Re: Changing widgets in events

[Brian <brian8192 fastmail fm>]

Yep, that did it!  Thanks for the advice.  Next time I'll check the
archives before posting.  I still think most of the documentation for
gtk is rather incomplete.  More examples would certainly help.  If
anyone from gtk.org is reading this and need volunteers to write
documentation then I can help on some stuff.  For example, tree view and
list store docs are empty.

thanks again,
brian.

On Thu, 2004-02-05 at 01:12, Richard Warren wrote:
> > Does anyone know a way to change widgets while running an event
> > handler?  For example, I created a window with a single button on it.  I
> > used gtk_signal_connect to connect a function to the button to fire when
> > it is pressed.  Inside the function, I just sleep for 20 seconds.
> > Before I issue the sleep call, I change the cursor to a "watch" cursor.
> > When the sleep is finished, I change it back to the default arrow.  When
> > I run this program, pressing the button makes it stop for 20 seconds,
> > but the cursor does not change.  If I remove the call to change the
> > cursor back to the arrow, the cursor changes to the watch, but only
> > after the 20 seconds is over (which I assume is after the event has
> > finished).  I have tried different combinations of changing cursors,
> > pulsing progress bars, etc.  I have also tried doing something time
> > consuming other than just sleeping (like computing the fib of 30, for
> > example).  I have looked over the documentation for signal handlers,
> > using both the deprecated gtk_signal* and the new g_signal*, neither of
> > them discuss this.  Am I doing something wrong?  I am using gtk 2.2, and
> > have tested this with the same results in Solaris 9 and Linux 2.4.
> >
> > Thanks in advance.
> >
> > brian.
>
>
> You're not giving the main GTK+ loop a chance to run.  Whilst you're in your
> sleep() (or any other time consuming action) you've got the processor busy
> and therefore the main loop can't update the GUI (so the cursor, progress
> bars and so on can't be changed).  All the requests you make to change
> things will be queued-up and actioned when you return from your signal
> handler after the delay.
>
> There are loads of questions along these lines in this mailing list so
> trying searching the archives.  If I remember rightly, you need to do
> something along the lines of the following in amongst your time-consuming
> function if you want the GUI to update:
>
>     while( gtk_events_pending() )
>     {
>         gtk_main_iteration();
>     }
>
> (NOTE that I can't remember precisely what the functions are called or
> whether they have arguments, so check the archives or docs).
>
> An alternative would be to spawn another thread to do the work and allow the
> GUI loop to run in the main thread (although note that you can't touch the
> GUI from your worker thread without a lot of care and attention to detail).
>
> Regards,
> Richard.
>
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