Fixed some proton 7 path issues and the override in settings.

ptlinux/doctor.py

@@ -11,6 +11,7 @@ import shutil
 from typing import Mapping
 
 from .launcher import find_wine_tools
+from .runtime import find_steam_proton7
 
 
 ARCH_FAMILY_DISTRIBUTIONS = frozenset(
@@ -176,19 +177,7 @@ def _package_hint(distribution: str) -> str | None:
 
 
 def _has_steam_proton7(environment: Mapping[str, str]) -> bool:
-	home_value = environment.get("HOME")
-	if not home_value:
-		return False
-	home = Path(home_value)
-	for steam_root in (
-		home / ".local/share/Steam",
-		home / ".steam/steam",
-		home / "snap/steam/common/.local/share/Steam",
-		home / ".var/app/com.valvesoftware.Steam/.local/share/Steam",
-	):
-		if (steam_root / "steamapps/common/Proton 7.0/proton").is_file():
-			return True
-	return False
+	return find_steam_proton7(environment) is not None
 
 
 def _platform_optional_tools(distribution: str, *, architecture: str) -> list[ToolStatus]:

ptlinux/runtime.py

@@ -9,6 +9,7 @@ import json
 import os
 from pathlib import Path, PurePosixPath
 import platform
+import re
 import shlex
 import shutil
 import sys
@@ -36,6 +37,12 @@ CURRENT_UMU_DISTRIBUTIONS = frozenset(
 	{"arch", "cachyos", "endeavouros", "garuda", "manjaro"}
 )
 GAME_RUNTIME_CONFIGURATION_VERSION = 1
+PROTON7_RELATIVE_PATH = Path("steamapps/common/Proton 7.0/proton")
+STEAM_LIBRARY_FOLDERS_RELATIVE_PATH = Path("steamapps/libraryfolders.vdf")
+STEAM_LIBRARY_FOLDERS_MAX_BYTES = 4 * 1024 * 1024
+_VDF_QUOTED_PAIR = re.compile(
+	r'"((?:\\.|[^"\\])*)"\s*"((?:\\.|[^"\\])*)"'
+)
 
 
 class RuntimeErrorPT(RuntimeError):
@@ -80,7 +87,7 @@ def select_runtime(
 		proton = Path(settings.proton_path).expanduser().resolve()
 		if not proton.is_file():
 			raise RuntimeErrorPT(f"configured Proton script does not exist: {proton}")
-		steam_root = _steam_root_for_proton(proton)
+		steam_root = _steam_root_for_proton(proton, env)
 		if settings.runtime == "proton7-container":
 			if not umu:
 				raise RuntimeErrorPT(
@@ -137,33 +144,108 @@ def select_runtime(
 def find_steam_proton7(
 	environment: Mapping[str, str] | None = None,
 ) -> tuple[Path, Path] | None:
+	"""Find Proton 7 in a Steam client root or one of its registered libraries.
+
+	The returned Steam root is always the client installation, even when the
+	Proton tool itself lives in a secondary library. Proton 7 uses that client
+	root for Steam's bundled media compatibility libraries.
+	"""
+
 	env = os.environ if environment is None else environment
-	home_value = env.get("HOME")
-	if not home_value:
+	for steam_root in _steam_client_roots(env):
+		for library_root in _steam_library_roots(steam_root):
+			proton = library_root / PROTON7_RELATIVE_PATH
+			if proton.is_file():
+				return proton.resolve(), steam_root
 	return None
-	home = Path(home_value).expanduser()
-	roots: list[Path] = []
-	explicit = env.get("STEAM_COMPAT_CLIENT_INSTALL_PATH")
+
+
+def _steam_client_roots(environment: Mapping[str, str]) -> tuple[Path, ...]:
+	candidates: list[Path] = []
+	explicit = environment.get("STEAM_COMPAT_CLIENT_INSTALL_PATH")
 	if explicit:
-		roots.append(Path(explicit).expanduser())
-	roots.extend(
+		candidates.append(Path(explicit).expanduser())
+	home_value = environment.get("HOME")
+	if home_value:
+		home = Path(home_value).expanduser()
+		candidates.extend(
 			(
 				home / ".local/share/Steam",
 				home / ".steam/steam",
+				home / ".steam/root",
+				home / ".steam/debian-installation",
 				home / "snap/steam/common/.local/share/Steam",
+				home / "snap/steam/common/.steam/steam",
 				home / ".var/app/com.valvesoftware.Steam/.local/share/Steam",
 			)
 		)
+	return _unique_resolved_paths(candidates)
+
+
+def _steam_library_roots(steam_root: Path) -> tuple[Path, ...]:
+	registered = _read_steam_library_folders(
+		steam_root / STEAM_LIBRARY_FOLDERS_RELATIVE_PATH
+	)
+	return _unique_resolved_paths((steam_root, *registered))
+
+
+def _read_steam_library_folders(path: Path) -> tuple[Path, ...]:
+	"""Read current and legacy Steam libraryfolders.vdf path records."""
+
+	try:
+		with path.open("rb") as handle:
+			content = handle.read(STEAM_LIBRARY_FOLDERS_MAX_BYTES + 1)
+	except OSError:
+		return ()
+	if len(content) > STEAM_LIBRARY_FOLDERS_MAX_BYTES:
+		return ()
+	text = content.decode("utf-8-sig", errors="replace")
+	result: list[Path] = []
+	for raw_key, raw_value in _VDF_QUOTED_PAIR.findall(text):
+		key = _decode_vdf_string(raw_key)
+		value = _decode_vdf_string(raw_value)
+		# Current files use a named "path" property. Older Steam clients used
+		# numeric top-level keys, which are distinguishable from app-size pairs
+		# because a Linux library path must be absolute.
+		if key.casefold() != "path" and not key.isdecimal():
+			continue
+		if not value or "\x00" in value:
+			continue
+		library = Path(value).expanduser()
+		if library.is_absolute():
+			result.append(library)
+	return tuple(result)
+
+
+def _decode_vdf_string(value: str) -> str:
+	result: list[str] = []
+	index = 0
+	while index < len(value):
+		character = value[index]
+		if character == "\\" and index + 1 < len(value):
+			next_character = value[index + 1]
+			if next_character in {'"', "\\"}:
+				result.append(next_character)
+				index += 2
+				continue
+		result.append(character)
+		index += 1
+	return "".join(result)
+
+
+def _unique_resolved_paths(paths: Sequence[Path]) -> tuple[Path, ...]:
+	result: list[Path] = []
 	seen: set[Path] = set()
-	for root in roots:
-		resolved = root.resolve()
+	for path in paths:
+		try:
+			resolved = path.resolve()
+		except (OSError, RuntimeError):
+			continue
 		if resolved in seen:
 			continue
 		seen.add(resolved)
-		proton = resolved / "steamapps/common/Proton 7.0/proton"
-		if proton.is_file():
-			return proton, resolved
-	return None
+		result.append(resolved)
+	return tuple(result)
 
 
 def prepare_game_runtime(
@@ -653,15 +735,27 @@ def _ensure_proton_game_link(paths: AppPaths) -> None:
 	link.symlink_to(paths.runtime_view, target_is_directory=True)
 
 
-def _steam_root_for_proton(proton: Path) -> Path:
-	parts = proton.parts
-	try:
-		index = parts.index("steamapps")
-	except ValueError as exc:
+def _steam_root_for_proton(
+	proton: Path,
+	environment: Mapping[str, str] | None = None,
+) -> Path:
+	steamapps = next(
+		(parent for parent in proton.parents if parent.name.casefold() == "steamapps"),
+		None,
+	)
+	if steamapps is None:
 		raise RuntimeErrorPT(
 			"configured Proton path must be inside a Steam steamapps directory"
-		) from exc
-	return Path(*parts[:index])
+		)
+	library_root = steamapps.parent.resolve()
+	env = os.environ if environment is None else environment
+	for steam_root in _steam_client_roots(env):
+		if library_root in _steam_library_roots(steam_root):
+			return steam_root
+	# Preserve support for an otherwise valid, manually managed Steam layout.
+	# Without a registered client root, the library root is the best available
+	# compatibility value and matches the launcher's historical behaviour.
+	return library_root
 
 
 def native_d3d_ready(prefix: Path) -> bool: