Ensure that Slerp returns a non-inf for opposing vectors.
In the case where the given vectors are opposite of each other, we
get a 0 denominator which causes inf/nan values which later down
the pipeline can result in CHECKs since the layer transform would have
nans as well.
R=vollick
BUG=506543
Review URL: https://codereview.chromium.org/1217773011
Cr-Commit-Position: refs/heads/master@{#337881}
diff --git a/ui/gfx/transform_util.cc b/ui/gfx/transform_util.cc
index 3eab6e2..33c5508 100644
--- a/ui/gfx/transform_util.cc
+++ b/ui/gfx/transform_util.cc
@@ -73,6 +73,18 @@
return true;
}
+ // TODO(vmpstr): In case the product is -1, the vectors are exactly opposite
+ // of each other. In this case, it's technically not correct to just pick one
+ // of the vectors, we instead need to pick how to interpolate. However, the
+ // spec isn't clear on this. If we don't handle the -1 case explicitly, it
+ // results in inf and nans however, which is worse. See crbug.com/506543 for
+ // more discussion.
+ if (std::abs(product + 1.0) < epsilon) {
+ for (int i = 0; i < 4; ++i)
+ out[i] = q1[i];
+ return true;
+ }
+
double denom = std::sqrt(1.0 - product * product);
double theta = std::acos(product);
double w = std::sin(progress * theta) * (1.0 / denom);
diff --git a/ui/gfx/transform_util_unittest.cc b/ui/gfx/transform_util_unittest.cc
index 404833c..02bf46a4 100644
--- a/ui/gfx/transform_util_unittest.cc
+++ b/ui/gfx/transform_util_unittest.cc
@@ -192,5 +192,18 @@
EXPECT_EQ(Point(-11, -20).ToString(), point.ToString());
}
+TEST(TransformUtilTest, BlendOppositeQuaternions) {
+ DecomposedTransform first;
+ DecomposedTransform second;
+ second.quaternion[3] = -second.quaternion[3];
+
+ DecomposedTransform result;
+ BlendDecomposedTransforms(&result, first, second, 0.25);
+ for (size_t i = 0; i < 4; ++i) {
+ EXPECT_TRUE(std::isfinite(result.quaternion[i]));
+ EXPECT_FALSE(std::isnan(result.quaternion[i]));
+ }
+}
+
} // namespace
} // namespace gfx
