The graphics drawing routines keep the current position of the drawing pen
in the rastport fields cp_x and cp_y, for the horizontal and vertical
positions, respectively. The coordinate location 0,0 is in the upper left
corner of the drawing area.  The x value increases proceeding to the
right; the y value increases proceeding toward the bottom of the drawing
area.

The variables rastport.penwidth and rastport.penheight are not currently
implemented.  These fields should not be read or written by applications.