Preserve fractional scroll offset for JS scrolling API

Source/platform/scroll/ScrollView.cpp

 /*
  * Copyright (C) 2006, 2007, 2008 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 105 matching lines @@
 
     if (horizontalLock)
         setHorizontalScrollbarLock();
 
     if (verticalLock)
         setVerticalScrollbarLock();
 
     if (!needsUpdate)
         return;
 
-    updateScrollbars(scrollOffset());
+    updateScrollbars(scrollOffsetDouble());
 
     if (!layerForScrolling())
         return;
     blink::WebLayer* layer = layerForScrolling()->platformLayer();
     if (!layer)
         return;
     layer->setUserScrollable(userInputScrollable(HorizontalScrollbar), userInputScrollable(VerticalScrollbar));
 }
 
 void ScrollView::scrollbarModes(ScrollbarMode& horizontalMode, ScrollbarMode& verticalMode) const
@@ skipping 57 matching lines @@
 IntSize ScrollView::contentsSize() const
 {
     return m_contentsSize;
 }
 
 void ScrollView::setContentsSize(const IntSize& newSize)
 {
     if (contentsSize() == newSize)
         return;
     m_contentsSize = newSize;
-    updateScrollbars(scrollOffset());
+    updateScrollbars(scrollOffsetDouble());
     updateOverhangAreas();
 }
 
 IntPoint ScrollView::maximumScrollPosition() const
 {
     IntPoint maximumOffset(contentsWidth() - visibleWidth() - scrollOrigin().x(), contentsHeight() - visibleHeight() - scrollOrigin().y());
     maximumOffset.clampNegativeToZero();
     return maximumOffset;
 }
 
@@ skipping 73 matching lines @@
     if (scrollbarsSuppressed())
         return;
 
     // FIXME: Change scrollContents() to take DoubleSize. crbug.com/414283.
     if (isFrameView())
         m_pendingScrollDelta += scrollDelta;
     else
         scrollContents(flooredIntSize(scrollDelta));
 }
 
-void ScrollView::setScrollPosition(const IntPoint& scrollPoint, ScrollBehavior scrollBehavior)
+void ScrollView::setScrollPosition(const DoublePoint& scrollPoint, ScrollBehavior scrollBehavior)
 {
-    IntPoint newScrollPosition = adjustScrollPositionWithinRange(scrollPoint);
+    DoublePoint newScrollPosition = adjustScrollPositionWithinRange(scrollPoint);
 
-    if (newScrollPosition == scrollPosition())
+    if (newScrollPosition == scrollPositionDouble())
         return;
 
-    if (scrollBehavior == ScrollBehaviorInstant)
-        updateScrollbars(IntSize(newScrollPosition.x(), newScrollPosition.y()));
-    else
-        programmaticallyScrollSmoothlyToOffset(newScrollPosition);
+    if (scrollBehavior == ScrollBehaviorInstant) {
+        DoubleSize newOffset(newScrollPosition.x(), newScrollPosition.y());
+        updateScrollbars(newOffset);
+    } else {
+        programmaticallyScrollSmoothlyToOffset(toFloatPoint(newScrollPosition));
+    }
 }
 
 bool ScrollView::scroll(ScrollDirection direction, ScrollGranularity granularity)
 {
     ScrollDirection physicalDirection =
         toPhysicalDirection(direction, isVerticalDocument(), isFlippedDocument());
 
     return ScrollableArea::scroll(physicalDirection, granularity);
 }
 
@@ skipping 13 matching lines @@
     if (currentScrollPosition.y() < minScrollPosition.y())
         stretch.setHeight(currentScrollPosition.y() - minScrollPosition.y());
     if (currentScrollPosition.y() > maxScrollPosition.y())
         stretch.setHeight(currentScrollPosition.y() - maxScrollPosition.y());
 
     return stretch;
 }
 
 void ScrollView::windowResizerRectChanged()
 {
-    updateScrollbars(scrollOffset());
+    updateScrollbars(scrollOffsetDouble());
 }
 
 static bool useOverlayScrollbars()
 {
     // FIXME: Need to detect the presence of CSS custom scrollbars, which are non-overlay regardless the ScrollbarTheme.
     return ScrollbarTheme::theme()->usesOverlayScrollbars();
 }
 
 void ScrollView::computeScrollbarExistence(bool& newHasHorizontalScrollbar, bool& newHasVerticalScrollbar, const IntSize& docSize, ComputeScrollbarExistenceOption option) const
 {
@@ skipping 110 matching lines @@
 
     if (m_scrollbarsSuppressed)
         return true;
 
     if (!useOverlayScrollbars())
         contentsResized();
     scrollbarExistenceDidChange();
     return true;
 }
 
-void ScrollView::updateScrollbars(const IntSize& desiredOffset)
+void ScrollView::updateScrollbars(const DoubleSize& desiredOffset)
 {
     if (scrollbarsDisabled()) {
         setScrollOffsetFromUpdateScrollbars(desiredOffset);
         return;
     }
 
     if (m_inUpdateScrollbars)
         return;
     InUpdateScrollbarsScope inUpdateScrollbarsScope(this);
 
@@ skipping 23 matching lines @@
             invalidateRect(IntRect(0, 0, newVisibleSize.width() - oldVisibleSize.width(), newVisibleSize.height()));
         else
             invalidateRect(IntRect(oldVisibleSize.width(), 0, newVisibleSize.width() - oldVisibleSize.width(), newVisibleSize.height()));
     }
     if (newVisibleSize.height() > oldVisibleSize.height())
         invalidateRect(IntRect(0, oldVisibleSize.height(), newVisibleSize.width(), newVisibleSize.height() - oldVisibleSize.height()));
 
     setScrollOffsetFromUpdateScrollbars(desiredOffset);
 }
 
-void ScrollView::setScrollOffsetFromUpdateScrollbars(const IntSize& offset)
+void ScrollView::setScrollOffsetFromUpdateScrollbars(const DoubleSize& offset)
 {
-    IntPoint adjustedScrollPosition = IntPoint(offset);
+    DoublePoint adjustedScrollPosition = DoublePoint(offset);
 
     if (!isRubberBandInProgress())
         adjustedScrollPosition = adjustScrollPositionWithinRange(adjustedScrollPosition);
 
-    if (adjustedScrollPosition != scrollPosition() || scrollOriginChanged()) {
-        ScrollableArea::scrollToOffsetWithoutAnimation(adjustedScrollPosition);
+    if (adjustedScrollPosition != scrollPositionDouble() || scrollOriginChanged()) {
+        ScrollableArea::scrollToOffsetWithoutAnimation(toFloatPoint(adjustedScrollPosition));
         resetScrollOriginChanged();
     }
 }
 
 const int panIconSizeLength = 16;
 
 IntRect ScrollView::rectToCopyOnScroll() const
 {
     IntRect scrollViewRect = convertToContainingWindow(IntRect((shouldPlaceVerticalScrollbarOnLeft() && verticalScrollbar()) ? verticalScrollbar()->width() : 0, 0, visibleWidth(), visibleHeight()));
     if (hasOverlayScrollbars()) {
@@ skipping 187 matching lines @@
 
 void ScrollView::setFrameRect(const IntRect& newRect)
 {
     IntRect oldRect = frameRect();
 
     if (newRect == oldRect)
         return;
 
     Widget::setFrameRect(newRect);
 
-    updateScrollbars(scrollOffset());
+    updateScrollbars(scrollOffsetDouble());
 
     frameRectsChanged();
 }
 
 void ScrollView::frameRectsChanged()
 {
     HashSet<RefPtr<Widget> >::const_iterator end = m_children.end();
     for (HashSet<RefPtr<Widget> >::const_iterator current = m_children.begin(); current != end; ++current)
         (*current)->frameRectsChanged();
 }
@@ skipping 89 matching lines @@
 
 bool ScrollView::isScrollCornerVisible() const
 {
     return !scrollCornerRect().isEmpty();
 }
 
 void ScrollView::scrollbarStyleChanged()
 {
     adjustScrollbarOpacity();
     contentsResized();
-    updateScrollbars(scrollOffset());
+    updateScrollbars(scrollOffsetDouble());
     positionScrollbarLayers();
 }
 
 void ScrollView::updateScrollCorner()
 {
 }
 
 void ScrollView::paintScrollCorner(GraphicsContext* context, const IntRect& cornerRect)
 {
     ScrollbarTheme::theme()->paintScrollCorner(context, cornerRect);
@@ skipping 275 matching lines @@
 
 void ScrollView::setScrollOrigin(const IntPoint& origin, bool updatePositionAtAll, bool updatePositionSynchronously)
 {
     if (scrollOrigin() == origin)
         return;
 
     ScrollableArea::setScrollOrigin(origin);
 
     // Update if the scroll origin changes, since our position will be different if the content size did not change.
     if (updatePositionAtAll && updatePositionSynchronously)
-        updateScrollbars(scrollOffset());
+        updateScrollbars(scrollOffsetDouble());
 }
 
 } // namespace blink