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Update 15/04/24 18:43GE-Proton 9-4 was released shortly after with these changes as well now:


GE-Proton 9-3 has been released, and it includes a fancy new option to hopefully prevent you having issues with modded games when moving between systems like a PC and a Steam Deck.

The new option is this Steam launch option COPYPREFIX=1 %command% and the mechanics behind it are a little on the complicated side, and you need to be careful not to mix it up if you do plan to use it as it will wipe your Proton prefix, which one depends on how you use it. Developer Thomas "GloriousEggroll" Crider explained it like this:

By default steam stores the wine prefixes in the steam library where the game is installed under SteamLibrary/steamapps/compatdata/ as well as shader cache files in shadercache/. When 'Steam Deck' session aka gamescope session is used, the -steamdeck option is appended to steam. This causes the default path for prefix compatdata and shadercache to change to the default steam install location ~/.steam/steam/steamapps/compatdata (or shadercache). This can be problematic if you are say for example switching from normal desktop steam to steamdeck. Or for example if you have a portable hard drive or SD card you keep your games on to use between the two. If you did something like say install mods for a game or played a game that doesnt work with cloud saves on the desktop, the prefix would not get used when you move the drive over from the desktop to steamdeck. Instead steamdeck would try to make a new one. The same goes in reverse for if you play games on the steam deck and try to move the game drive or sd card to a desktop.

What COPYPREFIX=1 DOES is if -steamdeck is applied it will check if a prefix exists on the game partition/drive. If it does, it will then WIPE the steamdeck prefix, and replace it with the one from the game partition/drive. . It does this with shader cache as well. This way steam will pick up your mods/saves that you had on your desktop or other PC you used the drive on before.

Alternatively, if -steamdeck is NOT applied -- it works in reverse. It will try to wipe the prefix on the game partition, and replace it with the one in steamdeck's default location. It does this with shader cache as well. A good use case for the reverse of the desktop -- say you've put in a ton of hours on a game with saves that don't work with steam cloud saving -- or have a bunch of mods you've applied on a game on your steam deck -- then you want to migrate to your desktop. In this case, put steam in desktop mode. Close steam then re-open it from the terminal using the steam command so that -steamdeck is NOT applied, then you can use COPYPREFIX to copy the steamdeck prefix to your game's partition/drive.

Again to clarify usage scenarios:

  • Steam launched in deck mode (-steamdeck applied) or from terminal with -steamdeck = copy FROM game partition prefix TO steamdeck prefix

OR

  • Steam launched from desktop shortcut or terminal without -steamdeck = copy FROM steamdeck prefix TO game partition prefix.

Other changes included in this update:

-wine updated to latest bleeding edge
-dxvk updated to latest git
-vkd3d-proton updated to latest git
-imported upstream proton changes
-imported upstream steamclient changes

Protonfixes:

UMU:

Pictured - Fallout 76

Article taken from GamingOnLinux.com.
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7 comments

Lachu Apr 15
I prefer to add library on SD card to both Deck and laptop. It was way simpler.
Spirimint Apr 15
Pagonia still not working :(
dpanter Apr 15
Hotfix 9-4 is out because of course!
Liam Dawe Apr 15
Quoting: dpanterHotfix 9-4 is out because of course!
Of course, updated.
Termy Apr 15
Quoting: LachuI prefer to add library on SD card to both Deck and laptop. It was way simpler.

That should not matter in this case:

Quoting: Thomas "GloriousEggroll" CriderThis causes the default path for prefix compatdata and shadercache to change to the default steam install location ~/.steam/steam/steamapps/compatdata (or shadercache).

That's new to me, too tbh, but still a nice addition if you have a game where (parts of) the mods reside outside the game folder.
Marlock Apr 15
why the heck didn't they use the same path on both environments from the start? and why not use the same from now on, transfering what's on the old path to the new as needed, and offering a gui if it finds both, when you click play?!


Last edited by Marlock on 15 April 2024 at 9:38 pm UTC
JoeyBobbson Apr 16
Would this be able to remove the steamdeck prefix from games like Atomic Heart, where graphics settings have been removed for deck users? Could it prevent steam input API from registering in games where it's forced and prevents using KB&M inputs bound to face buttons on deck, like how Warframe does it?
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