Change DPI on HiDPI laptop with two external monitors

Question

I have a Surface Pro 3 laptop (running Ubuntu Gnome) with two external monitors.
The laptop's screen has a resolution of 2160x1440, and the two monitors are 1920x1080.
The Surface Pro (eDP1) is on the left, and the two other monitors (DP1 & DP2) are on the right, with the central monitor being the primary monitor.

This causes everything on the Surface Pro display to be extremely small, so I want to change the DPI of this display to make everything a bit bigger.

However, I have no idea how to do that. I've tried using xrandr, but I can't get it to work.
Can anyone help?

Cheers, CJ

Answer 1

Try running the following command:

xrandr --output eDP1 --auto --output DP1 --auto --scale 2x2 --right-of eDP1 --output DP2 --auto --scale 2x2 --right-of DP1

This should make the HD monitors look smaller. You can also use this in conjunction with the following:

gsettings set org.gnome.desktop.interface scaling-factor 2

After running both of these commands, the Surface Pro 3 should look larger, but the external monitors should look the same size as they did before. Try adjusting the values to 1.5 if the Surface's display looks too 'big'.

Source: https://wiki.archlinux.org/index.php/HiDPI

Answer 2

Only scaling wont help. I have yoga 2 pro with resolution 3200x1800 and external FHD monitor. In my case i use xrandr panning option:

xrandr --output eDP1 --auto --output HDMI1 --auto --panning 3840x2160+3200+0 --scale 2x2 --right-of eDP1

Basically if your hidpi monitor is AxB pixels and your regular monitor is CxD and you are scaling by [ExF], the commandline for right-of is:

xrandr --output eDP1 --auto --output HDMI1 --auto --panning [C*E]x[D*F]+[A]+0 --scale [E]x[F] --right-of eDP1