[plt-scheme] newbie - plotting points
Hi,
I've not programmed much in Lisp or Scheme, and have done nothing at all
for quite some years, so this may be a very stupid question...
I'm trying to adapt the example at
http://schemecookbook.org/Cookbook/GUIHelloWorld to plot a point on an
empty canvas. I'm using PLT scheme, just downloaded, with the "Pretty
Big" language.
My code, which runs fine, but displays no dot, is below. Why don't I see
a red dot near one of the corners of the screen? (It doesn't work with
the deafult pen, either).
Thanks,
Andrew
(require (lib "mred.ss" "mred")
(lib "class.ss" "mzlib"))
(define the-frame
(new frame%
(label "Hello!")
(width 400)
(height 400)))
(define the-canvas
(new canvas%
(parent the-frame)))
(define the-pen
(let ((red (make-object color% 255 0 0)))
(make-object pen% red 5 'solid)))
(define the-dot
(let ((dc (send the-canvas get-dc )))
(send dc set-pen the-pen)
(send dc draw-point 5 5)))
(send the-frame show #t)
--
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