CC: Allow cubic-bezier timing inputs outside the range [0, 1]

cc/animation/keyframed_animation_curve_unittest.cc

Index: cc/animation/keyframed_animation_curve_unittest.cc
diff --git a/cc/animation/keyframed_animation_curve_unittest.cc b/cc/animation/keyframed_animation_curve_unittest.cc
index 0fd8da926693c25213b9bbf5d29f5aa598efc409..dc8537dfea06e056ab64e7ab80e5fcc58108a80a 100644
--- a/cc/animation/keyframed_animation_curve_unittest.cc
+++ b/cc/animation/keyframed_animation_curve_unittest.cc
@@ -725,6 +725,68 @@ TEST(KeyframedAnimationCurveTest, CurveAndKeyframeTiming) {
   EXPECT_FLOAT_EQ(1.f, curve->GetValue(base::TimeDelta::FromSecondsD(2.f)));
 }
 
+// Tests that a linear timing function works as expected for inputs outside of

[Ian Vollick, 2015/01/05 15:36:04]

A couple of dumb questions.

I'm a bit confused by the term inputs here. Are you referring to the outputs of
the timing function which will be the inputs to the keyframe
interpolation/extrapolation?

Also, this test looks like it's using a cubic timing function; is linear in
reference to the keyframe timing function?

[loyso (OOO), 2015/01/06 02:24:53]

Yes. The outputs of per-curve timing function will be an input for per-keyframe
timing functions.
See the changelist here:
https://codereview.chromium.org/598853003/patch/80001/90001
TransformedAnimationTime function transforms time.
Yes, it tests per-keyframe linear timing function. Cubic per-curve timing
function is the only way to get input outside of range [0,1].

Overall, what's important. It's mentioned in original bug and I had to copy it
here:

We need to support this blink change:
https://codereview.chromium.org/238573002
for compositor-side animations.

So the main idea is to be consistent with the blink side. And we have a plan to
remove cc/blink redundant code in the future.

+// range [0,1]
+TEST(KeyframedAnimationCurveTest, LinearTimingInputsOutsideZeroOneRange) {
+  scoped_ptr<KeyframedFloatAnimationCurve> curve(
+      KeyframedFloatAnimationCurve::Create());
+  curve->AddKeyframe(FloatKeyframe::Create(base::TimeDelta(), 0.f, nullptr));
+  curve->AddKeyframe(
+      FloatKeyframe::Create(base::TimeDelta::FromSecondsD(1.0), 2.f, nullptr));
+  // Curve timing function producing timing outputs outside of range [0,1].
+  curve->SetTimingFunction(
+      CubicBezierTimingFunction::Create(0.5f, -0.5f, 0.5f, 1.5f).Pass());
+
+  EXPECT_NEAR(-0.076f, curve->GetValue(base::TimeDelta::FromSecondsD(0.25f)),
+              0.001f);
+  EXPECT_NEAR(2.076f, curve->GetValue(base::TimeDelta::FromSecondsD(0.75f)),
+              0.001f);
+}
+
+// If a curve cubic-bezier timing function produces timing outputs outside
+// the range [0, 1] then a keyframe cubic-bezier timing function
+// should consume that input properly (using end-point gradients).
+TEST(KeyframedAnimationCurveTest, CurveTimingInputsOutsideZeroOneRange) {
+  scoped_ptr<KeyframedFloatAnimationCurve> curve(
+      KeyframedFloatAnimationCurve::Create());
+  // Keyframe timing function with 0.5 gradients at each end.
+  curve->AddKeyframe(FloatKeyframe::Create(
+      base::TimeDelta(), 0.f,
+      CubicBezierTimingFunction::Create(0.5f, 0.25f, 0.5f, 0.75f).Pass()));
+  curve->AddKeyframe(
+      FloatKeyframe::Create(base::TimeDelta::FromSecondsD(1.f), 1.f, nullptr));
+  // Curve timing function producing timing outputs outside of range [0,1].
+  curve->SetTimingFunction(
+      CubicBezierTimingFunction::Create(0.5f, -0.5f, 0.5f, 1.5f).Pass());
+
+  EXPECT_NEAR(-0.02f, curve->GetValue(base::TimeDelta::FromSecondsD(0.25f)),
+              0.002f);  // c(.25)=-.04, -.04*0.5=-0.02
+  EXPECT_NEAR(0.33f, curve->GetValue(base::TimeDelta::FromSecondsD(0.46f)),
+              0.002f);  // c(.46)=.38, k(.38)=.33
+
+  EXPECT_NEAR(0.67f, curve->GetValue(base::TimeDelta::FromSecondsD(0.54f)),
+              0.002f);  // c(.54)=.62, k(.62)=.67
+  EXPECT_NEAR(1.02f, curve->GetValue(base::TimeDelta::FromSecondsD(0.75f)),
+              0.002f);  // c(.75)=1.04 1+.04*0.5=1.02
+}
+
+// Tests that a step timing function works as expected for inputs outside of
+// range [0,1]
+TEST(KeyframedAnimationCurveTest, StepsTimingInputsOutsideZeroOneRange) {
+  scoped_ptr<KeyframedFloatAnimationCurve> curve(
+      KeyframedFloatAnimationCurve::Create());
+  curve->AddKeyframe(FloatKeyframe::Create(
+      base::TimeDelta(), 0.f, StepsTimingFunction::Create(4, 0.5f)));
+  curve->AddKeyframe(
+      FloatKeyframe::Create(base::TimeDelta::FromSecondsD(1.0), 2.f, nullptr));
+  // Curve timing function producing timing outputs outside of range [0,1].
+  curve->SetTimingFunction(
+      CubicBezierTimingFunction::Create(0.5f, -0.5f, 0.5f, 1.5f).Pass());
+
+  EXPECT_FLOAT_EQ(0.f, curve->GetValue(base::TimeDelta::FromSecondsD(0.25f)));
+  EXPECT_FLOAT_EQ(2.f, curve->GetValue(base::TimeDelta::FromSecondsD(0.75f)));
+}
+
 // Tests that an animation with a curve timing function and multiple keyframes
 // works as expected.
 TEST(KeyframedAnimationCurveTest, CurveTimingMultipleKeyframes) {