[animation worklet] CurrentTime from DocumentTimeline should be offset by StartTime

Currently upon collecting the inputs for the mutation on main thread, we
don't offset the current time by the start time which is incorrect.

Note:
The layout test animations/animationworklet/worklet-animation-currentTime.html
fails the release build because AnimationClock::currentTime is often
incorrectly ahead of rAF time so that when asking for the current time
in a rAF via getComputedStyle it returns obsolete result. This bug is
tracked by https://crbug.com/785940.

Bug: 905405
Change-Id: I0b7e293ae942e47b96eb8a7a2a8fefd94be66773
Reviewed-on: https://chromium-review.googlesource.com/c/1343558
Commit-Queue: Yi Gu <yigu@chromium.org>
Reviewed-by: Majid Valipour <majidvp@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612238}

third_party/blink/renderer/modules/animationworklet/worklet_animation.cc

@@ -619,6 +619,17 @@ bool WorkletAnimation::IsActiveAnimation() const {
   return IsActive(play_state_);
 }
 
+base::Optional<double> WorkletAnimation::CurrentTime() const {
+  bool is_null;
+  double timeline_time = timeline_->currentTime(is_null);
+  if (is_null)
+    return base::nullopt;
+  if (timeline_->IsScrollTimeline())
+    return timeline_time;
+  DCHECK(start_time_);
+  return timeline_time - start_time_->InSecondsF();
+}
+
 void WorkletAnimation::UpdateInputState(
     AnimationWorkletDispatcherInput* input_state) {
   if (!running_on_main_thread_) {
@@ -632,8 +643,8 @@ void WorkletAnimation::UpdateInputState(
   // ScrollTimeline animation doesn't require start_time_ to be set.
   DCHECK(start_time_ || timeline_->IsScrollTimeline());
   DCHECK(last_current_time_ || !was_active);
-  bool is_null;
-  double current_time = timeline_->currentTime(is_null);
+  double current_time =
+      CurrentTime().value_or(std::numeric_limits<double>::quiet_NaN());
 
   bool did_time_change =
       !last_current_time_ || current_time != last_current_time_->InSecondsF();
@@ -641,10 +652,7 @@ void WorkletAnimation::UpdateInputState(
   // is resolved, we apply the last current time to the animation if the scroll
   // timeline becomes newly inactive. See https://crbug.com/906050.
   last_current_time_ = base::TimeDelta::FromSecondsD(current_time);
-
   if (!was_active && is_active) {
-    // TODO(yigu): current_time should be offset by start_time_ for animations
-    // with document timeline. https://crbug.com/905405.
     input_state->Add(
         {id_,
          std::string(animator_name_.Ascii().data(), animator_name_.length()),

third_party/blink/renderer/modules/animationworklet/worklet_animation.h

@@ -145,6 +145,7 @@ class MODULES_EXPORT WorkletAnimation : public WorkletAnimationBase,
   void SetPlayState(const Animation::AnimationPlayState& state) {
     play_state_ = state;
   }
+  base::Optional<double> CurrentTime() const;
 
   unsigned sequence_number_;
 

third_party/blink/renderer/modules/animationworklet/worklet_animation_test.cc

@@ -10,7 +10,9 @@
 #include "third_party/blink/renderer/core/animation/element_animations.h"
 #include "third_party/blink/renderer/core/animation/keyframe_effect.h"
 #include "third_party/blink/renderer/core/animation/keyframe_effect_model.h"
+#include "third_party/blink/renderer/core/animation/scroll_timeline.h"
 #include "third_party/blink/renderer/core/dom/document.h"
+#include "third_party/blink/renderer/core/paint/paint_layer_scrollable_area.h"
 #include "third_party/blink/renderer/core/testing/core_unit_test_helper.h"
 #include "third_party/blink/renderer/core/testing/dummy_page_holder.h"
 
@@ -39,12 +41,16 @@ KeyframeEffect* CreateKeyframeEffect(Element* element) {
   return KeyframeEffect::Create(element, CreateEffectModel(), timing);
 }
 
-WorkletAnimation* CreateWorkletAnimation(ScriptState* script_state,
-                                         Element* element) {
+WorkletAnimation* CreateWorkletAnimation(
+    ScriptState* script_state,
+    Element* element,
+    ScrollTimeline* scroll_timeline = nullptr) {
   AnimationEffectOrAnimationEffectSequence effects;
   AnimationEffect* effect = CreateKeyframeEffect(element);
   effects.SetAnimationEffect(effect);
   DocumentTimelineOrScrollTimeline timeline;
+  if (scroll_timeline)
+    timeline.SetScrollTimeline(scroll_timeline);
   scoped_refptr<SerializedScriptValue> options;
 
   ScriptState::Scope scope(script_state);
@@ -95,4 +101,84 @@ TEST_F(WorkletAnimationTest, StyleHasCurrentAnimation) {
   EXPECT_EQ(true, style->HasCurrentOpacityAnimation());
 }
 
+TEST_F(WorkletAnimationTest,
+       CurrentTimeFromDocumentTimelineIsOffsetByStartTime) {
+  GetDocument().GetAnimationClock().ResetTimeForTesting();
+  double error = base::TimeDelta::FromMicrosecondsD(1).InMillisecondsF();
+  WorkletAnimationId id = worklet_animation_->GetWorkletAnimationId();
+  base::TimeTicks first_ticks =
+      base::TimeTicks() + base::TimeDelta::FromMillisecondsD(111);
+  base::TimeTicks second_ticks =
+      base::TimeTicks() + base::TimeDelta::FromMillisecondsD(111 + 123.4);
+
+  GetDocument().GetAnimationClock().UpdateTime(first_ticks);
+  DummyExceptionStateForTesting exception_state;
+  worklet_animation_->play(exception_state);
+  worklet_animation_->UpdateCompositingState();
+
+  std::unique_ptr<AnimationWorkletDispatcherInput> state =
+      std::make_unique<AnimationWorkletDispatcherInput>();
+  worklet_animation_->UpdateInputState(state.get());
+  // First state request sets the start time and thus current time should be 0.
+  std::unique_ptr<AnimationWorkletInput> input =
+      state->TakeWorkletState(id.scope_id);
+  EXPECT_NEAR(0, input->added_and_updated_animations[0].current_time, error);
+  state.reset(new AnimationWorkletDispatcherInput);
+  GetDocument().GetAnimationClock().UpdateTime(second_ticks);
+  worklet_animation_->UpdateInputState(state.get());
+  input = state->TakeWorkletState(id.scope_id);
+  EXPECT_NEAR(123.4, input->updated_animations[0].current_time, error);
+}
+
+TEST_F(WorkletAnimationTest,
+       CurrentTimeFromScrollTimelineNotOffsetByStartTime) {
+  SetBodyInnerHTML(R"HTML(
+    <style>
+      #scroller { overflow: scroll; width: 100px; height: 100px; }
+      #spacer { width: 200px; height: 200px; }
+    </style>
+    <div id='scroller'>
+      <div id ='spacer'></div>
+    </div>
+  )HTML");
+
+  LayoutBoxModelObject* scroller =
+      ToLayoutBoxModelObject(GetLayoutObjectByElementId("scroller"));
+  ASSERT_TRUE(scroller);
+  ASSERT_TRUE(scroller->HasOverflowClip());
+  PaintLayerScrollableArea* scrollable_area = scroller->GetScrollableArea();
+  ASSERT_TRUE(scrollable_area);
+  scrollable_area->SetScrollOffset(ScrollOffset(0, 20), kProgrammaticScroll);
+  ScrollTimelineOptions* options = ScrollTimelineOptions::Create();
+  DoubleOrScrollTimelineAutoKeyword time_range =
+      DoubleOrScrollTimelineAutoKeyword::FromDouble(100);
+  options->setTimeRange(time_range);
+  options->setScrollSource(GetElementById("scroller"));
+  ScrollTimeline* scroll_timeline =
+      ScrollTimeline::Create(GetDocument(), options, ASSERT_NO_EXCEPTION);
+  WorkletAnimation* worklet_animation =
+      CreateWorkletAnimation(GetScriptState(), element_, scroll_timeline);
+  WorkletAnimationId id = worklet_animation->GetWorkletAnimationId();
+
+  DummyExceptionStateForTesting exception_state;
+  worklet_animation->play(exception_state);
+  worklet_animation->UpdateCompositingState();
+
+  double error = base::TimeDelta::FromMicrosecondsD(1).InMillisecondsF();
+  scrollable_area->SetScrollOffset(ScrollOffset(0, 40), kProgrammaticScroll);
+  std::unique_ptr<AnimationWorkletDispatcherInput> state =
+      std::make_unique<AnimationWorkletDispatcherInput>();
+  worklet_animation->UpdateInputState(state.get());
+  std::unique_ptr<AnimationWorkletInput> input =
+      state->TakeWorkletState(id.scope_id);
+
+  EXPECT_NEAR(40, input->added_and_updated_animations[0].current_time, error);
+  state.reset(new AnimationWorkletDispatcherInput);
+
+  scrollable_area->SetScrollOffset(ScrollOffset(0, 70), kProgrammaticScroll);
+  worklet_animation->UpdateInputState(state.get());
+  input = state->TakeWorkletState(id.scope_id);
+  EXPECT_NEAR(70, input->updated_animations[0].current_time, error);
+}
+
 }  //  namespace blink

third_party/blink/web_tests/TestExpectations

@@ -5606,6 +5606,7 @@ crbug.com/886566 http/tests/csspaint/invalidation-border-image.html [ Pass Timeo
 crbug.com/886566 http/tests/csspaint/invalidation-content-image.html [ Pass Timeout ]
 
 # Enable AnimationWorklet tests for mainthread
+crbug.com/785940 [ Release ] animations/animationworklet/worklet-animation-local-time-after-duration.html [ Pass Failure ]
 crbug.com/887659 virtual/threaded/animations/animationworklet/worklet-animation-local-time-after-duration.html [ Failure ]
 
 # Sheriff 2018-09-25