Add --noblank, and fix install.sh exiting early when no relogin is needed

Wall displays must never blank. --noblank applies two layers: an Xorg
ServerFlags snippet with all four timeouts at 0 (covers the DM greeter, and
survives reboots) and an xset line in the i3 autostart (a session or DM can
re-enable the screensaver after X starts). Either alone is insufficient.

Documents the trap that cost time here: `sudo xset ...` targets root's X
connection and silently does nothing, so a `sudo bash noblank.sh` wrapper looks
like it worked while blanking stays fully armed.

Also fixes a latent bug: `[ "$relogin" = yes ] && echo ...` as the final
statement made install.sh exit non-zero under `set -e` -- and skip the closing
instructions -- whenever a relogin was not required.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

install.sh

@@ -4,7 +4,8 @@
 #   ./install.sh                 scripts + config + lisgd (build if missing)
 #   ./install.sh --xignore       ...and tell X to ignore the touch panel
 #   ./install.sh --i3            ...and add i3 autostart lines
-#   ./install.sh --xignore --i3  full display-host setup
+#   ./install.sh --noblank       ...and stop the screen blanking
+#   ./install.sh --xignore --i3 --noblank   full wall-display setup
 #
 # Safe to re-run: an existing config file is never overwritten, and the i3 edit
 # is skipped if already present.
@@ -15,15 +16,18 @@ BIN="$PREFIX/bin"
 ETC="$PREFIX/etc"
 CONF="$ETC/socktop-swipe.env"
 XCONF=/etc/X11/xorg.conf.d/99-ignore-touch-socktop-swipe.conf
+BCONF=/etc/X11/xorg.conf.d/10-no-blanking-socktop-swipe.conf
 SRC="$HOME/src/lisgd"
 
 here=$(cd "$(dirname "$0")" && pwd)
 do_xignore=no
 do_i3=no
+do_noblank=no
 for a in "$@"; do
 	case "$a" in
 	--xignore) do_xignore=yes ;;
 	--i3) do_i3=yes ;;
+	--noblank) do_noblank=yes ;;
 	*) echo "unknown option: $a" >&2; exit 2 ;;
 	esac
 done
@@ -100,6 +104,49 @@ EOF
 	relogin=yes
 fi
 
+# --- optional: stop the screen blanking -------------------------------------
+if [ "$do_noblank" = yes ]; then
+	echo "==> disabling screen blanking and DPMS"
+	# Two layers on purpose:
+	#  1. An Xorg ServerFlags snippet, so it applies to every X session including
+	#     the display manager greeter, and survives reboots.
+	#  2. An xset call at i3 startup, because a session or DM can re-enable the
+	#     screensaver after X starts.
+	# Note `xset` alone is NOT enough, and must run as the session user -- running
+	# it under sudo targets root's X connection and silently does nothing.
+	sudo mkdir -p /etc/X11/xorg.conf.d
+	sudo tee "$BCONF" >/dev/null <<'EOF'
+# Installed by socktop-swipe. This is a wall display: it must never blank.
+Section "ServerFlags"
+    Option "BlankTime"   "0"
+    Option "StandbyTime" "0"
+    Option "SuspendTime" "0"
+    Option "OffTime"     "0"
+EndSection
+EOF
+	echo "    wrote $BCONF"
+
+	# Apply immediately too, if a session is available.
+	if [ -n "${DISPLAY:-}" ]; then
+		xset s off s noblank -dpms 2>/dev/null || true
+		echo "    applied to the running session"
+	fi
+
+	i3conf="$HOME/.config/i3/config"
+	if [ -e "$i3conf" ] && ! grep -q "xset s off" "$i3conf"; then
+		bak="$i3conf.bak-$(date +%Y%m%d-%H%M%S)"
+		cp "$i3conf" "$bak"
+		printf '\n# Wall display: never blank (socktop-swipe --noblank)\nexec --no-startup-id xset s off s noblank -dpms\n' >>"$i3conf"
+		if i3 -C -c "$i3conf" >/dev/null 2>&1; then
+			echo "    added xset to i3 autostart (backup: $bak)"
+		else
+			cp "$bak" "$i3conf"
+			echo "!! i3 rejected the config; restored $bak" >&2
+		fi
+	fi
+	relogin=yes
+fi
+
 # --- optional: i3 autostart -------------------------------------------------
 if [ "$do_i3" = yes ]; then
 	i3conf="$HOME/.config/i3/config"
@@ -133,7 +180,9 @@ fi
 echo
 echo "=============================================================="
 echo "Installed."
-[ "$relogin" = yes ] && echo "LOG OUT and back in before use (group and/or X changes)."
+if [ "$relogin" = yes ]; then
+	echo "LOG OUT and back in before use (group and/or X changes)."
+fi
 cat <<EOF
 
 Start it by hand with: