Allow objects without scrollbars to be scrollable

Source/core/platform/Scrollbar.cpp

 /*
  * Copyright (C) 2004, 2006, 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 37 matching lines @@
 #define THUMB_POSITION_AFFECTS_BUTTONS
 #endif
 
 namespace WebCore {
 
 PassRefPtr<Scrollbar> Scrollbar::createNativeScrollbar(ScrollableArea* scrollableArea, ScrollbarOrientation orientation, ScrollbarControlSize size)
 {
     return adoptRef(new Scrollbar(scrollableArea, orientation, size));
 }
 
-int Scrollbar::maxOverlapBetweenPages()
-{
-    static int maxOverlapBetweenPages = ScrollbarTheme::theme()->maxOverlapBetweenPages();
-    return maxOverlapBetweenPages;
-}
-
 Scrollbar::Scrollbar(ScrollableArea* scrollableArea, ScrollbarOrientation orientation, ScrollbarControlSize controlSize,
                      ScrollbarTheme* theme)
     : m_scrollableArea(scrollableArea)
     , m_orientation(orientation)
     , m_controlSize(controlSize)
     , m_theme(theme)
     , m_visibleSize(0)
     , m_totalSize(0)
     , m_currentPos(0)
     , m_dragOrigin(0)
-    , m_lineStep(0)
-    , m_pageStep(0)
-    , m_pixelStep(1)
     , m_hoveredPart(NoPart)
     , m_pressedPart(NoPart)
     , m_pressedPos(0)
     , m_scrollPos(0)
     , m_draggingDocument(false)
     , m_documentDragPos(0)
     , m_enabled(true)
     , m_scrollTimer(this, &Scrollbar::autoscrollTimerFired)
     , m_overlapsResizer(false)
     , m_suppressInvalidation(false)
     , m_isAlphaLocked(false)
 {
     if (!m_theme)
         m_theme = ScrollbarTheme::theme();
 
     m_theme->registerScrollbar(this);
 
     // FIXME: This is ugly and would not be necessary if we fix cross-platform code to actually query for
     // scrollbar thickness and use it when sizing scrollbars (rather than leaving one dimension of the scrollbar
     // alone when sizing).
     int thickness = m_theme->scrollbarThickness(controlSize);
     Widget::setFrameRect(IntRect(0, 0, thickness, thickness));
 
-    if (m_scrollableArea)
-        m_currentPos = static_cast<float>(m_scrollableArea->scrollPosition(this));
+    m_currentPos = scrollableAreaCurrentPos();
 }
 
 Scrollbar::~Scrollbar()
 {
     if (AXObjectCache* cache = existingAXObjectCache())
         cache->remove(this);
     
     stopTimerIfNeeded();
     
     m_theme->unregisterScrollbar(this);
@@ skipping 17 matching lines @@
 
 bool Scrollbar::isScrollViewScrollbar() const
 {
     return parent() && parent()->isFrameView() && toFrameView(parent())->isScrollViewScrollbar(this);
 }
 
 void Scrollbar::offsetDidChange()
 {
     ASSERT(m_scrollableArea);
 
-    float position = static_cast<float>(m_scrollableArea->scrollPosition(this));
+    float position = scrollableAreaCurrentPos();
     if (position == m_currentPos)
         return;
 
     int oldThumbPosition = theme()->thumbPosition(this);
     m_currentPos = position;
     updateThumbPosition();
     if (m_pressedPart == ThumbPart)
         setPressedPos(m_pressedPos + theme()->thumbPosition(this) - oldThumbPosition);    
 }
 
 void Scrollbar::setProportion(int visibleSize, int totalSize)
 {
     if (visibleSize == m_visibleSize && totalSize == m_totalSize)
         return;
 
     m_visibleSize = visibleSize;
     m_totalSize = totalSize;
 
     updateThumbProportion();
 }
 
-void Scrollbar::setSteps(int lineStep, int pageStep, int pixelsPerStep)
-{
-    m_lineStep = lineStep;
-    m_pageStep = pageStep;
-    m_pixelStep = 1.0f / pixelsPerStep;
-}
-
 void Scrollbar::updateThumb()
 {
 #ifdef THUMB_POSITION_AFFECTS_BUTTONS
     invalidate();
 #else
     theme()->invalidateParts(this, ForwardTrackPart | BackTrackPart | ThumbPart);
 #endif
 }
 
 void Scrollbar::updateThumbPosition()
@@ skipping 416 matching lines @@
 }
 
 IntPoint Scrollbar::convertFromContainingView(const IntPoint& parentPoint) const
 {
     if (m_scrollableArea)
         return m_scrollableArea->convertFromContainingViewToScrollbar(this, parentPoint);
 
     return Widget::convertFromContainingView(parentPoint);
 }
 
+float Scrollbar::scrollableAreaCurrentPos() const
+{
+    if (!m_scrollableArea)
+        return 0;
+
+    if (m_orientation == HorizontalScrollbar)
+        return m_scrollableArea->scrollPosition().x() + m_scrollableArea->scrollOrigin().x();

[trchen, 2013/06/20 01:46:43]

I recommend phasing out scrollOrigin(). Please use scrollPosition() -
minimumScrollPosition() instead.

[bokan, 2013/06/20 19:00:16]

Done.

+
+    return m_scrollableArea->scrollPosition().y() + m_scrollableArea->scrollOrigin().y();
+}
+
 } // namespace WebCore