diff --git a/acconfig.h b/acconfig.h
index 7e0cc1656..5623e5743 100644
--- a/acconfig.h
+++ b/acconfig.h
@@ -9,3 +9,4 @@
 #undef GETTEXT_PACKAGE
 #undef HAVE_SHAPE_EXT
 #undef HAVE_XFT
+#undef HAVE_SM
diff --git a/configure.in b/configure.in
index b4631cc98..7150d9236 100644
--- a/configure.in
+++ b/configure.in
@@ -43,6 +43,25 @@ AM_GNU_GETTEXT
 ## here we get the flags we'll actually use
 PKG_CHECK_MODULES(METACITY, gtk+-2.0 >= 1.3.6)
 
+CFLAGS="$METACITY_CFLAGS $CFLAGS"
+
+found_sm=false
+case "$METACITY_LIBS" in
+ *-lSM*)
+    found_sm=true
+    ;;
+ *)
+  AC_CHECK_LIB(SM, SmcSaveYourselfDone, 
+               AC_CHECK_HEADERS(X11/SM/SMlib.h,
+                                METACITY_LIBS="-lSM -lICE $METACITY_LIBS" found_sm=true),
+               , $METACITY_LIBS)
+    ;;
+esac
+
+if test "$found_sm" = "true"; then
+   AC_DEFINE(HAVE_SM)
+fi
+
 # Check for shaped window extension
 AC_CHECK_LIB(Xext, XShapeCombineMask, AC_DEFINE(HAVE_SHAPE_EXT),,$METACITY_LIBS)
 
diff --git a/src/main.c b/src/main.c
index 6a5577af1..2793e7e61 100644
--- a/src/main.c
+++ b/src/main.c
@@ -24,6 +24,7 @@
 #include "display.h"
 #include "errors.h"
 #include "ui.h"
+#include "session.h"
 
 #include <glib-object.h>
 
@@ -37,13 +38,24 @@
 static MetaExitCode meta_exit_code = META_EXIT_SUCCESS;
 static GMainLoop *meta_main_loop = NULL;
 
+static void
+usage (void)
+{
+  g_print ("metacity [--disable-sm] [--sm-client-id=ID] [--display=DISPLAY]\n");
+  exit (0);
+}
+
 int
 main (int argc, char **argv)
 {
   struct sigaction act;
   sigset_t empty_mask;
   char *display_name;
-
+  int i;
+  const char *client_id;
+  gboolean disable_sm;
+  const char *prev_arg;
+  
   sigemptyset (&empty_mask);
   act.sa_handler = SIG_IGN;
   act.sa_mask    = empty_mask;
@@ -52,34 +64,125 @@ main (int argc, char **argv)
   
   g_set_prgname (PACKAGE);
   
-  meta_main_loop = g_main_loop_new (NULL, FALSE);
-  
   meta_set_verbose (TRUE);
   meta_set_debugging (TRUE);
   meta_set_syncing (g_getenv ("METACITY_SYNC") != NULL);
 
-  if (g_getenv ("METACITY_DISPLAY"))
+  /* Parse options lamely */
+
+  display_name = NULL;
+  client_id = NULL;
+  disable_sm = FALSE;
+  prev_arg = NULL;
+  i = 1;
+  while (i < argc)
+    {
+      const char *arg = argv[i];
+      
+      if (strcmp (arg, "--help") == 0 ||
+          strcmp (arg, "-h") == 0 ||
+          strcmp (arg, "-?") == 0)
+        usage ();
+      else if (strcmp (arg, "--sm-disable") == 0)
+        disable_sm = TRUE; 
+      else if (strstr (arg, "--display=") == arg)
+        {
+          const char *disp;
+
+          if (display_name != NULL)
+            meta_fatal ("Can't specify display twice\n");
+          
+          disp = strchr (arg, '=');
+          ++disp;
+          
+          display_name =
+            g_strconcat ("DISPLAY=", disp, NULL);
+        }
+      else if (prev_arg &&
+               strcmp (prev_arg, "--display") == 0)
+        {
+          if (display_name != NULL)
+            meta_fatal ("Can't specify display twice\n");
+
+          display_name = g_strconcat ("DISPLAY=", arg, NULL);
+        }
+      else if (strcmp (arg, "--display") == 0)
+        ; /* wait for next arg */
+      else if (strstr (arg, "--sm-client-id=") == arg)
+        {
+          const char *id;
+
+          if (client_id)
+            meta_fatal ("Can't specify client ID twice\n");
+          
+          id = strchr (arg, '=');
+          ++id;
+
+          client_id = g_strdup (id);
+        }
+      else if (prev_arg &&
+               strcmp (prev_arg, "--sm-client-id") == 0)
+        {
+          if (client_id)
+            meta_fatal ("Can't specify client ID twice\n");
+
+          client_id = g_strdup (arg);
+        }
+      else if (strcmp (arg, "--sm-client-id") == 0)
+        ; /* wait for next arg */
+      else
+        usage ();
+      
+      prev_arg = arg;
+      
+      ++i;
+    }
+    
+  meta_main_loop = g_main_loop_new (NULL, FALSE);
+  
+  if (display_name == NULL &&
+      g_getenv ("METACITY_DISPLAY"))
     {
       meta_verbose ("Using METACITY_DISPLAY %s\n",
                     g_getenv ("METACITY_DISPLAY"));
       display_name =
         g_strconcat ("DISPLAY=", g_getenv ("METACITY_DISPLAY"), NULL);
+    }
+
+  if (display_name)
+    {
       putenv (display_name);
       /* DO NOT FREE display_name, putenv() sucks */
     }
-
-
+  
   /* gtk_init() below overrides this, so it can be removed */
   meta_errors_init ();
   
   g_type_init (0); /* grumble */
-  meta_ui_init (&argc, &argv);
+
+  if (!disable_sm)
+    meta_session_init (client_id); /* client_id == NULL is fine */
+  
+  meta_ui_init (&argc, &argv);  
   
   if (!meta_display_open (NULL))
     meta_exit (META_EXIT_ERROR);
   
   g_main_run (meta_main_loop);
 
+  {
+    GSList *displays;
+    GSList *tmp;
+    
+    displays = meta_displays_list ();
+    tmp = displays;
+    while (tmp != NULL)
+      {
+        meta_display_close (tmp->data);
+        tmp = tmp->next;
+      }
+  }
+  
   return meta_exit_code;
 }
 
@@ -93,8 +196,9 @@ void
 meta_quit (MetaExitCode code)
 {
   meta_exit_code = code;
-  
-  g_main_quit (meta_main_loop);
+
+  if (g_main_is_running (meta_main_loop))
+    g_main_quit (meta_main_loop);
 }
 
 void
diff --git a/src/session.c b/src/session.c
index 6986d5f23..414b59881 100644
--- a/src/session.c
+++ b/src/session.c
@@ -1,7 +1,8 @@
 /* Metacity Session Management */
 
 /* 
- * Copyright (C) 2001 Havoc Pennington
+ * Copyright (C) 2001 Havoc Pennington (some code in here from
+ * libgnomeui, (C) Tom Tromey, Carsten Schaar)
  * 
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
@@ -16,12 +17,461 @@
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
- * 02111-1307, USA.
- */
+ * 02111-1307, USA.  */
 
 #include "session.h"
 
+#ifndef HAVE_SM
+void
+meta_session_init (const char *previous_id)
+{
+  meta_verbose ("Compiled without session management support\n");
+}
+#else /* HAVE_SM */
+
+#include <X11/ICE/ICElib.h>
+#include <X11/SM/SMlib.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <glib.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include "main.h"
+#include "util.h"
+
+static void ice_io_error_handler (IceConn connection);
+
+static void new_ice_connection (IceConn connection, IcePointer client_data, 
+				Bool opening, IcePointer *watch_data);
+
+/* This is called when data is available on an ICE connection.  */
+static gboolean
+process_ice_messages (GIOChannel *channel,
+                      GIOCondition condition,
+                      gpointer client_data)
+{
+  IceConn connection = (IceConn) client_data;
+  IceProcessMessagesStatus status;
+
+  status = IceProcessMessages (connection, NULL, NULL);
+
+  if (status == IceProcessMessagesIOError)
+    {
+#if 0
+      IcePointer context = IceGetConnectionContext (connection);
+#endif
+      
+      /* We were disconnected */
+      IceSetShutdownNegotiation (connection, False);
+      IceCloseConnection (connection);
+    }
+
+  return TRUE;
+}
+
+/* This is called when a new ICE connection is made.  It arranges for
+   the ICE connection to be handled via the event loop.  */
+static void
+new_ice_connection (IceConn connection, IcePointer client_data, Bool opening,
+		    IcePointer *watch_data)
+{
+  guint input_id;
+
+  if (opening)
+    {
+      /* Make sure we don't pass on these file descriptors to any
+       * exec'ed children
+       */
+      GIOChannel *channel;
+      
+      fcntl (IceConnectionNumber(connection),F_SETFD,
+             fcntl(IceConnectionNumber(connection),F_GETFD,0) | FD_CLOEXEC);
+
+      channel = g_io_channel_unix_new (IceConnectionNumber (connection));
+      
+      input_id = g_io_add_watch (channel,
+                                 G_IO_IN | G_IO_ERR,
+                                 process_ice_messages,
+                                 connection);
+
+      g_io_channel_unref (channel);
+      
+      *watch_data = (IcePointer) GUINT_TO_POINTER (input_id);
+    }
+  else 
+    {
+      input_id = GPOINTER_TO_UINT ((gpointer) *watch_data);
+
+      g_source_remove (input_id);
+    }
+}
+
+static IceIOErrorHandler gnome_ice_installed_handler;
+
+/* We call any handler installed before (or after) gnome_ice_init but 
+   avoid calling the default libICE handler which does an exit() */
+static void
+ice_io_error_handler (IceConn connection)
+{
+    if (gnome_ice_installed_handler)
+      (*gnome_ice_installed_handler) (connection);
+}    
+
+static void
+ice_init (void)
+{
+  static gboolean ice_initted = FALSE;
+
+  if (! ice_initted)
+    {
+      IceIOErrorHandler default_handler;
+
+      gnome_ice_installed_handler = IceSetIOErrorHandler (NULL);
+      default_handler = IceSetIOErrorHandler (ice_io_error_handler);
+
+      if (gnome_ice_installed_handler == default_handler)
+	gnome_ice_installed_handler = NULL;
+
+      IceAddConnectionWatch (new_ice_connection, NULL);
+
+      ice_initted = TRUE;
+    }
+}
+
+typedef enum
+{
+  STATE_DISCONNECTED,
+  STATE_IDLE,
+  STATE_SAVING_PHASE_1,
+  STATE_WAITING_FOR_PHASE_2,
+  STATE_SAVING_PHASE_2,
+  STATE_FROZEN,
+  STATE_REGISTERING
+} ClientState;
+
+static void save_phase_2_callback       (SmcConn   smc_conn,
+                                         SmPointer client_data);
+static void interact_callback           (SmcConn   smc_conn,
+                                         SmPointer client_data);
+static void shutdown_cancelled_callback (SmcConn   smc_conn,
+                                         SmPointer client_data);
+static void save_complete_callback      (SmcConn   smc_conn,
+                                         SmPointer client_data);
+static void die_callback                (SmcConn   smc_conn,
+                                         SmPointer client_data);
+static void save_yourself_callback      (SmcConn   smc_conn,
+                                         SmPointer client_data,
+                                         int       save_style,
+                                         Bool      shutdown,
+                                         int       interact_style,
+                                         Bool      fast);
+static void set_clone_restart_commands  (void);
+
+static gchar *client_id = NULL;
+static gpointer session_connection = NULL;
+static ClientState current_state = STATE_DISCONNECTED;
+
+void
+meta_session_init (const char *previous_id)
+{
+  /* Some code here from twm */
+  char buf[256];
+  unsigned long mask;
+  SmcCallbacks callbacks;
+
+  meta_verbose ("Initializing session with session ID '%s'\n",
+                previous_id ? previous_id : "(none)");
+  
+  ice_init ();
+  
+  mask = SmcSaveYourselfProcMask | SmcDieProcMask |
+    SmcSaveCompleteProcMask | SmcShutdownCancelledProcMask;
+  
+  callbacks.save_yourself.callback = save_yourself_callback;
+  callbacks.save_yourself.client_data = NULL;
+  
+  callbacks.die.callback = die_callback;
+  callbacks.die.client_data = NULL;
+  
+  callbacks.save_complete.callback = save_complete_callback;
+  callbacks.save_complete.client_data = NULL;
+  
+  callbacks.shutdown_cancelled.callback = shutdown_cancelled_callback;
+  callbacks.shutdown_cancelled.client_data = NULL;
+
+  session_connection =
+    SmcOpenConnection (NULL, /* use SESSION_MANAGER env */
+                       NULL, /* means use existing ICE connection */
+                       SmProtoMajor,
+                       SmProtoMinor,
+                       mask,
+                       &callbacks,
+                       previous_id,
+                       &client_id,
+                       255, buf);
+  
+  if (session_connection == NULL)
+    {
+      meta_warning ("Failed to open connection to session manager: %s\n", buf);
+      return;
+    }
+  else
+    meta_verbose ("Obtained session ID '%s'\n", client_id);
+
+  if (previous_id && strcmp (previous_id, client_id) == 0)
+    current_state = STATE_IDLE;
+  else
+    current_state = STATE_REGISTERING;
+  
+  {
+    SmProp prop1, prop2, prop3, prop4, prop5, *props[5];
+    SmPropValue prop1val, prop2val, prop3val, prop4val, prop5val;
+    char pid[32];
+    char hint = SmRestartIfRunning;
+    
+    prop1.name = SmProgram;
+    prop1.type = SmARRAY8;
+    prop1.num_vals = 1;
+    prop1.vals = &prop1val;
+    prop1val.value = "metacity";
+    prop1val.length = strlen ("metacity");
+
+    /* twm sets getuid() for this, but the SM spec plainly
+     * says pw_name, twm is on crack
+     */
+    prop2.name = SmUserID;
+    prop2.type = SmARRAY8;
+    prop2.num_vals = 1;
+    prop2.vals = &prop2val;
+    prop2val.value = g_get_user_name ();
+    prop2val.length = strlen (prop2val.value);
+	
+    prop3.name = SmRestartStyleHint;
+    prop3.type = SmCARD8;
+    prop3.num_vals = 1;
+    prop3.vals = &prop3val;
+    prop3val.value = &hint;
+    prop3val.length = 1;
+
+    sprintf (pid, "%d", getpid ());
+    prop4.name = SmProcessID;
+    prop4.type = SmARRAY8;
+    prop4.num_vals = 1;
+    prop4.vals = &prop4val;
+    prop4val.value = pid;
+    prop4val.length = strlen (prop4val.value);    
+
+    /* Always start in home directory */
+    prop5.name = SmCurrentDirectory;
+    prop5.type = SmARRAY8;
+    prop5.num_vals = 1;
+    prop5.vals = &prop5val;
+    prop5val.value = g_get_home_dir ();
+    prop5val.length = strlen (prop5val.value);
+    
+    props[0] = &prop1;
+    props[1] = &prop2;
+    props[2] = &prop3;
+    props[3] = &prop4;
+    props[4] = &prop5;
+    
+    SmcSetProperties (session_connection, 5, props);
+  }
+
+  set_clone_restart_commands ();
+}
+
+static void
+disconnect (void)
+{
+  SmcCloseConnection (session_connection, 0, NULL);
+  session_connection = NULL;
+  current_state = STATE_DISCONNECTED;
+}
+
+static void
+save_yourself_possibly_done (gboolean shutdown,
+                             gboolean successful)
+{
+  if (current_state == STATE_SAVING_PHASE_1)
+    {
+      Status status;
+      
+      status = SmcRequestSaveYourselfPhase2 (session_connection,
+                                             save_phase_2_callback,
+                                             GINT_TO_POINTER (shutdown));
+
+      if (status)
+        current_state = STATE_WAITING_FOR_PHASE_2;
+    }
+
+  if (current_state == STATE_SAVING_PHASE_1 ||
+      current_state == STATE_SAVING_PHASE_2)
+    {
+      SmcSaveYourselfDone (session_connection,
+                           successful);
+      
+      if (shutdown)
+        current_state = STATE_FROZEN;
+      else
+        current_state = STATE_IDLE;
+    }
+}
 
 
+static void 
+save_phase_2_callback (SmcConn smc_conn, SmPointer client_data)
+{
+  gboolean shutdown;
+
+  shutdown = GPOINTER_TO_INT (client_data);
+  
+  current_state = STATE_SAVING_PHASE_2;
+
+  save_yourself_possibly_done (shutdown, TRUE);
+}
+
+static void
+save_yourself_callback (SmcConn   smc_conn,
+                        SmPointer client_data,
+                        int       save_style,
+                        Bool      shutdown,
+                        int       interact_style,
+                        Bool      fast)
+{
+  gboolean successful;
+
+  successful = TRUE;
+  
+  /* The first SaveYourself after registering for the first time
+   * is a special case (SM specs 7.2).
+   *
+   * This SaveYourself seems to be included in the protocol to
+   * ask the client to specify its initial SmProperties since 
+   * there is little point saving a copy of the initial state.
+   *
+   * A bug in xsm means that it does not send us a SaveComplete 
+   * in response to this initial SaveYourself. Therefore, we 
+   * must not set a grab because it would never be released.
+   * Indeed, even telling the app that this SaveYourself has
+   * arrived is hazardous as the app may take its own steps
+   * to freeze its WM state while waiting for the SaveComplete.
+   *
+   * Fortunately, we have already set the SmProperties during
+   * gnome_client_connect so there is little lost in simply
+   * returning immediately.
+   *
+   * Apps which really want to save their initial states can 
+   * do so safely using gnome_client_save_yourself_request.
+   */
+
+  if (current_state == STATE_REGISTERING)
+    {
+      current_state = STATE_IDLE;
+
+      /* Double check that this is a section 7.2 SaveYourself: */
+      
+      if (save_style == SmSaveLocal && 
+	  interact_style == SmInteractStyleNone &&
+	  !shutdown && !fast)
+	{
+	  /* The protocol requires this even if xsm ignores it. */
+	  SmcSaveYourselfDone (session_connection, successful);
+	  return;
+	}
+    }
+
+  current_state = STATE_SAVING_PHASE_1;
+
+  set_clone_restart_commands ();
+
+  save_yourself_possibly_done (shutdown, successful);
+}
 
 
+static void
+die_callback (SmcConn smc_conn, SmPointer client_data)
+{
+  meta_verbose ("Exiting at request of session manager\n");
+  disconnect ();
+  meta_quit (META_EXIT_SUCCESS);
+}
+
+static void
+save_complete_callback (SmcConn smc_conn, SmPointer client_data)
+{
+  /* nothing */
+}
+
+static void
+shutdown_cancelled_callback (SmcConn smc_conn, SmPointer client_data)
+{
+  /* nothing */
+}
+
+static void 
+interact_callback (SmcConn smc_conn, SmPointer client_data)
+{
+  /* nothing */
+}
+
+static void
+set_clone_restart_commands (void)
+{
+  char *restartv[10];
+  char *clonev[10];
+  int i;
+  SmProp prop1, prop2, *props[2];
+
+  /* Restart (use same client ID) */
+  
+  prop1.name = SmRestartCommand;
+  prop1.type = SmLISTofARRAY8;
+  
+  i = 0;
+  restartv[i] = "metacity";
+  ++i;
+  restartv[i] = "--sm-client-id";
+  ++i;
+  restartv[i] = client_id;
+  ++i;
+  restartv[i] = NULL;
+
+  prop1.vals = g_new (SmPropValue, i);
+  i = 0;
+  while (restartv[i])
+    {
+      prop1.vals[i].value = restartv[i];
+      prop1.vals[i].length = strlen (restartv[i]);
+      ++i;
+    }
+  prop1.num_vals = i;
+
+  /* Clone (no client ID) */
+  
+  i = 0;
+  clonev[i] = "metacity";
+  ++i;
+  clonev[i] = NULL;
+
+  prop2.name = SmCloneCommand;
+  prop2.type = SmLISTofARRAY8;
+  
+  prop2.vals = g_new (SmPropValue, i);
+  i = 0;
+  while (clonev[i])
+    {
+      prop2.vals[i].value = clonev[i];
+      prop2.vals[i].length = strlen (clonev[i]);
+      ++i;
+    }
+  prop2.num_vals = i;
+
+  props[0] = &prop1;
+  props[1] = &prop2;
+    
+  SmcSetProperties (session_connection, 2, props);
+}
+
+#endif /* HAVE_SM */