Thanks, I copied your example and it seems it doesn't work ..
If I comment the code inside [paint-callback .. it also doesn't draw anything. In general I need to send 'messages' from 'outside' to the canvas object to visualize numerical experiment performed by separate function. I can implement experiment itself inside [pain-callback (lambda ... functions ) under definition of canvas, but it looks strange and clumsy. Sometimes I need just to run computations, but sometimes I need also to do visualization with animation. How could I achieve this? Best regards, Alex On 27 January 2015 at 19:54, Matthias Felleisen <[email protected]> wrote: > > Do you want something like this: > > #lang racket/gui > > (define frame (new frame% [label ""] [width 700] [height 500])) > (define canvas > (new canvas% > [parent frame] > [paint-callback > (lambda (c dc) > (send dc draw-line 1 1 100 100))])) > (send frame show #true) > > (define (my-draw) > (send (send canvas get-dc) draw-line 100 100 0 200)) > > > -- Matthias > > > > On Jan 27, 2015, at 12:09 PM, Alexandr M wrote: > > > Hello, > > > > How can I draw the line (for example) in the canvas object defined as: > > > > (define frame (new frame% [label ""] [width 700] [height 500])) > > (define canvas (new canvas% [parent frame] > > ;;;; - call from outside: [paint-callback (lambda (c dc) (send dc > draw-line 1 1 10 10) )] > > )) > > > > by calling a function like > > > > (define (MyDraw canvas-obj) .... (draw-line 1 1 10 10)) > > > > ? > > > > -- > > Best regards, > > Alex > > ____________________ > > Racket Users list: > > http://lists.racket-lang.org/users > > -- Best regards, Alexander Maslov
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