Re: Updating GUI during long operation

[Chris Vine <chris cvine freeserve co uk>]

On Sat, 20 Apr 2013 09:10:11 -0700
Kip Warner <kip thevertigo com> wrote:

> Hey list,
>
> I have a separate thread from the main loop that performs some long
> and resource intensive operation. The GUI displays an animated GIF
> while this process takes place via Gdk.PixbufAnimation. 
>
> Sometimes the animation and the rest of the GUI is very slow to
> repaint and respond to other event messages. What is the best way of
> giving the message pipeline a breather every now and then from
> outside of the main thread?
>
> I was using GObject.idle_add(self._updateGUI, ...) within the worker
> thread to specify a function to be called regularly that could provide
> some other GUI related update tasks, including the following within
> it...
>
>         # Pump the Gtk+ event handler...
>         while Gtk.events_pending():
>             Gtk.main_iteration()
>
> However, my application will crash if I do this with a stack overflow
> within updateGUI. I'm assuming that since idle_add posted the message
> to call the updateGUI callback, when the callback is invoked and
> tries to pump the message pipeline, the method is invoked again
> because it still hasn't cleared itself from the queue.
>
> I could have tried this aforementioned event pump from outside the
> updateGUI callback and done it from within the worker thread, but I
> didn't know if that was thread safe to do.

If you have a main loop running, this is completely unnecessary, unless
you are doing something to block the loop, which you shouldn't do.

Chris