[plt-scheme] graphical widgets

Hi,

In DrScheme it is possible to change the position of the division line
between two text fields (the upper editor, the lower evaluator).
How can I do that in my application? In which file is it implemented
in DrScheme? I assume it is a special implementation, since I did not
find that any widget can do that by default.

There is also a bug in MrEd. In version 208 in mred.ss in the function
"mk-file-selector" at line 6461 inside the "change-dir" callback function
definition. The function calls the "get-string-selection" method, but
when the user clicked on an empty area, then this method returns #f
which is not valid for build-path. (It is possible to click on an empty area
since it is possible that there are only one sub-directory in the current
directory. And the user may click anywhere. :-) )
So it should read something like this:

  (let ([sd (send d get-string-selection)])
    (if sd
     (begin
       (set! dir ...
       (reset-directory)
    )))

The reason I know this because, I needed a file selector so I took this.
However I did not manage to start-up the default windows file selector.
Is it possible to do that in a normal application? I mean in the same way
as MrEd does this, on Windows use the windows file selector on Unix
use the defined one.

Thanks for any help.

Peter Ivanyi