Fullscreen display behaves strangely on Steam Deck

[NoodleCollie]

I'm aware that this could well be a Steam Deck problem, but I suspect it's something to do with the way Wine is configured to handle fullscreen graphics currently on my system. If I can fix it in config, that would be great.

I'm currently trying to use Wine (via Lutris, but I've also tried with Wine itself) to run the first Harry Potter PC game (which I believe uses an ancient version of Unreal). When I first ran the game, it booted up fullscreen in 640x480, but the menu was partially cut off at the right hand side. I changed the resolution to 1024x768 and it crashed; I then changed it to 800x600 and things were still getting cut off.

However, after looking into the game's config file, I realised that the Y dimension of the screen was getting set to odd values. What I think is actually happening is that when the game attempts to start in a specified resolution (let's say 800x600), the Steam Deck is set to this resolution, but treats the orientation of the screen as portrait rather than landscape. The game doesn't seem to be aware of this and treats the screen as landscape, attempting to render an 800x600 window on a 600x800 canvas.

How would I go about remedying this in config? I'm not sure if it's the fault of the system configuration or Wine. If I can get the graphics canvas to orient itself the correct way around, I believe I can fix the rest of the issues with the game's configuration file iteslf.