#cs(module draw-sig mzscheme
     (provide core-draw^ draw^)
     (require (lib "unit.ss"))
     
     ;; xxx-solid-rect cannot be called xxx-solid-rectangle because that
     ;; interferes with the existing xxx-solid-rectangle name in our unit
     ;; calculus -- mf 
     
     (define-signature core-draw^
       (start 
        start/cartesian-plane
        stop 
        ;; --- 
        start-and-export 
        ;; like start but also consumes a hashtable 
        ;; adds the procedures that can be called during a sequnce to the hashtable
        ;; --- the following can be called during a draw sequence --- 
        draw-circle
        draw-solid-disk
        draw-solid-rect
        draw-solid-line
	draw-solid-string
        clear-circle
        clear-solid-disk
        clear-solid-rect
        clear-solid-line
	clear-solid-string
        clear-all
        ;; --- stupid stuff --- 
        sleep-for-a-while
        wait-for-mouse-click ; -> posn
        get-key-event   ; -> (union #f char symbol)
	get-mouse-event ; -> (union #f posn)
	;;
	;; "hidden" access to viewports (for htdc/[i]draw mostly)
        get-@VP         ; -> Viewport
	begin-draw-sequence ; Viewport Viewport -> #t
	end-draw-sequence   ; -> #t
	;; 
        big-bang        ; World -> true
        on-key-event    ; (union char symbol) World -> World 
        on-tick-event   ; World -> World 
        end-of-time     ; -> World
        ))
     
     (define-signature draw^ extends core-draw^ ()))