[Pkg-xfce-devel] Bug#852397: lightdm does not display a greeter dialog when accessed via XDMCP from a cygwin XWin server

[Paul Ausbeck]

Package: lightdm
Version: 1.18.3-1

I attempt to connect via XDMCP to a machine running Debian Sid/Stretch 
from a remote cygwin based Xserver. The remote session starts and 
displays a black screen with nothing but a mouse cursor in the very 
middle. The mouse cursor then jumps to the upper left corner of the 
screen and nothing further happens. I am expecting to see the lightdm 
greeter which never appears. I have several other machines running 
Debian Jessie and Debian Wheezy and can connect to them with no 
problems. I have two machines running Sid/Stretch and I can't connect to 
either. The problem is specific to Sid/Stretch and I would classify it 
as a regression.

I have included the lightdm greeter error log, 
/var/log/lightdm/(null)-greeter.log, from the Sid/Stretch machine below. 
The WARNING related to the upstart command and the WARNING related to 
negative dimensions are present in the greeter log for the physical 
monitor/keyboard so I guess that they are not related to the problem. I 
would guess that the problem lies with the gdk_pixbuf calls.

I have also included the lightdm greeter log from a successful 
connection to a Debian Jessie machine even further below. Note that the 
name of the greeter log file is "x-192.168.1.50-0-greeter.log" for a 
successful connection and "(null)-greeter.log" for an unsuccessful 
connection. Perhaps the name difference is related to the problem.

I don't know enough about the various pieces of this puzzle so I don't 
know if I should file this bug against Debian or cygwin. I'm thinking 
somehow that I shouldn't have to make changes to my Xserver to connect 
to a Sid/Stretch machine when I can connect just fine to Jessie and 
Wheezy machines with the same Xserver.

The problem machines are running  freshly updated/upgraded Debian 
Sid/Stretch: /etc/debian_version 9.0


Unsuccessful greeter log from Debian Sid/Stretch machine:

root at dn2800mt2:/var/log/lightdm# cat \(null\)-greeter.log
** Message: Starting lightdm-gtk-greeter 2.0.2 (Nov 16 2016, 20:48:17)
** Message: [Configuration] Reading file: 
/usr/share/lightdm/lightdm-gtk-greeter.conf.d/01_debian.conf
** Message: [Configuration] Reading file: 
/etc/lightdm/lightdm-gtk-greeter.conf
Activating service name='org.a11y.atspi.Registry'
Successfully activated service 'org.a11y.atspi.Registry'

** (lightdm-gtk-greeter:1422): WARNING **: [PIDs] Failed to execute 
command: upstart

(lightdm-gtk-greeter:1422): GdkPixbuf-CRITICAL **: gdk_pixbuf_new: 
assertion 'width > 0' failed

(lightdm-gtk-greeter:1422): GdkPixbuf-CRITICAL **: gdk_pixbuf_composite: 
assertion 'GDK_IS_PIXBUF (dest)' failed

(lightdm-gtk-greeter:1422): GLib-GObject-CRITICAL **: g_object_ref: 
assertion 'G_IS_OBJECT (object)' failed

** (lightdm-gtk-greeter:1422): WARNING **: [Background] Failed to read 
wallpaper: /usr/share/images/desktop-base/login-background.svg

(lightdm-gtk-greeter:1422): GLib-GObject-CRITICAL **: g_object_unref: 
assertion 'G_IS_OBJECT (object)' failed

(lightdm-gtk-greeter:1422): Gtk-WARNING **: Drawing a gadget with 
negative dimensions. Did you forget to allocate a size? (node menubar 
owner GreeterMenuBar)
Gdk-Message: lightdm-gtk-greeter: Fatal IO error 11 (Resource 
temporarily unavailable) on X server 192.168.1.50:0.


Successful greeter log from Debian Jessie machine:

root at dn2800mt:/var/log/lightdm# cat x-192.168.1.50-0-greeter.log
(lightdm-gtk-greeter:1686): Gtk-CRITICAL **: gtk_container_foreach: 
assertion 'GTK_IS_CONTAINER (container)' failed

(lightdm-gtk-greeter:1686): Gtk-CRITICAL **: gtk_container_foreach: 
assertion 'GTK_IS_CONTAINER (container)' failed

(lightdm-gtk-greeter:1686): Gtk-CRITICAL **: gtk_container_foreach: 
assertion 'GTK_IS_CONTAINER (container)' failed