Re: threads gdk/Xlib

[Stéphane Konstantaropoulos <stephane cs york ac uk>]

Le lundi 11 avril 2005 Ã 15:54 +0300, Olexiy Avramchenko a Ãcrit :
> StÃphane 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().
> You need to put gtk_main() between gdk_threads_enter/leave() if you start any 
> thread before. If you start thread from main loop somehow, these calls aren't 
> necessary.
>
> > 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.
> If you dont use threads in your application you can drop g_thread_init(), 
> gdk_threads_init() calls on the floor. The magic in your case is in 
> XInitThreads() somehow.
>
> > Question then:
> >
> > - Does Gdk call XLockdisplay() at all?
> No. gdk_threads_init/enter/leave() stuff acts like 
> XInitThreads(),XLockDisplay(),XUnlockDisplay().
>
> > - Do you need to call XInitThreads() before gdk_threads_init() ? -> that's the way it seems to work for 
> > me.
> No.
>
> > - Why is this (ie the interaction between Xlib threads and Gdk threads) not documented anywhere?
> What system are you using ? What kind of application do you have ? What version 
> of GTK+ ? Maybe you're linking to some library that wants X threads be initialized ?

As I said, I use the Xine library, that creates lots of threads amongst
which some that use Xlib calls (not Gtk+ calls). These are launched only
inside the gtk main loop.

So Gdk calls to Xlib must be done within a XLockedDisplay/XUnlockDisplay
pair.If I call XInitThreads() AFTER gdk_threads_init() it does not work
(Xlib async...).

This is Xorg 6.8 on Linux 2.6.7 with Gtk+ 2.6

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