DroidDeck/docs/development/game-environment.md

Steam game environment

Open Games → Game environment, directly below FEX preset, in Steam settings or the in-session drawer. Choose all Proton games, an installed game, or enter a Steam app ID. For a non-Steam shortcut, use its numeric compatdata directory ID (unsigned 32-bit). Changes apply on the next game launch, including when Steam is already running. A running game must be restarted. Native Linux games and Steam itself are outside this editor's scope.

The order is inherited process environment, selected FEX preset and built-in settings, shared edits, then game-specific edits. Editor entries therefore win over matching Steam launch-option variables. Remove explicitly unsets a variable. Restore inherited settings removes the override. Reset this profile clears only that profile's overrides. Values are literal strings, with no shell expansion; quotes are only needed when the consuming program expects them.

Defaults and available suggestions

The initial configuration enables Mesa shader caching with MESA_SHADER_CACHE_DISABLE=false, sets VKD3D_FEATURE_LEVEL=12_2 and VKD3D_SHADER_MODEL=6_9, and preserves the selected FEX preset. Existing edits and explicit removals take precedence over these defaults. FEX's own default remains the default preset. Shader caching in VKD3D/DXVK, synchronization, ray tracing and diagnostic logging otherwise retain the runtime's defaults.

On an Adreno 6xx, Turnip does not expose storageBuffer8BitAccess, which DXVK 3 requires. A Steam or desktop session installs DXVK 2.7.1 into any Proton whose DXVK is still the copy that Proton shipped, including after a Proton update put that copy back. A DXVK package chosen in Components stays for that Proton build.

The variable-name picker offers 24 predefined variables and a Custom entry. Like WinNative, known variables use toggles, value dropdowns, multi-select lists, or numeric/text fields. Feature-level and shader-model dropdowns also accept custom values. Custom variables have editable names and literal values.

Variable	Use
VKD3D_FEATURE_LEVEL	D3D12 capability override; defaults to 12_2.
VKD3D_SHADER_MODEL	Shader-model override; defaults to 6_9.
VKD3D_CONFIG	Per-game workarounds such as nodxr; not a universal performance preset.
MESA_SHADER_CACHE_MAX_SIZE	Storage budget for Mesa's shader cache, for example 1G.
mesa_glthread	OpenGL threading; test with the affected game.
DXVK_CONFIG	DXVK configuration options; recent builds accept dxvk.maxFrameRate = 60.
VKD3D_FRAME_RATE	D3D12 frame-rate limit.
DXVK_HUD, PROTON_LOG	Optional diagnostics; leave unset for ordinary play.
PROTON_USE_WINED3D	D3D9–11 OpenGL fallback for compatibility testing.
PROTON_USE_XALIA	Proton's gamepad-navigation helper toggle.

Forcing 12_2 or 6_9 changes reported capabilities; it cannot implement a missing Vulkan feature. Remove either entry to use automatic detection for that capability. Other picker suggestions are editable starting values and are enabled only when added and saved. Older or custom components can support a different set of options. Android Wine wrapper, ALSA-server, Box64 and patched async-DXVK options are identified in the editor as requiring a different/custom component; custom entries remain allowed. The old DXVK_FRAME_RATE environment variable was removed from current DXVK, so it is not offered as a suggestion. Prefer the session frame limiter for ordinary play.

DroidDeck Proton (Auto)

A proof of concept for per-game Proton assembly. steam-compatibility registers droiddeck-proton-auto ("DroidDeck Proton (Auto)") next to droiddeck-proton-arm64. It runs the same Valve ARM64 depot, and its launcher also exports DROIDDECK_RECIPES=1. Choose it per game in Steam's Properties → Compatibility. Every other tool behaves as before, including Components swaps and the forced DXVK on Adreno 6xx.

For a game launched through it, droiddeck-game-env asks droiddeck-recipe for the game's recipe. A recipe can name a DXVK, VKD3D-Proton and/or FEX package, plus environment variables. Proton is then started from ~/.local/share/droiddeck-recipes/dist/<key>/:

• real directories down to each directory a package replaces;
• every other entry a symlink to the depot;
• the component's own DLLs (the same set Components swaps) linked from the package.

The depot is never written. The key covers the depot, its version line and the packages, so a Steam update gives a fresh tree. Trees unused for 14 days are removed. esync builds its own tree on top, as it does for a depot. A recipe never stops a launch: a missing package or an error leaves that component, or the whole launch, on the stock Proton. The session log and droiddeck-recipes/launches.log record what was applied.

Recipe variables sit in the automatic-fixes layer: above shared entries, below the game's own entries. They are limited to tuning names: the DXVK_, VKD3D_, FEX_, MESA_ and PROTON_ families, mesa_glthread and WINEDLLOVERRIDES. Names that refer to a path, directory, file, library or preload are refused. The app (DdProtonRecipes) and the guest both enforce this.

Recipes come from the app's files/recipes.json when present (for development), otherwise from the bundled community library, assets/recipes/default.json. At session start the app picks each game's variants for the device's GPU family (GpuInfo.Family). It then fetches each named package from the Nightlies "-Linux" releases, the same way Components does, unpacks them into droiddeck-recipes/store/ and publishes ~/.config/droiddeck/recipes.json with those paths. A hand-written file can use version 1, which has one recipe per game:

{"version": 1, "games": {"<app or shortcut id>": {
  "dxvk": {"file": "dxvk-2.4-linux.wcp", "release": "Dxvk-Linux"},
  "env": {"DXVK_HUD": "version"},
  "note": "why this game needs it"}}}

The library uses version 2. Each game has a list of variants, and a variant can be limited to GPU families. Matching variants are merged in order: the first to name a component provides it, and later variables win.

{"version": 2, "games": {"489830": {"name": "The Elder Scrolls V: Skyrim Special Edition",
  "variants": [
    {"env": {"FEX_X87REDUCEDPRECISION": "1"}, "note": "community: 66 uploads, 65 sources"},
    {"gpu": ["A6XX"], "dxvk": {"file": "dxvk-gplasync-2.7.1-1-linux.wcp",
      "release": "Dxvk-gplasync-Linux"}, "env": {"DXVK_ASYNC": "1"}}]}}}

The community library

tools/recipes/convert.py builds the library from The412Banner's bannerhub-game-configs (GameHub and BannerHub uploads) and bannerlator-game-configs (which upload folder is which Steam app). Those configs describe Android Wine containers, so most of what they hold does not apply to Valve's ARM64 Proton under DroidDeck. The converter keeps only what carries over, and only where independent uploads agree:

• FEX: taken from arm64x containers on any GPU; arm64x is the same ARM64 Wine with FEX that Valve's ARM64 Proton uses. Only uploads where the player chose a FEX profile or changed a setting count; GameHub's own per-game recommendation does not. A value is kept when it differs from FEX's default.
• DXVK and VKD3D-Proton: chosen per Adreno family. A build carried by at least 10% of that family's uploads is the app default of its day, not a choice, and is ignored. The build must exist as a Nightlies Linux package. Async forks map to gplasync with DXVK_ASYNC=1.
• Other variables: only names the recipe allowlist accepts. Turnip's TU_DEBUG and file paths are dropped.

"Agree" means at least 3 independent sources, counted as distinct upload tokens (or devices for older uploads). At least 75% of the sources that chose something must pick the same value. For FEX they must also cover at least half of the game's sources. Folders without a Steam app ID (repacks, tools) are left out. Games tested by hand are recorded in tools/recipes/overrides.json: kept, replaced or blocked. The converter applies that file last.

The library and dd-proton-library.md, which lists every game with its evidence, are generated together. Refresh them with:

git clone --depth 1 https://github.com/The412Banner/bannerhub-game-configs /tmp/bh
git clone --depth 1 https://github.com/The412Banner/bannerlator-game-configs /tmp/bl
python3 tools/recipes/convert.py --bannerhub /tmp/bh --bannerlator /tmp/bl

Results from games tested on the Thor are in dd-proton-testing.md.

Launch path and references

WinNative's Linux session filters Android-only options, merges user variables over the FEX preset, and passes the result to env -i before starting Steam. Its Windows/Wine graphics helper also maps the selected feature level to VKD3D_FEATURE_LEVEL. Reviewed source: WinNative Linux session, variable editor, graphics configuration.

DroidDeck instead publishes an atomic JSON snapshot at /root/.config/droiddeck/game-environment.json. Both its Valve ARM64 Proton wrapper and adopted third-party Proton wrappers execute droiddeck-game-env, which reads that snapshot for each real game launch and uses execvpe to start Proton. Probe prefix compatdata/0 and non-launch verbs are unchanged. Malformed configuration falls back to the inherited environment without evaluating its contents. Signed non-Steam prefix IDs are normalized to unsigned IDs.

The published file also carries a dxvkConfig string the app's own file never has: the session menu's texture filtering (Effects page; core/TextureFiltering) as d3d9/d3d11.samplerAnisotropy and samplerLodBias options. The launcher appends it to DXVK_CONFIG after the profiles, so a user's own DXVK_CONFIG entry keeps its options. "Auto" texture sharpness is -log2(panel / session), derived when the session is sized, and applies from the next launch.

Upstream references: VKD3D capability parsing, VKD3D options, Proton runtime options, Mesa variables, DXVK variables, DXVK frame-limiter changes.

Validation: ./gradlew testDebugUnitTest, python3 -m unittest discover -s tools/tests -p test_game_environment.py and python3 -m unittest discover -s tools/tests -p test_recipe.py and python3 -m unittest discover -s tools/tests -p test_recipe_convert.py. Actual game compatibility depends on the installed Proton, VKD3D and Vulkan driver; these checks do not establish that every device supports feature level 12_2 or SM 6_9.