When drawing graphics in CLIM, you imagine that they appear on a
drawing plane. The drawing plane extends infinitely in four
directions and has infinite resolution (no pixels). The drawing
plane has no material existence and cannot be viewed directly.
The drawing plane provides an idealized version of the graphics
you draw. A line that you draw on the drawing plane is
infinitely thin. Of course, you intend that the graphics should
be visible to the user, so they must be presented on a real
display device. CLIM transfers the graphics from the drawing
plane to the window via the rendering process. Because the
window lives on hardware that has physical constraints, the
rendering process is forced to compromise when it draws the
graphics on the window. The actual visual appearance of the
window is only an approximation of the idealized drawing plane.
Figure 5. shows the conceptual model of the drawing functions
sending graphical output to the drawing plane, and the graphics
being transferred to a screen by render