When fractional scaling is enabled, games running with Proton report much higher monitor resolutions

[NoXPhasma]

Distribution

Arch Linux

Package version

6.0.4

Graphics hardware in use

AMD RX 7800XT

Frequency

Always

Bug description

When I have fractional scaling enabled, games report a much higher monitor resolution, than what is actually available. In my case the monitor resolution is 2560x1440 and games report a native resolution of 4096x2304.

The games actually run at that resolution and will be down scaled to the actual monitor resolution.

Steps to reproduce

1. Enable fractional scaling in the Display > Settings options.
2. launch a game with Proton in Steam (Games I tested were Apex Legends, DOOM Eternal and Grid (2009) with Proton 8.0)
3. Check the resolution

Expected behavior

The actual monitor resolution should not be different to what it actually is, when fractional scaling is enbaled.

Additional information

No response

[NoXPhasma]

Here's a screenshot of a game reporting a way too high resolution:

[jknockel]

I don't know if this game is using libsdl or how it is determining this resolution, but newer versions of libsdl advertise screen resolutions to games with the xrandr scaling already applied (see, e.g., libsdl-org/SDL#5427). This is because games are generally not xrandr scaling aware, and so if you advertise the physical resolution to the game without xrandr scaling applied, then the game will end up with a mistaken notion of the screen size and end up only rendering to a rectangle larger or smaller than your screen size, depending on the direction of the scaling. I agree that seeing the resolution with the xrandr scaling applied can be unintuitive to the user, and it is possible that libraries like libsdl can be further extended to somehow address this, but in any case I don't believe that this is a problem with muffin per se.