[XForms] Lightbutton bug - Button causes app to crash.

Serge Bromow serge at dineamix.ca
Sat Apr 11 14:45:04 CEST 2009

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Hi Dennis,

This behavior is normal for the code you provided. The app is not 
crashing but simply falling through the "fl_do_forms()" and ending 
properly. If a button has no call back then pressing the button will 
cause "fl_do_forms" to exit and proceed to the next step in your code.
To keep the program active, try;

while( 1 ) {   // TRUE

If "fl_do_forms" exits it will simply be start again. To exit the 
program you need to setup a callback that calls "exit()".

Hope this helps,


Dennis K wrote:
> To subscribers of the xforms list
> Sorry about all the e-mails, one last thing.
> the diffence between whether those buttons cause the app to crash, is
> wether something has been entered in the 'callback' secton of the
> attributes form.  No callback = program exit.  Callback = runs fine.
> Jens Thoms Toerring wrote:
>> Hi Dennis,
>> On Sat, Apr 11, 2009 at 10:23:29AM +0000, Dennis K wrote:
>>> Just want to make you aware of an issue present in version 1.0.91 and
>>> 1.0.92pre1.
>>> It seems I'm not the only one who has noticed this.
>>> http://www.ks.uiuc.edu/Research/vmd/vmd-1.5/devel.html
>>> The issue concerns the use of the 'lightbutton' widget.  When used
>>> placed in a form, and then pressed, the 'light' turns yellow.  When the
>>> mouse button is then released the program disappears, presumably because
>>> it has crashed.  When testing the form in fdesign, it runs correctly.
>>> My system is RedHat 7.3, gcc version 2.96
>>> Is the development team aware of this issue?  If there is anything I can
>>> do to assist, let me know.
>> No, I am not aware of that bug! Unfortunately, I can't reproduce
>> it here on my machine and I can't remember to have had a problem
>> with LightButtons. The entry on the VMD web page is quite old
>> (from 2000). Are you sure you're really using a new (1.0.91 or
>> newer) version and you're program isn't picking up an older
>> version of the library accidentally? (It should be easy to check:
>> just click somewhere within some window with the middle button
>> while pressing the <Alt> key - then a box with information about
>> the version should pop up.) If it's a newer version could you
>> perhaps send me an example program that exhibits the bug? That
>> would be very helpful!
>>                          Thanks and best regards, Jens

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