CC: Add support for iteration start in animations

This adds support for iteration start property from Web Animations to compositor accelerated animations.

BUG=414890

Review URL: https://codereview.chromium.org/573053002

Cr-Commit-Position: refs/heads/master@{#295380}

5 files changed, 83 insertions, 20 deletions

diff --git a/cc/animation/animation.cc b/cc/animation/animation.cc
index 47ebaa3..dc26a3e 100644
--- a/cc/animation/animation.cc
+++ b/cc/animation/animation.cc
@@ -64,6 +64,7 @@ Animation::Animation(scoped_ptr<AnimationCurve> curve,
       target_property_(target_property),
       run_state_(WaitingForTargetAvailability),
       iterations_(1),
+      iteration_start_(0),
       direction_(Normal),
       playback_rate_(1),
       needs_synchronized_start_time_(false),
@@ -162,8 +163,9 @@ double Animation::TrimTimeToCurrentIteration(
     base::TimeTicks monotonic_time) const {
   base::TimeTicks trimmed = monotonic_time + time_offset_;
 
-  // Zero playback rate not supported
+  // Check for valid parameters
   DCHECK(playback_rate_);
+  DCHECK_GE(iteration_start_, 0);
 
   // If we're paused, time is 'stuck' at the pause time.
   if (run_state_ == Paused)
@@ -195,41 +197,36 @@ double Animation::TrimTimeToCurrentIteration(
 
   double repeated_duration = iterations_ * curve_->Duration();
   double active_duration = repeated_duration / std::abs(playback_rate_);
+  double start_offset = iteration_start_ * curve_->Duration();
 
   // Check if we are past active duration
-  bool is_past_active_duration =
-      iterations_ > 0 && active_time >= active_duration;
+  if (iterations_ > 0 && active_time >= active_duration)
+    active_time = active_duration;
 
   // Calculate the scaled active time
   double scaled_active_time;
   if (playback_rate_ < 0)
-    scaled_active_time = (active_time - active_duration) * playback_rate_;
+    scaled_active_time =
+        (active_time - active_duration) * playback_rate_ + start_offset;
   else
-    scaled_active_time = active_time * playback_rate_;
+    scaled_active_time = active_time * playback_rate_ + start_offset;
 
   // Calculate the iteration time
   double iteration_time;
-  if (is_past_active_duration) {
-    // If we are past the active interval, return iteration duration of last
-    // iteration
-    double frac = fmod(repeated_duration, curve_->Duration());
-    iteration_time =
-        frac == 0 && scaled_active_time > 0 ? curve_->Duration() : frac;
-  } else if (scaled_active_time == repeated_duration) {
+  if (scaled_active_time - start_offset == repeated_duration &&
+      fmod(iterations_ + iteration_start_, 1) == 0)
     iteration_time = curve_->Duration();
-  } else {
+  else
     iteration_time = fmod(scaled_active_time, curve_->Duration());
-  }
 
   // Calculate the current iteration
   int iteration;
-  if (scaled_active_time <= 0) {
+  if (scaled_active_time <= 0)
     iteration = 0;
-  } else if (is_past_active_duration || iteration_time == curve_->Duration()) {
-    iteration = iterations_ - 1;
-  } else {
+  else if (iteration_time == curve_->Duration())
+    iteration = ceil(iteration_start_ + iterations_ - 1);
+  else
     iteration = static_cast<int>(scaled_active_time / curve_->Duration());
-  }
 
   // Check if we are running the animation in reverse direction for the current
   // iteration
@@ -239,7 +236,7 @@ double Animation::TrimTimeToCurrentIteration(
 
   // If we are running the animation in reverse direction, reverse the result
   if (reverse)
-    return curve_->Duration() - iteration_time;
+    iteration_time = curve_->Duration() - iteration_time;
 
   return iteration_time;
 }
@@ -250,6 +247,7 @@ scoped_ptr<Animation> Animation::CloneAndInitialize(
       new Animation(curve_->Clone(), id_, group_, target_property_));
   to_return->run_state_ = initial_run_state;
   to_return->iterations_ = iterations_;
+  to_return->iteration_start_ = iteration_start_;
   to_return->start_time_ = start_time_;
   to_return->pause_time_ = pause_time_;
   to_return->total_paused_time_ = total_paused_time_;
diff --git a/cc/animation/animation.h b/cc/animation/animation.h
index aac6d7b..89b09ba 100644
--- a/cc/animation/animation.h
+++ b/cc/animation/animation.h
@@ -71,6 +71,11 @@ class CC_EXPORT Animation {
   double iterations() const { return iterations_; }
   void set_iterations(double n) { iterations_ = n; }
 
+  double iteration_start() const { return iteration_start_; }
+  void set_iteration_start(double iteration_start) {
+    iteration_start_ = iteration_start;
+  }
+
   base::TimeTicks start_time() const { return start_time_; }
 
   void set_start_time(base::TimeTicks monotonic_time) {
@@ -167,6 +172,7 @@ class CC_EXPORT Animation {
   TargetProperty target_property_;
   RunState run_state_;
   double iterations_;
+  double iteration_start_;
   base::TimeTicks start_time_;
   Direction direction_;
   double playback_rate_;
diff --git a/cc/animation/animation_unittest.cc b/cc/animation/animation_unittest.cc
index c9b215b..ab9c909 100644
--- a/cc/animation/animation_unittest.cc
+++ b/cc/animation/animation_unittest.cc
@@ -617,5 +617,54 @@ TEST(AnimationTest,
   EXPECT_EQ(0.0, anim->TrimTimeToCurrentIteration(TicksFromSecondsF(4.5)));
 }
 
+TEST(AnimationTest, TrimTimeIterationStart) {
+  scoped_ptr<Animation> anim(CreateAnimation(2, 1, 1));
+  anim->set_iteration_start(0.5);
+  EXPECT_EQ(0.5, anim->TrimTimeToCurrentIteration(TicksFromSecondsF(0.0)));
+  EXPECT_EQ(0.0, anim->TrimTimeToCurrentIteration(TicksFromSecondsF(0.5)));
+  EXPECT_EQ(0.5, anim->TrimTimeToCurrentIteration(TicksFromSecondsF(1.0)));
+  EXPECT_EQ(0.0, anim->TrimTimeToCurrentIteration(TicksFromSecondsF(1.5)));
+  EXPECT_EQ(0.5, anim->TrimTimeToCurrentIteration(TicksFromSecondsF(2.0)));
+  EXPECT_EQ(0.5, anim->TrimTimeToCurrentIteration(TicksFromSecondsF(2.5)));
+}
+
+TEST(AnimationTest, TrimTimeIterationStartAlternate) {
+  scoped_ptr<Animation> anim(CreateAnimation(2, 1, 1));
+  anim->set_direction(Animation::Alternate);
+  anim->set_iteration_start(0.3);
+  EXPECT_EQ(0.3, anim->TrimTimeToCurrentIteration(TicksFromSecondsF(0.0)));
+  EXPECT_EQ(0.8, anim->TrimTimeToCurrentIteration(TicksFromSecondsF(0.5)));
+  EXPECT_EQ(1.0, anim->TrimTimeToCurrentIteration(TicksFromSecondsF(0.7)));
+  EXPECT_EQ(0.7, anim->TrimTimeToCurrentIteration(TicksFromSecondsF(1.0)));
+  EXPECT_EQ(0.5, anim->TrimTimeToCurrentIteration(TicksFromSecondsF(1.2)));
+  EXPECT_EQ(0.0, anim->TrimTimeToCurrentIteration(TicksFromSecondsF(1.7)));
+}
+
+TEST(AnimationTest, TrimTimeIterationStartAlternateThreeIterations) {
+  scoped_ptr<Animation> anim(CreateAnimation(3, 1, 1));
+  anim->set_direction(Animation::Alternate);
+  anim->set_iteration_start(1);
+  EXPECT_EQ(1.0, anim->TrimTimeToCurrentIteration(TicksFromSecondsF(0.0)));
+  EXPECT_EQ(0.5, anim->TrimTimeToCurrentIteration(TicksFromSecondsF(0.5)));
+  EXPECT_EQ(0.0, anim->TrimTimeToCurrentIteration(TicksFromSecondsF(1.0)));
+  EXPECT_EQ(0.5, anim->TrimTimeToCurrentIteration(TicksFromSecondsF(1.5)));
+  EXPECT_EQ(1.0, anim->TrimTimeToCurrentIteration(TicksFromSecondsF(2.0)));
+  EXPECT_EQ(0.5, anim->TrimTimeToCurrentIteration(TicksFromSecondsF(2.5)));
+  EXPECT_EQ(0.0, anim->TrimTimeToCurrentIteration(TicksFromSecondsF(3.0)));
+  EXPECT_EQ(0.0, anim->TrimTimeToCurrentIteration(TicksFromSecondsF(3.5)));
+}
+
+TEST(AnimationTest,
+     TrimTimeIterationStartAlternateThreeIterationsPlaybackReverse) {
+  scoped_ptr<Animation> anim(CreateAnimation(3, 1, -1));
+  anim->set_direction(Animation::Alternate);
+  anim->set_iteration_start(1);
+  EXPECT_EQ(0.0, anim->TrimTimeToCurrentIteration(TicksFromSecondsF(0.0)));
+  EXPECT_EQ(1.0, anim->TrimTimeToCurrentIteration(TicksFromSecondsF(1.0)));
+  EXPECT_EQ(0.0, anim->TrimTimeToCurrentIteration(TicksFromSecondsF(2.0)));
+  EXPECT_EQ(1.0, anim->TrimTimeToCurrentIteration(TicksFromSecondsF(3.0)));
+  EXPECT_EQ(1.0, anim->TrimTimeToCurrentIteration(TicksFromSecondsF(3.5)));
+}
+
 }  // namespace
 }  // namespace cc
diff --git a/cc/blink/web_animation_impl.cc b/cc/blink/web_animation_impl.cc
index 1f19937..a819cec 100644
--- a/cc/blink/web_animation_impl.cc
+++ b/cc/blink/web_animation_impl.cc
@@ -97,6 +97,14 @@ void WebCompositorAnimationImpl::setIterations(int n) {
 }
 #endif
 
+double WebCompositorAnimationImpl::iterationStart() const {
+  return animation_->iteration_start();
+}
+
+void WebCompositorAnimationImpl::setIterationStart(double iteration_start) {
+  animation_->set_iteration_start(iteration_start);
+}
+
 double WebCompositorAnimationImpl::startTime() const {
   return (animation_->start_time() - base::TimeTicks()).InSecondsF();
 }
diff --git a/cc/blink/web_animation_impl.h b/cc/blink/web_animation_impl.h
index f2b2f07..1c61af0 100644
--- a/cc/blink/web_animation_impl.h
+++ b/cc/blink/web_animation_impl.h
@@ -38,6 +38,8 @@ class WebCompositorAnimationImpl : public blink::WebCompositorAnimation {
   virtual int iterations() const;
   virtual void setIterations(int iterations);
 #endif
+  virtual double iterationStart() const;
+  virtual void setIterationStart(double iteration_start);
   virtual double startTime() const;
   virtual void setStartTime(double monotonic_time);
   virtual double timeOffset() const;