Re: How to reconnect to a new X Server

[Sebastian Reitenbach]

On Wednesday, May 22, 2013 11:55 CEST, "Dr. H. Nikolaus Schaller" 
<hns@goldelico.com> wrote: 
 
> 
> Am 22.05.2013 um 11:34 schrieb Sebastian Reitenbach:
> 
> > Hi,
> > 
> > working with Riccardo on GAPs loginpanel, made some progress, but ran into 
> > trouble now.
> > 
> > What I do is starting the X Server, before I then start the loginpanel 
> > application.
> > Then the loginpanel actually has an X server running, where it can connect 
> > to.
> > 
> > So far, that works well. I can login. When I logout, then I am killing the 
> > X server, and
> > want to restart it, and spawn the loginpanel again.
> > 
> > First I tried in loginpanels main function:
> > 
> >   while (1)
> >     {
> >       [XManager startXServer];
> >       putenv("DISPLAY=:0.0");
> > 
> >       NSApplicationMain(argc, argv);
> > 
> >     }
> > 
> > 
> > That probably was too naive from me thinking it might work ;) Reading up 
> > NSApplication
> > documentation, I see that everything after NSApplicationMain(argc, argv); 
> > will not be 
> > exectuted, so the while loop will only runs once :(
> > 
> > Anyways, then I tried to start the XServer again, after I teared it down.
> > That works so far, but when the loginpanel wants to reset its window on the 
> > X server, 
> > I see it crying on the console, that the connection to the XServer broke:
> > 
> > X connection to :0.0 broken (explicit kill or server shutdown)
> > 
> > Even if there is a new server spawned already on the same display.
> > 
> > Is there a way to tell the application that the X Server disappeared, and it
> > should reconnect to the new one? Or tell it to kind of respawn itself?
> 
> I think what you are looking for should be done in the startx or xinit 
> scripts of
> your system. They are usually responsible for restarting X servers. Also
> initd and its run-levels play some role.
> 
> So the loginpanel should also be restarted by the same mechanism.
> I.e. you could try to make it sort of a display and/or window manager.

I thought more the lines of XDM, when the X server it spawns gets killed,
its restarting it, showing the login greeter again.

I looked at Login.app from mGSTEP as an example:
http://www.illumenos.com/os/mgstep/projects.html

I could write an init script , that runs the while (1) loop, and restarts
every time. Otherwise, I could potentially just write a wrapper binary, which
execve() the application in a while loop.


Sebastian

> 
> Nikolaus