Re: Signal emission in multi-threading environment

["Ben Lau" <xbenlau gmail com>]

Hi Stefan,

It is the simplest method!

Thanks Stefan and all people replied on this thread.

On Dec 8, 2007 6:23 PM, Stefan Kost <ensonic hora-obscura de> wrote:
> Hi Ben,
>
> Ben Lau schrieb:
> > hi all,
> >
> >    I am implementing a GObject (a simple video player) that creates a
> > GStreamer pipeline for video processing. Soon it receives a new
> > GstBuffer of video frame from the pipeline, it will emit a signal. As
> > GStreamer processes the pipeline with multiple threads.  The signal
> > handler may not be involved inside the main thread. If my GObject
> > calls g_signal_emit() within the handler, then client's callback
> > function may also not be involved from the main thread.
> >
> You should use the GstBus. In the signal handler create an application message
> and post it to the bus. The bus will marshall data and invoke signal handler in
> you application thread. your app need to have signal handlers on the bus to
> listen for the application message.
> Here is an example:
> http://buzztard.cvs.sourceforge.net/buzztard/buzztard/src/ui/edit/main-toolbar.c?view=markup
> look for
> on_channels_negotiated()
>
> Stefan
>
> >
> >   If the callback uses any Gdk/Gtk functions, then it may cause a race
> > condition. Ofcoz it could be avoided by using
> > gdk_threads_enter/gdk_threads_leave pair. However, I want to hide the
> > multi-threading issue from user ,so that they don't need to care
> > about.
> >
> >  To achieve this purpose, the signal should be emitted within the main
> > thread. Could anybody suggest a method to ensure that a signal is
> > emitted within the main thread?
> >
> >  I am thinking about to create a GSource to attach to the main
> > context. Soon a new frame is ready, it will dispatch the event to my
> > video player in main thread. But I wonder would it have any other
> > simpler method to achieve the goal?
> >
> > Thanks for any advise.
> > _______________________________________________
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> > gtk-app-devel-list gnome org
> > http://mail.gnome.org/mailman/listinfo/gtk-app-devel-list
>
>