I’m currently toying around with some semi-broken games and noticed the Xephir options at the bottom in the system options dialogue for the game entry. In this case Moto Racer 1-3 from GOG and Diablo specifically.
For MR1 setting WINE to use a virtual desktop (1280x800 resolution) and additionally enabling Xephyr (+ same resolution in 16bit color depth) the game is launched in 1080p fullscreen only using the defined resolution for WINE. When launching MR1 from it’s launcher it switches to the games native 640x480 and runs in 640x400 during races as selected in the games options.
Here are some shots:
As you can see everything behaves as described above and the game runs flawlessly (aside from the accelerated menu when not restricted to a single core). My suggestion would be to add a toggle to switch fullscreen on/off for Xephyr.
Though I still have my doubts if it makes sense, as I couldn’t find any word in the ‘Xephyr -help’ or unfortunately minimal documentation if there’s a possibility to lock the the defined window size and thus enabling “fake” scaling for low resolution games. If anybody know an answer to that, I’d be happy to hear about it.