Refactor ScrollableArea::setScrollPosition.

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
  * modify it under the terms of the GNU Library General Public
@@ skipping 238 matching lines @@
       if (isOrthogonalWritingModeRoot())
         markOrthogonalWritingModeRoot();
       else
         unmarkOrthogonalWritingModeRoot();
     }
 
     clearPercentHeightDescendants();
   }
 
   // If our zoom factor changes and we have a defined scrollLeft/Top, we need to adjust that value into the
-  // new zoomed coordinate space.
+  // new zoomed coordinate space.  Note that the new scroll position may be outside the normal min/max
+  // range of the scrollable area, which is weird but OK, because the scrollable area will update its
+  // min/max in updateAfterLayout().
   if (hasOverflowClip() && oldStyle &&
       oldStyle->effectiveZoom() != newStyle.effectiveZoom()) {
     PaintLayerScrollableArea* scrollableArea = this->getScrollableArea();
     ASSERT(scrollableArea);
-    if (int left = scrollableArea->scrollXOffset()) {
-      left = (left / oldStyle->effectiveZoom()) * newStyle.effectiveZoom();
-      scrollableArea->scrollToXOffset(left);
-    }
-    if (int top = scrollableArea->scrollYOffset()) {
-      top = (top / oldStyle->effectiveZoom()) * newStyle.effectiveZoom();
-      scrollableArea->scrollToYOffset(top);
+    // We use scrollPosition() rather than offsetFromOrigin(), because scrollPosition is the distance
+    // from the beginning of flow for the box, which is the dimension we want to preserve.
+    DoublePoint oldPosition = scrollableArea->scrollPositionDouble();
+    if (oldPosition.x() || oldPosition.y()) {
+      DoublePoint newPosition = oldPosition.scaledBy(newStyle.effectiveZoom() /
+                                                     oldStyle->effectiveZoom());
+      scrollableArea->setScrollPositionUnconditionally(newPosition);
     }
   }
 
   // Our opaqueness might have changed without triggering layout.
   if (diff.needsPaintInvalidation()) {
     LayoutObject* parentToInvalidate = parent();
     for (unsigned i = 0;
          i < backgroundObscurationTestMaxDepth && parentToInvalidate; ++i) {
       parentToInvalidate->invalidateBackgroundObscurationStatus();
       parentToInvalidate = parentToInvalidate->parent();
@@ skipping 224 matching lines @@
 
 LayoutUnit LayoutBox::scrollHeight() const {
   if (hasOverflowClip())
     return getScrollableArea()->scrollHeight();
   // For objects with visible overflow, this matches IE.
   // FIXME: Need to work right with writing modes.
   return std::max(clientHeight(), layoutOverflowRect().maxY() - borderTop());
 }
 
 LayoutUnit LayoutBox::scrollLeft() const {
-  return hasOverflowClip() ? LayoutUnit(getScrollableArea()->scrollXOffset())
-                           : LayoutUnit();
+  return hasOverflowClip()
+             ? LayoutUnit(getScrollableArea()->offsetFromOrigin().width())
+             : LayoutUnit();
 }
 
 LayoutUnit LayoutBox::scrollTop() const {
-  return hasOverflowClip() ? LayoutUnit(getScrollableArea()->scrollYOffset())
-                           : LayoutUnit();
+  return hasOverflowClip()
+             ? LayoutUnit(getScrollableArea()->offsetFromOrigin().height())
+             : LayoutUnit();
 }
 
 int LayoutBox::pixelSnappedScrollWidth() const {
   return snapSizeToPixel(scrollWidth(), location().x() + clientLeft());
 }
 
 int LayoutBox::pixelSnappedScrollHeight() const {
   if (hasOverflowClip())
     return snapSizeToPixel(getScrollableArea()->scrollHeight(),
                            location().y() + clientTop());
   // For objects with visible overflow, this matches IE.
   // FIXME: Need to work right with writing modes.
   return snapSizeToPixel(scrollHeight(), location().y() + clientTop());
 }
 
 void LayoutBox::setScrollLeft(LayoutUnit newLeft) {
   // This doesn't hit in any tests, but since the equivalent code in setScrollTop
   // does, presumably this code does as well.
   DisableCompositingQueryAsserts disabler;
 
-  if (hasOverflowClip())
-    getScrollableArea()->scrollToXOffset(newLeft, ScrollOffsetClamped,
-                                         ScrollBehaviorAuto);
+  if (!hasOverflowClip())
+    return;
+
+  PaintLayerScrollableArea* scrollableArea = getScrollableArea();
+  DoubleSize newOffset(newLeft, scrollableArea->offsetFromOrigin().height());
+  scrollableArea->scrollToOffsetFromOrigin(newOffset, ScrollBehaviorAuto);
 }
 
 void LayoutBox::setScrollTop(LayoutUnit newTop) {
   // Hits in compositing/overflow/do-not-assert-on-invisible-composited-layers.html
   DisableCompositingQueryAsserts disabler;
 
-  if (hasOverflowClip())
-    getScrollableArea()->scrollToYOffset(newTop, ScrollOffsetClamped,
-                                         ScrollBehaviorAuto);
+  if (!hasOverflowClip())
+    return;
+
+  PaintLayerScrollableArea* scrollableArea = getScrollableArea();
+  DoubleSize newOffset(scrollableArea->offsetFromOrigin().width(), newTop);
+  scrollableArea->scrollToOffsetFromOrigin(newOffset, ScrollBehaviorAuto);
 }
 
 void LayoutBox::scrollToOffset(const DoubleSize& offset,
                                ScrollBehavior scrollBehavior) {
   // This doesn't hit in any tests, but since the equivalent code in setScrollTop
   // does, presumably this code does as well.
   DisableCompositingQueryAsserts disabler;
 
-  if (hasOverflowClip())
-    getScrollableArea()->scrollToOffset(offset, ScrollOffsetClamped,
-                                        scrollBehavior);
+  if (!hasOverflowClip())
+    return;
+
+  getScrollableArea()->scrollToOffsetFromOrigin(offset, scrollBehavior);
 }
 
 // Returns true iff we are attempting an autoscroll inside an iframe with scrolling="no".
 static bool isDisallowedAutoscroll(HTMLFrameOwnerElement* ownerElement,
                                    FrameView* frameView) {
   if (ownerElement && isHTMLFrameElementBase(*ownerElement)) {
     HTMLFrameElementBase* frameElementBase =
         toHTMLFrameElementBase(ownerElement);
     if (Page* page = frameView->frame().page()) {
       return page->autoscrollController().autoscrollInProgress() &&
@@ skipping 494 matching lines @@
   if (abs(delta.width()) <=
       AutoscrollController::
           noMiddleClickAutoscrollRadius)  // at the center we let the space for the icon
     delta.setWidth(0);
   if (abs(delta.height()) <=
       AutoscrollController::noMiddleClickAutoscrollRadius)
     delta.setHeight(0);
   scroll(ScrollByPixel, FloatSize(adjustedScrollDelta(delta)));
 }
 
-void LayoutBox::scrollByRecursively(const DoubleSize& delta,
-                                    ScrollOffsetClamping clamp) {
+void LayoutBox::scrollByRecursively(const DoubleSize& delta) {
   if (delta.isZero())
     return;
 
   bool restrictedByLineClamp = false;
   if (parent())
     restrictedByLineClamp = !parent()->style()->lineClamp().isNone();
 
   if (hasOverflowClip() && !restrictedByLineClamp) {
     PaintLayerScrollableArea* scrollableArea = this->getScrollableArea();
     ASSERT(scrollableArea);
 
-    DoubleSize newScrollOffset = scrollableArea->adjustedScrollOffset() + delta;
-    scrollableArea->scrollToOffset(newScrollOffset, clamp);
+    DoubleSize newScrollOffset = scrollableArea->offsetFromOrigin() + delta;
+    scrollableArea->scrollToOffsetFromOrigin(newScrollOffset);
 
     // If this layer can't do the scroll we ask the next layer up that can scroll to try
     DoubleSize remainingScrollOffset =
-        newScrollOffset - scrollableArea->adjustedScrollOffset();
+        newScrollOffset - scrollableArea->offsetFromOrigin();
     if (!remainingScrollOffset.isZero() && parent()) {
       if (LayoutBox* scrollableBox = enclosingScrollableBox())
-        scrollableBox->scrollByRecursively(remainingScrollOffset, clamp);
+        scrollableBox->scrollByRecursively(remainingScrollOffset);
 
       LocalFrame* frame = this->frame();
       if (frame && frame->page())
         frame->page()->autoscrollController().updateAutoscrollLayoutObject();
     }
   } else if (view()->frameView()) {
     // If we are here, we were called on a layoutObject that can be programmatically scrolled, but doesn't
     // have an overflow clip. Which means that it is a document node that can be scrolled.
     // FIXME: Pass in DoubleSize. crbug.com/414283.
     view()->frameView()->scrollBy(flooredIntSize(delta), UserScroll);
@@ skipping 17 matching lines @@
     size.expand(adjustmentWidth, 0);
   }
   return size;
 }
 
 IntSize LayoutBox::scrolledContentOffset() const {
   ASSERT(hasOverflowClip());
   ASSERT(hasLayer());
   // FIXME: Return DoubleSize here. crbug.com/414283.
   PaintLayerScrollableArea* scrollableArea = getScrollableArea();
-  IntSize result = flooredIntSize(scrollableArea->scrollOffset()) +
+  IntSize result = flooredIntSize(scrollableArea->scrollPosition()) +
                    originAdjustmentForScrollbars();
   if (isHorizontalWritingMode() &&
       shouldPlaceBlockDirectionScrollbarOnLogicalLeft())
     result.expand(-verticalScrollbarWidth(), 0);
   return result;
 }
 
 LayoutRect LayoutBox::clippingRect() const {
   LayoutRect result = LayoutRect(LayoutRect::infiniteIntRect());
   if (hasOverflowClip() || style()->containsPaint())
@@ skipping 4315 matching lines @@
   LayoutRect rect = frameRect();
 
   LayoutBlock* block = containingBlock();
   if (block)
     block->adjustChildDebugRect(rect);
 
   return rect;
 }
 
 }  // namespace blink