Add DesktopRectTest for UnionWith() function

webrtc/modules/desktop_capture/desktop_geometry_unittest.cc

+/*
+ *  Copyright (c) 2017 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/desktop_geometry.h"
+
+#include "webrtc/test/gtest.h"
+
+namespace webrtc {
+
+TEST(DesktopRectTest, UnionBetweenTwoNonEmptyRects) {
+  DesktopRect rect = DesktopRect::MakeXYWH(1, 1, 1, 1);
+  rect.UnionWith(DesktopRect::MakeXYWH(-2, -2, 1, 1));
+  ASSERT_TRUE(rect.equals(DesktopRect::MakeXYWH(-2, -2, 4, 4)));

[Do not use (sergeyu), 2017/05/18 17:37:53]

nit: this test would be easier to read if it used MakeLTRB instead of MakeXYWH

[Hzj_jie, 2017/05/18 19:24:00]

Done.

+}
+
+TEST(DesktopRectTest, UnionWithEmptyRect) {
+  DesktopRect rect = DesktopRect::MakeWH(1, 1);
+  rect.UnionWith(DesktopRect());
+  ASSERT_TRUE(rect.equals(DesktopRect::MakeWH(1, 1)));
+
+  rect = DesktopRect::MakeXYWH(1, 1, 2, 2);
+  rect.UnionWith(DesktopRect());
+  ASSERT_TRUE(rect.equals(DesktopRect::MakeXYWH(1, 1, 2, 2)));
+
+  rect = DesktopRect::MakeXYWH(1, 1, 2, 2);
+  rect.UnionWith(DesktopRect::MakeXYWH(3, 3, 0, 0));
+  ASSERT_TRUE(rect.equals(DesktopRect::MakeXYWH(1, 1, 2, 2)));
+}
+
+TEST(DesktopRectTest, EmptyRectUnionWithNonEmptyOne) {
+  DesktopRect rect;
+  rect.UnionWith(DesktopRect::MakeWH(1, 1));
+  ASSERT_TRUE(rect.equals(DesktopRect::MakeWH(1, 1)));
+
+  rect = DesktopRect();
+  rect.UnionWith(DesktopRect::MakeXYWH(1, 1, 2, 2));
+  ASSERT_TRUE(rect.equals(DesktopRect::MakeXYWH(1, 1, 2, 2)));
+
+  rect = DesktopRect::MakeXYWH(3, 3, 0, 0);
+  rect.UnionWith(DesktopRect::MakeXYWH(1, 1, 2, 2));
+  ASSERT_TRUE(rect.equals(DesktopRect::MakeXYWH(1, 1, 2, 2)));
+}
+
+TEST(DesktopRectTest, EmptyRectUnionWithEmptyOne) {
+  DesktopRect rect;
+  rect.UnionWith(DesktopRect());
+  ASSERT_TRUE(rect.equals(DesktopRect()));

[Do not use (sergeyu), 2017/05/18 17:37:53]

rect.is_empty()?

[Hzj_jie, 2017/05/18 19:24:00]

Done.

+
+  rect = DesktopRect::MakeXYWH(1, 1, 0, 0);
+  rect.UnionWith(DesktopRect());
+  ASSERT_TRUE(rect.is_empty());
+
+  rect = DesktopRect();
+  rect.UnionWith(DesktopRect::MakeXYWH(1, 1, 0, 0));
+  ASSERT_TRUE(rect.is_empty());
+
+  rect = DesktopRect::MakeXYWH(1, 1, 0, 0);
+  rect.UnionWith(DesktopRect::MakeXYWH(-1, -1, 0, 0));
+  ASSERT_TRUE(rect.is_empty());
+}
+
+}  // namespace webrtc