[Fwd: Re: where is error? (Glib::spawn_async)]

[Michael J M Thomson <mjmt internode on net>]

-------- Original Message --------
Subject: Re: where is error? (Glib::spawn_async)
Date: Fri, 03 Nov 2006 14:11:46 +1100
From: Michael J M Thomson <mjmt internode on net>
To: Jonathon Jongsma <jonathon jongsma gmail com>
References: <200611030106 36174 pogonyshev gmx net>	 
<454A987E 8010507 internode on net> 
<ee2fcb570611021750n5aa14e57ga86eda709905e7d9 mail gmail com>

Jonathon Jongsma wrote:
> On 11/2/06, Michael J M Thomson <mjmt internode on net> wrote:
> > Paul Pogonyshev wrote:
> > > Hi.
> > >
> > > Where is error in this code fragment?
> > >
> > >       std::vector <std::string>  yelp_arguments;
> > >
> > >       yelp_arguments.push_back ("yelp");
> > >       yelp_arguments.push_back 
> > ("ghelp:///usr/share/gnome/help/gedit/C/gedit.xml");
> > >
> > >       try
> > >       {
> > >         Glib::spawn_async (".", yelp_arguments, std::vector 
> > <std::string> (),
> > >                            Glib::SPAWN_SEARCH_PATH);
> > >         return;
> > >       }
> > >       catch (Glib::Error& exception)
> > >       {
> > >         g_print ("%s...\n", exception.what ().c_str ());
> > >       }
> > >
> > > I get this in terminal:
> > >
> > >     (yelp:14036): Gtk-WARNING **: cannot open display:
> > >
> > > and Yelp window is never shown.
> > >
> > > Paul
> > > _______________________________________________
> > > gtkmm-list mailing list
> > > gtkmm-list gnome org
> > > http://mail.gnome.org/mailman/listinfo/gtkmm-list
> > >
> >
> > The third argument you're passing to Glib::spawn_async(),
> > std::vector<std::string>(), you shouldn't (and don't need to). It 
> > becomes the
> > set of environment variables seen by the spawned child, instead of 
> > those already
> > present in the parent process' environment. And while it may seem more 
> > secure or
> > neater or something to change it, some variables are vital, e.g. 
> > without DISPLAY
> > most Xlib-based programs won't work, and in GNOME's (and probably 
> > KDE's and
> > other desktops) case there are several variables that allow session 
> > management
> > and other desktop stuff to work properly. Non-GUI programs might also 
> > crap out,
> > if they rely on e.g. HOME or USER (even though they shouldn't). Not 
> > sure but Mac
> > OS X and probably Windows mightn't appreciate certain environment 
> > variables not
> > being set properly ,either.
> > _______________________________________________
> > gtkmm-list mailing list
> > gtkmm-list gnome org
> > http://mail.gnome.org/mailman/listinfo/gtkmm-list
>
> what makes you say that you don't need to pass the third parameter?
> the function expects a reference to an array here so you must pass it
> something.  Am I missing something?

No I probably wasn't clear, sorry. Just there are several overloads of
Glib::spawn_async(), one of which doesn't expect that argument:

Glib::spawn_async(const std::string& working_directory,
                  const Glib::ArrayHandle<std::string>& argv,
                  SpawnFlags flags = SpawnFlags(0),
                  const sigc::slot<void>& child_setup = sigc::slot<void>(),
                  Pid* child_pid = 0);

Kind of makes sense IMHO, if you consider vector<string>() as equivalent to
passing an empty array (char* env[1] = { NULL }) rather than NULL.