Pre-defined Steam launch options: picker menu

app/src/main/app/shell/LibraryGameLaunchScreen.kt

@@ -50,6 +50,7 @@ import androidx.compose.material.icons.outlined.DesktopWindows
 import androidx.compose.material.icons.outlined.EmojiEvents
 import androidx.compose.material.icons.outlined.History
 import androidx.compose.material.icons.outlined.Refresh
+import androidx.compose.material.icons.outlined.RocketLaunch
 import androidx.compose.material.icons.outlined.Home
 import androidx.compose.material.icons.outlined.PlayArrow
 import androidx.compose.material.icons.outlined.Save
@@ -140,6 +141,8 @@ internal fun LibraryGameLaunchScreen(
     showVerifyFiles: Boolean = true,
     showCheckForUpdate: Boolean = true,
     showWorkshop: Boolean = true,
+    showLaunchOptions: Boolean = false,
+    onLaunchOptions: () -> Unit = {},
     playEnabled: Boolean = true,
     playDisabledLabel: String? = null,
     onBack: () -> Unit,
@@ -278,11 +281,13 @@ internal fun LibraryGameLaunchScreen(
                 showCheckForUpdate = showCheckForUpdate,
                 showWorkshop = showWorkshop,
                 showAchievements = onAchievements != null,
+                showLaunchOptions = showLaunchOptions,
                 areSteamActionsEnabled = areSteamActionsEnabled,
                 onVerifyFiles = onVerifyFiles,
                 onCheckForUpdate = onCheckForUpdate,
                 onWorkshop = onWorkshop,
                 onAchievements = { onAchievements?.invoke() },
+                onLaunchOptions = onLaunchOptions,
             )
         }
 
@@ -821,11 +826,13 @@ private fun SourceTag(
     showCheckForUpdate: Boolean = true,
     showWorkshop: Boolean = true,
     showAchievements: Boolean = false,
+    showLaunchOptions: Boolean = false,
     areSteamActionsEnabled: Boolean = true,
     onVerifyFiles: () -> Unit = {},
     onCheckForUpdate: () -> Unit = {},
     onWorkshop: () -> Unit = {},
     onAchievements: () -> Unit = {},
+    onLaunchOptions: () -> Unit = {},
 ) {
     var menuOpen by remember { mutableStateOf(false) }
     var anchorHeightPx by remember { mutableStateOf(0) }
@@ -902,6 +909,13 @@ private fun SourceTag(
                         label = stringResource(R.string.steam_achievements_title),
                     ) { menuOpen = false; onAchievements() }
                 }
+                if (showLaunchOptions) {
+                    LaunchSourceMenuItem(
+                        icon = Icons.Outlined.RocketLaunch,
+                        label = stringResource(R.string.store_game_launch_options),
+                        enabled = areSteamActionsEnabled,
+                    ) { menuOpen = false; onLaunchOptions() }
+                }
             }
         }
     }

app/src/main/app/shell/StoreGameDetailScreen.kt

@@ -57,6 +57,7 @@ import androidx.compose.material.icons.outlined.ExpandMore
 import androidx.compose.material.icons.outlined.Extension
 import androidx.compose.material.icons.outlined.Folder
 import androidx.compose.material.icons.outlined.Refresh
+import androidx.compose.material.icons.outlined.RocketLaunch
 import androidx.compose.material.icons.outlined.SportsEsports
 import androidx.compose.material.icons.outlined.Storage
 import androidx.compose.material.icons.outlined.SystemUpdate
@@ -155,6 +156,8 @@ internal fun StoreGameDetailScreen(
     showWorkshop: Boolean = false,
     showVerifyFiles: Boolean = false,
     areSteamActionsEnabled: Boolean = true,
+    showLaunchOptions: Boolean = false,
+    onLaunchOptions: () -> Unit = {},
     dlcs: List<StoreDlcItem> = emptyList(),
     selectedDlcIds: Set<Int> = emptySet(),
     isDlcSelectionEnabled: Boolean = true,
@@ -202,7 +205,9 @@ internal fun StoreGameDetailScreen(
         val showUpdateCta = updateCheckAvailable && isUpdateAvailable
         val verifyFilesAvailable = showVerifyFiles && isInstalled
         val workshopAvailable = showWorkshop && isInstalled
-        val sourceMenuEnabled = updateCheckAvailable || verifyFilesAvailable || workshopAvailable
+        val launchOptionsAvailable = showLaunchOptions && isInstalled
+        val sourceMenuEnabled =
+            updateCheckAvailable || verifyFilesAvailable || workshopAvailable || launchOptionsAvailable
         val showDlcCard = dlcs.isNotEmpty()
         val showActionColumn =
             showDownloadCta || showUpdateCta ||
@@ -313,6 +318,7 @@ internal fun StoreGameDetailScreen(
                 showCheckForUpdate = updateCheckAvailable,
                 showVerifyFiles = verifyFilesAvailable,
                 showWorkshop = workshopAvailable,
+                showLaunchOptions = launchOptionsAvailable,
                 isCheckingForUpdate = isCheckingForUpdate,
                 areSteamActionsEnabled = areSteamActionsEnabled,
                 isUpdateCheckEnabled =
@@ -323,6 +329,7 @@ internal fun StoreGameDetailScreen(
                 onVerifyFiles = onVerifyFiles,
                 onCheckForUpdate = onCheckForUpdate,
                 onWorkshop = onWorkshop,
+                onLaunchOptions = onLaunchOptions,
             )
         }
 
@@ -824,12 +831,14 @@ private fun StoreSourceTag(
     showCheckForUpdate: Boolean = false,
     showVerifyFiles: Boolean = false,
     showWorkshop: Boolean = false,
+    showLaunchOptions: Boolean = false,
     isCheckingForUpdate: Boolean = false,
     areSteamActionsEnabled: Boolean = true,
     isUpdateCheckEnabled: Boolean = true,
     onVerifyFiles: () -> Unit = {},
     onCheckForUpdate: () -> Unit = {},
     onWorkshop: () -> Unit = {},
+    onLaunchOptions: () -> Unit = {},
 ) {
     var anchorHeightPx by remember { mutableIntStateOf(0) }
     Box {
@@ -913,6 +922,13 @@ private fun StoreSourceTag(
                             enabled = areSteamActionsEnabled,
                         ) { onMenuOpenChange(false); onWorkshop() }
                     }
+                    if (showLaunchOptions) {
+                        StoreSourceMenuItem(
+                            icon = Icons.Outlined.RocketLaunch,
+                            label = stringResource(R.string.store_game_launch_options),
+                            enabled = areSteamActionsEnabled,
+                        ) { onMenuOpenChange(false); onLaunchOptions() }
+                    }
                 }
             }
         }

app/src/main/app/shell/UnifiedActivity.kt

@@ -5656,6 +5656,9 @@ class UnifiedActivity :
         val isEpic = app.id >= 2000000000
         val isGog = gogGame != null
         val epicId = if (isEpic) app.id - 2000000000 else 0
+        val isSteamLibraryGame = !isCustom && !isEpic && !isGog
+
+        val launchOptionsState = rememberSteamLaunchOptionsState(app.id, enabled = isSteamLibraryGame)
 
         val libraryDownloadRecords by com.winlator.cmod.app.service.download.DownloadCoordinator.records.collectAsState(
             initial = com.winlator.cmod.app.service.download.DownloadCoordinator.snapshotRecords(),
@@ -6387,6 +6390,8 @@ class UnifiedActivity :
                                         (!isEpic || epicGame?.isInstalled == true) &&
                                         (!isGog || gogGame?.isInstalled == true),
                                     showWorkshop = !isEpic && !isGog,
+                                    showLaunchOptions = launchOptionsState.options.size >= 2,
+                                    onLaunchOptions = launchOptionsState::show,
                                     areSteamActionsEnabled =
                                         when {
                                             isEpic -> !hasBlockingEpicDownloadForLibrary
@@ -6885,6 +6890,8 @@ class UnifiedActivity :
                         onDismissRequest = { showWorkshopDialog = false },
                     )
                 }
+
+                SteamLaunchOptionsDialogHost(app.id, app.name, launchOptionsState)
             }
         }
     }
@@ -9936,6 +9943,7 @@ class UnifiedActivity :
         var isCheckingForUpdate by remember(app.id) { mutableStateOf(false) }
         var isUpdateCheckCoolingDown by remember(app.id) { mutableStateOf(false) }
         var showWorkshopDialog by remember(app.id) { mutableStateOf(false) }
+        val launchOptionsState = rememberSteamLaunchOptionsState(app.id, enabled = installed == true)
         var updateInfo by remember(app.id) { mutableStateOf<SteamService.SteamUpdateInfo?>(null) }
         var updateStatusText by remember(app.id) { mutableStateOf<String?>(null) }
         val downloadRecords by com.winlator.cmod.app.service.download.DownloadCoordinator.records.collectAsState(
@@ -10122,6 +10130,8 @@ class UnifiedActivity :
                     showWorkshop = isReallyInstalled,
                     showVerifyFiles = isReallyInstalled,
                     areSteamActionsEnabled = !hasBlockingSteamDownload,
+                    showLaunchOptions = launchOptionsState.options.size >= 2,
+                    onLaunchOptions = launchOptionsState::show,
                     dlcs = dlcItems,
                     selectedDlcIds = selectedDlcIds.toSet(),
                     isDlcSelectionEnabled = steamDownloadRecord == null,
@@ -10261,6 +10271,8 @@ class UnifiedActivity :
                 onDismissRequest = { showWorkshopDialog = false },
             )
         }
+
+        SteamLaunchOptionsDialogHost(app.id, app.name, launchOptionsState)
     }
 
     @Composable

app/src/main/cpp/wn-steam-launcher/src/main.cpp

@@ -304,18 +304,90 @@ static int count_game_processes(const char* exeName) {
     return count;
 }
 
+static bool append_char(char* buf, size_t cap, size_t* n, char c) {
+    if (*n + 1 >= cap) return false;
+    buf[(*n)++] = c;
+    return true;
+}
+
+// Appends one argv element re-quoted per CommandLineToArgvW rules (backslash runs
+// before an emitted quote must be doubled); false when the buffer would overflow.
+static bool append_quoted_arg(char* buf, size_t cap, size_t* n, const char* a) {
+    const bool quote = (a[0] == '\0') || strpbrk(a, " \t\"") != NULL;
+    if (!quote) {
+        for (const char* p = a; *p; ++p)
+            if (!append_char(buf, cap, n, *p)) return false;
+        return true;
+    }
+    if (!append_char(buf, cap, n, '"')) return false;
+    const char* p = a;
+    while (*p) {
+        size_t backslashes = 0;
+        while (*p == '\\') { backslashes++; p++; }
+        if (*p == '\0') {
+            // Run ends the arg: double it so the closing quote stays a delimiter.
+            for (size_t k = 0; k < backslashes * 2; k++)
+                if (!append_char(buf, cap, n, '\\')) return false;
+            break;
+        }
+        if (*p == '"') {
+            for (size_t k = 0; k < backslashes * 2 + 1; k++)
+                if (!append_char(buf, cap, n, '\\')) return false;
+        } else {
+            for (size_t k = 0; k < backslashes; k++)
+                if (!append_char(buf, cap, n, '\\')) return false;
+        }
+        if (!append_char(buf, cap, n, *p)) return false;
+        p++;
+    }
+    return append_char(buf, cap, n, '"');
+}
+
+// Re-joins argv[2..] for forwarding onto the game's command line; on overflow
+// whole trailing args are dropped (never a half token) with a logged warning.
+static const char* build_extra_args(int argc, char** argv) {
+    static char buf[4096];
+    size_t n = 0;
+    buf[0] = '\0';
+    for (int i = 2; i < argc; i++) {
+        size_t before = n;
+        bool ok = (n == 0) || append_char(buf, sizeof(buf), &n, ' ');
+        ok = ok && append_quoted_arg(buf, sizeof(buf), &n, argv[i]);
+        if (!ok) {
+            n = before;
+            log_line("[wn-launcher] extra args exceed %zu bytes - dropped %d trailing arg(s)",
+                     sizeof(buf), argc - i);
+            break;
+        }
+    }
+    buf[n] = '\0';
+    return buf;
+}
+
 // Direct launch when LaunchApp dispatches cleanly but never spawns the game (no
 // real Steam UI/reaper under Wine to consume the request). Safe vs AlreadyRunning
 // because the clean-shutdown arm reaps the CM session on exit. Logs the "game
 // process started pid=" marker WnLauncherStatusTailer treats as launch-complete.
-static bool create_process_game(const char* gameExe, const char* exeName) {
+static bool create_process_game(const char* gameExe, const char* exeName,
+                                const char* extraArgs) {
     char cwd[MAX_PATH];
     snprintf(cwd, sizeof(cwd), "%s", gameExe);
     char* slash = strrchr(cwd, '\\');
     if (slash) *slash = '\0'; else cwd[0] = '\0';
 
-    char cmd[MAX_PATH + 8];
-    snprintf(cmd, sizeof(cmd), "\"%s\"", gameExe);
+    char cmd[MAX_PATH + 4096 + 16];
+    int written;
+    if (extraArgs && extraArgs[0]) {
+        written = snprintf(cmd, sizeof(cmd), "\"%s\" %s", gameExe, extraArgs);
+    } else {
+        written = snprintf(cmd, sizeof(cmd), "\"%s\"", gameExe);
+    }
+    if (written < 0 || written >= (int) sizeof(cmd)) {
+        log_line("[wn-launcher] CreateProcess cmd truncated (%d bytes)", written);
+    }
+    // Args content stays out of the log — execArgs can carry +password style credentials.
+    log_line("[wn-launcher] CreateProcess exe=\"%s\" argsLen=%zu",
+             gameExe, (extraArgs && extraArgs[0]) ? strlen(extraArgs) : (size_t) 0);
 
     STARTUPINFOA si;
     memset(&si, 0, sizeof(si));
@@ -758,13 +830,15 @@ int main(int argc, char** argv) {
     const char* token    = getenv("WN_STEAM_TOKEN");
     uint64_t    steamId  = env_u64("WN_STEAM_STEAMID");
     const char* gameExe  = (argc > 1) ? argv[1] : NULL;
+    const char* extraArgs = build_extra_args(argc, argv);
     uint32_t    appId    = appIdStr ? (uint32_t) strtoul(appIdStr, NULL, 10) : 0;
 
-    log_line("[wn-launcher] env appId=%u steamId=%llu user=%s exe=%s",
+    log_line("[wn-launcher] env appId=%u steamId=%llu user=%s exe=%s argsLen=%zu",
              appId,
              (unsigned long long) steamId,
              user ? user : "(null)",
-             gameExe ? gameExe : "(null)");
+             gameExe ? gameExe : "(null)",
+             strlen(extraArgs));
     if (token && *token) {
         size_t tokenLen = strlen(token);
         log_line("[wn-launcher] token len=%zu prefix=%.*s suffix=%.*s",
@@ -1393,7 +1467,7 @@ int main(int argc, char** argv) {
                      "— falling back to CreateProcess (%s)",
                      exeName, launchFailureReason);
         }
-        launchedViaFallback = create_process_game(gameExe, exeName);
+        launchedViaFallback = create_process_game(gameExe, exeName, extraArgs);
     }
 
     if (launchedViaApp || launchedViaFallback) {

app/src/main/feature/library/GameSettings.kt

@@ -344,6 +344,9 @@ class GameSettingsStateHolder {
     val name = mutableStateOf("")
     val launchExePath = mutableStateOf("")
     val launchExeDisplayPath = mutableStateOf("")
+
+    // Read-only: args the selected Steam launch option appends at launch (display only).
+    val launchOptionArgs = mutableStateOf("")
     val containerEntries = mutableStateOf<List<String>>(emptyList())
     val selectedContainer = mutableIntStateOf(0)
     val screenSizeEntries = mutableStateOf<List<String>>(emptyList())
@@ -3654,6 +3657,15 @@ private fun AdvancedSection(
             )
         }
 
+        if (state.launchOptionArgs.value.isNotBlank()) {
+            Spacer(Modifier.height(SettingTightGap))
+            Text(
+                stringResource(R.string.shortcut_launch_option_args, state.launchOptionArgs.value),
+                color = TextDim,
+                fontSize = 10.sp
+            )
+        }
+
         Spacer(Modifier.height(SettingItemGap))
 
         SettingCheckbox(

app/src/main/feature/shortcuts/ShortcutSettingsComposeDialog.kt

@@ -49,6 +49,7 @@ import com.winlator.cmod.feature.settings.GraphicsDriverConfigUtils
 import com.winlator.cmod.feature.settings.WineD3DConfigUtils
 import com.winlator.cmod.feature.setup.SetupWizardActivity
 import com.winlator.cmod.feature.stores.steam.events.AndroidEvent
+import com.winlator.cmod.feature.stores.steam.service.SteamService
 import com.winlator.cmod.runtime.compat.box64.Box64Preset
 import com.winlator.cmod.runtime.compat.box64.Box64PresetManager
 import com.winlator.cmod.runtime.container.Container
@@ -358,6 +359,7 @@ class ShortcutSettingsComposeDialog private constructor(
         state.name.value = shortcut.name
         state.launchExePath.value = resolveInitialLaunchExePath()
         state.launchExeDisplayPath.value = resolveLaunchExeDisplayPath(state.launchExePath.value)
+        state.launchOptionArgs.value = shortcut.getExtra("launch_exe_args")
         syncLibraryArtworkState()
 
         val inputType = Integer.parseInt(
@@ -1192,6 +1194,14 @@ class ShortcutSettingsComposeDialog private constructor(
             // Launch EXE path
             val launchExePath = normalizeLaunchExeForShortcut(state.launchExePath.value)
             if (launchExePath.isNotEmpty()) {
+                val storedExePath = SteamService.normalizeRelativeExe(shortcut.getExtra("launch_exe_path"))
+                // A manual exe CHANGE turns the Steam launch option off ("" marker, not key removal).
+                // Normalized compare: appinfo '\'/case variants of the same exe must not false-trigger.
+                if (!SteamService.normalizeRelativeExe(launchExePath).equals(storedExePath, ignoreCase = true)) {
+                    shortcut.putExtra("launch_exe_args", null)
+                    shortcut.putExtra("launch_option_exe", "")
+                    shortcut.putExtra("launch_option_args", null)
+                }
                 shortcut.putExtra("launch_exe_path", launchExePath)
                 val gameSource = shortcut.getExtra("game_source", "")
                 if (gameSource == "CUSTOM") {

app/src/main/feature/stores/steam/data/LaunchInfo.kt

@@ -11,6 +11,8 @@ data class LaunchInfo(
     val workingDir: String,
     val description: String,
     val type: String,
+    // Default keeps already-cached appinfo JSON (without this key) decodable.
+    val arguments: String = "",
     @Serializable(with = OsEnumSetSerializer::class)
     val configOS: java.util.EnumSet<OS>,
     val configArch: OSArch,