* The integer accepted by this function can be a value equivalent to C_NO_FRAME or any other value. If it is C_NO_FRAME, then no frame should be drawn '''even if the current widget was constructed bordered'''. * Child classes should adjust their drawn content so as '''not to overlap the border''' if a border will be drawn.* If a frame is in fullscreen mode (width < 0 or height < 0) then no border should be drawn.