Re: threads gdk/Xlib

[Stéphane Konstantaropoulos <stephane cs york ac uk>]

On Mon, 2005-04-11 at 09:51 -0400, Owen Taylor wrote:
> On Mon, 2005-04-11 at 13:06 +0100, Stéphane Konstantaropoulos wrote:
> > Hello all,
> >
> > I am programming a testing app for a gtk widget that embeds Xine and I
> > am facing little problems with threads and XLib: the application crashes
> > all the time whith "Xlib: unexpected async reply"
> >
> > It got fixed only when I called the following functions in the following
> > sequence:
> >
> > XInitThreads ();
> > g_thread_init(NULL);        
> > gdk_threads_init();
> > gtk_init(&argc, &argv);
> >
> > There is no need to put gtk_main() between gdk_threads_enter() and gdk_threads_leave().
>
> If you use a debugging threads library, you'll then see warnings about
> "unlocking an unlocked mutex" or similar. If you call gdk_threads_init
> (), then all calls to GDK must be within the GDK lock. On the other
> hand, there is no reason to call gdk_threads_init() if you are using
> GDK from only one thread.
>
> > To sum up: there are calls to Xlib from other threads, created by Xine. Gdk also calls Xlib but only from 
> > the
> > main thread (my app does not create any). Xine always calls XLockDisplay() before doing any of these 
> > calls.
> >
> > Question then:
> >
> > - Does Gdk call XLockdisplay() at all?
>
> When necessary, yes. You only need to call XLockDisplay() if you are
> doing incredibly grotty low-level Xlib programming. GDK does some of
> that, it's conceivable that Xine does too, though I rather doubt it.

> > - Do you need to call XInitThreads() before gdk_threads_init() ? -> that's the way it seems to work for 
> > me.
>
> No, I don't think so. You *do* need to call XInitThreads before making
> any other GDK/GTK+ calls (like gtk_init() 
> since they might call Xlib functions)

Great! No need for Gdk threads so I removed the call to gdk_threads_init
() and just kept the call to XInitThreads() before doing anything else
and -- it works...

Thanks a lot Owen,

-- 
Stéphane Konstantaropoulos
- Research Student, Computer Science
-- University of York, http://www-users.cs.york.ac.uk/~stephane