[plt-scheme] using inherit-field when making new gui widgets

At Thu, 4 Oct 2007 15:09:23 +0100, "Stephen De Gabrielle" wrote:
> timeline-selector.ss::158: class*: superclass does not provide field:
> min-width for class: timeline-selector%
> (note the character offset - rather than the line number/character position
> reported in bug 8954)
> 
> I think I am using inherit field correctly, and the pane% I am using as a
> superclass does have a 'min-width' field.

The pane% class has a `min-width' method, not a field.

The pane% class also has a `min-width' initialization argument. But you
don't need to explicitly inherit it to use `min-width' with `super-new'
or `super-initialize'.

I think you want

  (define timeline-selector% (class pane% ()
                               (init min-width)
                               ; Make the drawing area
                               (super-new [min-width min-width]
                                          ....)
                               ....
                               (define canvas (new canvas% 
                                                   [parent this]
                                                   ....
                                                   [min-width min-width]
                                                   ....))
                                ....))

or maybe


  (define timeline-selector% (class pane% ()
                               (inherit min-width) ; inherit method
                               ; Make the drawing area
                               (super-new ....)
                               ....
                               (define canvas (new canvas% 
                                                   [parent this]
                                                   ....
                                                   ;; call method to get arg:
                                                   [min-width (min-width)]
                                                   ....))
                                ....))


Matthew