BUG: Display settings not applied until login

Question

I've installed Juno release and all it's amazing, except that when I block my notebook, that have a secondary display, the display settings is lost.

My notebook is on the left side and my main screen is his, the secondary screen is on the right side. When the compute is locked, the login screen is showed on my secondary display, instead of the notebook screen (my main display). The position of screens is lost too, like my notebook is on the right and secondary monitor (now primary) is on the left

Answer 1

StackExchange is not really the right place for reporting bugs, take a look at this issue on Github. Anyway, the following seems to be a workaround:

1. Create a file called set-primary-monitor-pantheon-greeter in /usr/local/bin/ (source):

#!/bin/bash
#
# Created: 2017-07-02 16:20
# Updated: 2018-02-09 12:23
# Creator: Ryan Miller
# Website: http://devopsmachine.com/
# File:    /usr/local/bin/set-primary-monitor-pantheon-greeter
#

PRIMARY_DISPLAY='[PRIMARYDISPLAY]'

# Get list of connected monitors
x_out=$(xrandr -q | grep -e '\( \)connected' | awk -F' ' '{ print $1 }')

# Safety - Check if PRIMARY_DISPLAY is connected; if not, bail out of script
[[ $(grep ${PRIMARY_DISPLAY} <<< ${x_out}) ]] || exit 0

# Iterate over x_out and disable all monitors except for PRIMARY_DISPLAY
for monitor in ${x_out[@]} ; do
    if [[ ${monitor} = ${PRIMARY_DISPLAY} ]] ; then
        xrandr --output ${monitor} --primary
    else
        xrandr --output ${monitor} --off
    fi

2. Change [PRIMARYDISPLAY] to the name of your primary display. You can get a list of all displays with xrandr (for example DisplayPort-2 in my case)
3. Make the file executable: sudo chmod +a /usr/local/bin/set-primary-monitor-pantheon-greeter
4. Add the following at the end of /usr/share/lightdm/lightdm.conf.d/40-io.elementary.greeter.conf: greeter-setup-script=/usr/local/bin/set-primary-monitor-pantheon-greeter

This will run the script when the greeter is set up. The script will then set the specified output as the primary output.