IOhannes, you found the magic bullet (or forum post, that is)!

Awesome, I can confirm this works in a little test script and screenshot.  It's a button to toggle
hidden file display as expected.

On Wed, 2008-04-02 at 10:55 +0200, IOhannes m zmoelnig wrote: 
Hans-Christoph Steiner wrote:
> This would be huge, it would greatly help the newbies.  In workshops,  
> a lot of people had trouble with those open/save panels.
> 
> There are quite a few apps written with Tcl/Tk for GNU/Linux, so I am  
> sure we are not the first to want this feature.  I would be very  
> surprised if another Tcl/Tk app hasn't solved this already.

according to http://www.groupsrv.com/computers/about266840.html it is 
acutally already built into tk-8.4 but not exposed!

quoting this article:
 >
 > If you have Tcl/Tk 8.4.12, find the file "tkfbox.tcl" in your Tk
 > installation. At line 777, you will see:
 >
 > set ::tk::dialog::file::showHiddenBtn 0
 > set ::tk::dialog::file::showHiddenVar 1
 >
 > Replace them by:
 >
 > set ::tk::dialog::file::showHiddenBtn 1
 > set ::tk::dialog::file::showHiddenVar 0
 >
 > And you're done...

mfgasd.r
IOhannes



-- 
Dan Wilcox
robotcowboy.com