Implement transform snapping for gfx::Transforms.

ui/gfx/transform_util_unittest.cc

Index: ui/gfx/transform_util_unittest.cc
diff --git a/ui/gfx/transform_util_unittest.cc b/ui/gfx/transform_util_unittest.cc
index 94195c29bb92f90641e8eecdfb87ae3bcb966b27..51bca573008c4bfeadb121a67a6c14fb9b86c21b 100644
--- a/ui/gfx/transform_util_unittest.cc
+++ b/ui/gfx/transform_util_unittest.cc
@@ -6,6 +6,8 @@
 
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/gfx/point.h"
+#include "ui/gfx/point3_f.h"
+#include "ui/gfx/rect_f.h"
 
 namespace gfx {
 namespace {
@@ -30,5 +32,51 @@ TEST(TransformUtilTest, GetScaleTransform) {
   }
 }
 
+TEST(TransformUtilTest, SnapRotation) {
+  gfx::Transform transform;
+  transform.RotateAboutZAxis(89.99);
+
+  DecomposedTransform decomposed, result;
+
+  DecomposeTransform(&decomposed, transform);
+
+  RectF viewport(1920.0, 1200.0);
+  bool snapped = SnapRotation(&result, decomposed, transform, viewport);
+
+  EXPECT_TRUE(snapped) << "Viewport should snap for this rotation.";
+}
+
+TEST(TransformUtilTest, SnapDistantRotation) {
+  const int kOffset = 5000;
+  gfx::Transform transform;
+
+  transform.RotateAboutZAxis(89.99);
+
+  DecomposedTransform decomposed, result;
+
+  DecomposeTransform(&decomposed, transform);
+
+  RectF viewport(1920.0 + kOffset, 1200.0 + kOffset);
+  bool snapped = SnapRotation(&result, decomposed, transform, viewport);
+
+  EXPECT_FALSE(snapped) << "Distant viewport shouldn't snap by more than 1px.";
+}
+
+TEST(TransformUtilTest, NoSnapRotation) {
+  gfx::Transform transform;
+  const int kOffset = 5000;
+
+  transform.RotateAboutZAxis(89.9);
+
+  DecomposedTransform decomposed, result;
+
+  DecomposeTransform(&decomposed, transform);
+
+  RectF viewport(1920.0 + kOffset, 1200.0 + kOffset);
+  bool snapped = SnapRotation(&result, decomposed, transform, viewport);
+
+  EXPECT_FALSE(snapped) << "Viewport should not snap for this rotation.";
+}
+
 }  // namespace
 }  // namespace gfx