Re: [gtk-list] Re: Event propogation problem

[Owen Taylor <otaylor redhat com>]

Ian Britten <britten@universal.ca> writes:

> On 20 Jan 2000, Owen Taylor wrote:
> 
> > Three different sets of handlers are run for each signal emission:
> > 
> >  - handlers connected with gtk_signal_connect()
> >  - the default handler for the widget
> >  - handlers connected with gtk_signal_connect_after()
> > 
> > Only the _last_ return value matters. The default handlers is running
> > after your signal handler and returning FALSE.
> > 
> > So you have two choices:
> > 
> >  - If you want to override the default handler, use gtk_signal_connect(),
> >    and then call gtk_signal_emit_stop_by_name() before returning TRUE
> > 
> >  - If you want to supplement the default handler use gtk_signal_connect_after().
> 
> Ok, now I understand (I think...).  It's not quite the same way Motif
> works...  (Not that that's a bad thing :-)
> 
> > Key snoopers are called before any other handling of the key press. They
> > really aren't intended for general use - perhaps you want an accelerator
> > instead. (Or simply want to connect to ::key_press_event on the toplevel.)
 
> Ok, if snoopers aren't for general use, perhaps you can suggest a solution
> to my problem for me.

> I'm inside I time-consuming loop, and am looking for a way to break out of
> the loop in response to a user action (Typically, the Escape key being
> pressed).

> Because I'm in a loop, I haven't returned to the main loop, meaning that
> received events aren't being processed yet.  Thus, I can't set up a signal
> handler, as it won't be called until I return from my loop.  What I'm
> doing is peeking into the event queue to see if the the key press is
> there, and if it is, I break out of the loop.
> Under X, I was using XCheckIfEvent().  What should I do under GTK?
> Ian

Generally what you want to do in this circumstance is to occasionally 
process the events from the main events loop using:

 while (g_main_iteration (FALSE))
   /* Nothing */;

Then when you get an escape key (using, for instance, a ::key_press_event handler),
you set a flag that you check after calling g_main_iterate.

Regards,
                                        Owen