DPI Scaling Fix for Ubuntu on HiDPI 3840x2160 eDP1 with 1920x1080 External Monitor

sh

#!/bin/bash

# Assumes that our global DPI default is for the Highest Resolution Monitor

# --scale 2x2:       Our external monitor scale is 2x of our 4K monitor.
# --output <Name>:   Just run xrandr without arguments to list device names.
# --mode:            The supported mode of the --output monitor.
# --fb:              1920 * 2 x 1080 * 2 + 1080, or 3840x3240. Sets this monitors to fit this space.
# --pos:             Set my external monitor's location starting at 0x0
xrandr --output HDMI2 --scale 2x2 --mode 1920x1080 --fb 3840x3240 --pos 0x0

# --scale 1x1:       Our laptop monitor is equal to our global DPI setting.
# --pos 960x2160:    Move our screen down so it does not overlap the external monitor. (1920 * 2 - 1920) / 2 x 1080 * 2, or 960x2160
xrandr --output eDP1 --scale 1x1 --pos 960x2160

UbuntuHiDPI.md

Based on the contents http://blog.jamiek.it/2015/04/manually-fixing-multiple-screens-with.html

• Set your Ubuntu to the highest DPI from the System Configurations
• If not using Ubuntu, then you may need to configure based on instructions here and use a DPI calclator.
• Please referer to the full blog post and give thanks to the OP.
• This is just notes and a cached script for my personal laptop
• My External Monitor (HDMI2) is Above my Laptop Screen (eDP1)

Note: There is a known isue of blurriness in the lower resolution monitor with this solution.

This is a lifesaver. Thanks so much.

Lifesaver indeed !

For information. XPS 2014 15" / Ubuntu 18.10

Here are the working commands:

xrandr --listmonitors # remplace HDMI-1 by maybe HDMI-1-1 and same for eDP
xrandr --output HDMI-1 --scale 2x2 --mode 1920x1080 --fb 3200x1800 --pos 0x0
xrandr --output eDP-1 --scale 1x1 --pos 960x2160

Not sure it's the best but it works.

[edit] Ubuntu 19.04 : just switch to wayland. It's working great, no command line needed. Thanks canonical.