Umu Launcher is a unified tool designed to run Windows games on Linux using Valve's Proton technology, but without the dependency on the Steam client. It functions as a standalone version of the Steam Linux Runtime, allowing users to launch games from other storefronts or locations within the same containerized environment that makes Proton so effective.
The launcher simplifies the process of game compatibility by using a unified database to automatically apply necessary game fixes (protonfixes). It handles environment variables, WINEPREFIX creation, and Proton version management, enabling a 'plug-and-play' experience for Windows games on Linux. Integration with other launchers like Lutris and Bottles allows for a cohesive gaming ecosystem on Linux.
Use Cases:
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This is a unified launcher for Windows games on Linux. It is essentially a copy of the Steam Runtime Tools (https://gitlab.steamos.cloud/steamrt/steam-runtime-tools) and Steam Linux Runtime (https://gitlab.steamos.cloud/steamrt/steam-runtime-tools/-/blob/main/docs/container-runtime.md) that Valve uses for Proton (https://github.com/ValveSoftware/Proton), with some modifications made so that it can be used outside of Steam.
An umu is an above-ground oven of hot volcanic stones originating from Polynesian culture. After the stones are heated, the top layer is removed and the food placed on top to heat/cook. We chose the name because Valve's containerization tool is named pressure-vessel. We're "preparing" the pressure vessel similar to how you would use a stove top pressure-cooker -- by placing it on our umu's "stovetop"
When Steam launches a Proton game, it launches it like this:
/home/tcrider/.local/share/Steam/ubuntu12_32/reaper SteamLaunch AppId=348550 -- /home/tcrider/.local/share/Steam/ubuntu12_32/steam-launch-wrapper -- /home/tcrider/.local/share/Steam/steamapps/common/SteamLinuxRuntime_sniper/_v2-entry-point --verb=waitforexitandrun -- /home/tcrider/.local/share/Steam/compatibilitytools.d/GE-Proton8-27/proton waitforexitandrun /home/tcrider/.local/share/Steam/steamapps/common/Guilty Gear XX Accent Core Plus R/GGXXACPR_Win.exe
We can ignore this /home/tcrider/.local/share/Steam/ubuntu12_32/steam-launch-wrapper, it's just a process runner with no real value other than forwarding environment variables (more on that later).
I managed to pull the environment variables it uses by making Steam run printenv for the game's command line. We needed these envvars because Proton expects them in order to function. With them we can essentially make Proton run without needing steam at all.
Next this part /home/tcrider/.local/share/Steam/steamapps/common/SteamLinuxRuntime_sniper/_v2-entry-point
The first part /home/tcrider/.local/share/Steam/steamapps/common/SteamLinuxRuntime_sniper/ is steam-runtime-tools compiled and is used alongside the sniper runtime container used during Proton builds.
The second part _v2-entry-point is just a bash script which loads Proton into the container and runs the game.
So, umu is basically a copy paste of SteamLinuxRuntime_sniper, which is a compiled version of steam-runtime-tools. We've renamed _v2-entry-point to umu and added umu-run to replace steam-launch-wrapper.
When you use umu-run to run a game, it uses the specified WINEPREFIX, Proton version, executable, and arguments passed to it to run the game in Proton, inside Steam's runtime container JUST like if you were running the game through Steam, except now you're no longer limited to Steam's game library or forced to add the game to Steam's library. In fact, you don't even have to have Steam installed.
umu-run "$HOME/Games/epic-games-store/drive_c/Program Files (x86)/Epic Games/Launcher/Portal/Binaries/Win32/EpicGamesLauncher.exe" -opengl -SkipBuildPatchPrereq
Optionally, with WINEPREFIX, GAMEID, STORE, and PROTONPATH:
WINEPREFIX=$HOME/Games/epic-games-store GAMEID=umu-dauntless STORE=egs PROTONPATH="$HOME/.steam/steam/compatibilitytools.d/GE-Proton8-28" umu-run "$HOME/Games/epic-games-store/drive_c/Program Files (x86)/Epic Games/Launcher/Portal/Binaries/Win32/EpicGamesLauncher.exe" -opengl -SkipBuildPatchPrereq
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