graphical ->clip: [area]Clip subsequent drawing actions to the indicated rectangle. If the
rectangle is @default,
all operations are clipped to the
graphical<-area
of the graphical. Note that on entry of graphical->_redraw_area
clipping is set to the argument area, which will normally be larger than graphical<-area.
Each graphical->clip
must be undone by an graphical->unclip
before graphical->_redraw_area
returns. See also graphical->_redraw_area, graphical->graphics_state
graphical->draw_line,
etc.
