Change X Window DPI, make everything on screen bigger

I use an old computer as media box, it’s connected through HDMI to a FullHD TV. Sound goes through the HDMI cable to the TV, if you need help with that, look at this post

The problem is that X Window auto configures the DPI to 96, which is ok for a monitor that’s 50 cm away from you, but not for a TV that’s 3 meters away. I want a DPI of 192, this will have the effect of making everything on screen bigger. Ideally there should be a setting accessible with a mouse click, but this depends on the desktop environment. My method is universal, it works at a lower lever.

The newer X Window starts up without a configuration file, but it still can be customized. It only needs a few simple lines. I tested this on Leap 42.1, with an nVidia card, nouveau driver. It should apply to other versions or distributions as well.

First of all, gather some information by running this in Konsole or Gnome Terminal.

xrandr --query

It should output something like this, the interesting information is purple

Screen 0: minimum 320 x 200, current 3840 x 1080, maximum 16384 x 16384
HDMI-1 connected primary 1920x1080+0+0 (...) 477mm x 268mm
 1920x1080 60.00*+
 1600x900 60.00 
 1280x1024 75.02 60.02 
 1152x864 75.00 
 1024x768 75.08 60.00 
 800x600 75.00 60.32 
 640x480 75.00 60.00 
 720x400 70.08

As root, add these lines to /etc/X11/xorg.conf.d/50-monitor.conf

Section "Monitor"
  Identifier "HDMI-1"
  DisplaySize 238 134
EndSection

The value for Identifier is the same as what xrandr –query reports and DisplaySize values are half of what you get with xrandr –query. Practically, you trick X Window into thinking you have a smaller display, so it will display bigger graphics.

Relogin into your account to activate the changes.