[pygtk] Refreshing a Tree Store/Tree View within a thread crashes randomly

[John Stowers]

On Sun, 2009-01-25 at 02:57 +0100, Lionel Dricot wrote:
> Hello,
> 
> I'm displaying a TreeStore in a TreeView and I want to refresh them
> when I receive the gobject signal "refresh".
> 
> Because my refresh can be heavy and I don't want to refresh 10 times
> when not needed, the refresh is handled in a thread. The principle is
> the following :

Simple, Gtk is not threadsafe!

Do not touch the GUI from the non main thread (unless you acquire the
gtk lock)

Advice on handling Threads with (py)Gtk can be found 

http://faq.pygtk.org/index.py?req=show&file=faq20.001.htp
http://www.johnstowers.co.nz/blog/index.php/2007/03/12/threading-and-pygtk/
http://unpythonic.blogspot.com/2007/08/using-threads-in-pygtk.html
http://www.oreillynet.com/onlamp/blog/2006/07/pygtk_and_threading.html

John

> 
> SignalEmitter.connect("refresh",self.do_refresh)
> 
> do_refresh()
>     thread(self.general_refresh)
> 
> general_refresh()
>     if self.lock.acquire(False) :
>         refresh_treestore()
>         self.lock.release()
> 
> refresh_treestore() :
> At first, I was emptying the TreeStore then added the elements but
> I've seen somewhere on the web that it might be better to create a new
> TreeStore then to set_model on the TreeView
> 
> 
> Unfortunatly, it crashes randomly with the error :
> 
> /home/ploum/code/gtg/taskbrowser/browser.py:180: GtkWarning:
> gtk_tree_store_get_value: assertion `VALID_ITER (iter, tree_store)'
> failed
>   gtk.main()
> /home/ploum/code/gtg/taskbrowser/browser.py:180: Warning:
> g_object_set_property: assertion `G_IS_VALUE (value)' failed
>   gtk.main()
> /home/ploum/code/gtg/taskbrowser/browser.py:180: Warning:
> g_value_unset: assertion `G_IS_VALUE (value)' failed
>   gtk.main()
> 
> The crash can happen at start, it can happen after 10 minutes, it's
> completely random. Also, the crash always happens after the lock is
> released.
> 
> I've no idea why it crashes like this and any help would be greatly
> appreciated !
> 
> 
> If you are motivated enough to try the real code, I've put a bzr
> branch on https://code.edge.launchpad.net/~gtg/gtg/threaded. simply
> do :
> 
> bzr branch lp:~gtg/gtg/threaded
> 
> The code is in taskbrowser/browser.py  (refresh_treestore is called
> refresh_ts).
> 
> (and if you want to see the application in its normal shape, just do
> bzr branch lp:gtg )
> 
> Thanks a lot for your (future) help,
> 
> Lionel
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