Provide approximate type functions for SkMatrix44.

ui/gfx/transform_unittest.cc

 // Copyright (c) 2011 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.
 
 // MSVC++ requires this to be set before any other includes to get M_PI.
 #define _USE_MATH_DEFINES
 
 #include "ui/gfx/transform.h"
 
 #include <cmath>
@@ skipping 123 matching lines @@
   matrix.set(2, 3, 44.f);
   matrix.set(3, 3, 45.f);
 
   // Sanity check
   EXPECT_ROW1_EQ(30.0f, 34.0f, 38.0f, 42.0f, (*transform));
   EXPECT_ROW2_EQ(31.0f, 35.0f, 39.0f, 43.0f, (*transform));
   EXPECT_ROW3_EQ(32.0f, 36.0f, 40.0f, 44.0f, (*transform));
   EXPECT_ROW4_EQ(33.0f, 37.0f, 41.0f, 45.0f, (*transform));
 }
 
+const SkMScalar kApproxZero =
+    SkFloatToMScalar(std::numeric_limits<float>::epsilon());
+const SkMScalar kApproxOne = 1 - kApproxZero;
+
+void InitializeApproxIdentityMatrix(Transform* transform) {
+  SkMatrix44& matrix = transform->matrix();
+  matrix.set(0, 0, kApproxOne);
+  matrix.set(0, 1, kApproxZero);
+  matrix.set(0, 2, kApproxZero);
+  matrix.set(0, 3, kApproxZero);
+
+  matrix.set(1, 0, kApproxZero);
+  matrix.set(1, 1, kApproxOne);
+  matrix.set(1, 2, kApproxZero);
+  matrix.set(1, 3, kApproxZero);
+
+  matrix.set(2, 0, kApproxZero);
+  matrix.set(2, 1, kApproxZero);
+  matrix.set(2, 2, kApproxOne);
+  matrix.set(2, 3, kApproxZero);
+
+  matrix.set(3, 0, kApproxZero);
+  matrix.set(3, 1, kApproxZero);
+  matrix.set(3, 2, kApproxZero);
+  matrix.set(3, 3, kApproxOne);
+}
+
 #ifdef SK_MSCALAR_IS_DOUBLE
 #define ERROR_THRESHOLD 1e-14
 #else
 #define ERROR_THRESHOLD 1e-7
 #endif
 #define LOOSE_ERROR_THRESHOLD 1e-7
 
 TEST(XFormTest, Equality) {
   Transform lhs, rhs, interpolated;
   rhs.matrix().set3x3(1, 2, 3,
@@ skipping 2050 matching lines @@
   // Note carefully - expecting true here.
   A.MakeIdentity();
   A.matrix().set(2, 3, 2.f);
   EXPECT_TRUE(A.IsIdentityOrTranslation());
 
   A.MakeIdentity();
   A.matrix().set(3, 3, 2.f);
   EXPECT_FALSE(A.IsIdentityOrTranslation());
 }
 
+TEST(XFormTest, verifyIsApproximatelyIdentityOrTranslation) {
+  Transform A;
+  SkMatrix44& matrix = A.matrix();
+
+  // Exact pure translation.
+  A.MakeIdentity();
+
+  // Set translate values to values other than 0 or 1.
+  matrix.set(0, 3, 3.4f);
+  matrix.set(1, 3, 4.4f);
+  matrix.set(2, 3, 5.6f);
+
+  EXPECT_TRUE(A.IsApproximatelyIdentityOrTranslation(0));
+  EXPECT_TRUE(A.IsApproximatelyIdentityOrTranslation(kApproxZero));
+
+  // Approximately pure translation.
+  InitializeApproxIdentityMatrix(&A);
+
+  // Some values must be exact.
+  matrix.set(3, 0, 0);
+  matrix.set(3, 1, 0);
+  matrix.set(3, 2, 0);
+  matrix.set(3, 3, 1);
+
+  // Set translate values to values other than 0 or 1.
+  matrix.set(0, 3, 3.4f);
+  matrix.set(1, 3, 4.4f);
+  matrix.set(2, 3, 5.6f);
+
+  EXPECT_FALSE(A.IsApproximatelyIdentityOrTranslation(0));
+  EXPECT_TRUE(A.IsApproximatelyIdentityOrTranslation(kApproxZero));
+
+  // Not approximately pure translation.
+  InitializeApproxIdentityMatrix(&A);
+
+  // Some values must be exact.
+  matrix.set(3, 0, 0);
+  matrix.set(3, 1, 0);
+  matrix.set(3, 2, 0);
+  matrix.set(3, 3, 1);
+
+  // Set some values (not translate values) to values other than 0 or 1.
+  matrix.set(0, 1, 3.4f);
+  matrix.set(3, 2, 4.4f);
+  matrix.set(2, 0, 5.6f);
+
+  EXPECT_FALSE(A.IsApproximatelyIdentityOrTranslation(0));
+  EXPECT_FALSE(A.IsApproximatelyIdentityOrTranslation(kApproxZero));
+}
+
 TEST(XFormTest, verifyIsScaleOrTranslation) {
   Transform A;
 
   InitializeTestMatrix(&A);
   EXPECT_FALSE(A.IsScaleOrTranslation());
 
   A.MakeIdentity();
   EXPECT_TRUE(A.IsScaleOrTranslation());
 
   // Modifying any non-scale or non-translation components should cause
@@ skipping 348 matching lines @@
   EXPECT_EQ(expected.ToString(), box.ToString());
 
   Transform singular;
   singular.Scale3d(0.f, 0.f, 0.f);
   EXPECT_FALSE(singular.TransformBoxReverse(&box));
 }
 
 }  // namespace
 
 }  // namespace gfx