Re: Glib 2.32.x, Win32 and threading

[Chris Vine <chris cvine freeserve co uk>]

On Wed, 04 Jul 2012 13:18:18 +0200
"Martin Schlemmer" <Martin Schlemmer nwu ac za> wrote:
> >>> On 7/4/2012 at 10:30 AM, Chris Vine <chris cvine freeserve co uk>
> wrote:
[snip]
> > GTK+/GDK has never been thread-safe on Win32.  If the GDK global
> lock
> > appeared to work for you in the past you just got lucky.  From the
> > documentation at
> > http://developer.gnome.org/gdk/stable/gdk-Threads.html :
> > 
> > "GTK+ is "thread aware" but not thread safe * it provides a global
> lock
> > controlled by gdk_threads_enter()/gdk_threads_leave() which protects
> > all use of GTK+. That is, only one thread can use GTK+ at any given
> > time.
> > 
> > "Unfortunately the above holds with the X11 backend only. With the
> Win32
> > backend, GDK calls should not be attempted from multiple threads at
> > all."
> > 
> > In due course
> gdk_threads_init()/gdk_threads_enter()/gdk_threads_leave()
> > are to be deprecated in the X11 backend, although that is not
> relevant
> > to your code.
> > 
> > Win32 users (and in due course X11 users) should use
> > g_idle_add()/g_idle_add_full() to send event callbacks from worker
> > threads to the gui thread which invoke the GTK+ functions you want
> to
> > call. With glib < 2.32, you will need to call g_thread_init()
> > (g_thread_init() is not needed on glib >= 2.32 and is a no-op.) 
> This
> > also happens to be a much cleaner design than using the GDK global
> lock.
> > 
> > The FAQ on this is, I agree, misleading - I should file a
> documentation
> > bug.
> > 
> 
> I understand this, and that is why I modified the example to do
> exactly that - use g_idle_add().

It didn't.  The code you posted makes calls to gdk_threads_init(),
gdk_threads_enter(), gdk_threads_leave() and gdk_threads_add_idle().

As I have said, it is pointless trying to invoke the GDK lock
(which these do) in Win32 and in your case seems to have created a
deadlock.  Remove these gdk calls, refactor your code to pass events,
use g_thread_init() and g_idle_add(), and it should work.

Chris