Use SkMatrix44 for the underlying implementation of ui::Transform

ui/gfx/transform.h

Index: ui/gfx/transform.h
diff --git a/ui/gfx/transform.h b/ui/gfx/transform.h
index 3fdfc3235a36c79eab4508d7481e9c05e8a83278..10309939f84dc47f99b641c036a76ede38a761e9 100644
--- a/ui/gfx/transform.h
+++ b/ui/gfx/transform.h
@@ -6,20 +6,22 @@
 #define UI_GFX_TRANSFORM_H_
 #pragma once
 
+#include "base/template_util.h"
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
-#include "third_party/skia/include/core/SkMatrix.h"
+#include "third_party/skia/include/utils/SkMatrix44.h"
+#include "ui/gfx/point.h"
+
+#include <cmath>
 
 namespace gfx {
-class Point;
 class Rect;
 }
 
 namespace ui {
 
-// 3x3 transformation matrix. Transform is cheap and explicitly allows
+// 4x4 transformation matrix. Transform is cheap and explicitly allows
 // copy/assign.
-// TODO: make this a 4x4.
 class Transform {
  public:
   Transform();
@@ -57,43 +59,112 @@ class Transform {
   void ConcatTranslate(float x, float y);
 
   // Applies a transformation on the current transformation
-  // (i.e. 'this = this * transform;'). Returns true if the result can be
-  // represented.
-  bool PreconcatTransform(const Transform& transform);
+  // (i.e. 'this = this * transform;').
+  void PreconcatTransform(const Transform& transform);
 
   // Applies a transformation on the current transformation
-  // (i.e. 'this = transform * this;'). Returns true if the result can be
-  // represented.
-  bool ConcatTransform(const Transform& transform);
+  // (i.e. 'this = transform * this;').
+  void ConcatTransform(const Transform& transform);
 
   // Does the transformation change anything?
   bool HasChange() const;
 
   // Applies the transformation on the point. Returns true if the point is
   // transformed successfully.
-  bool TransformPoint(gfx::Point* point);
+  template <class T>
+  bool TransformPoint(T& point) const;
 
-  // Applies the reverse transformation on the point. Returns true if the point
-  // is transformed successfully.
-  bool TransformPointReverse(gfx::Point* point);
+  // Applies the reverse transformation on the point. Returns true if the
+  // transformation can be inverted
+  template <class T>
+  bool TransformPointReverse(T& point) const;
 
   // Applies transformation on the rectangle. Returns true if the rectangle is
   // transformed successfully.
-  bool TransformRect(gfx::Rect* rect);
+  bool TransformRect(gfx::Rect* rect) const;
 
   // Applies the reverse transformation on the rectangle. Returns true if the
   // rectangle is transformed successfully.
-  bool TransformRectReverse(gfx::Rect* rect);
+  bool TransformRectReverse(gfx::Rect* rect) const;
 
   // Returns the underlying matrix.
-  const SkMatrix& matrix() const { return matrix_; }
+  const SkMatrix44& matrix() const { return matrix_; }
 
  private:
-  SkMatrix matrix_;
+  template <typename T>
+  void TransformPointInternal(const SkMatrix44& xform, T& point) const;
+
+  template <typename T>
+  static int SymmetricRound(T value);
+
+  SkMatrix44 matrix_;
 
   // copy/assign are allowed.
 };
 
-}  // namespace ui
+template <class T>
+bool Transform::TransformPoint(T& point) const {
+  TransformPointInternal(matrix_, point);
+  return true;
+}
+
+template <class T>
+bool Transform::TransformPointReverse(T& point) const {
+  // TODO(sad): Try to avoid trying to invert the matrix.
+  SkMatrix44 inverse;
+  if (!matrix_.invert(&inverse))
+    return false;
+
+  TransformPointInternal(inverse, point);
+  return true;
+}
+
+template <typename T>
+void Transform::TransformPointInternal(const SkMatrix44& xform,
+                                       T& point) const {
+  SkScalar p[4] = {
+    point[0],
+    point[1],
+    point[2],
+    1 };
+
+  xform.map(p);
+
+  if (p[3] != 1 && abs(p[3]) > 0) {
+    point[0] = p[0] / p[3];
+    point[1] = p[1] / p[3];
+    point[2] = p[2] / p[3];
+  } else {
+    point[0] = p[0];
+    point[1] = p[1];
+    point[2] = p[2];
+  }
+}
+
+template <>
+inline void Transform::TransformPointInternal<gfx::Point>(
+  const SkMatrix44& xform,
+  gfx::Point& point) const {
+
+  SkScalar p[4] = {
+    SkIntToScalar(point.x()),
+    SkIntToScalar(point.y()),
+    0,
+    1 };
+
+  xform.map(p);
+  point.SetPoint(SymmetricRound(p[0]),
+                 SymmetricRound(p[1]));
+}
+
+template <typename T>
+int Transform::SymmetricRound(T x) {
+  return static_cast<int>(
+    x > 0.0f
+      ? std::floor(x + 0.5f)
+      : std::ceil(x - 0.5f));
+}
+
+}// namespace ui
 
 #endif  // UI_GFX_TRANSFORM_H_