javax/swing/JViewport.java

506       *  parentWidth/childWidth are positive and childAt can be negative.
508     private int positionAdjustment(int parentWidth, int childWidth, int childAt)    {
513         if (childAt >= 0 && childWidth + childAt <= parentWidth)    {
520         if (childAt <= 0 && childWidth + childAt >= parentWidth) {
527         if (childAt > 0 && childWidth <= parentWidth)    {
528             return -childAt + parentWidth - childWidth;
534         if (childAt >= 0 && childWidth >= parentWidth)   {
541         if (childAt <= 0 && childWidth <= parentWidth)   {
548         if (childAt < 0 && childWidth >= parentWidth)    {
549             return -childAt + parentWidth - childWidth;