I would like to talk about the specifics / oddities of Proton:
1. the environment - Steam Runtime 2. the steam.exe shim + lsteamclient 3. the Steam integration patches for Wine
I want to explain what those are for, how to work with them and how to rebase the minimal set of changes to get current Wine upstream master running your games.
On Tue, Aug 05, 2025 at 12:41:39PM +0300, Arkadiusz Hiler wrote:
I would like to talk about the specifics / oddities of Proton:
- the environment - Steam Runtime
- the steam.exe shim + lsteamclient
- the Steam integration patches for Wine
I want to explain what those are for, how to work with them and how to rebase the minimal set of changes to get current Wine upstream master running your games.
Ah, forgot to mention - the standard 40 min slot (~20 min talking, rest for Q&A) is perfect.
Link: https://hiler.eu/presentations/minimal-protonification.txt
also inline below
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what makes Proton a Proton
by ivyl
# What Is Proton?
Proton is a downstream Wine distribution that includes a lot of extras:
- **dxvk** - alternative D3D8-D3D11 implementation to wined3d - **vkd3d-proton** - alternative D3D12 implementation to vkd3d - **dxvk-nvapi** - Nvidia's nvapi implementation - **fonts** patched for metric compatibility - **piper** - speech synthesis - **kaldi** - speech recognition - ...
And some custom bits:
- **steamapi bridge** - **steam.exe shim** - **proton** launch script - tones of **patches** for game compatibility
Proton is intended to run inside of the **Steam Runtime**.
# What Would A Minimal "Proton" Be?
- runs at least some games - access to Steam API - launchable via Steam - as close to upstream Wine - no Proton build system involved - no runtimes involved
Let start stripping things down!
# Start Fresh
We are dropping all the external libraries and just start with a clean `wine-10.15` tree.
We are going to bring back only the bare mnimum.
# Steam.exe Shim?
- lives in `steam_helper/steam.c` - built using modified `makedep` - some games expect to be descendants of a `steam.exe` - sets registry values relatied to currently running steam instance - calls lsteamclient's `steamclient_init_registry()` - setups vrclient - waits to be ptraced when is set `PROTON_WAIT_ATTACH=1`
Most games don't need it, but significant number does.
You definitely don't need it when running software without Steam integration.
I was on the fence but **we are dropping it for our miniminal example.**
# lsteamclient.dll
- `lsteamclient/` - built using modified `makedep` - exposes win32 version of Steamworks API (`steamclient*.dll`) - we have a Wine patch to set up trampolines from the original DLL - calls into the `steamclient.so` - code mostly autogenerated using Steamworks SDK headers + libclang - does some extra work like converting paths unix <-> dos, etc.
You don't need it when running software without Steam integration. Some games are also fail gracefully and are fine without it.
**We'll include this!** We can import it into `dlls/` and add the new directory to the `configure.ac` file.
# Wine Patches
Wine has hundreds of patches that make games run or run better - adding hacks, dll overrides, dlls that are part of driver installation on Windows, etc.
**Only 4 patches are needed** to have a working 'Wine tree'-based Proton build!
I've tried to group the patches in a way that makes for easy cherry-picking on top of any Wine tree to get a rebase running quickly. They are directly on top of the upstream `wine-10.0` tag.
I'll keep on iterating on the patch organization each rebase to make the changes more self contained and make what's essential clearer.
# The Cherry Picks!
Necessary for building lsteamclient.dll:
1d400e3aea5c ("makedep: Allow building modules with C++ sources.")
Redirecting `steamapi*.dll`s to lsteamclient:
38e8f39bda73 ("HACK: steam: ntdll: Setup steamclient trampolines to lsteamclient.")
Misc Steam ingegration:
912e1b4b9fe9 ("HACK: steam: kernelbase: Substitute the current pid for the Steam client pid.") 447ecf2a3333 ("HACK: steam: wine.inf: Add required Steam registry entries.")
# The `proton` Script
A complicated Python script that:
- `WINEPREFIX=$STEAM_COMPAT_DATA_PATH/pfx` - reflinks/links/copies `default_pfx` to speed up the first start - ... and help with per-game prefix space usage - copies some dlls provided by Steam to correct directories - contains special handling for prefix upgrades / downgrades - copies some files provided by Steam that the games may expect - applies workarounds based on `SteamAppId` - starts the actual target via `steam.exe` - redirects logging, etc.
**We'll be replacing it.**
# The Replacement
`proton waitforexitandrun regedit.exe`
```sh #!/bin/sh
export WINEPREFIX="$STEAM_COMPAT_DATA_PATH/pfx"
mkdir -p "$STEAM_COMPAT_DATA_PATH/pfx/drive_c/Program Files (x86)/Steam/" for file in steamclient.dll steamclient64.dll; do cp "$STEAM_COMPAT_CLIENT_INSTALL_PATH/$file" \ "$STEAM_COMPAT_DATA_PATH/pfx/drive_c/Program Files (x86)/Steam/" done
if [ "$1" != "waitforexitandrun" ]; then echo "Unknown verb $1." exit 1 fi shift
dir="$(CDPATH= cd -- "$(dirname -- "$0")" && pwd)"
"$dir/wine/wine" "$@" ```
# Steam Runtime
Proton is built to run inside of the Steam Runtime.
Steam uses `pressure-vessel` (modified bubblewrap + extra tooling) to create a namespace for the runtime and run things inside of it - think Flatpak-lite.
Pressure-vessel also **imports hosts graphics stack** with dependencies and checks all the imported host libraries to meet the **ABI guarantees**.
There's a community project to allow running Proton inside of the runtime using other launchers: https://www.openwinecomponents.org/
Proton is built inside Proton SDK OCI image based on the Steam Runtime SDK: https://github.com/ValveSoftware/Proton/tree/proton_10.0/docker
# Why A Runtime?
It's designed to benefit Steam, native games and anything else pre-compiled people may want to redistribute on the platform.
Design docs, host distribution assumptions, debugging instructions, etc.: https://gitlab.steamos.cloud/steamrt/steam-runtime-tools/-/tree/main/docs https://github.com/ValveSoftware/steam-runtime/tree/HEAD/doc
**For Proton** the biggest benefit was running in a more predictable environment.
Once we switched away from the old `LD_LIBRARY_PATH`-style a whole class of bugs reports was gone - **ABI incompatibility** due to distribution patching libraries, compiling with unexpected flags causing missing exports or files being located in unexpected places.
Linux user-space is not really great at ABI compatibility and requires extra steps added somewhere.
# Compatibility Tool Metadata And Layering
We'll need `toolmanifest.vdf` to tell Steam we are a Proton.
The default file looks like this:
``` "manifest" { "version" "2" "commandline" "/proton %verb%" "require_tool_appid" "1628350" "use_sessions" "1" "compatmanager_layer_name" "proton" } ```
Note the `require_tool_app_id`.
# Is Steam Runtime Mandatory?
For good experience and getting help? **Yes.**
For tinkering and trying things out? No.
Just remove `require_tool_app_id` and restart Steam. Providing all the dependencies on the host is on you. Good luck!
# What About Escaping The Runtime Steam Itself Uses?
We really don't need to escape it, everything should run fine at this point.
You still can do this though:
`STEAM_RUNTIME=0 STEAM_RUNTIME_HEAVY=0 steam`
This requires much more 32 bit libs on host and may be broken in unexpected ways. Extremely not supported. May disappear at any time.
# The Last Step
We also need to add a `compatibilitytool.vdf` next to our `proton` replacement.
``` "compatibilitytools" { "compat_tools" { "miniproton" { "install_path" "."
"display_name" "miniproton"
"from_oslist" "windows" "to_oslist" "linux" } } } ```
An put everything in `~/.steam/root/compatibilitytools.d/`
# By Those Powers Combined
wine-10.15 + a dozen or so patches + lstemclient dll included in the tree.
https://gitlab.winehq.org/ivyl/wine/-/tree/miniproton-wine-10.15
Check `miniproton/README` for instructions on how to run it.
**DEMO IF TIME ALLOWS**
-
Arek Hiler -
Arkadiusz Hiler