Provide approximate type functions for SkMatrix44.

cc/base/math_util.h

 // Copyright 2012 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.
 
 #ifndef CC_BASE_MATH_UTIL_H_
 #define CC_BASE_MATH_UTIL_H_
 
 #include <algorithm>
 #include <cmath>
 
@@ skipping 159 matching lines @@
   static bool FromValue(const base::Value*, gfx::Rect* out_rect);
   static scoped_ptr<base::Value> AsValue(gfx::PointF q);
   static scoped_ptr<base::Value> AsValue(const gfx::QuadF& q);
   static scoped_ptr<base::Value> AsValue(const gfx::RectF& rect);
   static scoped_ptr<base::Value> AsValue(const gfx::Transform& transform);
 
   // Returns a base::Value representation of the floating point value.
   // If the value is inf, returns max double/float representation.
   static scoped_ptr<base::Value> AsValueSafely(double value);
   static scoped_ptr<base::Value> AsValueSafely(float value);
+
+  // Check if matrices are of a certain type using approximate math. Each
+  // function gets a tolerance parameter to specify the maximum allowed
+  // absolute difference to the exact values.
+  static bool IsMatrixApproximatelyPureTranslation(const SkMatrix44& matrix,

[danakj, 2013/10/15 15:34:35]

s/Pure//

[Dominik Grewe, 2013/10/15 17:04:19]

I think "Pure" was chosen to indicate that the matrix is a translation matrix
but nothing else (it doesn't have a scale, for example). I'm not the expert in
this area though, so I'm happy to change it. Just thought I'd double check.

+                                                   SkMScalar tolerance);
+  static bool IsMatrixApproximatelyIntegerTransform(const SkMatrix44& matrix,
+                                                    SkMScalar tolerance);
 };
 
 }  // namespace cc
 
 #endif  // CC_BASE_MATH_UTIL_H_