Thanks Matthew for the prompt reply. Just noticed the dot and the part in the docs referring to the geometry management.
On 03/31/2011 05:58 PM, Matthew Flatt wrote: > A plain `panel%' doesn't perform any geometry management of its > children, and so `invisible-canvas' isn't moved and resized to fill the > frame. On my screen, I can see a little white dot where the canvas is 1 > pixel by 1 pixel. > > Normally, you want either `vertical-panel%' or `horizontal-panel%', or > you make a subclass of `panel%' to implement a different kind of > geometry management. > > > At Thu, 31 Mar 2011 17:29:14 -0300, Eduardo Bellani wrote: >> Could someone please explain why there is an invisible canvas in this >> example? >> >> Env: >> Linux 2.6.31-23-generic Ubuntu i686 GNU/Linux >> racket 5.1.0.4 >> >> #lang racket >> >> (require racket/gui) >> >> (define bitmap-canvas% >> (class canvas% >> (init-field [bitmap #f]) >> (inherit get-dc) >> (define/override (on-paint) >> (send (get-dc) draw-bitmap bitmap 0 0)) >> (super-new))) >> >> >> (define bitmap (read-bitmap "data/image_0.jpg")) >> >> (define f (new frame% [label "foo"] [width 100] [height 100])) >> (define p (new panel% [parent f])) >> (define p2 (new vertical-panel% [parent f])) >> >> ;; why is this invisible? >> (define invisible-canvas (new bitmap-canvas% >> [parent p] >> [bitmap bitmap])) >> (define visible-canvas (new bitmap-canvas% >> [parent p2] >> [bitmap bitmap])) >> >> (send f show #t) >> >> >> >> >> -- >> Eduardo Bellani >> >> omnia mutantur, nihil interit. >> _________________________________________________ >> For list-related administrative tasks: >> http://lists.racket-lang.org/listinfo/users -- Eduardo Bellani omnia mutantur, nihil interit. _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
