Re: Simple bitmap question

[Jens Axel Søgaard <jensaxel@soegaard.net>]

Robby:
> Yep, you need to use on-paint. Try this:
>
> (define bm-canvas%
>    (class canvas%
>      (inherit get-dc)
>      (define/override (on-paint)
>        (send (get-dc) draw-bitmap bitmap 0 0))
>      (super-instantiate ())))
>

This works. But I still don't understand why I need to override on-paint.

The help desk states this about on-paint:

    Called when the canvas is exposed or resized so that the image in the
    canvas can be repainted.

My program ends like this:

    (send frame show #t)
    (define dc (send canvas get-dc))
    (send dc draw-bitmap bitmap 0 0 )

I understand that (send frame show #t) triggers an on-paint event.
But I draw my bitmap afterwards. Does draw-bitmap trigger an on-paint event
too,
or is it something else that comes into play?

--
Jens Axel