The scan-line conversions of the drawing functions are very much host-dependent. In other words, you cannot assume that, for example (draw-point port x y) has exactly the same effect on all machines. Some machines might put pixels down and to the right of integer coordinates (x y) while others may center the pixel at (x y) .
UNIX note: The stipple, pattern , mask-x, and mask-y slots of the graphics state are also used.
See also the LispWorks Reference Manual entries for draw-circle (which draws a circle) and draw-ellipse (which draws an ellipse), and the LispWorks CAPI Reference Manual for full reference entries of all the drawing functions.