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

patches/steamify-gdm-relogin.sh

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+#!/bin/bash
+# Log the autologin user in again, into the session steam-set-session picked
+# (Steamify prototype, GDM). Run as root through sudo, from inside the session
+# that is being left. GDM logs in by itself only when the daemon starts, and
+# a new session refuses to start while the old user manager still runs
+# ("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.
+if [[ "$1" != --work ]]; then
+    [[ -n "${SUDO_USER:-}" ]] || exit 1
+    exec systemd-run --no-block --collect --unit=steamify-gdm-relogin "$0" --work "$SUDO_USER"
+fi
+USER_NAME="$2"
+# No waiting for the old user manager to go: systemd starts the new login
+# after it, and waiting only keeps GDM's login screen up in the meantime.
+loginctl terminate-user "$USER_NAME"
+systemctl restart gdm.service

patches/steamify-gdm-session-select.sh

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+#!/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

patches/steamify-gdm-steam-set-session.sh

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+#!/bin/bash
+# steam-set-session with GDM support (Steamify prototype). CachyOS's own only
+# knows plasma-login-manager and SDDM and quietly does nothing on GDM. GDM
+# has no autologin fragment: it takes the user's session from
+# AccountsService, so that is where the session goes.
+set -e
+
+DM_ID="$(systemctl show -p Id --value display-manager)"
+DM_ID="${DM_ID%.service}"
+SESSION="${1:-gamescope-session.desktop}"
+
+case "$DM_ID" in
+    plasmalogin) CONF_FILE="/etc/plasmalogin.conf.d/zz-steamos-autologin.conf" ;;
+    sddm) CONF_FILE="/etc/sddm.conf.d/zz-steamos-autologin.conf" ;;
+    gdm)
+        if [[ -n "${PKEXEC_UID:-}" ]]; then TARGET_USER="$(id -un "$PKEXEC_UID")"
+        else TARGET_USER="${SUDO_USER:-$(logname 2>/dev/null)}"; fi
+        # At boot (steamify-boot-desktop.service) nobody is logged in: the autologin user.
+        [[ -n "$TARGET_USER" ]] || TARGET_USER="$(sed -n 's/^AutomaticLogin=//p' /etc/gdm/custom.conf 2>/dev/null)"
+        [[ -n "$TARGET_USER" ]] || exit 0
+        ACCOUNT="/var/lib/AccountsService/users/$TARGET_USER"
+        SESSION_ID="${SESSION%.desktop}"
+        mkdir -p /var/lib/AccountsService/users
+        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=$SESSION_ID|" "$ACCOUNT"
+            else sed -i "/^\[User\]/a $key=$SESSION_ID" "$ACCOUNT"; fi
+        done
+        systemctl restart accounts-daemon 2>/dev/null || true
+        exit 0 ;;
+esac
+
+# Any other login manager: nothing to do.
+[[ -n "${CONF_FILE:-}" ]] || exit 0
+mkdir -p "$(dirname "$CONF_FILE")"
+printf '[Autologin]\nSession=%s\n' "$SESSION" > "$CONF_FILE"

patches/steamify-gdm.hook

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+[Trigger]
+Operation = Install
+Operation = Upgrade
+Type = Package
+Target = gamescope-session-cachyos
+
+[Action]
+Description = Steamify: GDM support for gamescope-session-cachyos...
+When = PostTransaction
+Exec = /bin/sh -c 'install -m755 @DIR@/steam-set-session /usr/lib/steamos/steam-set-session && install -m755 @DIR@/steamos-session-select /usr/bin/steamos-session-select'