proton: use Darktide's native AGS without amdxc64 on AMD-only systems

Warhammer 40,000: Darktide only offers FSR 4.1.1 on RDNA3 with its own
amd_ags_x64.dll and without our amdxc64 FSR4 provider. The reporter
confirmed that neither change alone is enough, and PROTON_FSR4_UPGRADE
doesn't bring it back either.

Default to both for the game, only when every DRM device is AMD, since
native AGS relies on Wine's builtin ADL. PROTON_NATIVE_AGS=0, an amdxc64
entry in WINEDLLOVERRIDES, or the FSR4 upgrade option opt out.

https://github.com/GloriousEggroll/proton-ge-custom/issues/869

Co-Authored-By: Claude Opus 5.5 <[email protected]>

proton

@@ -213,6 +213,23 @@ def file_exists(s, *, follow_symlinks):
 def nonzero(s):
     return len(s) > 0 and s != "0"
 
+def host_gpu_vendors():
+    """PCI vendor IDs of the host's DRM devices, e.g. {"0x1002"} for AMD."""
+    vendors = set()
+    try:
+        cards = os.listdir("/sys/class/drm")
+    except OSError:
+        return vendors
+    for card in cards:
+        if not re.fullmatch(r"card[0-9]+", card):
+            continue
+        try:
+            with open("/sys/class/drm/" + card + "/device/vendor", "r") as f:
+                vendors.add(f.read().strip().lower())
+        except OSError:
+            pass
+    return vendors
+
 def prepend_to_env_str(env, variable, prepend_str, separator):
     if variable not in env:
         env[variable] = prepend_str
@@ -1950,6 +1967,19 @@ class Session:
         if appid == "1702330":
             self.env.setdefault("PROTON_STEAM_INPUT_XBOX_PROMPTS", "1")
 
+        # Darktide only offers its own FSR 4.1.1 on RDNA3 with its native AGS and
+        # without our amdxc64 FSR4 provider. Only on AMD-only systems: native AGS
+        # uses Wine's builtin ADL, which other vendors don't have on Windows.
+        # PROTON_NATIVE_AGS=0 or an amdxc64 entry in WINEDLLOVERRIDES opts out, and
+        # PROTON_FSR4_UPGRADE keeps amdxc64. #869
+        if appid == "1361210" and host_gpu_vendors() == {"0x1002"}:  # Warhammer 40,000: Darktide
+            self.env.setdefault("PROTON_NATIVE_AGS", "1")
+            if (nonzero(self.env["PROTON_NATIVE_AGS"]) and
+                    "amdxc64" not in self.env.get("WINEDLLOVERRIDES", "") and
+                    "PROTON_FSR4_UPGRADE" not in self.env and
+                    "fsr4" not in self.compat_config):
+                self.dlloverrides["amdxc64"] = "d"
+
         # Diablo IV supports native DualSense, but does not recognize the Edge PID.
         # Winebus leaves Steam Input and the physical audio/haptics identity intact.
         if appid == "2344520":  # Diablo IV