The center of a rect is x+width/2, y+height/2

ui/gfx/rect_unittest.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/basictypes.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/gfx/rect.h"
 #include "ui/gfx/rect_conversions.h"
 #include "ui/gfx/skia_util.h"
 
@@ skipping 289 matching lines @@
   gfx::Rect(10, 10, 0, 10).SplitVertically(&left_half, &right_half);
   EXPECT_TRUE(left_half.Equals(gfx::Rect(10, 10, 0, 10)));
   EXPECT_TRUE(right_half.Equals(gfx::Rect(10, 10, 0, 10)));
 
   // Splitting a rectangle of odd width.
   gfx::Rect(10, 10, 5, 10).SplitVertically(&left_half, &right_half);
   EXPECT_TRUE(left_half.Equals(gfx::Rect(10, 10, 2, 10)));
   EXPECT_TRUE(right_half.Equals(gfx::Rect(12, 10, 3, 10)));
 }
 
+TEST(RectTest, CenterPoint) {
+  gfx::Point center;
+
+  // When origin is (0, 0).
+  center = gfx::Rect(0, 0, 20, 20).CenterPoint();
+  EXPECT_TRUE(center == gfx::Point(10, 10));

[sky, 2012/10/09 15:55:50]

Use EXPECT_EQ("10,10", center) for these. Doing so makes for more readable error
messages when things go wrong.

+
+  // When origin is even.
+  center = gfx::Rect(10, 10, 20, 20).CenterPoint();
+  EXPECT_TRUE(center == gfx::Point(20, 20));
+
+  // When origin is odd.
+  center = gfx::Rect(11, 11, 20, 20).CenterPoint();
+  EXPECT_TRUE(center == gfx::Point(21, 21));
+
+  // When 0 width or height.
+  center = gfx::Rect(10, 10, 0, 20).CenterPoint();
+  EXPECT_TRUE(center == gfx::Point(10, 20));
+  center = gfx::Rect(10, 10, 20, 0).CenterPoint();
+  EXPECT_TRUE(center == gfx::Point(20, 10));
+
+  // When an odd size.
+  center = gfx::Rect(10, 10, 21, 21).CenterPoint();
+  EXPECT_TRUE(center == gfx::Point(20, 20));
+
+  // When an odd size and position.
+  center = gfx::Rect(11, 11, 21, 21).CenterPoint();
+  EXPECT_TRUE(center == gfx::Point(21, 21));
+}
+
+TEST(RectTest, CenterPointF) {
+  gfx::PointF center;
+
+  // When origin is (0, 0).
+  center = gfx::RectF(0, 0, 20, 20).CenterPoint();
+  EXPECT_TRUE(center == gfx::PointF(10, 10));
+
+  // When origin is even.
+  center = gfx::RectF(10, 10, 20, 20).CenterPoint();
+  EXPECT_TRUE(center == gfx::PointF(20, 20));
+
+  // When origin is odd.
+  center = gfx::RectF(11, 11, 20, 20).CenterPoint();
+  EXPECT_TRUE(center == gfx::PointF(21, 21));
+
+  // When 0 width or height.
+  center = gfx::RectF(10, 10, 0, 20).CenterPoint();
+  EXPECT_TRUE(center == gfx::PointF(10, 20));
+  center = gfx::RectF(10, 10, 20, 0).CenterPoint();
+  EXPECT_TRUE(center == gfx::PointF(20, 10));
+
+  // When an odd size.
+  center = gfx::RectF(10, 10, 21, 21).CenterPoint();
+  EXPECT_TRUE(center == gfx::PointF(20.5f, 20.5f));
+
+  // When an odd size and position.
+  center = gfx::RectF(11, 11, 21, 21).CenterPoint();
+  EXPECT_TRUE(center == gfx::PointF(21.5f, 21.5f));
+}
+
 TEST(RectTest, SharesEdgeWith) {
   gfx::Rect r(2, 3, 4, 5);
 
   // Must be non-overlapping
   EXPECT_FALSE(r.SharesEdgeWith(r));
 
   gfx::Rect just_above(2, 1, 4, 2);
   gfx::Rect just_below(2, 8, 4, 2);
   gfx::Rect just_left(0, 3, 2, 5);
   gfx::Rect just_right(6, 3, 2, 5);
@@ skipping 182 matching lines @@
 #if defined(OS_WIN)
 TEST(RectTest, ConstructAndAssign) {
   const RECT rect_1 = { 0, 0, 10, 10 };
   const RECT rect_2 = { 0, 0, -10, -10 };
   gfx::Rect test1(rect_1);
   gfx::Rect test2(rect_2);
 }
 #endif
 
 }  // namespace ui