void PaintRect(DesktopFrame* frame, DesktopRect rect, uint32_t color) {
 }
 
 // Paints pixels in |region| of |frame| to |color|.
-void PaintRegion(DesktopFrame* frame, DesktopRegion* region, uint32_t color) {
+void PaintRegion(DesktopFrame* frame,
+                 DesktopRegion* region,
+                 RgbaColor rgba_color) {
   region->IntersectWith(DesktopRect::MakeSize(frame->size()));
   for (DesktopRegion::Iterator it(*region); !it.IsAtEnd(); it.Advance()) {
-    PaintRect(frame, it.rect(), color);
+    PaintRect(frame, it.rect(), rgba_color);
   }
 }
 
@@ -171,7 +175,7 @@ bool BlackWhiteDesktopFramePainter::Paint(DesktopFrame* frame,
                                           DesktopRegion* updated_region) {
   RTC_DCHECK(updated_region->is_empty());
   memset(frame->data(), 0, frame->stride() * frame->size().height());
-  PaintRegion(frame, &updated_region_, UINT32_MAX);
+  PaintRegion(frame, &updated_region_, RgbaColor(0xFFFFFFFF));
   updated_region_.Swap(updated_region);
   return true;
 }

webrtc/modules/desktop_capture/rgba_color.cc

@@ -10,6 +10,8 @@
 
 #include "webrtc/modules/desktop_capture/rgba_color.h"
 
+#include "webrtc/typedefs.h"
+
 namespace webrtc {
 
 namespace {
@@ -36,6 +38,9 @@ RgbaColor::RgbaColor(uint8_t blue, uint8_t green, uint8_t red)
 RgbaColor::RgbaColor(const uint8_t* bgra)
     : RgbaColor(bgra[0], bgra[1], bgra[2], bgra[3]) {}
 
+RgbaColor::RgbaColor(uint32_t bgra)
+    : RgbaColor(reinterpret_cast<uint8_t*>(&bgra)) {}
+
 bool RgbaColor::operator==(const RgbaColor& right) const {
   return blue == right.blue && green == right.green && red == right.red &&
          AlphaEquals(alpha, right.alpha);
@@ -45,4 +50,12 @@ bool RgbaColor::operator!=(const RgbaColor& right) const {
   return !(*this == right);
 }
 
+uint32_t RgbaColor::ToUInt32() const {
+#if defined(WEBRTC_ARCH_LITTLE_ENDIAN)
+  return blue | (green << 8) | (red << 16) | (alpha << 24);
+#else
+  return (blue << 24) | (green << 16) | (red << 8) | alpha;
+#endif
+}
+
 }  // namespace webrtc

webrtc/modules/desktop_capture/rgba_color.h

@@ -34,12 +34,20 @@ struct RgbaColor final {
   // Creates a color from four-byte in BGRA order, i.e. DesktopFrame::data().
   explicit RgbaColor(const uint8_t* bgra);
 
+  // Creates a color from BGRA channels in a uint format. Consumers should make
+  // sure the memory order of the uint32_t is always BGRA from left to right, no
+  // matter the system endian. This function creates an equivalent RgbaColor
+  // instance from the ToUInt32() result of another RgbaColor instance.
+  explicit RgbaColor(uint32_t bgra);
+
   // Returns true if |this| and |right| is the same color.
   bool operator==(const RgbaColor& right) const;
 
   // Returns true if |this| and |right| are different colors.
   bool operator!=(const RgbaColor& right) const;
 
+  uint32_t ToUInt32() const;
+
   uint8_t blue;
   uint8_t green;
   uint8_t red;

webrtc/modules/desktop_capture/rgba_color_unittest.cc

@@ -0,0 +1,44 @@
+/*
+ *  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.
+ */
+
+#include "webrtc/modules/desktop_capture/rgba_color.h"
+
+#include <vector>
+
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace webrtc {
+
+TEST(RgbaColorTest, ConvertFromAndToUInt32) {
+  static const std::vector<uint32_t> cases{
+      0,         1000,       2693,       3725,       4097,      12532,
+      19902,     27002,      27723,      30944,      65535,     65536,
+      231194,    255985,     322871,     883798,     9585200,   12410056,
+      12641940,  30496970,   105735668,  110117847,  482769275, 542368468,
+      798173396, 2678656711, 3231043200, UINT32_MAX,
+  };
+
+  for (uint32_t value : cases) {
+    RgbaColor left(value);
+    ASSERT_EQ(left.ToUInt32(), value);
+    RgbaColor right(left);
+    ASSERT_EQ(left.ToUInt32(), right.ToUInt32());
+  }
+}
+
+TEST(RgbaColorTest, AlphaChannelEquality) {
+  RgbaColor left(10, 10, 10, 0);
+  RgbaColor right(10, 10, 10, 255);
+  ASSERT_EQ(left, right);
+  right.alpha = 128;
+  ASSERT_NE(left, right);
+}
+
+}  // namespace webrtc