[plt-scheme] Help with unfinished multi-column listbox

Thanks, that has pointed me in the right direction. I've figured out 
that the selection wasn't displayed because of the incorrect logic of 
my private-lock.

The rest should be a piece of cake... (*should* doesn't imply *will 
be*, though).

Best regards,

Erich

> For example, if you add
>
>                (send this set-caret-owner #f 'display)
>                (select-line 2)
>
> to the selection callback, then a click selects the second line in the
> list.
>
> Matthew
>