ScrollOffsetChanged
virtual void ScrollOffsetChanged(BPoint oldOffset,
virtual void ScrollOffsetChanged(BPoint oldOffset,
ScrollOffsetChanged(oldOffset, fScrollOffset);
fScrollSource->ScrollOffsetChanged(oldOffset, fScrollOffset);
virtual void ScrollOffsetChanged(BPoint oldOffset,
virtual void ScrollOffsetChanged(BPoint oldOffset,
virtual void ScrollOffsetChanged(BPoint oldOffset,
virtual void ScrollOffsetChanged(BPoint oldOffset,