Basic Commands

•   (open-viewport name horiz vert scale)
  open-viewport takes a string name and integers horiz and vert and creates a new window called name. The window is horiz*scale pixels wide and vert*scale pixels high. The scale value is used for all drawing commands, so the drawing area is horix by vert units. The scale argument can be omitted; it defaults to 1.0. For backward compatibility, a single posn value (see below) can be submitted in the place of horiz and vert. (In this case, the scale argument is not allowed.) open-viewport returns a viewport descriptor.

  

•   (open-pixmap name horiz vert scale)
  open-pixmap is exactly like open-viewport, but the resulting viewport is not displayed on the screen. Offscreen pixmaps are useful for executing a sequence of drawing commands and displaying them at once with copy-viewport.
•   (close-viewport viewport)
  close-viewport takes a viewport descriptor. It removes the viewport from the screen and makes subsequent operations dealing with the viewport illegal.
•   (set-viewport-scaleviewport scale)
  set-viewport-scale takes a viewport descriptor and a scale factor. It clears the viewport and changes its scale for drawing commands.