Can you send me a program to run and remind me which platform you're using?
This must be a bug at some level below your code, because `this` should never be `#f`. I expect that the problem is in the binding to the native GUI library, where it's incorrectly allowing a callback too early. At Thu, 15 Sep 2016 17:57:08 +0100, Erich Rast wrote: > I have a subclass of list-box% which overrides on-size and calculates > relative column sizes based on get-client-size and some values provided > by an init variable. > > However, if I don't check for "this" being an object, I get: > > send: target is not an object > target: #f > method name: get-client-size > > But despite the additional check I still sometimes get the error. Not > always, but most of the time. I also get it if I wrap > set-column-dimensions like this > > (define (set-column-dimensions) > (when this > ...)) > > It also doesn't matter whether I call it as inherited method or as > (send this get-client-size). > > How can I ensure that get-client-size works within on-size? Is > there a safe way to check that the GUI element is "graphically > initialized"? > > Best, > > Erich > > > > (define/override (on-size width height) > (when (object? this) > (set-column-dimensions))) > > (define/public (set-column-dimensions) > (let-values (((w h) (get-client-size))) > (for ([min-width (in-list minimum-widths)] > [perc (in-list percentages)] > [i (in-naturals)]) > (let* ((perc-width (truncate (* w (/ perc 100)))) > (actual-width (if (< perc-width min-width) > min-width > perc-width))) > (set-column-width i actual-width > min-width > actual-width))))) > > where minimum-widths and percentages are defined and set by an init > variable column-specs. > > -- > You received this message because you are subscribed to the Google Groups > "Racket Users" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to racket-users+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
