Re: Signaling TreeView to update

[Joaquim Schmidlap <schmidlap schmidlap org>]

On Sun, Jul 29, 2007 at 04:34:05PM +0100, Chris Vine wrote:

> The work-around suggested to you is not safe either if (as it appears)
> you are updating the Gtk::TreeModel from other than the GUI thread -
> that depends on whether doing so invokes any GDK functions in the
> updating thread, but I think it almost certainly does, via the internal
> callbacks of the Gtk:TreeView object.  The suggested work-around does
> the software equivalent of waving your mouse over it.  The best thing is
> for the thread delivering data to put it onto a thread safe queue and
> then emit from a Glib::Dispatcher object.  The callback of the
> Glib::Dispatcher object can then extract from the queue and put the data
> into the Gtk::TreeModel object - Glib::Dispatcher callbacks execute not
> in the signalling thread, but in the thread in which the main program
> loop runs, and is intended for this very purpose.  An alternative is to
> go down to the C layer and use g_idle_add() - the glibmm version of this
> is not thread safe for the reasons set out in this thread:
> http://mail.gnome.org/archives/gtkmm-list/2007-January/msg00051.html

I did indeed have to wrap my writes to the Gtk::TreeModel with
gdk_threads_enter and _leave. Once I did so, the app performs stably, no
core dumps, etc.

I'd be happy to post the data back to the main thread via a Dispatcher, and
it would indeed result in cleaner code (and possibly improve performance by
eliminating the global lock). But I can't find a decent example of how to
get arbitrary data from point A to point B. The documenation for
Glib::Dispatcher that I've seen is quite thin, and I can't see anyway to
communicate any data back to the receiving thread. Perhaps I haven't found
the right doc, or perhaps all it does is "void" signaling and I am on my own
for implementing a queue.

I'd be much obliged if someone could point me at some example code...

Thanks to all for the help and contributions.

JS