Let me spell out Richard's comment in some detail. The docs for on-paint in
get-dc say that the function is called on no arguments (other than this) and
produce no values. So this demands
(define/override (on-paint) ...)
because other methods in the superclass call this method like this (on-
I dont know enough about this stuff, other than to 'rather slavishly' follow
your code and make it work. :O)
Try this:
...
(define/override (on-paint) ; eliminate the argument
(define dc (send this get-dc)) ; 'this' is the current instance
...
On Aug 23, 2012, at 6:29 PM, Gregory Woodho
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
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