Re: gtk multithreaded apps and glib signals

[Todd Fisher <taf2 lehigh edu>]

Hi,
   I worked on a similar project.  The way I solved the problem of 
sending a signal from a thread that is not in the main event loop thread 
was to  use g_timeout_add and polling every 2 or 3 milliseconds for 
messages from the decoding thread.  So, the object that is shared 
between the main thread
and the decoding thread would be a GAsyncQueue.  Then all you have to do 
is in your idle func do a try_pop to check if any data has been pushed onto
the queue.  If the data is on the queue then process it however you like 
perhaps by calling g_signal_emit or some other task.  If there is 
nothing in the
queue then just fall through.  The decoding thread would just push a 
data message into the queue when its ready to send a stream-ended 
signal.  At least
that's basically what i did to get my decoder thread to notify the main 
thread that it was time to start up another decoder after finishing a 
track in my playlist.

The source code for the media player I wrote is here if you're 
interested in more of the details:  
http://severna.homeip.net/code.php#gtkmusic
The important parts are in play_list.cc search fro g_timeout_add.

hope, this helps
-todd

Brian J. Tarricone wrote: 

> hi all-
>
> i'm getting a bit confused as to what i'm supposed to do to make sure 
> multithreaded gtk apps don't do evil things.  i'm writing a music 
> player (which is a GObject), and the audio decoding and output are 
> handled in a separate thread (let's call this "thread #2").  when an 
> audio stream finishes playing, i want it to send a glib signal 
> ("stream-ended").  obviously, thread #2 is what knows about the stream 
> ending, and so logically it will call g_signal_emit().  do the signal 
> handlers get called in thread #2, or in the main thread?  if in thread 
> #2, i assume i have to surround any gtk calls in the signal handler 
> with gdk_threads_enter/leave(), correct?
>
> if the signals are handled in thread #2, is there a way to have the 
> signal get handled in the main thread?  perhaps using g_idle_add() or 
> g_timeout_add()?  in that case, do i still nead the 
> gdk_threads_enter/leave() pair?
>
> i'm just trying to figure out the best way to do this; any suggestions 
> would be appreciated.
>
> thanks,
> brian
> _______________________________________________
> gtk-app-devel-list mailing list
> gtk-app-devel-list gnome org
> http://mail.gnome.org/mailman/listinfo/gtk-app-devel-list