I recently got myself a fresh 3440x1440 monitor. Very nice, but the obviously problem is that my GPU won't be pushing all those pixels for every game. I can easily set it to 2560x1440, but for some games even that is too much.

To fix that I was trying to get reduced resolution modes. However, since I despise scaling, I want them to stick to native pixels. This is not a problem in theory. I can use nvidia settings to create a smaller resolution viewport on a higher resolution screen and place it anywhere and have the unused space black. I'm sure I can do that with xrandr as well.

The problem is these viewport aren't really recognised by games. Unity3D games use it if you don't touch the settings. But Feral games only list the modes that xrandr lists prepare a full screen frame which gets placed only partially in the viewport. Also, I don't really want to be doing this manually.

Does anybody know if you can get these modes with smaller viewports registered as a screen mode that I can select in games?