Running multiple titles out of the same Proton sandbox?

[BeyondPerfectly]

In fiddling around trying to install games that weren't available on Steam but I wanted to try running anyway on the Deck via Proton, I discovered that the way Proton handles convincing .exes that they're running on Windows is by spoofing an entire Windows operating system for every game using Proton individually. These filesystems can be found at

~/deck/.local/share/Steam/steamapps/compdata/[ID of game]/

Because steam instantiates a new Windows spoof folder for every game you add to Steam, it's not immediately obvious that it's possible to run multiple games at once out of the same Windows sandbox. This is specifically problematic when attempting to run games that use non-Steam launchers such as Ubisoft Uplay or EGS, as each game would require its own Windows sandbox and therefore its own instance of the launcher, which is very space-inefficient.

Attempting to add another .exe to Steam within an existing Windows sandbox will simply reference that one file and create a new Windows sandbox just for it, which of course won't work if that .exe (a game off EGS, for instance) has dependencies within the Windows sandbox it originated.

This behavior makes the installation process for a non-Steam Windows game on Deck rather involved:

1. Download the installer .exe you want for your game/launcher
   
2. Add the .exe as a 3rd party game to your Steam library
   
3. Go into game preferences and specify Proton as the game's compatibility tool
   
4. Run the installer and install your game/launcher
   
5. Go into the game's preferences and change the path from the path to the installer in your downloads to the path to the game/launcher in ~/deck/.local/share/Steam/steamapps/compdata/
   
6. If you're using a 3rd party launcher, do the same process to install the game via the launcher, then change the path in Steam to the game you just installed

Does anyone know of a way to add multiple games into Steam such that Proton opens them in the same Windows sandbox? I'd like to install multiple games I have on Uplay and I don't want to go through the entire nasty process of getting the Ubisoft Launcher set up every time I want to install a game.

[@R+5]

you can also use lutris to install and manage different versions steam (you can launch steam for linux, or steam for windows installed via wine), and different versions of proton, plus things like video resolution (also run games in a virtual window with a different resolution, which can fix or improve performance of many games) and other options.

https://www.youtube.com/watch?v=ea9_JQ40eYY

https://www.youtube.com/watch?v=6S8zsfqsgfw

[Marlock]

yes, there is a way... but it will be a lot of work getting it setup properly...

see item 9 here:
https://steamcommunity.com/app/221410/discussions/0/1636417404917541481/

the guide linked at the end of that item discusses how to get several games running from a single prefix (among many other things)

there is also this post discussing how to add a mod manager as a custom steam entry, then make it run via proton and then ensure it runs from the same proton prefix as the target game... which is basically what you need except for all games and with a carefully prepared prefix that has everything every game might need (absolutely non-trivial, hence why Valve chose to go for 1 prefix per game)
https://steamcommunity.com/app/221410/discussions/0/3112542578499983736/#c3112542578501073633

[BeyondPerfectly]

Originally posted by Marlock:

words

This is exactly what I was looking for, thanks! I’m consistently impressed at how open Valve is about stuff like this. This post has everything I would ever need.