GNOME prototype: detect GNOME/GDM, GDM autologin and session switching

patches/steamify-gdm-session-select.sh

@@ -0,0 +1,45 @@
+#!/bin/bash
+# steamos-session-select for GDM (Steamify prototype): CachyOS's own ends the
+# session with a KDE-only D-Bus call. GDM logs in by itself only when it
+# starts, so after the new session is set the user is ended and GDM restarted
+# (patches/steamify-gdm-relogin.sh): it then logs the autologin user straight into it.
+set -e
+
+DM_ID="$(systemctl show -p Id --value display-manager)"
+DM_ID="${DM_ID%.service}"
+DESKTOP_SESSION=@DESKTOP_SESSION@
+
+relogin() {
+    # Out of the running session into the one that was set.
+    case "$DM_ID" in
+        gdm) sudo -n /usr/local/libexec/steamify-gdm-relogin ;;
+        *) qdbus6 org.kde.Shutdown /Shutdown org.kde.Shutdown.logout ;;
+    esac
+}
+
+case "$1" in
+    persistent)
+        systemctl --user mask cachyos-gamescope-autologin.service
+        pkexec /usr/lib/steamos/steam-set-session "$DESKTOP_SESSION" ;;
+    oneshot)
+        systemctl --user unmask cachyos-gamescope-autologin.service
+        pkexec /usr/lib/steamos/steam-set-session gamescope-session.desktop ;;
+    gamescope)
+        pkexec /usr/lib/steamos/steam-set-session gamescope-session.desktop
+        relogin ;;
+    desktop|plasma|gnome)
+        pkexec /usr/lib/steamos/steam-set-session "$DESKTOP_SESSION"
+        steam -shutdown || true
+        systemctl --user stop gamescope-session.target || true
+        # Under GDM nothing logs in again by itself after the session ends.
+        [[ "$DM_ID" == gdm ]] && relogin ;;
+    *)
+        [[ -n "$1" ]] && echo -e "Unknown session '$1'\n"
+        echo "Usage: $(basename "$0") persistent|oneshot|gamescope|desktop"
+        exit 1 ;;
+esac
+
+if [[ -e /dev/input/.hidden ]]; then
+    pkexec mv /dev/input/.hidden/* /dev/input
+    pkexec rm -r /dev/input/.hidden
+fi