Mozart: Compute hits using 4x4 matrix.

services/gfx/compositor/graph/transform_pair.cc

+// Copyright 2016 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 "services/gfx/compositor/graph/transform_pair.h"
+
+namespace compositor {
+
+TransformPair::TransformPair(const SkMatrix44& forward)
+    : forward_(forward),
+      cached_inverse_(SkMatrix44::kUninitialized_Constructor) {}
+
+TransformPair::~TransformPair() {}
+
+const SkMatrix44& TransformPair::GetInverse() const {
+  if (!cached_inverse_valid_) {
+    if (!forward_.invert(&cached_inverse_)) {
+      // Matrix is singular!
+      // Return [0,0,0,0][0,0,0,0][0,0,0,0][0,0,0,1] (all zeroes except
+      // last component).  This causes all points to be mapped to the origin
+      // when transformed.
+      cached_inverse_.setScale(0.f, 0.f, 0.f);
+    }
+    cached_inverse_valid_ = true;
+  }
+  return cached_inverse_;
+}
+
+const SkPoint TransformPair::InverseMapPoint(const SkPoint& point) const {
+  SkScalar vec[4] = {point.x(), point.y(), 0.f, 1.f};
+  GetInverse().mapScalars(vec);
+  return SkPoint::Make(vec[0], vec[1]);
+}
+
+}  // namespace compositor