I'm trying to run older software that I want to run in 640x480 and/or 800圆00 in fullscreen, but my DVI-connected monitor is not 4:3. Just be aware that, at this time, xrandr's -set 'scaling mode' seems to be limited to outputting at your monitor's first-listed EDID refresh which is commonly 60Hz on even higher-refreshing monitors despite the OS claiming to be running at a higher refresh rate, so you may want to keep it disabled by default and instead use a bash script to launch a given program to enable -set 'scaling mode' and then have it disable when the program is closed and then subsequently be sure to set your refresh rate back to whatever greater-than-60Hz refresh you'd normally run at.

This even works for custom resolution greater than you monitor, effectively allowing for an easy way to run games with 'downsampling' or super-sample anti-aliasing. The same also goes for if you run a program or game that wants to change your output desktop resolution - even then it'll still remember to preserve the aspect ratio. Then after that, if I change my resolution to anything else whether in the 'Display' application or via xrandr even without specifying a 'scalling mode', it'd automatically remember to preserve the aspect ratio.

Running software through gamescope is simple enough by just doing the following:Ĭode: Select all xrandr -output DVI-0 -set 'scaling mode' 'Full aspect' UPDATE 2: If you're on Intel graphics (it works on AMD as well, but simply using the xrandr method below has much better compatibility unless you specifically want to use AMD FSR scaling), then the best solution may be to use Gamescope since, when you set Gamescope itself to fullscreen, it basically forces your desired program to run in 'borderless window' style of fullscreen scaled up to your current desktop resolution with the aspect ratio preserved.

Furthermore, some external displays, primarily TVs (but some monitors as well), have their own built-in aspect ratio control which negates the need for GPU-based aspect ratio preservation (same goes for if you're using a CRT which needs no scaling at all). REMINDER: This is specifically with regards to external displays, not internal laptop or tablet displays (on such internal displays, the xrandr method will 'just work' even on Intel graphics). Relevant issue that was closed over 2 years ago yet still exists according to my own testing:

Dosbox resolution 1920x1080