How to mirror a display with different resolutions?

Question

I want to give a presentation and type on my laptop knowing the projector shows exactly what I see. Here is the abbreviated xrandr output:

~$ xrandr
Screen 0: minimum 8 x 8, current 2560 x 1440, maximum 16384 x 16384
eDP-1-1 connected 2560x1440+0+0 (normal left inverted right x axis y axis) 310mm x 170mm
   2560x1440     60.00*+  48.00
   1920x1440     60.00
   1856x1392     60.01
   1792x1344     60.01
   1600x1200     60.00
   1400x1050     59.98
   1280x1024     60.02
   1280x960      60.00
   1024x768      60.04    60.00
HDMI-1-2 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 598mm x 336mm
   1920x1080     60.00*+  50.00    59.94
   1920x1080i    60.00    50.00    59.94
   1280x1024     75.02    60.02
   1152x864      75.00

Running Xorg server 1.19 with xrandr program version 1.5.0, I simply want to mirror the output of my laptop screen (eDP-1-1) onto the external projector (HDMI-1-2). How do I best do that considering there is no matching screen resolutions?

Btw the transform/scale options mentioned here https://dgl.cx/2014/08/xrandr-tips seem to have no impact whatsoever on the external screen HDMI-1-2, but they did for eDP-1-1.

Solution 1

As beautifully described in a bug report, what I wanted was:

Considering the current name of my displays (it changes), the answer was:

xrandr --output HDMI2 --auto --scale-from 2560x1440 --output eDP1

Nonetheless I highly recommend you use mons to manage your Xorg multi-monitor displays.

Solution 2

You haven't said exactly what you've tried, but the scale option worked for me. Note also the scale-from option which might be easier in your case.

$ xrandr --output DP1-1 --same-as DP1-8 --scale 2.7x2.7 --output eDP1 --same-as DP1-8 --scale 1.3x1.3

Note also various answers here.

Comments

[hendry]

Need to try github.com/Ventto/mons/issues/9#issuecomment-326645967

[Jamie Kitson]

--scale-from, as I said.

[atevm]

I was stuck with this just before a presentation, your answer saved me kind sir :)