I tried to resize my display and discovered the mode I wanted was not available. Interestingly, the current mode was also not listed but that is a separate issue. Adding a new mode is not as straight-forward as I had hoped, so it is worth making a note (this post) of how to do it.
First thing needed is a mode-line, which can be generated with the
cvt command (in this example for 1720x1440px at 60Hz refresh rate):
$ cvt 1720 1440 60 # 1720x1440 59.94 Hz (CVT) hsync: 89.48 kHz; pclk: 209.75 MHz Modeline "1720x1440_60.00" 209.75 1720 1848 3032 2344 1440 1443 1453 1493 -hsync +vsync
With that mode-line, we can add the mode to xrandr:
xrandr --newmode "1720x1440_60.00" 209.75 1720 1848 3032 2344 1440 1443 1453 1493 -hsync +vsync
Before it can be used, the mode needs to be added to the output (
HDMI-2 in my case):
xrandr --addmode HDMI-2 "1720x1440_60.00"
Finally(!), the mode can be used:
xrandr --size 1720x1440