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 612 matching lines @@
              frameElementBase->scrollingMode() == ScrollbarAlwaysOff;
     }
   }
   return false;
 }
 
 void LayoutBox::scrollRectToVisible(const LayoutRect& rect,
                                     const ScrollAlignment& alignX,
                                     const ScrollAlignment& alignY,
                                     ScrollType scrollType,
-                                    bool makeVisibleInVisualViewport) {
+                                    bool makeVisibleInVisualViewport,
+                                    ScrollBehavior scrollBehavior) {
   ASSERT(scrollType == ProgrammaticScroll || scrollType == UserScroll);
   // Presumably the same issue as in setScrollTop. See crbug.com/343132.
   DisableCompositingQueryAsserts disabler;
 
   LayoutRect rectToScroll = rect;
   if (rectToScroll.width() <= 0)
     rectToScroll.setWidth(LayoutUnit(1));
   if (rectToScroll.height() <= 0)
     rectToScroll.setHeight(LayoutUnit(1));
 
   LayoutBox* parentBox = nullptr;
   LayoutRect newRect = rectToScroll;
 
   bool restrictedByLineClamp = false;
   if (containingBlock()) {
     parentBox = containingBlock();
     restrictedByLineClamp = !containingBlock()->style()->lineClamp().isNone();
   }
 
+  ScrollBehavior behavior = ScrollBehaviorAuto;

[bokan, 2017/02/21 21:33:00]

This should be ScrollBehaviorInstant so that we pass either Smooth or Instant to
scrollIntoView. scrollIntoView should either DCHECK that it's not Auto or make
the param an isSmooth bool.

[sunyunjia, 2017/02/24 19:11:48]

Done.

+  if (scrollBehavior == ScrollBehaviorSmooth ||
+      (scrollBehavior == ScrollBehaviorAuto &&
+       style()->getScrollBehavior() == ScrollBehaviorSmooth)) {
+    behavior = ScrollBehaviorSmooth;
+  }
+
   if (hasOverflowClip() && !restrictedByLineClamp) {
     // 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.
     newRect = getScrollableArea()->scrollIntoView(rectToScroll, alignX, alignY,
-                                                  scrollType);
+                                                  scrollType, behavior);
     if (newRect.isEmpty())
       return;
   } else if (!parentBox && canBeProgramaticallyScrolled()) {
     if (FrameView* frameView = this->frameView()) {
       HTMLFrameOwnerElement* ownerElement = document().localOwner();
       if (!isDisallowedAutoscroll(ownerElement, frameView)) {
         if (makeVisibleInVisualViewport) {
-          frameView->getScrollableArea()->scrollIntoView(rectToScroll, alignX,
-                                                         alignY, scrollType);
+          frameView->getScrollableArea()->scrollIntoView(
+              rectToScroll, alignX, alignY, scrollType, behavior);
         } else {
           frameView->layoutViewportScrollableArea()->scrollIntoView(
-              rectToScroll, alignX, alignY, scrollType);
+              rectToScroll, alignX, alignY, scrollType, behavior);
         }
         if (ownerElement && ownerElement->layoutObject()) {
           if (frameView->safeToPropagateScrollToParent()) {
             parentBox = ownerElement->layoutObject()->enclosingBox();
             LayoutView* parentView = ownerElement->layoutObject()->view();
             newRect = enclosingLayoutRect(
                 view()
                     ->localToAncestorQuad(
                         FloatRect(rectToScroll), parentView,
                         UseTransforms | TraverseDocumentBoundaries)
                     .boundingBox());
           } else {
             parentBox = nullptr;
           }
         }
       }
     }
   }
 
   // If we are fixed-position and stick to the viewport, it is useless to
   // scroll the parent.
   if (style()->position() == FixedPosition &&
       containerForFixedPosition() == view()) {
     return;
   }
 
   if (frame()->page()->autoscrollController().autoscrollInProgress())
     parentBox = enclosingScrollableBox();
 
-  if (parentBox)
+  if (parentBox) {
     parentBox->scrollRectToVisible(newRect, alignX, alignY, scrollType,
-                                   makeVisibleInVisualViewport);
+                                   makeVisibleInVisualViewport, scrollBehavior);
+  }
 }
 
 void LayoutBox::absoluteRects(Vector<IntRect>& rects,
                               const LayoutPoint& accumulatedOffset) const {
   rects.push_back(pixelSnappedIntRect(accumulatedOffset, size()));
 }
 
 void LayoutBox::absoluteQuads(Vector<FloatQuad>& quads,
                               MapCoordinatesFlags mode) const {
   if (LayoutFlowThread* flowThread = flowThreadContainingBlock()) {
@@ skipping 4979 matching lines @@
     block->adjustChildDebugRect(rect);
 
   return rect;
 }
 
 bool LayoutBox::shouldClipOverflow() const {
   return hasOverflowClip() || styleRef().containsPaint() || hasControlClip();
 }
 
 }  // namespace blink