Delay scrollContents until the next paint

Source/platform/scroll/ScrollView.h

 /*
  * Copyright (C) 2004, 2006, 2007, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Holger Hans Peter Freyther
  *
  * 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
@@ skipping 126 matching lines @@
     // Functions for getting/setting the size of the document contained inside the ScrollView (as an IntSize or as individual width and height
     // values).
     virtual IntSize contentsSize() const OVERRIDE; // Always at least as big as the visibleWidth()/visibleHeight().
     int contentsWidth() const { return contentsSize().width(); }
     int contentsHeight() const { return contentsSize().height(); }
     virtual void setContentsSize(const IntSize&);
 
     // Functions for querying the current scrolled position (both as a point, a size, or as individual X and Y values).
     virtual IntPoint scrollPosition() const OVERRIDE { return visibleContentRect().location(); }
     IntSize scrollOffset() const { return toIntSize(visibleContentRect().location()); } // Gets the scrolled position as an IntSize. Convenient for adding to other sizes.
+    IntSize scrollDelta() const { return m_scrollDelta; }
     virtual IntPoint maximumScrollPosition() const OVERRIDE; // The maximum position we can be scrolled to.
     virtual IntPoint minimumScrollPosition() const OVERRIDE; // The minimum position we can be scrolled to.
     // Adjust the passed in scroll position to keep it between the minimum and maximum positions.
     IntPoint adjustScrollPositionWithinRange(const IntPoint&) const;
     int scrollX() const { return scrollPosition().x(); }
     int scrollY() const { return scrollPosition().y(); }
 
     virtual IntSize overhangAmount() const OVERRIDE;
 
     void cacheCurrentScrollPosition() { m_cachedScrollPosition = scrollPosition(); }
     IntPoint cachedScrollPosition() const { return m_cachedScrollPosition; }
 
     // Functions for scrolling the view.
     virtual void setScrollPosition(const IntPoint&);
     void scrollBy(const IntSize& s) { return setScrollPosition(scrollPosition() + s); }
 
     bool scroll(ScrollDirection, ScrollGranularity);
 
     // Scroll the actual contents of the view (either blitting or invalidating as needed).
+    void scrollContentsIfNeeded();
     void scrollContents(const IntSize& scrollDelta);
 
     // This gives us a means of blocking painting on our scrollbars until the first layout has occurred.
     void setScrollbarsSuppressed(bool suppressed, bool repaintOnUnsuppress = false);
     bool scrollbarsSuppressed() const { return m_scrollbarsSuppressed; }
 
     IntPoint rootViewToContents(const IntPoint&) const;
     IntPoint contentsToRootView(const IntPoint&) const;
     IntRect rootViewToContents(const IntRect&) const;
     IntRect contentsToRootView(const IntRect&) const;
@@ skipping 112 matching lines @@
     RefPtr<Scrollbar> m_horizontalScrollbar;
     RefPtr<Scrollbar> m_verticalScrollbar;
     ScrollbarMode m_horizontalScrollbarMode;
     ScrollbarMode m_verticalScrollbarMode;
 
     bool m_horizontalScrollbarLock;
     bool m_verticalScrollbarLock;
 
     HashSet<RefPtr<Widget> > m_children;
 
+    IntSize m_scrollDelta;

[abarth-chromium, 2014/03/08 06:54:52]

m_pendingScrollDelta?

The word "pending" might hint that we're waiting to apply this scroll delta.

[ykyyip, 2014/03/11 01:59:39]

Done.

     IntSize m_scrollOffset; // FIXME: Would rather store this as a position, but we will wait to make this change until more code is shared.
     IntPoint m_cachedScrollPosition;
     IntSize m_contentsSize;
 
     int m_scrollbarsAvoidingResizer;
     bool m_scrollbarsSuppressed;
 
     bool m_inUpdateScrollbars;
     unsigned m_updateScrollbarsPass;
 
     IntPoint m_panScrollIconPoint;
     bool m_drawPanScrollIcon;
 
     bool m_paintsEntireContents;
     bool m_clipsRepaints;
 
     void init();
     void destroy();
 
     IntRect rectToCopyOnScroll() const;
 
     // Called when the scroll position within this view changes.  FrameView overrides this to generate repaint invalidations.
+    virtual void invalidateFixedElementsBeforeScrolling(const IntSize&, const IntRect&) { }
     virtual void repaintFixedElementsAfterScrolling() { }
     virtual void updateFixedElementsAfterScrolling() { }
 
     void calculateOverhangAreasForPainting(IntRect& horizontalOverhangRect, IntRect& verticalOverhangRect);
     void updateOverhangAreas();
 
     virtual int pageStep(ScrollbarOrientation) const OVERRIDE;
 }; // class ScrollView
 
 DEFINE_TYPE_CASTS(ScrollView, Widget, widget, widget->isScrollView(), widget.isScrollView());
 
 } // namespace WebCore
 
 #endif // ScrollView_h