On an HP ProBook 6470b with Intel HD 4000 graphics, adding the following line to /usr/share/X11/xorg.conf.d/20-intel.conf resolved this issue in addition to fixing the resolution of my external monitor at the login screen:
Option "ReprobeOutputs" "true" -- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to xserver-xorg-video-intel in Ubuntu. https://bugs.launchpad.net/bugs/1531224 Title: lightdm-gtk-greeter flickers once little after lightdm starts To manage notifications about this bug go to: https://bugs.launchpad.net/lightdm-gtk-greeter/+bug/1531224/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~ubuntu-x-swat Post to : ubuntu-x-swat@lists.launchpad.net Unsubscribe : https://launchpad.net/~ubuntu-x-swat More help : https://help.launchpad.net/ListHelp
