Move temporary MathUtil wrappers to permanent home in gfx::Transform

ui/gfx/transform.cc

Index: ui/gfx/transform.cc
diff --git a/ui/gfx/transform.cc b/ui/gfx/transform.cc
index 19b59dac2039be7debb9485a34d817392e79b978..ef87c70d3f3db4b6fdeb3814e0807fe0c4b6b2ac 100644
--- a/ui/gfx/transform.cc
+++ b/ui/gfx/transform.cc
@@ -185,10 +185,75 @@ bool Transform::IsIdentity() const {
   return matrix_.isIdentity();
 }
 
+bool Transform::IsIdentityOrTranslation() const {
+  bool has_no_perspective = !matrix_.getDouble(3, 0) &&
+                            !matrix_.getDouble(3, 1) &&
+                            !matrix_.getDouble(3, 2) &&
+                            (matrix_.getDouble(3, 3) == 1);
+
+  bool has_no_rotation_or_skew = !matrix_.getDouble(0, 1) &&
+                                 !matrix_.getDouble(0, 2) &&
+                                 !matrix_.getDouble(1, 0) &&
+                                 !matrix_.getDouble(1, 2) &&
+                                 !matrix_.getDouble(2, 0) &&
+                                 !matrix_.getDouble(2, 1);
+
+  bool has_no_scale = matrix_.getDouble(0, 0) == 1 &&
+                      matrix_.getDouble(1, 1) == 1 &&
+                      matrix_.getDouble(2, 2) == 1;
+
+  return has_no_perspective && has_no_rotation_or_skew && has_no_scale;
+}
+
+bool Transform::IsScaleOrTranslation() const {
+  bool has_no_perspective = !matrix_.getDouble(3, 0) &&
+                            !matrix_.getDouble(3, 1) &&
+                            !matrix_.getDouble(3, 2) &&
+                            (matrix_.getDouble(3, 3) == 1);
+
+  bool has_no_rotation_or_skew = !matrix_.getDouble(0, 1) &&
+                                 !matrix_.getDouble(0, 2) &&
+                                 !matrix_.getDouble(1, 0) &&
+                                 !matrix_.getDouble(1, 2) &&
+                                 !matrix_.getDouble(2, 0) &&
+                                 !matrix_.getDouble(2, 1);
+
+  return has_no_perspective && has_no_rotation_or_skew;
+}
+
+bool Transform::HasPerspective() const {
+  return matrix_.getDouble(3, 0) ||
+         matrix_.getDouble(3, 1) ||
+         matrix_.getDouble(3, 2) ||
+         (matrix_.getDouble(3, 3) != 1);
+}
+
 bool Transform::IsInvertible() const {
   return std::abs(matrix_.determinant()) > kTooSmallForDeterminant;
 }
 
+bool Transform::IsBackFaceVisible() const {
+  // Compute whether a layer with a forward-facing normal of (0, 0, 1) would
+  // have its back face visible after applying the transform.
+  //
+  // This is done by transforming the normal and seeing if the resulting z
+  // value is positive or negative. However, note that transforming a normal
+  // actually requires using the inverse-transpose of the original transform.
+
+  // TODO (shawnsingh) make this perform more efficiently - we do not

[danakj, 2012/11/28 00:42:12]

is there a bug for this, for M25?

+  // actually need to instantiate/invert/transpose any matrices, exploiting the
+  // fact that we only need to transform (0, 0, 1, 0).
+  SkMatrix44 inverse;
+  bool invertible = matrix_.invert(&inverse);
+
+  // Assume the transform does not apply if it's not invertible, so it's
+  // front face remains visible.
+  if (!invertible)
+    return false;
+
+  return inverse.getDouble(2, 2) < 0;
+}
+
 bool Transform::GetInverse(Transform* transform) const {
   return matrix_.invert(&transform->matrix_);
 }