Turning off part of a monitor

Question

I'm trying to disable the right third of my monitor, since it's broken. I can get less to be displayed using xrandr, but the monitor will then center the displayed stuff, so that's not quite what I want.

I'm using Ubuntu 14.04. Please let me know if more information would be useful, preferably along with a method for finding that info :P.

Answer 1

Monitor settings

You said you already got xrandr to display on a smaller portion of the screen, but that it’s centered. If there is any way in your monitor settings to move the displayed portion to the left edge of the screen, then you’re done.

Nesting X Servers

Try Xephyr or Xnest. They allow you to run an X server inside another X server. So something like this might work:

Xephyr -screen 1200x1080 :1

Set the resolution to whatever viewable area you have on your screen. Then you have an X server that only takes a portion of the screen.

For your first X server, you may not need to run a window manager, if you can get your .xinitrc to start Xephyr in the right size and location on the screen. Xephyr -geometry 800x600+0+0 doesn’t work for me though.

You’ll need to run a window manager/desktop environment inside Xephyr. I don’t know the best way to do this at the moment.

Making your window manager avoid part of the screen

This is kind of an ugly fix, but you could create a large panel with nothing in it that covers the dead part of the screen. Set the panel so that no windows can cover it. This won’t help if a program (like a video player) tries to draw on the full screen.

Reference

Question on Stack Overflow: X in a window in X

Answer 2

For anyone seeing this x years later...

A large 4K TV with the left 1/4 of the screen disabled can still be useful with the following settings:

Use the Nvidia X Server Settings app -> XServer Display Configuration. Hit Advanced and set the ViewPortOut to 3072x2160+1024+0

This will add a metamodes line to your /etc/xorg.conf screen section:

Section "Screen"
    ...
    Option         "metamodes" "4096x2160 +0+0 {viewportout=3072x2160+1024+0}"
    ...
EndSection

But be warned - this can cause issues with some apps. If your Steam Proton-based game isn't even starting; try removing the above mod and make sure the two 'Composition Pipeline' settings are off.