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Forza Horizon 5 on Linux? Yeah okay fine, Proton Experimental was updated

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So it wasn't enough that Age of Empires 4 from Xbox Game Studios was now playable on Linux, Proton Experimental has once again been upgraded to get Forza Horizon 5 off the starting line. That's right, you can now play the latest (and greatest?) from Playground Games and Xbox Game Studios on Linux.

That was the single change noted in the update notes from Valve for Proton Experimental for November 11. It should work across both AMD and NVIDIA GPUs now too, although it's all still experimental of course and currently multiplayer is problematic. Buy at your own peril for now but hey — a couple days from release is pretty damn good for the latest title to begin working. Have to hand it to the developers at Valve and CodeWeavers working on Proton, they certainly know their stuff.


Screenshot - Steam.

See the Proton Experimental changelog to see all the current differences.

Need to know how to actually use Proton Experimental? Here's a simple HOWTO (as it's not complicated!). Make sure it's installed by searching for it in your Steam Library, then select it from the Compatibility menu in the Properties section of a game. See our quick video below:

For an explainer in text form:

  1. Search for Proton Experimental and install if not already.
  2. Right click any game on Steam and go to Properties.
  3. Select the Compatibility menu on the right side.
  4. Ensure the "Force the use of a specific Steam Play compatibility tool" is ticked.
  5. From the dropdown box that appears select Proton Experimental.

You can buy Forza Horizon 5 on Steam.

Article taken from GamingOnLinux.com.
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20 comments
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NameHere 12 Nov
I often see this sort of thing and wonder: are these general fixes to proton that have been missed?

Or is there now a line in proton something like:
if
Age of Empires 4 do these things,
else if
Forza Horizon 5 do these other things

Why are game specific fixes or hacks needed so often?
Liam Dawe 12 Nov
Quoting: NameHereI often see this sort of thing and wonder: are these general fixes to proton that have been missed?

Or is there now a line in proton something like:
if
Age of Empires 4 do these things,
else if
Forza Horizon 5 do these other things

Why are game specific fixes or hacks needed so often?
A lot of it is because Wine, DXVK and VKD3D-Proton are incomplete and chasing often moving targets. It's a matter of completing API support for Direct 3D, Windows APIs and so on. In some cases, there are specific fixes for certain games, like forcing your GPU to be shown as a specific vendor and stuff like this.
whizse 12 Nov
  • Supporter
Quoting: NameHereI often see this sort of thing and wonder: are these general fixes to proton that have been missed?
It's mostly incomplete or unimplemented functions and libraries with a few hacks mixed in.

You can grep the changelog for FH5 to see what was needed:
https://github.com/ValveSoftware/wine/commits/experimental_6.3

Some of it will probably be merged in upstream Wine, some will not.
tgurr 12 Nov
Did someone try this yet and can actually comfirm it works on plain "Proton Experimental"? I'm asking because https://github.com/ValveSoftware/Proton/issues/5285 is a huge mess with questionable workarounds and people throwing in all kind of non related and obsolete information in all over the place.

As the official ChangeLog is just saying it works I just want to ask if:

* Does it *really* work on NVIDIA?
* Does multiplayer work as well?
Beamboom 12 Nov
Quoting: NameHereI often see this sort of thing and wonder: are these general fixes to proton that have been missed?

Or is there now a line in proton something like:
if
Age of Empires 4 do these things,
else if
Forza Horizon 5 do these other things

Why are game specific fixes or hacks needed so often?
This has me confused too. People say it's just an API that's not fully implemented, but what are really the odds of this particular game using a part of a given API that NONE of the other hundreds of games, massive complex AAA included, has not used?
It just doesn't make sense to me. It doesn't add up.
mirv 12 Nov
View PC info
  • Supporter Plus
Quoting: Beamboom
Quoting: NameHereI often see this sort of thing and wonder: are these general fixes to proton that have been missed?

Or is there now a line in proton something like:
if
Age of Empires 4 do these things,
else if
Forza Horizon 5 do these other things

Why are game specific fixes or hacks needed so often?
This has me confused too. People say it's just an API that's not fully implemented, but what are really the odds of this particular game using a part of a given API that NONE of the other hundreds of games, massive complex AAA included, has not used?
It just doesn't make sense to me. It doesn't add up.

Generally I think it's more about a combination of API interactions, expectations of behaviour from the game, and it might well fix other games along that way (they're just not tested or as headline-worth). So it's not a single API fix that only impacts a single game.
whizse 12 Nov
  • Supporter
Quoting: Beamboomwhat are really the odds of this particular game using a part of a given API that NONE of the other hundreds of games, massive complex AAA included, has not used?
Pretty big.

Try grepping the Wine sources for things like "stub", "unimplemented" and "FIXME".

Edited to add:

There might even be a bigger chance of this happening with big AAA releases. There's a bit of a mono-culture in gaming these days. Most games will use an existing engine like Unity or Unreal. This is good for Wine since adding support for one such game usually means many others will be supported inadvertently.

An AAA title might mean a totally new engine, or something very customized. It might very well use other, previously untested parts of an API or use it differently and trip up Wine.


Last edited by whizse on 12 November 2021 at 3:58 pm UTC
Quoting: tgurr* Does it *really* work on NVIDIA?
* Does multiplayer work as well?

The issues reported there for nvidia look very similar to the same issues that still exist today in Forza Horizon 4. With that game it did a weird thing for me where it crashed a lot when I started, but then gradually got less crashy. Maybe related to shader compiling?
sulix 12 Nov
Quoting: NameHereI often see this sort of thing and wonder: are these general fixes to proton that have been missed?

Or is there now a line in proton something like:
if
Age of Empires 4 do these things,
else if
Forza Horizon 5 do these other things

Why are game specific fixes or hacks needed so often?

In the case of Age of Empires IV at least, none of the changes needed were game specific hacks. Only three changes were needed to get the game to work, and all of them were general fixes which could apply to other games:

First, a missing function needed to be added, or the game wouldn't start up:
https://source.winehq.org/git/wine.git/commit/06104aec963f827ddd4f9d41d1ae72983779859f

Then, all of the buildings and units were invisible due to a bug in how things were arranged in video memory:
https://github.com/HansKristian-Work/vkd3d-proton/commit/2a8b5471cadd379720cf383377bc78c44b78e7b9

Finally, a crash would occur as the game used some invalid printf() format specifiers, which windows would ignore, but wine previously didn't:
https://source.winehq.org/git/wine.git/commit/0c6bab9339d62c8952692911f055ccbc95d956f6
whizse 12 Nov
  • Supporter
I'm guessing most of you already knows this, but here's a simplified turn of events for Proton/Wine development that's hopefully not altogether incorrect:

The story of Game.exe

Game.exe is released but crashes on start in Wine. It requires Foo() and Bar() library.dll. Foo and Bar are implemented by someone reading the API documentation from Microsoft. Bar isn't really used by the game so a minimal version is added to fulfil the dependency for the game. The game works.

The sequel Game2.exe is released but crashes on start because it needs the full implementation of Bar. Bar is implemented in Wine, the game works.

An update to Game2.exe is released and crashes on start in Wine. Turns out that Game2.exe now calls Bar with NULL instead of the expected integer value. This is undocumented behaviour but works on Windows, so the behaviour in Wine is changed to match Windows. The game works again.

Game3.exe for Windows 11 is released. It crashes on start in Wine. It requires library2.dll to run. Someone figures out that if the game runs on Windows 10 the older library.dll is used instead, a game specific hack that reports version 10 for Game3.exe is added and the game works.

Now multiply this for all the dlls and functions a game need to run and things get complex fast.

(The movie rights to this original short story have already been acquired by Sony Pictures Entertainment™)


Last edited by whizse on 12 November 2021 at 2:33 pm UTC
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