Server: Allow X cleanup script to be specified

Referring to #490, it is necessary to set $userDBus=1; in
turbovncserver.conf to prevent GNOME shell issues with the Cinnamon
window manager on Mint 22.3 or Ubuntu 24.04.  However, with this
configuration, cinnamon-session fails to shut down when Xvnc is killed.
I observed this issue with TigerVNC's systemd-friendly vncsession
approach as well, although the OP did not.

This commit introduces a new $xcleanup variable that allows an optional
X cleanup script to be specified.  If specified, vncserver executes the
X cleanup script just before attempting to kill Xvnc.  Specifying
$xcleanup="cinnamon-session-quit --logout --no-prompt"; in
turbovncserver.conf effectively works around the issue with Cinnamon.

Author: dcommander

unix/turbovncserver.conf

@@ -65,6 +65,8 @@
 ##                  [equivalent of -x509key command-line option]
 ##  $xstartup    -- path to alternative X startup script
 ##                  [equivalent of -xstartup command-line option]
+##  $xcleanup    -- path to optional X cleanup script to execute before Xvnc is
+##                  killed
 ##
 
 ## These settings are the default.  Uncomment and edit to change.
@@ -86,6 +88,7 @@
 # $vncUserDir = "$ENV{HOME}/.vnc";
 # $wm = "";
 # $xstartup = "${exedir}xstartup.turbovnc";
+# $xcleanup = "";
 
 ## Here is an example of setting the font path:
 #

unix/vncserver.in

@@ -1,6 +1,6 @@
 #!/usr/bin/env perl
 #
-# Copyright (C) 2009-2018, 2020-2022, 2024-2025 D. R. Commander.
+# Copyright (C) 2009-2018, 2020-2022, 2024-2026 D. R. Commander.
 #                                               All Rights Reserved.
 # Copyright (C) 2021 Steffen Kieß
 # Copyright (C) 2010 University Corporation for Atmospheric Research.
@@ -1082,6 +1082,11 @@ sub Kill
     }
   }
 
+  if ($xcleanup) {
+    warn "Running X cleanup script $xcleanup\n";
+    system("$xcleanup");
+  }
+
   unless (-r $pidFile) {
     die "\nCan't find file $pidFile\n".
         "You'll have to kill the Xvnc process manually\n\n";
@@ -1303,7 +1308,8 @@ sub ReadConfiguration
        wm
        x509CertFile
        x509KeyFile
-       xstartup);
+       xstartup
+       xcleanup);
 
   if (open CONF, "<$configFile") {
     while (<CONF>) {