From: Clifford Heath <no@...>
Date: 2005-08-16T08:26:15+09:00
Subject: Re: Asynchronous events in GTK application?

Masao Mutoh wrote:
> Do you mean to call Gtk.events_pending?  ?

No, I'm happy if it blocks inside main_iteration, as long as the
timeout I added makes main_iteration return - which it does.

>>but in this version, main_iteration always returns true. I guess
>>that's a change from the 0.9.1 version.)
> Hmm. I've not change the behavior of Gtk.main_iteration for long time.

Well, then either the documentation or the code is wrong, because it
always returns true. I don't see how I can tell when quit has been
called...?

> Anyway, if you don't call Gtk.main anywhere, Gtk.main_iteration
> doesn't work correctly.

Ouch! I can't do that, I don't think. What is the effect if main
never gets called?

>>In case there are no GUI events, I added a timeout which pumps
>>the loop.
> How about to use Gtk.timeout_add ?

That's what I did, I just didn't want to confuse the issue with too
much code. A bigger snippet of what I'm doing follows:

	device_change = false
	Gtk.timeout_add(500) {
             return true if (@busy)
	    device_change = true if checkDevice
             true
         }
         while true
             if device_change
                 processDeviceChange
                 device_change = false
             end
             puts "iteration"
             p Gtk.main_iteration
	end

If the timeout is set to 500 or more, all works well. If I set it to
250 or less, then the GUI doesn't refresh, even though "iteration" is
printed continuously.

Ok, I see what I need to do. Where I call main_iteration, I have to
continue calling it while events_pending?, before looping to check
for a device_change again. That seems to work better! I should've
realised.

The reason I'm doing all this is because I don't want the "process"
to occur in the middle of a flurry of GUI events, but at the end.

If I add an "idle" callback, I'll have the problem that it will chew
CPU. For an app that uses idle not to busy wait, should it call
main_iteration once to block before returning? What I really want is
a method that says "wait until the next event", but I can't see one
inthe documentation.

Also, I moved my Debian installation to "unstable", from "testing",
and I find I now have ruby-gnome2 version 1.13.0, yaay!

> P.S.
> I think gtk-demo(in Ruby-GNOME2 tar ball) scripts may be helpful.

I'll check that out, thanks.

Clifford Heath.