Implement Element.scrollIntoView for scroll-behavior: smooth.

third_party/WebKit/Source/core/layout/LayoutBox.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc.
  *               All rights reserved.
  * Copyright (C) 2013 Adobe Systems Incorporated. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 627 matching lines @@
              frame_element_base->ScrollingMode() == kScrollbarAlwaysOff;
     }
   }
   return false;
 }
 
 void LayoutBox::ScrollRectToVisible(const LayoutRect& rect,
                                     const ScrollAlignment& align_x,
                                     const ScrollAlignment& align_y,
                                     ScrollType scroll_type,
-                                    bool make_visible_in_visual_viewport) {
+                                    bool make_visible_in_visual_viewport,
+                                    ScrollBehavior scroll_behavior) {
   DCHECK(scroll_type == kProgrammaticScroll || scroll_type == kUserScroll);
   // Presumably the same issue as in setScrollTop. See crbug.com/343132.
   DisableCompositingQueryAsserts disabler;
 
   LayoutRect rect_to_scroll = rect;
   if (rect_to_scroll.Width() <= 0)
     rect_to_scroll.SetWidth(LayoutUnit(1));
   if (rect_to_scroll.Height() <= 0)
     rect_to_scroll.SetHeight(LayoutUnit(1));
 
   LayoutBox* parent_box = nullptr;
   LayoutRect new_rect = rect_to_scroll;
 
   bool restricted_by_line_clamp = false;
   if (ContainingBlock()) {
     parent_box = ContainingBlock();
     restricted_by_line_clamp =
         !ContainingBlock()->Style()->LineClamp().IsNone();
   }
 
+  bool is_smooth = false;
+  if (scroll_behavior == kScrollBehaviorSmooth ||
+      (scroll_behavior == kScrollBehaviorAuto &&
+       Style()->GetScrollBehavior() == kScrollBehaviorSmooth)) {
+    is_smooth = true;

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

This is another way of saying:

bool is_smooth = 
    scroll_behavior == kScrollBehaviorSmooth ||
        (scroll_behavior == kScrollBehaviorAuto && 
         Style()->GetScrollBehavior() == kScrollBehaviorSmooth);

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

Done.

+  }
+
   if (HasOverflowClip() && !restricted_by_line_clamp) {
     // Don't scroll to reveal an overflow layer that is restricted by the
     // -webkit-line-clamp property. This will prevent us from revealing text
     // hidden by the slider in Safari RSS.
     // TODO(eae): We probably don't need this any more as we don't share any
     //            code with the Safari RSS reeder.
-    new_rect = GetScrollableArea()->ScrollIntoView(rect_to_scroll, align_x,
-                                                   align_y, scroll_type);
+    new_rect = GetScrollableArea()->ScrollIntoView(
+        rect_to_scroll, align_x, align_y, scroll_type, is_smooth);
     if (new_rect.IsEmpty())
       return;
   } else if (!parent_box && CanBeProgramaticallyScrolled()) {
     if (FrameView* frame_view = this->GetFrameView()) {
       HTMLFrameOwnerElement* owner_element = GetDocument().LocalOwner();
       if (!IsDisallowedAutoscroll(owner_element, frame_view)) {
         if (make_visible_in_visual_viewport) {
           frame_view->GetScrollableArea()->ScrollIntoView(
-              rect_to_scroll, align_x, align_y, scroll_type);
+              rect_to_scroll, align_x, align_y, scroll_type, is_smooth);
         } else {
           frame_view->LayoutViewportScrollableArea()->ScrollIntoView(
-              rect_to_scroll, align_x, align_y, scroll_type);
+              rect_to_scroll, align_x, align_y, scroll_type, is_smooth);
         }
         if (owner_element && owner_element->GetLayoutObject()) {
           if (frame_view->SafeToPropagateScrollToParent()) {
             parent_box = owner_element->GetLayoutObject()->EnclosingBox();
             LayoutView* parent_view = owner_element->GetLayoutObject()->View();
             new_rect = EnclosingLayoutRect(
                 View()
                     ->LocalToAncestorQuad(
                         FloatRect(rect_to_scroll), parent_view,
                         kUseTransforms | kTraverseDocumentBoundaries)
                     .BoundingBox());
           } else {
             parent_box = nullptr;
           }
         }
       }
     }
   }
 
   // If we are fixed-position and stick to the viewport, it is useless to
   // scroll the parent.
   if (Style()->GetPosition() == EPosition::kFixed &&
       ContainerForFixedPosition() == View()) {
     return;
   }
 
   if (GetFrame()->GetPage()->GetAutoscrollController().AutoscrollInProgress())
     parent_box = EnclosingScrollableBox();
 
-  if (parent_box)
+  if (parent_box) {
     parent_box->ScrollRectToVisible(new_rect, align_x, align_y, scroll_type,
-                                    make_visible_in_visual_viewport);
+                                    make_visible_in_visual_viewport,
+                                    scroll_behavior);
+  }
 }
 
 void LayoutBox::AbsoluteRects(Vector<IntRect>& rects,
                               const LayoutPoint& accumulated_offset) const {
   rects.push_back(PixelSnappedIntRect(accumulated_offset, Size()));
 }
 
 void LayoutBox::AbsoluteQuads(Vector<FloatQuad>& quads,
                               MapCoordinatesFlags mode) const {
   if (LayoutFlowThread* flow_thread = FlowThreadContainingBlock()) {
@@ skipping 5130 matching lines @@
 void LayoutBox::MutableForPainting::
     SavePreviousContentBoxSizeAndLayoutOverflowRect() {
   auto& rare_data = GetLayoutBox().EnsureRareData();
   rare_data.has_previous_content_box_size_and_layout_overflow_rect_ = true;
   rare_data.previous_content_box_size_ = GetLayoutBox().ContentBoxRect().Size();
   rare_data.previous_layout_overflow_rect_ =
       GetLayoutBox().LayoutOverflowRect();
 }
 
 }  // namespace blink