focus stealing prevention in xfdesktop

[Olivier Fourdan]

Olivier Fourdan wrote:
> "The special value of zero on a newly mapped window can be used to 
> request that the window not be initially focused when it is mapped."
> 
[...]
> 
> Anyway, I'll have to revert my patch to be in line with that standard. 
> I'll try to investigate something like:
> 
> gdk_x11_window_set_user_time(GTK_WIDGET (itf->tweaks_dialog)->window,
>      gdk_x11_get_server_time (GTK_WIDGET (itf->tweaks_dialog)->window));

Ok, that seems to do the job quite accurately, so I've updated my 
changes and also your code too (hope you don't mind).

Cheers,
Olivier.