unity - lightdm login screen almost unusable with NVidia drivers

I cannot use lightdm to login, while using NVIDIA drivers. I just see a tiny area at the left corner with the icons, and the password text field. Though I can login, I can't choose my session or login. My unity greeter errors (/var/log/lightdm/seat0-greeter.log) I don't have any errors in .xession-errors or /var/log/lightdm/lightdm.log

  (unity-greeter:1662): Gtk-WARNING **: Allocating size to Background 0x55dae3d5c1f0 without calling gtk_widget_get_preferred_width/height(). How does the code know the size to allocate?
    [+0.30s] DEBUG: background.vala:485: Regenerating backgrounds
    [+0.30s] DEBUG: background.vala:68: Making background /usr/share/backgrounds/warty-final-ubuntu.png at 0x0

    [+0.30s] DEBUG: background.vala:68: Making background /usr/share/backgrounds/xfce/xfce-teal.jpg at 0x0
    [+0.31s] DEBUG: unity-greeter.vala:227: starting system-ready sound
    [+0.37s] CRITICAL: gdk_pixbuf_new: assertion 'width > 0' failed
    [+0.37s] CRITICAL: gdk_pixbuf_scale: assertion 'GDK_IS_PIXBUF (dest)' failed
    [+0.38s] CRITICAL: gdk_pixbuf_new: assertion 'width > 0' failed
    [+0.38s] CRITICAL: gdk_pixbuf_scale: assertion 'GDK_IS_PIXBUF (dest)' failed
    [+0.38s] CRITICAL: gdk_pixbuf_new: assertion 'width > 0' failed
    [+0.38s] CRITICAL: gdk_pixbuf_scale: assertion 'GDK_IS_PIXBUF (dest)' failed

    (nm-applet:1696): GLib-GObject-WARNING **: invalid unclassed pointer in cast to 'GtkWidget'


    (nm-applet:1696): Gtk-CRITICAL **: gtk_widget_show: assertion 'GTK_IS_WIDGET (widget)' failed

    (nm-applet:1696): GLib-GObject-WARNING **: invalid unclassed pointer in cast to 'GtkWidget'

    (nm-applet:1696): Gtk-CRITICAL **: gtk_widget_show: assertion 'GTK_IS_WIDGET (widget)' failed

    (nm-applet:1696): GLib-GObject-WARNING **: invalid unclassed pointer in cast to 'GtkWidget'

    (nm-applet:1696): Gtk-CRITICAL **: gtk_widget_show: assertion 'GTK_IS_WIDGET (widget)' failed


    (nm-applet:1696): GLib-GObject-WARNING **: invalid unclassed pointer in cast to 'GtkWidget'

    (nm-applet:1696): Gtk-CRITICAL **: gtk_widget_show: assertion 'GTK_IS_WIDGET (widget)' failed
    [+6.24s] DEBUG: background.vala:121: Render of background /usr/share/backgrounds/xfce/xfce-teal.jpg complete
    [+6.24s] DEBUG: background.vala:138: images[0] was null for /usr/share/backgrounds/xfce/xfce-teal.jpg
    [+6.24s] DEBUG: background.vala:121: Render of background /usr/share/backgrounds/xfce/xfce-teal.jpg complete
    [+6.24s] DEBUG: background.vala:138: images[0] was null for /usr/share/backgrounds/xfce/xfce-teal.jpg
    [+6.24s] DEBUG: background.vala:121: Render of background /usr/share/backgrounds/warty-final-ubuntu.png complete
    [+6.24s] DEBUG: background.vala:138: images[0] was null for /usr/share/backgrounds/warty-final-ubuntu.png

    [+6.26s] DEBUG: user-list.vala:1030: Adding/updating user swadnerkar ()
    [+9.65s] DEBUG: Providing response to display manager
    [+9.65s] DEBUG: Wrote 24 bytes to daemon
    [+9.72s] DEBUG: Read 8 bytes from daemon
    [+9.72s] DEBUG: Read 22 bytes from daemon
    [+9.72s] DEBUG: Authentication complete for user swadnerkar with return code 0
    [+9.72s] DEBUG: Starting session i3
    [+9.72s] DEBUG: Wrote 14 bytes to daemon
    upstart: indicator-bluetooth main process (1702) killed by TERM signal
    upstart: indicator-power main process (1703) killed by TERM signal

    upstart: indicator-datetime main process (1704) killed by TERM signal
    upstart: indicator-session main process (1707) killed by TERM signal
    upstart: indicator-application main process (1717) killed by TERM signal
    upstart: indicator-messages main process (1701) killed by HUP signal
    upstart: indicator-keyboard main process (1705) killed by HUP signal
    upstart: indicator-sound main process (1706) killed by HUP signal

I have no problem with lxdm. My Ubuntu release:

   $ cat /etc/lsb-release 
    DISTRIB_ID=Ubuntu
    DISTRIB_RELEASE=17.04
    DISTRIB_CODENAME=zesty
    DISTRIB_DESCRIPTION="Ubuntu Zesty Zapus (development branch)"

I have been facing this problem since Xenial. So, it's not about the latest Ubuntu release.

I accidentally found the solution. I installed lubuntu-core, which installed lubuntu-default-settings package which installed correct configuration for lightdm-gtk-greeter in /etc/lightdm, after which lightdm started working. For GNOME, there is ubuntu-gnome-default-settings, and for xubuntu, xubuntu-default-settings. So, it looks like we just need to make sure one of the *-default-settings package is installed.

Previously, I did not have any desktop environment installed (I was only using i3 like WM). So, it looks like in Ubuntu, we need to have at least one desktop environment installed, otherwise some things won't work correctly. At home, I have been happily using Arch with no desktop environment with lightdm. Ubuntu is my work desktop.