Yet another way to attach widgets is to place an edge opposite edges of another widget.
This is achieved by setting the XmNtopAttachment etc. resources to XmATTACH_OPPOSITE_WIDGET. Just as XmATTACH_WIDGET a widget has to be associated with the XmNwidget resource.
NOTE: With the opposite attachment ``similar'' edges are attached.
So in form3.c we attach the right edge of button2 to the right edge of button1, the left edge of button3 with the left of button1 and so on.