Restart GNOME logs in to GNOME, not the account's default session (gaming mode after the conversion); the default is put back afterwards

CHANGELOG.md

@@ -17,6 +17,7 @@ one per merged pull request.
 - **fix: the app on a desktop (a window, however large, also fullscreen) keeps the desktop's own scale instead of blowing its 1280x720 layout up to the screen's height (twice as big on a 1440p or ultrawide monitor): the layout fills the window at the scale of GNOME or KDE, and only a window smaller than 1280x720 shrinks it. The TV mode (`--fullscreen`, gamescope) still scales to the screen**
 - **fix: in the app a click on a row only selects it (a second click on the selected row used to flip it, so a click on a switch needed two); a click on the switch itself, or on the BIOS update button, acts at once and selects the row too**
 - **feat: a run that only needs a new GNOME login (the theme, no reboot) ends with a countdown on the done screen ("Restarting GNOME in 10 s", with Restart GNOME now and Cancel) and then logs in again by itself, the counterpart of KDE restarting plasmashell (GNOME Shell on Wayland is the compositor too and can't restart in place). A run that needs a reboot keeps "Restart now" (it loads GNOME fresh): before, the Restart GNOME button was hidden then, and nothing started by itself**
+- **fix: Restart GNOME logs in to GNOME: after the SteamOS conversion the account's session is gaming mode, and the relogin went there (a restart that took a minute: Steam starting in gaming mode). `steamify-gdm-relogin` takes the session to log in to (the one the app runs in) for this login only and puts the account's session, the one the next boot goes to, back once the new session is up**
 
 ## 2.12.0 - 2026-10-13
 

lib/gnome-theme.sh

@@ -123,7 +123,7 @@ gnometheme_relogin() {
     # steamos-session-select, which would make GNOME the one gaming mode's boot goes back to). Without that helper there
     # is no autologin: a plain logout, and the user logs in again.
     local helper=/usr/local/libexec/steamify-gdm-relogin
-    if [[ -x "$helper" ]] && sudo -n "$helper"; then return 0; fi
+    if [[ -x "$helper" ]] && sudo -n "$helper" "${XDG_SESSION_DESKTOP:-gnome}"; then return 0; fi
     gnome-session-quit --logout --no-prompt
 }
 

patches/steamify-gdm-relogin.sh

@@ -6,11 +6,36 @@
 # ("A graphical session is already running!"): so the user is ended first,
 # then GDM restarted. That work runs in its own transient unit, because
 # ending the user kills this process too.
+#
+# An optional session id as the argument ("gnome"): that session is logged in
+# for this time only. The session in AccountsService (what the next boot goes
+# to: gaming mode after the SteamOS conversion) is put back once the new
+# session is up.
 if [[ "$1" != --work ]]; then
     [[ -n "${SUDO_USER:-}" ]] || exit 1
-    exec systemd-run --no-block --collect --unit=steamify-gdm-relogin "$0" --work "$SUDO_USER"
+    exec systemd-run --no-block --collect --unit=steamify-gdm-relogin "$0" --work "$SUDO_USER" "${1:-}"
 fi
 USER_NAME="$2"
+SESSION="$3"
+ACCOUNT="/var/lib/AccountsService/users/$USER_NAME"
+
+# Session= and XSession= of the user, as GDM reads them at the next login.
+get_session() { sed -n "s/^$1=//p" "$ACCOUNT" 2>/dev/null | head -1; }
+set_session() {
+    local key
+    touch "$ACCOUNT"
+    grep -q '^\[User\]' "$ACCOUNT" || echo "[User]" >> "$ACCOUNT"
+    for key in Session XSession; do
+        if grep -q "^$key=" "$ACCOUNT"; then sed -i "s|^$key=.*|$key=$1|" "$ACCOUNT"
+        else sed -i "/^\[User\]/a $key=$1" "$ACCOUNT"; fi
+    done
+    systemctl restart accounts-daemon 2>/dev/null || true
+}
+if [[ -n "$SESSION" ]]; then
+    OLD_SESSION="$(get_session Session)"; OLD_XSESSION="$(get_session XSession)"
+    set_session "${SESSION%.desktop}"
+fi
+
 # GDM is stopped first, so its login screen doesn't show while the old user
 # manager shuts down; a new login right away fails ("A graphical session is
 # already running!", or the session dies at once), so wait until it is gone.
@@ -20,3 +45,14 @@ loginctl terminate-user "$USER_NAME"
 USER_RUNTIME="/run/user/$(id -u "$USER_NAME")"
 for _ in $(seq 120); do [[ -d "$USER_RUNTIME" ]] || break; sleep 0.25; done
 systemctl start gdm.service
+
+if [[ -n "$SESSION" ]]; then
+    # The new session has read what it logs in to once its user manager runs; then the next boot's session goes back.
+    for _ in $(seq 120); do [[ -d "$USER_RUNTIME" ]] && break; sleep 0.25; done
+    sleep 8
+    if [[ -n "$OLD_SESSION" ]]; then
+        sed -i "s|^Session=.*|Session=$OLD_SESSION|" "$ACCOUNT"
+        if [[ -n "$OLD_XSESSION" ]]; then sed -i "s|^XSession=.*|XSession=$OLD_XSESSION|" "$ACCOUNT"; fi
+        systemctl restart accounts-daemon 2>/dev/null || true
+    fi
+fi

ui/steamify-ui

@@ -351,7 +351,9 @@ class Backend(QObject):
         # Steamify's helper logs the user straight back in; else a plain logout.
         import subprocess
         helper = "/usr/local/libexec/steamify-gdm-relogin"
-        if os.access(helper, os.X_OK) and subprocess.run(["sudo", "-n", helper], capture_output=True).returncode == 0:
+        # The session this one is, for this login only: the default (gaming mode, after the conversion) would log in there.
+        session = os.environ.get("XDG_SESSION_DESKTOP") or "gnome"
+        if os.access(helper, os.X_OK) and subprocess.run(["sudo", "-n", helper, session], capture_output=True).returncode == 0:
             return
         QProcess.startDetached("gnome-session-quit", ["--logout", "--no-prompt"])