Implement Element.scrollIntoView for scroll-behavior: smooth.

third_party/WebKit/Source/platform/scroll/ProgrammaticScrollAnimator.cpp

 // Copyright 2014 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.
 
 #include "platform/scroll/ProgrammaticScrollAnimator.h"
 
 #include <memory>
 #include "platform/animation/CompositorAnimation.h"
 #include "platform/animation/CompositorScrollOffsetAnimationCurve.h"
 #include "platform/geometry/IntSize.h"
 #include "platform/graphics/GraphicsLayer.h"
 #include "platform/scroll/ScrollableArea.h"
+#include "platform/scroll/SmoothScrollSequencer.h"
 #include "platform/wtf/PtrUtil.h"
 #include "public/platform/Platform.h"
 #include "public/platform/WebCompositorSupport.h"
 
 namespace blink {
 
 ProgrammaticScrollAnimator::ProgrammaticScrollAnimator(
     ScrollableArea* scrollable_area)
     : scrollable_area_(scrollable_area), start_time_(0.0) {}
 
 ProgrammaticScrollAnimator::~ProgrammaticScrollAnimator() {}
 
 void ProgrammaticScrollAnimator::ResetAnimationState() {
   ScrollAnimatorCompositorCoordinator::ResetAnimationState();
   animation_curve_.reset();
   start_time_ = 0.0;
 }
 
 void ProgrammaticScrollAnimator::NotifyOffsetChanged(
     const ScrollOffset& offset) {
-  ScrollOffsetChanged(offset, kProgrammaticScroll);
+  if (sequenced_for_smooth_scroll_)

[bokan, 2017/06/07 17:56:00]

nit: scroll_type = sequenced_for_smooth_scroll ? kSequenced : kProgrammatic

[sunyunjia, 2017/06/07 18:34:10]

Done.

+    ScrollOffsetChanged(offset, kSequencedSmoothScroll);
+  else
+    ScrollOffsetChanged(offset, kProgrammaticScroll);
 }
 
 void ProgrammaticScrollAnimator::ScrollToOffsetWithoutAnimation(
     const ScrollOffset& offset) {
   CancelAnimation();
   NotifyOffsetChanged(offset);
 }
 
-void ProgrammaticScrollAnimator::AnimateToOffset(const ScrollOffset& offset) {
+void ProgrammaticScrollAnimator::AnimateToOffset(
+    const ScrollOffset& offset,
+    bool sequenced_for_smooth_scroll) {
   if (run_state_ == RunState::kPostAnimationCleanup)
     ResetAnimationState();
 
   start_time_ = 0.0;
   target_offset_ = offset;
+  sequenced_for_smooth_scroll_ = sequenced_for_smooth_scroll;
   animation_curve_ = CompositorScrollOffsetAnimationCurve::Create(
       CompositorOffsetFromBlinkOffset(target_offset_),
       CompositorScrollOffsetAnimationCurve::kScrollDurationDeltaBased);
 
   scrollable_area_->RegisterForAnimation();
   if (!scrollable_area_->ScheduleAnimation()) {
     ResetAnimationState();
     NotifyOffsetChanged(offset);
   }
   run_state_ = RunState::kWaitingToSendToCompositor;
@@ skipping 11 matching lines @@
   if (!start_time_)
     start_time_ = monotonic_time;
   double elapsed_time = monotonic_time - start_time_;
   bool is_finished = (elapsed_time > animation_curve_->Duration());
   ScrollOffset offset =
       BlinkOffsetFromCompositorOffset(animation_curve_->GetValue(elapsed_time));
   NotifyOffsetChanged(offset);
 
   if (is_finished) {
     run_state_ = RunState::kPostAnimationCleanup;
+    AnimationFinished();
   } else if (!scrollable_area_->ScheduleAnimation()) {
     NotifyOffsetChanged(offset);
     ResetAnimationState();
   }
 }
 
 void ProgrammaticScrollAnimator::UpdateCompositorAnimations() {
   if (run_state_ == RunState::kPostAnimationCleanup) {
     // No special cleanup, simply reset animation state. We have this state
     // here because the state machine is shared with ScrollAnimator which
@@ skipping 20 matching lines @@
     }
   }
 
   if (run_state_ == RunState::kWaitingToSendToCompositor) {
     if (!compositor_animation_attached_to_element_id_)
       ReattachCompositorPlayerIfNeeded(
           GetScrollableArea()->GetCompositorAnimationTimeline());
 
     bool sent_to_compositor = false;
 
-    if (!scrollable_area_->ShouldScrollOnMainThread()) {
+    // TODO(sunyunjia): Sequenced Smooth Scroll should also be able to
+    // scroll on the compositor thread. We should send the ScrollType
+    // information to the compositor thread.

[bokan, 2017/06/07 17:56:53]

Oh, and please file a bug to make this work with compositor. Add the bug # here.

[sunyunjia, 2017/06/07 18:34:10]

Done.

+    if (!scrollable_area_->ShouldScrollOnMainThread() &&
+        !sequenced_for_smooth_scroll_) {
       std::unique_ptr<CompositorAnimation> animation =
           CompositorAnimation::Create(
               *animation_curve_, CompositorTargetProperty::SCROLL_OFFSET, 0, 0);
 
       int animation_id = animation->Id();
       int animation_group_id = animation->Group();
 
       if (AddAnimation(std::move(animation))) {
         sent_to_compositor = true;
         run_state_ = RunState::kRunningOnCompositor;
@@ skipping 32 matching lines @@
       ResetAnimationState();
       NotifyOffsetChanged(target_offset_);
     }
   }
 }
 
 void ProgrammaticScrollAnimator::NotifyCompositorAnimationFinished(
     int group_id) {
   DCHECK_NE(run_state_, RunState::kRunningOnCompositorButNeedsUpdate);
   ScrollAnimatorCompositorCoordinator::CompositorAnimationFinished(group_id);
+  AnimationFinished();
+}
+
+void ProgrammaticScrollAnimator::AnimationFinished() {
+  if (sequenced_for_smooth_scroll_) {
+    sequenced_for_smooth_scroll_ = false;
+    if (SmoothScrollSequencer* sequencer =
+            GetScrollableArea()->GetSmoothScrollSequencer())
+      sequencer->RunQueuedAnimations();
+  }
 }
 
 DEFINE_TRACE(ProgrammaticScrollAnimator) {
   visitor->Trace(scrollable_area_);
   ScrollAnimatorCompositorCoordinator::Trace(visitor);
 }
 
 }  // namespace blink