XMir hangs in xf86OpenConsole() WAS: Re: Fwd: [Bug 1256116] Re: Documentation instructs to install the package unity-system-compositor, but this is not sufficient for having Mir

[Christopher James Halse Rogers]

On Wed, Apr 9, 2014 at 5:44 PM, Thomas Hellstrom 
<thellstrom at vmware.com> wrote:
> Hi!
> 
> Thanks for the reply.
> I've done a bit of debugging, and this happens because the 
> unity-greeter
> tries to create up a pixmap of size (0,0). X  doesn't allow that and
> sends an error to unity-greeter that shuts down. Lightdm then shuts 
> down
> Mir and XMir and tries to start a new non-XMir X server and that's the
> one that hangs. So the hang seems to be a symptom of a bug /
> inconsistency in the lightdm error path.
> 
> So why does unity-greeter (actually gtk::screen) think the screen is 
> of
> size (0,0)? I tried to dump the gtk <-> Xserver communication and it
> appears like gtk queries the crtcs / outputs and gets (0,0) answers,
> although X replies the root window is of size 800x600, so I need to
> somehow make XMir respond with the correct modes on crtcs / outputs.
> Reading the XMir code it appears like nothing really performs an 
> initial
> modeset, although an initial mode configuration is performed.
> 
> Is the XMir-enabled DDX driver responsible for calling
> xf86SetDesiredModes(), and in that case, where is a suitable place for
> the driver to do that?

Yeah, we currently expect XMir-enabled DDXen to call 
xf86SetDesiredModes themselves, at the same point as they'd normally 
call call it (and after xmir_mode_pre_init()).

We could do it in the XMir module itself, but I was leary of side 
effects the DDXen weren't expecting.