Unifies ScrollView and RenderLayer to use non-shifted [minPos, maxPos] scroll offset

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 270 matching lines @@
     if (m_pressedPart == BackButtonStartPart || m_pressedPart == BackButtonEndPart ||  m_pressedPart == ForwardButtonStartPart || m_pressedPart == ForwardButtonEndPart)
         return ScrollByLine;
     return ScrollByPage;
 }
 
 void Scrollbar::moveThumb(int pos, bool draggingDocument)
 {
     if (!m_scrollableArea)
         return;
 
+    float minPos = (m_orientation == HorizontalScrollbar) ? m_scrollableArea->minimumScrollPosition().x() : m_scrollableArea->minimumScrollPosition().y();
+    float maxPos = (m_orientation == HorizontalScrollbar) ? m_scrollableArea->maximumScrollPosition().x() : m_scrollableArea->maximumScrollPosition().y();

[jamesr, 2013/05/03 05:59:22]

I think I've seen these lines before - can we share this code somehow?

+
     int delta = pos - m_pressedPos;
 
     if (draggingDocument) {
         if (m_draggingDocument)
             delta = pos - m_documentDragPos;
         m_draggingDocument = true;
         FloatPoint currentPosition = m_scrollableArea->scrollAnimator()->currentPosition();
-        int destinationPosition = (m_orientation == HorizontalScrollbar ? currentPosition.x() : currentPosition.y()) + delta;
-        if (delta > 0)
-            destinationPosition = min(destinationPosition + delta, maximum());
-        else if (delta < 0)
-            destinationPosition = max(destinationPosition + delta, 0);
+        float destinationPosition = (m_orientation == HorizontalScrollbar ? currentPosition.x() : currentPosition.y()) + delta;
+        destinationPosition = max(min(destinationPosition, maxPos), minPos);
         m_scrollableArea->scrollToOffsetWithoutAnimation(m_orientation, destinationPosition);
         m_documentDragPos = pos;
         return;
     }
 
     if (m_draggingDocument) {
         delta += m_pressedPos - m_documentDragPos;
         m_draggingDocument = false;
     }
 
     // Drag the thumb.
     int thumbPos = theme()->thumbPosition(this);
     int thumbLen = theme()->thumbLength(this);
     int trackLen = theme()->trackLength(this);
-    int maxPos = trackLen - thumbLen;
     if (delta > 0)
-        delta = min(maxPos - thumbPos, delta);
+        delta = min(trackLen - thumbLen - thumbPos, delta);
     else if (delta < 0)
         delta = max(-thumbPos, delta);
     
     if (delta) {
-        float newPosition = static_cast<float>(thumbPos + delta) * maximum() / (trackLen - thumbLen);
+        float newPosition = static_cast<float>(thumbPos + delta) * (maxPos - minPos) / (trackLen - thumbLen) + minPos;
         m_scrollableArea->scrollToOffsetWithoutAnimation(m_orientation, newPosition);
     }
 }
 
 void Scrollbar::setHoveredPart(ScrollbarPart part)
 {
     if (part == m_hoveredPart)
         return;
 
     if ((m_hoveredPart == NoPart || part == NoPart) && theme()->invalidateOnMouseEnterExit())
@@ skipping 264 matching lines @@
 
 IntPoint Scrollbar::convertFromContainingView(const IntPoint& parentPoint) const
 {
     if (m_scrollableArea)
         return m_scrollableArea->convertFromContainingViewToScrollbar(this, parentPoint);
 
     return Widget::convertFromContainingView(parentPoint);
 }
 
 } // namespace WebCore