Re: Updating a TextView with the results of a long, processor-intensive process

[Ross McFarland <rwmcfa1 neces com>]

On Wed, 2004-04-14 at 17:36, Bob Wilkinson wrote:
> On Wed, Apr 14, 2004 at 10:42:58PM +0200, Jan Hudec wrote:
> > On Wed, Apr 14, 2004 at 19:41:30 +0100, Bob Wilkinson wrote:
> > > On Tue, Apr 13, 2004 at 11:17:21PM -0400, muppet wrote:
> > > > On Tuesday, April 13, 2004, at 05:23 PM, Bob Wilkinson wrote:
> > > >
> > > > > I have read the FAQ Q: How do i keep my gui updating while doing a 
> > > > > long file read?
> > > > > and added code to the process_infile routine.
> > > > <snip>
> > > > > However, it only updated my TextView at the end of the processing.
> > > >
> > > > Some sanity-check questions:
> > > > - Are you returning control to the event loop?
> > >
> > > Implicitly. once the processing routine is finished control returns.
> > > How would I do this explicitly, once the processing routine is
> > > started?
> >
> > Since all problems you described later seem to be this one:
> >
> > You should know, that Gtk+ applications are NOT threaded (normaly).
> > Things don't happen in parallel in them. Instead they run from a big
> > event loop, that waits for something to happen and calls appropriate
> > function that responds. All the redrawing is tightly bound to events
> > sent by the X server. Thus it can only happen from the mainloop^*. So
> > you need to pass control to the main loop for ANYTHING to be redrawn.
> >
> > There are two ways to pass control to mainloop.
> > 1) Returning. You must set an idle handler to do the rest of the work
> >    (it will be called once pending events are processed).
> > 2) Calling gtk_main_iteration()/Gtk2->main_iteration(). That will
> >    process pending events once and return. So you have to call it
> >    regularly from a long-running routine.
>
> I have   
>
> Glib::Idle->add( sub {while (Gtk2->events_pending()) {Gtk2->main_iteration()}});

i don't know exactly what you're trying to do, but you don't want to do
that.

Glib::Idle's will only happen while you're in a main loop. it doesn't do
anything productive to have a main iteration happening in an idle that
would be called from a main loop. beyond that it's likely that the idle
loop would only happen once, since you're probably not returning 1
(true) to keep it installed.

basically if you're watching a file descriptor and updating a text
widget with it then you probably want to use a the io watch stuff. where
it will sit in a mainloop and call your code when there's something for
it to do. 

if you're just doing complicated calculations or other non-io stuff that
takes a long time then you should periodically do the while events
pending handle some events stuff. i haven't been following this thread
close enough to tell you what's right for your situation, perhaps others
on the list have and can give you better answers.

-rm