[pygtk] idle_add questions

Steve McClure smcclure at racemi.com
Fri Aug 20 20:05:40 WST 2004

On Thu, 2004-08-19 at 23:34, Doug Quale wrote:
> Steve McClure <smcclure at racemi.com> writes:
> > > My basic problem is this, I have a dialog that takes ages to load data. 
> > > I thought I would do the data retrieval and dialog update in an idle
> > > function.  However, my initial dialog never gets displayed making me
> > > think that I'm not getting back to the event loop before the idle task
> > > runs.  That really doesn't seem to be the case though since the GUI
> > > responds to user input, albeit, incredibly slow. So slow as to really be
> > > unusable.
> > 
> > It seems to be working fine, now that I found the real priority numbers.
> > If I can just figure out why everything comes to a screeching halt as
> > soon as I return gtk.FALSE from my idle function.
> I hope someone else can give you more definitive answer, but I wanted
> to point out something about idle functions in gtk+.  Idle functions
> aren't designed for long running computations unless they can be
> broken up into small, quick pieces.  I think you will want to
> cooperatively handle gui events during your long computation or use a
> separate thread.
> See the pygtk FAQ item 3.7 for a discussion of this.
> http://www.async.com.br/faq/pygtk/index.py?req=show&file=faq03.007.htp
> Idle functions are scheduled when gtk+ doesn't have any other work to
> perform, but gtk+ doesn't preempt them.  Each idle function will run
> to completion once it's started.  Using a high priority actually makes
> things worse rather than better since gtk+ will then run the slow
> computation instead of handling gui events and the gui will freeze.
> (The gtk+ docs say "Note that you will interfere with GTK+ if you use
> a priority above GTK_PRIORITY_RESIZE.")
> You can process gui events in your idle function using
> gtk.main_iteration() if you can run this every so often
>     while gtk.events_pending():
>         gtk.main_iteration()
> If there's no way to break up your computation to run the main loop
> then you should consider using a separate thread.  [Another
> possibility that avoids threads is to use an event driven framework
> like twisted.]

Understood. I use threads often to provide user feedback while running
long processes.

In this case, I do break up my processing by using fetchmany, processing
those records, exit.

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Steve McClure <smcclure at racemi.com>

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