From 6dc74523c3f12fc0daccd807ebd8230b882b07fa Mon Sep 17 00:00:00 2001
From: MaxsTechReview <maxjividen@gmail.com>
Date: Sun, 4 Oct 2026 13:44:10 -0400
Subject: [PATCH] Start every title with a Valve pick on the Compatible Proton
 (#224)

The client runs in Steam Deck mode, where a title's "Default" is not the
"0" mapping but Valve's own pick for it: the Steam Deck compatibility
recommended_runtime (proton-stable, a pinned Proton, or native for the
Steam Linux Runtime) or an app_mappings entry in the SteamPlay manifests.
A title the session had not mapped yet - not installed, or installed
while the client was running on a build without the live helper - showed
"Default (Proton Stable)" and launched with a Proton that cannot run
here.

Every playable Windows title in the appinfo cache with such a pick is now
mapped to the default tool up front, before the client starts and in the
live helper, the same way installed titles are. A runnable tool the user
picks for one of them is kept, and they follow a change of the default.
---
 .../usr/local/bin/droiddeck-steam-compat      |   5 +-
 .../overlay/usr/local/bin/steam-compatibility | 111 ++++++++++++------
 tools/tests/test_droiddeck_fex.py             |  40 ++++++-
 3 files changed, 117 insertions(+), 39 deletions(-)

diff --git a/tools/linuxfs/overlay/usr/local/bin/droiddeck-steam-compat b/tools/linuxfs/overlay/usr/local/bin/droiddeck-steam-compat
index e3520f4d9..f2adc5581 100755
--- a/tools/linuxfs/overlay/usr/local/bin/droiddeck-steam-compat
+++ b/tools/linuxfs/overlay/usr/local/bin/droiddeck-steam-compat
@@ -397,11 +397,12 @@ class Helper:
             default, state = COMPAT["choose_default"](top["selected"], state, request, live, apply_request=not waiting)
             installed = COMPAT["installed_apps"](self.steam_root)
             self.installed = installed
-            apps = sorted(set(installed) | set(state.get("auto", {})), key=COMPAT["app_order"])
+            picks = COMPAT["valve_picks"](self.steam_root)
+            apps = sorted(set(installed) | set(picks) | set(state.get("auto", {})), key=COMPAT["app_order"])
             current = dict(page.compat("many(%s)" % json.dumps(apps)) or {})
             current["0"] = top["selected"]
             native = COMPAT["native_targets"](self.steam_root, installed)
-            changes, auto = COMPAT["plan_mapping"](current, installed, [t["name"] for t in live], default, COMPAT["followers"](state, current), native)
+            changes, auto = COMPAT["plan_mapping"](current, installed, [t["name"] for t in live], default, COMPAT["followers"](state, current), native, picks)
             for app, tool in sorted(changes.items(), key=lambda item: COMPAT["app_order"](item[0])):
                 page.compat("set(%d, %s)" % (int(app), json.dumps(tool)))
                 say("%s -> %s" % ("default" if app == "0" else "app %s" % app, tool))
diff --git a/tools/linuxfs/overlay/usr/local/bin/steam-compatibility b/tools/linuxfs/overlay/usr/local/bin/steam-compatibility
index f3600e557..ee1f1eea1 100755
--- a/tools/linuxfs/overlay/usr/local/bin/steam-compatibility
+++ b/tools/linuxfs/overlay/usr/local/bin/steam-compatibility
@@ -632,17 +632,18 @@ def installed_apps(steam_root):
 
 
 APPINFO_CACHE = {}
+STEAM_PLAY_MANIFESTS = 891390
 
 
-def appinfo_platforms(path, wanted):
+def appinfo_entries(path):
     import struct
     try:
         stamp = os.stat(path).st_mtime_ns
     except OSError:
         return {}
     cached = APPINFO_CACHE.get(path)
-    if cached and cached[0] == stamp and wanted <= cached[1].keys() | cached[2]:
-        return {app: cached[1][app] for app in wanted if app in cached[1]}
+    if cached and cached[0] == stamp:
+        return cached[1]
     try:
         with open(path, "rb") as f:
             data = f.read()
@@ -655,16 +656,19 @@ def appinfo_platforms(path, wanted):
         return {}
     offset = 8
     strings = None
-    if magic == 0x07564429:
-        table = struct.unpack_from("<q", data, offset)[0]
-        offset += 8
-        count = struct.unpack_from("<I", data, table)[0]
-        position = table + 4
-        strings = []
-        for _ in range(count):
-            end = data.index(b"\0", position)
-            strings.append(data[position:end].decode("utf-8", "replace"))
-            position = end + 1
+    try:
+        if magic == 0x07564429:
+            table = struct.unpack_from("<q", data, offset)[0]
+            offset += 8
+            count = struct.unpack_from("<I", data, table)[0]
+            position = table + 4
+            strings = []
+            for _ in range(count):
+                end = data.index(b"\0", position)
+                strings.append(data[position:end].decode("utf-8", "replace"))
+                position = end + 1
+    except (ValueError, IndexError, struct.error):
+        return {}
     header = 4 + 4 + 8 + 20 + 4 + (20 if magic >= 0x07564428 else 0)
 
     def section(position):
@@ -697,23 +701,58 @@ def appinfo_platforms(path, wanted):
                 raise ValueError("unknown appinfo field type %d" % kind)
 
     found = {}
-    try:
-        while offset + 8 <= len(data):
+    while offset + 8 <= len(data):
+        try:
             app, size = struct.unpack_from("<II", data, offset)
-            if app == 0:
-                break
-            start = offset + 8
-            offset = start + size
-            if str(app) not in wanted:
-                continue
+        except struct.error:
+            break
+        if app == 0:
+            break
+        start = offset + 8
+        offset = start + size
+        try:
             info = section(start + header)[0].get("appinfo", {})
-            common = info.get("common", {}) if isinstance(info, dict) else {}
-            oslist = {part.strip().lower() for part in str(common.get("oslist", "")).split(",") if part.strip()}
-            found[str(app)] = (oslist, str(common.get("osarch", "")).lower(), str(common.get("type", "")).lower())
-    except (ValueError, IndexError, struct.error):
-        return {}
-    APPINFO_CACHE[path] = (stamp, found, set(wanted))
-    return {app: found[app] for app in wanted if app in found}
+        except (ValueError, IndexError, struct.error):
+            continue
+        if not isinstance(info, dict):
+            continue
+        common = info.get("common", {}) if isinstance(info.get("common"), dict) else {}
+        deck = common.get("steam_deck_compatibility")
+        configuration = deck.get("configuration") if isinstance(deck, dict) else None
+        recommended = configuration.get("recommended_runtime", "") if isinstance(configuration, dict) else ""
+        entry = {
+            "oslist": {part.strip().lower() for part in str(common.get("oslist", "")).split(",") if part.strip()},
+            "osarch": str(common.get("osarch", "")).lower(),
+            "type": str(common.get("type", "")).lower(),
+            "recommended": str(recommended),
+        }
+        if app == STEAM_PLAY_MANIFESTS:
+            extended = info.get("extended", {})
+            mappings = extended.get("app_mappings", {}) if isinstance(extended, dict) else {}
+            entry["app_mappings"] = {str(m.get("appid", key)): str(m.get("tool", "")) for key, m in mappings.items()
+                                     if isinstance(m, dict)} if isinstance(mappings, dict) else {}
+        found[str(app)] = entry
+    APPINFO_CACHE[path] = (stamp, found)
+    return found
+
+
+def appinfo_platforms(path, wanted):
+    entries = appinfo_entries(path)
+    return {app: (entries[app]["oslist"], entries[app]["osarch"], entries[app]["type"]) for app in wanted if app in entries}
+
+
+def valve_picks(steam_root):
+    entries = appinfo_entries(os.path.join(steam_root, "appcache", "appinfo.vdf"))
+    mapped = {app for app, tool in entries.get(str(STEAM_PLAY_MANIFESTS), {}).get("app_mappings", {}).items() if tool}
+    picks = set()
+    for app, entry in entries.items():
+        if app in NOT_GAMES or entry["type"] not in PLAYABLE_TYPES:
+            continue
+        if entry["oslist"] and "windows" not in entry["oslist"]:
+            continue
+        if entry["recommended"] or app in mapped:
+            picks.add(app)
+    return sorted(picks, key=int)
 
 
 def native_targets(steam_root, apps):
@@ -811,21 +850,22 @@ def app_order(app):
     return (len(app), app)
 
 
-def plan_mapping(current, installed, runnable, default, auto, native=None):
+def plan_mapping(current, installed, runnable, default, auto, native=None, picks=()):
     runnable = {n.lower() for n in runnable}
     installed = set(installed)
+    picks = set(picks)
     native = native or {}
     changes, kept = {}, {}
     if current.get("0", "") != default:
         changes["0"] = default
-    for app in sorted((set(current) | installed | set(auto)) - {"0"}, key=app_order):
+    for app in sorted((set(current) | installed | picks | set(auto)) - {"0"}, key=app_order):
         name = current.get(app, "")
         mine = auto.get(app)
         target = native.get(app, default)
         stale = unrunnable(name, runnable) or (app in native and linux_runtime_tool(name))
         if name and not stale and (mine is None or name != mine):
             continue
-        if not name and app not in installed:
+        if not name and app not in installed and app not in picks:
             continue
         if name != target:
             changes[app] = target
@@ -976,7 +1016,7 @@ def live_helper_running(directory=None):
         return False
 
 
-def register_default(config_path, apps=(), protect=(), default=None, catalog=None, directory=None, settle=False):
+def register_default(config_path, apps=(), protect=(), default=None, catalog=None, directory=None, settle=False, picks=()):
     """Writes the mapping: the "0" default and every title that follows it (see plan_mapping).
     With settle, the default itself is decided first (see choose_default): before the client
     starts, config.vdf holds what the client last kept, menu changes included."""
@@ -999,7 +1039,7 @@ def register_default(config_path, apps=(), protect=(), default=None, catalog=Non
             else:
                 default = state.get("default") if state.get("default") in names else TOOL
         steam_root = os.path.dirname(os.path.dirname(os.path.abspath(config_path)))
-        changes, auto = plan_mapping(current, apps, names, default, followers(state, current), native_targets(steam_root, apps))
+        changes, auto = plan_mapping(current, apps, names, default, followers(state, current), native_targets(steam_root, apps), picks)
         for app, tool in changes.items():
             set_mapping(tokens, mapping, app, tool)
         text = serialize(tokens)
@@ -1096,8 +1136,9 @@ def main():
         print("steam-compatibility: the live helper keeps the client's mapping; tools listed")
     elif os.path.isfile(config):
         apps = installed_apps(steam_root)
-        default = register_default(config, apps, protect=extras, catalog=catalog, settle=not steam_running())
-        print("steam-compatibility: default and %d installed title(s) set to %s" % (len(apps), default))
+        picks = valve_picks(steam_root)
+        default = register_default(config, apps, protect=extras, catalog=catalog, settle=not steam_running(), picks=picks)
+        print("steam-compatibility: default, %d installed title(s) and %d title(s) with a Valve pick set to %s" % (len(apps), len(picks), default))
     sync = os.path.join(os.path.dirname(os.path.realpath(__file__)), "droiddeck-esync")
     if os.path.isfile(sync):
         try:
diff --git a/tools/tests/test_droiddeck_fex.py b/tools/tests/test_droiddeck_fex.py
index a79c7567f..bee563f78 100644
--- a/tools/tests/test_droiddeck_fex.py
+++ b/tools/tests/test_droiddeck_fex.py
@@ -465,8 +465,12 @@ class AppInfoTest(unittest.TestCase):
             return out + b"\x08"
 
         body = b""
-        for app, (oslist, osarch, kind) in apps.items():
-            data = section({"appinfo": {"appid": str(app), "common": {"type": kind, "oslist": oslist, "osarch": osarch}}})
+        for app, entry in apps.items():
+            if isinstance(entry, dict):
+                data = section({"appinfo": dict(entry, appid=str(app))})
+            else:
+                oslist, osarch, kind = entry
+                data = section({"appinfo": {"appid": str(app), "common": {"type": kind, "oslist": oslist, "osarch": osarch}}})
             header = struct.pack("<IIQ", 2, 0, 0) + b"\0" * 20 + struct.pack("<I", 1) + (b"\0" * 20 if magic >= 0x07564428 else b"")
             body += struct.pack("<II", app, len(header) + len(data)) + header + data
         body += struct.pack("<I", 0)
@@ -490,6 +494,38 @@ class AppInfoTest(unittest.TestCase):
                 targets = self.COMPAT["native_targets"](str(steam), ["10", "20", "30", "40", "50", "70", "80", "90", "1628350", "60"])
                 self.assertEqual(targets, {"20": "droiddeck-fex", "50": "droiddeck-fex"}, hex(magic))
 
+    def test_titles_with_a_valve_pick_are_found_installed_or_not(self):
+        def deck(oslist, runtime, kind="game"):
+            common = {"type": kind, "oslist": oslist, "steam_deck_compatibility": {"configuration": {"recommended_runtime": runtime}}}
+            if oslist is None:
+                del common["oslist"]
+            return {"common": common}
+        for magic in (0x07564427, 0x07564428, 0x07564429):
+            with tempfile.TemporaryDirectory() as tmp:
+                steam = Path(tmp)
+                (steam / "appcache").mkdir()
+                (steam / "appcache/appinfo.vdf").write_bytes(self.appinfo({
+                    10: deck("windows", "proton-stable"), 11: deck("windows,linux", "native"), 12: deck(None, "proton-7.0-5"),
+                    13: deck("linux", "native"), 14: deck("windows", "proton-stable", "Tool"), 15: ("windows", "", "game"),
+                    16: ("windows", "", "game"), 1628350: deck("linux", "native", "game"),
+                    891390: {"common": {"type": "Config"}, "extended": {"app_mappings": {
+                        "16": {"appid": "16", "tool": "proton-stable"}, "17": {"appid": "17", "tool": ""}}}},
+                }, magic))
+                self.COMPAT["APPINFO_CACHE"].clear()
+                self.assertEqual(self.COMPAT["valve_picks"](str(steam)), ["10", "11", "12", "16"], hex(magic))
+
+    def test_titles_with_a_valve_pick_follow_the_default_until_the_user_picks(self):
+        tool = self.COMPAT["TOOL"]
+        changes, auto = self.COMPAT["plan_mapping"](
+            {"0": tool, "31": "GE-Proton11-7", "32": "proton_11_arm64", "33": "steamlinuxruntime"},
+            ["40"], [tool, "GE-Proton11-7"], tool, {}, {}, ["30", "31", "32", "33"])
+        self.assertEqual(changes, {"30": tool, "32": tool, "40": tool})
+        self.assertEqual(auto, {"30": tool, "32": tool, "40": tool})
+        changes, auto = self.COMPAT["plan_mapping"](
+            {"0": "GE-Proton11-7", "30": tool, "31": "GE-Proton11-7", "32": tool}, [], [tool, "GE-Proton11-7"], "GE-Proton11-7", auto, {}, ["30", "31", "32"])
+        self.assertEqual(changes, {"30": "GE-Proton11-7", "32": "GE-Proton11-7"})
+        self.assertEqual(auto, {"30": "GE-Proton11-7", "32": "GE-Proton11-7"})
+
     def test_the_mapping_sends_native_titles_to_fex_and_keeps_picks(self):
         tool, fex = self.COMPAT["TOOL"], self.COMPAT["FEX_TOOL"]
         changes, auto = self.COMPAT["plan_mapping"](