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);
 }
 
 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;
+    if (sequenced_for_smooth_scroll_) {
+      sequenced_for_smooth_scroll_ = false;
+      GetScrollableArea()->GetSmoothScrollSequencer()->RunQueuedAnimations();

[bokan, 2017/05/15 17:15:28]

You need to handle the case where GetSmoothScrollSequencer returns nullptr (here
and anywhere else you call it).

[sunyunjia, 2017/05/19 16:24:29]

Done.

+    }
   } 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 73 matching lines @@
       ResetAnimationState();
       NotifyOffsetChanged(target_offset_);
     }
   }
 }
 
 void ProgrammaticScrollAnimator::NotifyCompositorAnimationFinished(
     int group_id) {
   DCHECK_NE(run_state_, RunState::kRunningOnCompositorButNeedsUpdate);
   ScrollAnimatorCompositorCoordinator::CompositorAnimationFinished(group_id);
+  if (sequenced_for_smooth_scroll_) {

[bokan, 2017/05/15 17:15:28]

Put these into an "AnimationFinished" helper and call that from both places.

[sunyunjia, 2017/05/19 16:24:29]

Done.

+    sequenced_for_smooth_scroll_ = false;
+    GetScrollableArea()->GetSmoothScrollSequencer()->RunQueuedAnimations();
+  }
 }
 
 DEFINE_TRACE(ProgrammaticScrollAnimator) {
   visitor->Trace(scrollable_area_);
   ScrollAnimatorCompositorCoordinator::Trace(visitor);
 }
 
 }  // namespace blink