fDraggingStartPos
if (fDraggingStartPos.x >= 0 || ScrollBar(B_HORIZONTAL) == NULL)
fDraggingStartPos = where;
if (fDraggingStartPos.x < 0
fDraggingStartPos.x = -1;
if (fDraggingStartPos.x < 0)
+ fDraggingStartPos.x - where.x);
BPoint fDraggingStartPos;