I apologize in advance for the elementary nature of this question, and for the
amount of code included below. I'm having a tough time following the
documentation for racket/gui and racket/draw. My first attempt to create a
Sudoku grid follows the example in the documentation rather slavishly and works
fine
(define frame (new frame% [label "Sudoku"]
[width 300]
[height 300]))
(define grid-canvas (new canvas% [parent frame]
[min-width 300]
[min-height 300]
[paint-callback
(lambda (canvas dc)
(let
([w (send canvas get-width)]
[h (send canvas get-height)])
(send dc set-pen "black" 3 'solid)
(for ([i (in-range 3)])
(send dc draw-line 0 (* i (/ h 3)) w (* i (/ h 3)))
(send dc draw-line (* i (/ w 3)) 0 (* i (/ w 3)) h))
(send dc set-pen "black" 1 'solid)
(for ([i (in-range 9)])
(send dc draw-line 0 (* i (/ h 9)) w (* i (/ h 9))))
(for ([i (in-range 9)])
(send dc draw-line (* i (/ w 9)) 0 (* i (/ w 9)) h))))]))
; Show the frame by calling its show method
(send frame show #t)
But this does not work
(define frame (new frame% [label "Sudoku"]
[width 300]
[height 300]))
(define grid-canvas%
(class canvas%
(define/override (on-paint dc)
(let
([w (send this get-width)]
[h (send this get-height)])
(send dc set-pen "black" 3 'solid)
(for ([i (in-range 3)])
(send dc draw-line 0 (* i (/ h 3)) w (* i (/ h 3)))
(send dc draw-line (* i (/ w 3)) 0 (* i (/ w 3)) h))
(send dc set-pen "black" 1 'solid)
(for ([i (in-range 9)])
(send dc draw-line 0 (* i (/ h 9)) w (* i (/ h 9))))
(for ([i (in-range 9)])
(send dc draw-line (* i (/ w 9)) 0 (* i (/ w 9)) h))))
(super-new)))
(define the-grid (new grid-canvas% [parent frame]
[min-width 300]
[min-height 300]))
I get an arity mismatch in on-paint.
The reason for not wanting in to pass in the paint-callback is that I want to
be able to augment it somewhat in grid-canvas% (specifically, I need to draw in
the digits based on the contents of the grid!) It's not clear (to me) how to do
this, or if I should be taking an entirely different approach.
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