Provide approximate type functions for SkMatrix44.

cc/base/math_util.cc

Index: cc/base/math_util.cc
diff --git a/cc/base/math_util.cc b/cc/base/math_util.cc
index eeb1523db46a080aff9850caaf126c1c3f8b0509..ee7b3cafecdfd8472b284a75d1e14792910b43b3 100644
--- a/cc/base/math_util.cc
+++ b/cc/base/math_util.cc
@@ -17,6 +17,21 @@
 #include "ui/gfx/vector2d_f.h"
 
 namespace cc {
+namespace {
+
+static inline bool SkMScalarApproximatelyEqual(SkMScalar x, SkMScalar y,

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

can you drop the SkMScalar prefix from these methods? That makes them sound like
they live in the Skia namespace (which doesn't have an actual c++ namespace).

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

Done.

+                                               SkMScalar tolerance) {
+  DCHECK_GE(tolerance, 0);
+  return SkTAbs<SkMScalar>(x-y) <= tolerance;

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

use std::abs()

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

Done.

+}
+
+static inline bool SkMScalarApproximatelyInteger(SkMScalar x,

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

drop the anonymous namespace, or drop the "static" they are redundant.

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

Done.

+                                                 SkMScalar tolerance) {
+  SkMScalar nearestInteger = std::floor(x + SkDoubleToMScalar(0.5));

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

how about just "0.5f" instead of "SkDoubleToMScalar(0.5)"

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

nearest_integer

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

Done.

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

I wanted to keep it independent of whether SkMScalar is float or double (afaik
it's double for now).

+  return SkMScalarApproximatelyEqual(x, nearestInteger, tolerance);
+}
+
+}  // namespace
 
 const double MathUtil::kPiDouble = 3.14159265358979323846;
 const float MathUtil::kPiFloat = 3.14159265358979323846f;
@@ -593,4 +608,44 @@ scoped_ptr<base::Value> MathUtil::AsValueSafely(float value) {
       std::min(value, std::numeric_limits<float>::max())));
 }
 
+bool MathUtil::IsMatrixApproximatelyPureTranslation(const SkMatrix44& matrix,

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

Can you make these methods take a gfx::Transform instead of a SkMatrix44? Then
the callsites do not need to unwrap it.

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

How about overloading it for both types? Would make testing easier as well.

+                                                    SkMScalar tolerance) {
+  return
+      SkMScalarApproximatelyEqual(matrix.get(0, 0), 1, tolerance) &&

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

1.f (don't use integer literals for floating point) here and below.

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

How about "SkFloatToMScalar(1.f)" to keep it independent of SkMScalar?

+      SkMScalarApproximatelyEqual(matrix.get(1, 0), 0, tolerance) &&
+      SkMScalarApproximatelyEqual(matrix.get(2, 0), 0, tolerance) &&
+      matrix.get(3, 0) == 0 &&
+      SkMScalarApproximatelyEqual(matrix.get(0, 1), 0, tolerance) &&
+      SkMScalarApproximatelyEqual(matrix.get(1, 1), 1, tolerance) &&
+      SkMScalarApproximatelyEqual(matrix.get(2, 1), 0, tolerance) &&
+      matrix.get(3, 1) == 0 &&
+      SkMScalarApproximatelyEqual(matrix.get(0, 2), 0, tolerance) &&
+      SkMScalarApproximatelyEqual(matrix.get(1, 2), 0, tolerance) &&
+      SkMScalarApproximatelyEqual(matrix.get(2, 2), 1, tolerance) &&
+      matrix.get(3, 2) == 0 &&
+      matrix.get(3, 3) == 1;
+}
+
+bool MathUtil::IsMatrixApproximatelyIntegerTransform(const SkMatrix44& matrix,
+                                                     SkMScalar tolerance) {
+  return
+      SkMScalarApproximatelyInteger(matrix.get(0, 0), tolerance) &&
+      SkMScalarApproximatelyEqual(matrix.get(0, 1), 0, tolerance) &&
+      SkMScalarApproximatelyEqual(matrix.get(0, 2), 0, tolerance) &&
+      SkMScalarApproximatelyInteger(matrix.get(0, 3), tolerance) &&
+
+      SkMScalarApproximatelyEqual(matrix.get(1, 0), 0, tolerance) &&
+      SkMScalarApproximatelyInteger(matrix.get(1, 1), tolerance) &&
+      SkMScalarApproximatelyEqual(matrix.get(1, 2), 0, tolerance) &&
+      SkMScalarApproximatelyInteger(matrix.get(1, 3), tolerance) &&
+
+      SkMScalarApproximatelyEqual(matrix.get(2, 0), 0, tolerance) &&
+      SkMScalarApproximatelyEqual(matrix.get(2, 1), 0, tolerance) &&
+
+      SkMScalarApproximatelyEqual(matrix.get(3, 0), 0, tolerance) &&
+      SkMScalarApproximatelyEqual(matrix.get(3, 1), 0, tolerance) &&
+      SkMScalarApproximatelyEqual(matrix.get(3, 2), 0, tolerance) &&
+      SkMScalarApproximatelyEqual(matrix.get(3, 3), 1, tolerance);
+}
+
 }  // namespace cc