Add transform*rect and transform*size operators

Summary:
Adding 2 `transform*rect` and `transform*size` operations.
Changelog: [Internal]

Reviewed By: JoshuaGross

Differential Revision: D20304247

fbshipit-source-id: 7bde67c96a21ce15e9da0464bcfccc61ab8fe13d

ReactCommon/fabric/graphics/Transform.cpp

@@ -180,5 +180,25 @@ Point operator*(Point const &point, Transform const &transform) {
   return result;
 }
 
+Rect operator*(Rect const &rect, Transform const &transform) {
+  auto transformedSize = rect.size * transform;
+  auto pointAdjustment = Point{(rect.size.width - transformedSize.width) / 2,
+                               (rect.size.height - transformedSize.height) / 2};
+
+  return {rect.origin + pointAdjustment, transformedSize};
+}
+
+Size operator*(Size const &size, Transform const &transform) {
+  if (transform == Transform::Identity()) {
+    return size;
+  }
+
+  auto result = Size{};
+  result.width = transform.at(0, 0) * size.width;
+  result.height = transform.at(1, 1) * size.height;
+
+  return result;
+}
+
 } // namespace react
 } // namespace facebook

ReactCommon/fabric/graphics/Transform.h

@@ -79,6 +79,17 @@ struct Transform {
  */
 Point operator*(Point const &point, Transform const &transform);
 
+/*
+ * Applies tranformation to the given size.
+ */
+Size operator*(Size const &size, Transform const &transform);
+
+/*
+ * Applies tranformation to the given rect.
+ * ONLY SUPPORTS scale transformation.
+ */
+Rect operator*(Rect const &rect, Transform const &transform);
+
 } // namespace react
 } // namespace facebook
 

ReactCommon/fabric/graphics/tests/TransformTest.cpp

@@ -0,0 +1,40 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#include <react/graphics/Transform.h>
+#include <gtest/gtest.h>
+
+using namespace facebook::react;
+
+TEST(TransformTest, transformingSize) {
+  auto size = facebook::react::Size{100, 200};
+  auto scaledSize = size * Transform::Scale(0.5, 0.5, 1);
+
+  EXPECT_EQ(scaledSize.width, 50);
+  EXPECT_EQ(scaledSize.height, 100);
+}
+
+TEST(TransformTest, transformingPoint) {
+  auto point = facebook::react::Point{100, 200};
+  auto translatedPoint = point * Transform::Translate(-50, -100, 0);
+
+  EXPECT_EQ(translatedPoint.x, 50);
+  EXPECT_EQ(translatedPoint.y, 100);
+}
+
+TEST(TransformTest, transformingRect) {
+  auto point = facebook::react::Point{100, 200};
+  auto size = facebook::react::Size{300, 400};
+  auto rect = facebook::react::Rect{point, size};
+
+  auto transformedRect = rect * Transform::Scale(0.5, 0.5, 1);
+
+  EXPECT_EQ(transformedRect.origin.x, 175);
+  EXPECT_EQ(transformedRect.origin.y, 300);
+  EXPECT_EQ(transformedRect.size.width, 150);
+  EXPECT_EQ(transformedRect.size.height, 200);
+}