Re: Update progress bar without returning to main loop?

[Toralf Lund <toralf procaptura com>]

Bob Caryl wrote:

> I would suggest that you connect a callback slot to the idle loop that 
> will advance the progress bar.  This will preclude a separate thread 
> to do it...  If that is not satisfactory, create a timer and connect a 
> callback slot to that, having it update the progress bar 
> periodically.  Again, no thread.
Perhaps, but doesn't this also imply executing the update "in the 
background"? If I wanted to do that, I wouldn't object that much to 
threads, either - although what you suggest probably is simpler in terms 
of not having to worry about the overheads, and also syncing/shared data 
issues. In any case, parallel execution is precisely what I do not want. 
In principle, I want the application to "lock up" while it's doing the 
job discussed here - with the small exception that I want some 
indication in the UI that it hasn't died completely on the poor user 
waiting for it.

Anyhow, I didn't mean to work with this now. More tests tomorrow.


- Toralf

>  
> Bob Caryl
>  
> /-------Original Message-------/
>  
> /*From:*/ Toralf Lund <mailto:toralf procaptura com>
> /*Date:*/ 09/26/05 14:59:44
> /*To:*/ Paul Davis <mailto:pjdavis engineering uiowa edu>
> /*Cc:*/ GTK-- Mailing List <mailto:gtkmm-list gnome org>
> /*Subject:*/ Re: Update progress bar without returning to main loop?
>  
> Paul Davis wrote:
>  
> > Threads are easy enough.
> >
> > Oh, and I forgot to attach the tar file.
> >
> > Its not hard at all.
>  
> Threads are not that hard to program, but they still represent a major
> complexity "behind the scenes". One that shouldn't be introduced just
> like that, IMO, and, if the toolkit requires me to do it just to achieve
> a *simple* GUI update, then I really think there is something
> fundamentally wrong with its design.  But I'm thinking there must be
> another way...
>  
> >
> > Toralf Lund wrote:
> >
> >> Paul Davis wrote:
> >>
> >>> No time to explain. I'm running late.
> >>>
> >>> Here it is.  Use threads.  Email questions.
> >>
> >>
> >>
> >> It's a very simple app, the complexity of threads has no place in it.
> >> Especially if it's just to make the GUI behave. In fact, introducing
> >> threads just for this seems very wrong for any program...
> >>
> >>>
> >>> Good luck.
> >>>
> >>> Toralf Lund wrote:
> >>>
> >>>> I have what I believe is a classic issue with progress bars, but I
> >>>> have never found a good solution in the docs or via a web search:
> >>>>
> >>>> I'm trying to indicate progress of a signal handler that takes a
> >>>> *long* time via a Gtk::ProgressBar and multiple calls (as the work
> >>>> progresses) using the set_fraction() method. The problem is that
> >>>> these calls have no real effect, since the actual GUI update isn't
> >>>> done until after the application returns to the main loop (i.e.
> >>>> when the handler is done and the progress has reached 100%). The
> >>>> only way I've found to ensure it's redrawn as the work progresses,
> >>>> is to flush events using something like:
> >>>>
> >>>> while(Gtk::Main::events_pending())
> >>>>   Gtk::Main::iteration(false);
> >>>>
> >>>> But this has some nasty side effects. In particular, it means that
> >>>> user input like button clicks, text field updates also handled,
> >>>> which is not what I want; I need the window to be unresponsive
> >>>> while the above mentioned callback is being executed.
> >>>>
> >>>> Is there an alternative?
> >>>>
> >>>> - Toralf
> >>>>
> >>>>
> >>>>
> >>>> _______________________________________________
> >>>> gtkmm-list mailing list
> >>>> gtkmm-list gnome org <mailto:gtkmm-list gnome org>
> >>>> http://mail.gnome.org/mailman/listinfo/gtkmm-list
> >>>
> >>>
> >>>
> >>>
> >>>
> >>
> >
>  
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