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

Source/core/platform/Scrollbar.cpp

Index: Source/core/platform/Scrollbar.cpp
diff --git a/Source/core/platform/Scrollbar.cpp b/Source/core/platform/Scrollbar.cpp
index 1811023455171fb5b196ef4d5d7a59d51cbf57a2..c98906cf47d0d1ad415fc1b4c7f8fe33b1eedad4 100644
--- a/Source/core/platform/Scrollbar.cpp
+++ b/Source/core/platform/Scrollbar.cpp
@@ -288,6 +288,9 @@ 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) {
@@ -295,11 +298,8 @@ void Scrollbar::moveThumb(int pos, bool 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;
@@ -314,14 +314,13 @@ void Scrollbar::moveThumb(int pos, bool draggingDocument)
     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);
     }
 }