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..41bfc40783a805caa8ce78fc0cd36b29c034b7b1 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.h"
 
 namespace gfx {
 namespace {
@@ -30,5 +32,149 @@ TEST(TransformUtilTest, GetScaleTransform) {
   }
 }
 
+TEST(TransformUtilTest, SnapRotation) {
+  Transform result(Transform::kSkipInitialization);
+  Transform transform;
+  transform.RotateAboutZAxis(89.99);
+
+  Rect viewport(1920, 1200);
+  bool snapped = SnapTransform(&result, transform, viewport);
+
+  EXPECT_TRUE(snapped) << "Viewport should snap for this rotation.";
+}
+
+TEST(TransformUtilTest, SnapRotationDistantViewport) {
+  const int kOffset = 5000;
+  Transform result(Transform::kSkipInitialization);
+  Transform transform;
+
+  transform.RotateAboutZAxis(89.99);
+
+  Rect viewport(kOffset, kOffset, 1920, 1200);
+  bool snapped = SnapTransform(&result, transform, viewport);
+
+  EXPECT_FALSE(snapped) << "Distant viewport shouldn't snap by more than 1px.";
+}
+
+TEST(TransformUtilTest, NoSnapRotation) {
+  Transform result(Transform::kSkipInitialization);
+  Transform transform;
+  const int kOffset = 5000;
+
+  transform.RotateAboutZAxis(89.9);
+
+  Rect viewport(kOffset, kOffset, 1920, 1200);
+  bool snapped = SnapTransform(&result, transform, viewport);
+
+  EXPECT_FALSE(snapped) << "Viewport should not snap for this rotation.";
+}
+
+// Translations should always be snappable, the most we would move is 0.5
+// pixels towards either direction to the nearest value in each component.
+TEST(TransformUtilTest, SnapTranslation) {
+  Transform result(Transform::kSkipInitialization);
+  Transform transform;
+
+  transform.Translate3d(
+      SkDoubleToMScalar(1.01), SkDoubleToMScalar(1.99), SkDoubleToMScalar(3.0));
+
+  Rect viewport(1920, 1200);
+  bool snapped = SnapTransform(&result, transform, viewport);
+
+  EXPECT_TRUE(snapped) << "Viewport should snap for this translation.";
+}
+
+TEST(TransformUtilTest, SnapTranslationDistantViewport) {
+  Transform result(Transform::kSkipInitialization);
+  Transform transform;
+  const int kOffset = 5000;
+
+  transform.Translate3d(
+      SkDoubleToMScalar(1.01), SkDoubleToMScalar(1.99), SkDoubleToMScalar(3.0));
+
+  Rect viewport(kOffset, kOffset, 1920, 1200);
+  bool snapped = SnapTransform(&result, transform, viewport);
+
+  EXPECT_TRUE(snapped)
+      << "Distant viewport should still snap by less than 1px.";
+}
+
+TEST(TransformUtilTest, SnapScale) {
+  Transform result(Transform::kSkipInitialization);
+  Transform transform;
+
+  transform.Scale3d(SkDoubleToMScalar(5.0),
+                    SkDoubleToMScalar(2.00001),
+                    SkDoubleToMScalar(1.0));
+  Rect viewport(1920, 1200);
+  bool snapped = SnapTransform(&result, transform, viewport);
+
+  EXPECT_TRUE(snapped) << "Viewport should snap for this scaling.";
+}
+
+TEST(TransformUtilTest, NoSnapScale) {
+  Transform result(Transform::kSkipInitialization);
+  Transform transform;
+
+  transform.Scale3d(
+    SkDoubleToMScalar(5.0), SkDoubleToMScalar(2.1), SkDoubleToMScalar(1.0));
+  Rect viewport(1920, 1200);
+  bool snapped = SnapTransform(&result, transform, viewport);
+
+  EXPECT_FALSE(snapped) << "Viewport shouldn't snap for this scaling.";
+}
+
+TEST(TransformUtilTest, SnapCompositeTransform) {
+  Transform result(Transform::kSkipInitialization);
+  Transform transform;
+
+  transform.Translate3d(SkDoubleToMScalar(30.5), SkDoubleToMScalar(20.0),
+                        SkDoubleToMScalar(10.1));
+  transform.RotateAboutZAxis(89.99);
+  transform.Scale3d(SkDoubleToMScalar(1.0),
+                    SkDoubleToMScalar(3.00001),
+                    SkDoubleToMScalar(2.0));
+
+  Rect viewport(1920, 1200);
+  bool snapped = SnapTransform(&result, transform, viewport);
+  ASSERT_TRUE(snapped) << "Viewport should snap all components.";
+
+  Point3F point;
+
+  point = Point3F(viewport.origin());
+  result.TransformPoint(&point);
+  EXPECT_EQ(Point3F(31.f, 20.f, 10.f), point) << "Transformed origin";
+
+  point = Point3F(viewport.top_right());
+  result.TransformPoint(&point);
+  EXPECT_EQ(Point3F(31.f, 1940.f, 10.f), point) << "Transformed top-right";
+
+  point = Point3F(viewport.bottom_left());
+  result.TransformPoint(&point);
+  EXPECT_EQ(Point3F(-3569.f, 20.f, 10.f), point) << "Transformed bottom-left";
+
+  point = Point3F(viewport.bottom_right());
+  result.TransformPoint(&point);
+  EXPECT_EQ(Point3F(-3569.f, 1940.f, 10.f), point)
+      << "Transformed bottom-right";
+}
+
+TEST(TransformUtilTest, NoSnapSkewedCompositeTransform) {
+  Transform result(Transform::kSkipInitialization);
+  Transform transform;
+
+
+  transform.RotateAboutZAxis(89.99);
+  transform.Scale3d(SkDoubleToMScalar(1.0),
+                    SkDoubleToMScalar(3.00001),
+                    SkDoubleToMScalar(2.0));
+  transform.Translate3d(SkDoubleToMScalar(30.5), SkDoubleToMScalar(20.0),
+                        SkDoubleToMScalar(10.1));
+  transform.SkewX(20.0);
+  Rect viewport(1920, 1200);
+  bool snapped = SnapTransform(&result, transform, viewport);
+  EXPECT_FALSE(snapped) << "Skewed viewport should not snap.";
+}
+
 }  // namespace
 }  // namespace gfx