* configure.in: add DBUS_BINDIR as a #define to C source code.

	* tools/dbus-launch.c
	* tools/dbus-launch.h
	* tools/dbus-launch-x11.c:
	* tools/dbus-launch.1: Add the --autolaunch option to
	dbus-launch, which makes it scan for an existing session
	started with --autolaunch. With that option, it also creates
	an X11 window and saves the bus address and PID to it.

	* dbus/dbus-sysdeps.h:
	* dbus/dbus-sysdeps-unix.c (_dbus_get_autolaunch_address): Add
	a function that runs "dbus-launch --autolaunch" to retrieve
	the running D-Bus session address (or start one if none was running)

	* dbus/dbus-transport.c: Add the handler for the "autolaunch:"
        address protocol, which tries to get the running session from
        dbus-launch.

	* dbus/dbus-bus.c:
	* dbus/dbus-internals.h: Make "autolaunch:" be the default
	D-Bus session bus address.

	* dbus/dbus-connection.c: Fix horrible typo in error message.

13 files changed, 900 insertions, 127 deletions

diff --git a/ChangeLog b/ChangeLog
index 49a32704..55a88c88 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,30 @@
+2006-09-30  Thiago Macieira  <thiago@kde.org>
+
+	* configure.in: add DBUS_BINDIR as a #define to C source code.
+
+	* tools/dbus-launch.c
+	* tools/dbus-launch.h
+	* tools/dbus-launch-x11.c:
+	* tools/dbus-launch.1: Add the --autolaunch option to
+	dbus-launch, which makes it scan for an existing session
+	started with --autolaunch. With that option, it also creates
+	an X11 window and saves the bus address and PID to it.
+
+	* dbus/dbus-sysdeps.h:
+	* dbus/dbus-sysdeps-unix.c (_dbus_get_autolaunch_address): Add
+	a function that runs "dbus-launch --autolaunch" to retrieve
+	the running D-Bus session address (or start one if none was running)
+
+	* dbus/dbus-transport.c: Add the handler for the "autolaunch:"
+        address protocol, which tries to get the running session from
+        dbus-launch.
+
+	* dbus/dbus-bus.c:
+	* dbus/dbus-internals.h: Make "autolaunch:" be the default
+	D-Bus session bus address.
+
+	* dbus/dbus-connection.c: Fix horrible typo in error message.
+
 2006-09-18  John (J5) Palmieri  <johnp@redhat.com>
 
 	* tools/Makefile.am: use @EXPANDED_DATADIR@ instead of @DATADIRNAME@  
diff --git a/configure.in b/configure.in
index e87fdef0..0c70bb31 100644
--- a/configure.in
+++ b/configure.in
@@ -1052,6 +1052,11 @@ fi
 AC_SUBST(DBUS_DAEMONDIR)
 AC_DEFINE_UNQUOTED(DBUS_DAEMONDIR,"$DBUS_DAEMONDIR", [Directory for installing the DBUS daemon])
 
+#### Directory to install the other binaries
+DBUS_BINDIR=$EXPANDED_BINDIR
+AC_SUBST(DBUS_BINDIR)
+AC_DEFINE_UNQUOTED(DBUS_BINDIR,"$DBUS_BINDIR", [Directory for installing the binaries])
+
 #### Tell tests where to find certain stuff in builddir
 
 DBUS_PWD=`pwd`
diff --git a/dbus/dbus-bus.c b/dbus/dbus-bus.c
index 5f5c3395..eb6b3ab3 100644
--- a/dbus/dbus-bus.c
+++ b/dbus/dbus-bus.c
@@ -175,6 +175,13 @@ init_connections_unlocked (void)
           if (!get_from_env (&bus_connection_addresses[DBUS_BUS_SESSION],
                              "DBUS_SESSION_BUS_ADDRESS"))
             return FALSE;
+
+	  if (bus_connection_addresses[DBUS_BUS_SESSION] == NULL)
+	    bus_connection_addresses[DBUS_BUS_SESSION] =
+	      _dbus_strdup (DBUS_SESSION_BUS_DEFAULT_ADDRESS);
+           if (bus_connection_addresses[DBUS_BUS_SESSION] == NULL)
+             return FALSE;
+
           _dbus_verbose ("  \"%s\"\n", bus_connection_addresses[DBUS_BUS_SESSION] ?
                          bus_connection_addresses[DBUS_BUS_SESSION] : "none set");
         }
diff --git a/dbus/dbus-connection.c b/dbus/dbus-connection.c
index 2b4dd8d8..d60816c3 100644
--- a/dbus/dbus-connection.c
+++ b/dbus/dbus-connection.c
@@ -2783,7 +2783,7 @@ _dbus_connection_block_pending_call (DBusPendingCall *pending)
 
       error_msg = generate_local_error_message (client_serial,
                                                 DBUS_ERROR_DISCONNECTED, 
-                                                "Connection was dissconnected before a reply was recived"); 
+                                                "Connection was disconnected before a reply was received"); 
 
       /* on OOM error_msg is set to NULL */
       complete_pending_call_and_unlock (connection, pending, error_msg);
diff --git a/dbus/dbus-internals.h b/dbus/dbus-internals.h
index a12821db..520d6dfe 100644
--- a/dbus/dbus-internals.h
+++ b/dbus/dbus-internals.h
@@ -37,6 +37,8 @@
 
 DBUS_BEGIN_DECLS
 
+#define DBUS_SESSION_BUS_DEFAULT_ADDRESS	"autolaunch:"
+
 void _dbus_warn               (const char *format,
                                ...) _DBUS_GNUC_PRINTF (1, 2);
 
diff --git a/dbus/dbus-sysdeps-unix.c b/dbus/dbus-sysdeps-unix.c
index 38adebb1..c0540175 100644
--- a/dbus/dbus-sysdeps-unix.c
+++ b/dbus/dbus-sysdeps-unix.c
@@ -27,6 +27,7 @@
 #include "dbus-sysdeps-unix.h"
 #include "dbus-threads.h"
 #include "dbus-protocol.h"
+#include "dbus-transport.h"
 #include "dbus-string.h"
 #include <sys/types.h>
 #include <stdlib.h>
@@ -2275,6 +2276,118 @@ _dbus_get_tmpdir(void)
   return tmpdir;
 }
 
+/**
+ * Determines the address of the session bus by querying a
+ * platform-specific method.
+ *
+ * If successful, returns #TRUE and appends the address to @p
+ * address. If a failure happens, returns #FALSE and
+ * sets an error in @p error.
+ *
+ * @param address a DBusString where the address can be stored
+ * @param error a DBusError to store the error in case of failure
+ * @returns #TRUE on success, #FALSE if an error happened
+ */
+dbus_bool_t
+_dbus_get_autolaunch_address (DBusString *address, DBusError *error)
+{
+  static char *argv[] = { DBUS_BINDIR "/dbus-launch", "--autolaunch",
+                          "--binary-syntax", NULL };
+  int address_pipe[2];
+  pid_t pid;
+  int ret;
+  int status;
+  int orig_len = _dbus_string_get_length (address);
+
+  _DBUS_ASSERT_ERROR_IS_CLEAR (error);
+
+#define READ_END        0
+#define WRITE_END       1
+  if (pipe (address_pipe) < 0)
+    {
+      dbus_set_error (error, _dbus_error_from_errno (errno),
+                      "Failed to create a pipe: %s",
+                      _dbus_strerror (errno));
+      _dbus_verbose ("Failed to create a pipe to call dbus-launch: %s\n",
+                     _dbus_strerror (errno));
+      return FALSE;
+    }
+
+  pid = fork ();
+  if (pid < 0)
+    {
+      dbus_set_error (error, _dbus_error_from_errno (errno),
+                      "Failed to fork(): %s",
+                      _dbus_strerror (errno));
+      _dbus_verbose ("Failed to fork() to call dbus-launch: %s\n",
+                     _dbus_strerror (errno));
+      return FALSE;
+    }
+
+  if (pid == 0)
+    {
+      /* child process */
+      int fd = open ("/dev/null", O_RDWR);
+      if (fd == -1)
+        /* huh?! can't open /dev/null? */
+        _exit (1);
+
+      /* set-up stdXXX */
+      close (address_pipe[READ_END]);
+      close (0);                /* close stdin */
+      close (1);                /* close stdout */
+      close (2);                /* close stderr */
+
+      if (dup2 (fd, 0) == -1)
+        _exit (1);
+      if (dup2 (address_pipe[WRITE_END], 1) == -1)
+        _exit (1);
+      if (dup2 (fd, 2) == -1)
+        _exit (1);
+
+      close (fd);
+      close (address_pipe[WRITE_END]);
+
+      execv (argv[0], argv);
+
+      /* failed, try searching PATH */
+      argv[0] = "dbus-launch";
+      execvp ("dbus-launch", argv);
+
+      /* still nothing, we failed */
+      _exit (1);
+    }
+
+  /* parent process */
+  close (address_pipe[WRITE_END]);
+  ret = 0;
+  do 
+    {
+      ret = _dbus_read (address_pipe[READ_END], address, 1024);
+    }
+  while (ret > 0);
+
+  /* reap the child process to avoid it lingering as zombie */
+  do
+    {
+      ret = waitpid (pid, &status, 0);
+    }
+  while (ret == -1 && errno == EINTR);
+
+  /* We succeeded if the process exited with status 0 and
+     anything was read */
+  if (!WIFEXITED (status) || WEXITSTATUS (status) != 0 ||
+      _dbus_string_get_length (address) == orig_len)
+    {
+      /* The process ended with error */
+      _dbus_string_set_length (address, orig_len);
+      dbus_set_error (error, DBUS_ERROR_SPAWN_EXEC_FAILED,
+                      "Failed to execute dbus-launch to autolaunch D-Bus session");
+      return FALSE;
+    }
+  return TRUE;
+}
+
 /** @} end of sysdeps */
 
 /* tests in dbus-sysdeps-util.c */
diff --git a/dbus/dbus-sysdeps.h b/dbus/dbus-sysdeps.h
index c1ed533a..3541a721 100644
--- a/dbus/dbus-sysdeps.h
+++ b/dbus/dbus-sysdeps.h
@@ -376,6 +376,9 @@ dbus_bool_t _dbus_user_at_console (const char *username,
 dbus_bool_t _dbus_parse_uid (const DBusString  *uid_str,
                              dbus_uid_t        *uid);
 
+dbus_bool_t _dbus_get_autolaunch_address (DBusString *address, 
+					  DBusError *error);
+
 DBUS_END_DECLS
 
 #endif /* DBUS_SYSDEPS_H */
diff --git a/dbus/dbus-transport.c b/dbus/dbus-transport.c
index 89d79ffe..f43dd3d2 100644
--- a/dbus/dbus-transport.c
+++ b/dbus/dbus-transport.c
@@ -201,13 +201,118 @@ _dbus_transport_finalize_base (DBusTransport *transport)
   dbus_free (transport->expected_guid);
 }
 
+
+/**
+ * Verifies if a given D-Bus address is a valid address
+ * by attempting to connect to it. If it is, returns the
+ * opened DBusTransport object. If it isn't, returns #NULL
+ * and sets @p error.
+ *
+ * @param error address where an error can be returned.
+ * @returns a new transport, or #NULL on failure.
+ */
+static DBusTransport*
+check_address (const char *address, DBusError *error)
+{
+  DBusAddressEntry **entries;
+  DBusTransport *transport = NULL;
+  int len, i;
+
+  _dbus_assert (address != NULL);
+  _dbus_assert (*address != '\0');
+
+  if (!dbus_parse_address (address, &entries, &len, error))
+    return FALSE;              /* not a valid address */
+
+  for (i = 0; i < len; i++)
+    {
+      transport = _dbus_transport_open (entries[i], error);
+      if (transport != NULL)
+        break;
+    }
+
+  dbus_address_entries_free (entries);
+  return transport;
+}
+
+/**
+ * Creates a new transport for the "autostart" method.
+ * This creates a client-side of a transport.
+ *
+ * @param error address where an error can be returned.
+ * @returns a new transport, or #NULL on failure.
+ */
+static DBusTransport*
+_dbus_transport_new_for_autolaunch (DBusError      *error)
+{
+  DBusString address;
+  DBusTransport *result = NULL;
+
+  _DBUS_ASSERT_ERROR_IS_CLEAR (error);
+
+  if (!_dbus_string_init (&address))
+    {
+      dbus_set_error (error, DBUS_ERROR_NO_MEMORY, NULL);
+      return NULL;
+    }
+
+  if (!_dbus_get_autolaunch_address (&address, error))
+    {
+      _DBUS_ASSERT_ERROR_IS_SET (error);
+      goto out;
+    }
+
+  result = check_address (_dbus_string_get_const_data (&address), error);
+  if (result == NULL)
+    _DBUS_ASSERT_ERROR_IS_SET (error);
+  else
+    _DBUS_ASSERT_ERROR_IS_CLEAR (error);
+
+ out:
+  _dbus_string_free (&address);
+  return result;
+}
+
+static DBusTransportOpenResult
+_dbus_transport_open_autolaunch (DBusAddressEntry  *entry,
+                                 DBusTransport    **transport_p,
+                                 DBusError         *error)
+{
+  const char *method;
+  
+  method = dbus_address_entry_get_method (entry);
+  _dbus_assert (method != NULL);
+
+  if (strcmp (method, "autolaunch") == 0)
+    {
+      *transport_p = _dbus_transport_new_for_autolaunch (error);
+
+      if (*transport_p == NULL)
+        {
+          _DBUS_ASSERT_ERROR_IS_SET (error);
+          return DBUS_TRANSPORT_OPEN_DID_NOT_CONNECT;
+        }
+      else
+        {
+          _DBUS_ASSERT_ERROR_IS_CLEAR (error);
+          return DBUS_TRANSPORT_OPEN_OK;
+        }      
+    }
+  else
+    {
+      _DBUS_ASSERT_ERROR_IS_CLEAR (error);
+      return DBUS_TRANSPORT_OPEN_NOT_HANDLED;
+    }
+}
+
 static const struct {
   DBusTransportOpenResult (* func) (DBusAddressEntry *entry,
                                     DBusTransport   **transport_p,
                                     DBusError        *error);
 } open_funcs[] = {
   { _dbus_transport_open_socket },
-  { _dbus_transport_open_platform_specific }
+  { _dbus_transport_open_platform_specific },
+  { _dbus_transport_open_autolaunch }
 #ifdef DBUS_BUILD_TESTS
   , { _dbus_transport_open_debug_pipe }
 #endif
diff --git a/tools/Makefile.am b/tools/Makefile.am
index eb19ddb7..05c3618e 100644
--- a/tools/Makefile.am
+++ b/tools/Makefile.am
@@ -13,7 +13,8 @@ dbus_monitor_SOURCES=				\
 	dbus-print-message.h
 
 dbus_launch_SOURCES=				\
-	dbus-launch.c
+	dbus-launch.c				\
+	dbus-launch-x11.c
 
 dbus_cleanup_sockets_SOURCES=			\
 	dbus-cleanup-sockets.c
diff --git a/tools/dbus-launch-x11.c b/tools/dbus-launch-x11.c
new file mode 100644
index 00000000..ac356219
--- /dev/null
+++ b/tools/dbus-launch-x11.c
@@ -0,0 +1,392 @@
+/* -*- mode: C; c-file-style: "gnu" -*- */
+/* dbus-launch.h  dbus-launch utility
+ *
+ * Copyright (C) 2006 Thiago Macieira <thiago@kde.org>
+ *
+ * Licensed under the Academic Free License version 2.1
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * 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
+ *
+ */
+#include "dbus-launch.h"
+
+#ifdef DBUS_BUILD_X11
+#include <stdlib.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <stdio.h>
+#include <string.h>
+#include <pwd.h>
+#include <X11/Xlib.h>
+#include <X11/Xatom.h>
+
+Display *xdisplay;
+static Atom selection_atom;
+static Atom address_atom;
+static Atom pid_atom;
+
+static int
+x_io_error_handler (Display *xdisplay)
+{
+  verbose ("X IO error\n");
+  kill_bus_and_exit (0);
+  return 0;
+}
+
+static char *
+get_local_hostname (void)
+{
+  static const int increment = 128;
+  static char *cache = NULL;
+  char *buffer = NULL;
+  int size = 0;
+
+  while (cache == NULL)
+    {
+      size += increment;
+      buffer = realloc (buffer, size);
+      if (buffer == NULL)
+        return NULL;            /* out of memory */
+
+      if (gethostname (buffer, size - 1) == -1 &&
+          errno != ENAMETOOLONG)
+        return NULL;
+
+      buffer[size - 1] = '\0';  /* to make sure */
+      cache = buffer;
+    }
+
+  return cache;
+}
+
+static char *
+get_session_file (void)
+{
+  static const char prefix[] = "/.dbus-session-file_";
+  char *hostname;
+  char *display;
+  char *home;
+  char *result;
+  char *p;
+
+  display = xstrdup (getenv ("DISPLAY"));
+  if (display == NULL)
+    {
+      verbose ("X11 integration disabled because X11 is not running\n");
+      return NULL;
+    }
+
+  /* remove the screen part of the display name */
+  p = strrchr (display, ':');
+  if (p != NULL)
+    for ( ; *p; ++p)
+      if (*p == '.')
+        {
+          *p = '\0';
+          break;
+        }
+
+  /* replace the : in the display with _ */
+  for (p = display; *p; ++p)
+    if (*p == ':')
+      *p = '_';
+
+  hostname = get_local_hostname ();
+  if (hostname == NULL)
+    {
+      /* out of memory */
+      free (display);
+      return NULL;
+    }
+
+  home = getenv ("HOME");
+  if (home == NULL)
+    {
+      /* try from the user database */
+      struct passwd *user = getpwuid (getuid());
+      if (user == NULL)
+        {
+          verbose ("X11 integration disabled because the home directory"
+                   " could not be determined\n");
+          free (display);
+          return NULL;
+        }
+
+      home = user->pw_dir;
+    }
+
+  result = malloc (strlen (home) + strlen (prefix) + strlen (hostname) +
+                   strlen (display) + 2);
+  if (result == NULL)
+    {
+      /* out of memory */
+      free (display);
+      return NULL;
+    }
+
+  strcpy (result, home);
+  strcat (result, prefix);
+  strcat (result, hostname);
+  strcat (result, "_");
+  strcat (result, display);
+  free (display);
+
+  verbose ("session file: %s\n", result);
+  return result;
+}
+
+static Display *
+open_x11 (void)
+{
+  if (xdisplay != NULL)
+    return xdisplay;
+
+  xdisplay = XOpenDisplay (NULL);
+  if (xdisplay != NULL)
+    {
+      verbose ("Connected to X11 display '%s'\n", DisplayString (xdisplay));
+      XSetIOErrorHandler (x_io_error_handler);
+    }
+  return xdisplay;
+}
+
+static int
+init_x_atoms (Display *display)
+{
+  static const char selection_prefix[] = "DBUS_SESSION_SELECTION_";
+  static const char address_prefix[] = "DBUS_SESSION_ADDRESS";
+  static const char pid_prefix[] = "DBUS_SESSION_PID";
+  static int init = FALSE;
+  char *atom_name;
+  char *hostname;
+  char *user_name;
+  struct passwd *user;
+
+  if (init)
+    return TRUE;
+
+  user = getpwuid (getuid ());
+  if (user == NULL)
+    {
+      verbose ("Could not determine the user informations; aborting X11 integration.\n");
+      return FALSE;
+    }
+  user_name = xstrdup(user->pw_name);
+
+  hostname = get_local_hostname ();
+  if (hostname == NULL)
+    {
+      verbose ("Could not create X11 atoms; aborting X11 integration.\n");
+      free (user_name);
+      return FALSE;
+    }
+
+  atom_name = malloc (strlen (hostname) + strlen (user_name) + 2 +
+                      MAX (strlen (selection_prefix),
+                           MAX (strlen (address_prefix),
+                                strlen (pid_prefix))));
+  if (atom_name == NULL)
+    {
+      verbose ("Could not create X11 atoms; aborting X11 integration.\n");
+      free (user_name);
+      return FALSE;
+    }
+
+  /* create the selection atom */
+  strcpy (atom_name, selection_prefix);
+  strcat (atom_name, user_name);
+  strcat (atom_name, "_");
+  strcat (atom_name, hostname);
+  selection_atom = XInternAtom (display, atom_name, FALSE);
+
+  /* create the address property atom */
+  strcpy (atom_name, address_prefix);
+  address_atom = XInternAtom (display, atom_name, FALSE);
+
+  /* create the PID property atom */
+  strcpy (atom_name, pid_prefix);
+  pid_atom = XInternAtom (display, atom_name, FALSE);
+
+  free (atom_name);
+  free (user_name);
+  init = TRUE;
+  return TRUE;
+}
+
+/*
+ * Gets the daemon address from the X11 display.
+ * Returns FALSE if there was an error. Returning
+ * TRUE does not mean the address exists.
+ */
+int
+x11_get_address (char **paddress, pid_t *pid, long *wid)
+{
+  Atom type;
+  Window owner;
+  int format;
+  unsigned long items;
+  unsigned long after;
+  char *data;
+
+  *paddress = NULL;
+
+  /* locate the selection owner */
+  owner = XGetSelectionOwner (xdisplay, selection_atom);
+  if (owner == None)
+    return TRUE;                /* no owner */
+  if (wid != NULL)
+    *wid = (long) owner;
+
+  /* get the bus address */
+  XGetWindowProperty (xdisplay, owner, address_atom, 0, 1024, False,
+                      XA_STRING, &type, &format, &items, &after,
+                      (unsigned char **) &data);
+  if (type == None || after != 0 || data == NULL || format != 8)
+    return FALSE;               /* error */
+
+  *paddress = xstrdup (data);
+  XFree (data);
+
+  /* get the PID */
+  if (pid != NULL)
+    {
+      *pid = 0;
+      XGetWindowProperty (xdisplay, owner, pid_atom, 0, sizeof pid, False,
+                          XA_CARDINAL, &type, &format, &items, &after,
+                          (unsigned char **) &data);
+      if (type != None && after == 0 && data != NULL && format == 32)
+        *pid = (pid_t) *(long*) data;
+      XFree (data);
+    }
+
+  return TRUE;                  /* success */
+}
+
+/*
+ * Saves the address in the X11 display. Returns 0 on success.
+ * If an error occurs, returns -1. If the selection already exists,
+ * returns 1. (i.e. another daemon is already running)
+ */
+static Window
+set_address_in_x11(char *address, pid_t pid)
+{
+  char *current_address;
+  Window wid;
+
+  /* lock the X11 display to make sure we're doing this atomically */
+  XGrabServer (xdisplay);
+
+  if (!x11_get_address (&current_address, NULL, NULL))
+    {
+      /* error! */
+      XUngrabServer (xdisplay);
+      return None;
+    }
+
+  if (current_address != NULL)
+    {
+      /* someone saved the address in the meantime */
+      XUngrabServer (xdisplay);
+      free (current_address);
+      return None;
+    }
+
+  /* Create our window */
+  wid = XCreateSimpleWindow (xdisplay, RootWindow (xdisplay, 0), -20, -20, 10, 10,
+                             0, WhitePixel (xdisplay, 0),
+                             BlackPixel (xdisplay, 0));
+  verbose ("Created window %d\n", wid);
+
+  /* Save the property in the window */
+  XChangeProperty (xdisplay, wid, address_atom, XA_STRING, 8, PropModeReplace,
+                   (unsigned char *)address, strlen (address));
+  XChangeProperty (xdisplay, wid, pid_atom, XA_CARDINAL, 32, PropModeReplace,
+                   (unsigned char *)&pid, sizeof(pid) / 4);
+
+  /* Now grab the selection */
+  XSetSelectionOwner (xdisplay, selection_atom, wid, CurrentTime);
+
+  /* Ungrab the server to let other people use it too */
+  XUngrabServer (xdisplay);
+
+  XFlush (xdisplay);
+
+  return wid;
+}
+
+/*
+ * Saves the session address in session file. Returns TRUE on
+ * success, FALSE if an error occurs.
+ */
+static int
+set_address_in_file (char *address, pid_t pid, Window wid)
+{
+  char *session_file;
+  FILE *f;
+
+  session_file = get_session_file();
+  if (session_file == NULL)
+    return FALSE;
+
+  f = fopen (session_file, "w");
+  if (f == NULL)
+    return FALSE;               /* some kind of error */
+  fprintf (f, "%s\n%ld\n%ld\n", address, (long)pid, (long)wid);
+
+  fclose (f);
+  free (session_file);
+
+  return TRUE;
+}
+
+int
+x11_save_address (char *address, pid_t pid, long *wid)
+{
+  Window id = set_address_in_x11 (address, pid);
+  if (id != None)
+    {
+      if (!set_address_in_file (address, pid, id))
+        return FALSE;
+
+      if (wid != NULL)
+        *wid = (long) id;
+      return TRUE;
+    }
+  return FALSE;
+}
+
+int
+x11_init (void)
+{
+  return open_x11 () != NULL && init_x_atoms (xdisplay);
+}
+
+void
+x11_handle_event (void)
+{
+  if (xdisplay != NULL)
+    {      
+      while (XPending (xdisplay))
+        {
+          XEvent ignored;
+          XNextEvent (xdisplay, &ignored);
+        }
+    }
+}  
+
+#else
+void dummy_dbus_launch_x11 (void) { }
+#endif
diff --git a/tools/dbus-launch.1 b/tools/dbus-launch.1
index a3180f69..3c505e7b 100644
--- a/tools/dbus-launch.1
+++ b/tools/dbus-launch.1
@@ -7,7 +7,7 @@
 dbus-launch \- Utility to start a message bus from a shell script
 .SH SYNOPSIS
 .PP
-.B dbus-launch [\-\-version] [\-\-sh-syntax] [\-\-csh-syntax] [\-\-auto-syntax] [\-\-exit-with-session] [\-\-config-file=FILENAME] [PROGRAM] [ARGS...]
+.B dbus-launch [\-\-version] [\-\-sh-syntax] [\-\-csh-syntax] [\-\-auto-syntax] [\-\-exit-with-session] [\-\-autolaunch] [\-\-config-file=FILENAME] [PROGRAM] [ARGS...]
 
 .SH DESCRIPTION
 
@@ -90,6 +90,13 @@ server. If this process gets a HUP on stdin or loses its X connection,
 it kills the message bus daemon.
 
 .TP
+.I "--autolaunch"
+This option implies that \fIdbus-launch\fP should scan for a
+previously-started session and reuse the values found there. If no
+session is found, it will start a new session. The
+\-\-exit-with-session option is implied if \-\-autolaunch is given.
+
+.TP
 .I "--sh-syntax"
 Emit Bourne-shell compatible code to set up environment variables.
 
diff --git a/tools/dbus-launch.c b/tools/dbus-launch.c
index 18a6d156..fb993e4e 100644
--- a/tools/dbus-launch.c
+++ b/tools/dbus-launch.c
@@ -20,7 +20,7 @@
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  *
  */
-#include <config.h>
+#include "dbus-launch.h"
 #include <stdlib.h>
 #include <unistd.h>
 #include <fcntl.h>
@@ -32,22 +32,14 @@
 #include <signal.h>
 #include <stdarg.h>
 #include <sys/select.h>
+#include <time.h>
+
 #ifdef DBUS_BUILD_X11
 #include <X11/Xlib.h>
+extern Display *xdisplay;
 #endif
 
-#ifndef TRUE
-#define TRUE (1)
-#endif
-
-#ifndef FALSE
-#define FALSE (0)
-#endif
-
-#undef	MAX
-#define MAX(a, b)  (((a) > (b)) ? (a) : (b))
-
-static void
+void
 verbose (const char *format,
          ...)
 {
@@ -95,7 +87,7 @@ version (void)
   exit (0);
 }
 
-static char *
+char *
 xstrdup (const char *str)
 {
   int len;
@@ -276,8 +268,8 @@ do_waitpid (pid_t pid)
 
 static pid_t bus_pid_to_kill = -1;
 
-static void
-kill_bus_and_exit (void)
+void
+kill_bus_and_exit (int exitcode)
 {
   verbose ("Killing message bus and exiting babysitter\n");
   
@@ -290,18 +282,38 @@ kill_bus_and_exit (void)
   sleep (3);
   kill (bus_pid_to_kill, SIGKILL);
 
-  exit (0);
+  exit (exitcode);
 }
 
-#ifdef DBUS_BUILD_X11
-static int
-x_io_error_handler (Display *xdisplay)
+static void
+print_variables (const char *bus_address, pid_t bus_pid, long bus_wid,
+		 int c_shell_syntax, int bourne_shell_syntax,
+		 int binary_syntax)
 {
-  verbose ("X IO error\n");
-  kill_bus_and_exit ();
-  return 0;
+  if (binary_syntax)
+    {
+      write (1, bus_address, strlen (bus_address) + 1);
+      write (1, &bus_pid, sizeof bus_pid);
+      write (1, &bus_wid, sizeof bus_wid);
+      return;
+    }
+  else if (c_shell_syntax)
+    {
+      printf ("setenv DBUS_SESSION_BUS_ADDRESS '%s';\n", bus_address);	
+      printf ("set DBUS_SESSION_BUS_PID=%ld;\n", (long) bus_pid);
+      if (bus_wid)
+	printf ("set DBUS_SESSION_BUS_WINDOWID=%ld;\n", (long) bus_wid);
+    }
+  else
+    {
+      printf ("DBUS_SESSION_BUS_ADDRESS='%s';\n", bus_address);
+      if (bourne_shell_syntax)
+	printf ("export DBUS_SESSION_BUS_ADDRESS;\n");
+      printf ("DBUS_SESSION_BUS_PID=%ld;\n", (long) bus_pid);
+      if (bus_wid)
+	printf ("DBUS_SESSION_BUS_WINDOWID=%ld;\n", (long) bus_wid);
+    }
 }
-#endif
 
 static int got_sighup = FALSE;
 
@@ -326,9 +338,6 @@ kill_bus_when_session_ends (void)
   fd_set err_set;
   struct sigaction act;
   sigset_t empty_mask;
-#ifdef DBUS_BUILD_X11
-  Display *xdisplay;
-#endif
   
   /* install SIGHUP handler */
   got_sighup = FALSE;
@@ -340,17 +349,14 @@ kill_bus_when_session_ends (void)
   sigaction (SIGTERM,  &act, NULL);
   
 #ifdef DBUS_BUILD_X11
-  xdisplay = XOpenDisplay (NULL);
+  x11_init();
   if (xdisplay != NULL)
     {
-      verbose ("Successfully opened X display\n");
       x_fd = ConnectionNumber (xdisplay);
-      XSetIOErrorHandler (x_io_error_handler);
     }
   else
     x_fd = -1;
 #else
-  verbose ("Compiled without X11 support\n");
   x_fd = -1;
 #endif
 
@@ -393,7 +399,7 @@ kill_bus_when_session_ends (void)
       if (got_sighup)
         {
           verbose ("Got SIGHUP, exiting\n");
-          kill_bus_and_exit ();
+          kill_bus_and_exit (0);
         }
       
 #ifdef DBUS_BUILD_X11
@@ -405,15 +411,7 @@ kill_bus_when_session_ends (void)
         verbose ("X fd condition reading = %d error = %d\n",
                  FD_ISSET (x_fd, &read_set),
                  FD_ISSET (x_fd, &err_set));
-      
-      if (xdisplay != NULL)
-        {      
-          while (XPending (xdisplay))
-            {
-              XEvent ignored;
-              XNextEvent (xdisplay, &ignored);
-            }
-        }
+      x11_handle_event ();
 #endif
 
       if (tty_fd >= 0)
@@ -431,7 +429,7 @@ kill_bus_when_session_ends (void)
                        bytes_read, errno);
               
               if (bytes_read == 0)
-                kill_bus_and_exit (); /* EOF */
+                kill_bus_and_exit (0); /* EOF */
               else if (bytes_read < 0 && errno != EINTR)
                 {
                   /* This shouldn't happen I don't think; to avoid
@@ -439,14 +437,14 @@ kill_bus_when_session_ends (void)
                    */
                   fprintf (stderr, "dbus-launch: error reading from stdin: %s\n",
                            strerror (errno));
-                  kill_bus_and_exit ();
+                  kill_bus_and_exit (0);
                 }
             }
           else if (FD_ISSET (tty_fd, &err_set))
             {
               verbose ("TTY has error condition\n");
               
-              kill_bus_and_exit ();
+              kill_bus_and_exit (0);
             }
         }
     }
@@ -455,19 +453,14 @@ kill_bus_when_session_ends (void)
 static void
 babysit (int   exit_with_session,
          pid_t child_pid,
-         int   read_bus_pid_fd,  /* read pid from here */
-         int   write_bus_pid_fd) /* forward pid to here */
+         int   read_bus_pid_fd)  /* read pid from here */
 {
   int ret;
-#define MAX_PID_LEN 64
-  char buf[MAX_PID_LEN];
-  long val;
-  char *end;
   int dev_null_fd;
   const char *s;
 
-  verbose ("babysitting, exit_with_session = %d, child_pid = %ld, read_bus_pid_fd = %d, write_bus_pid_fd = %d\n",
-           exit_with_session, (long) child_pid, read_bus_pid_fd, write_bus_pid_fd);
+  verbose ("babysitting, exit_with_session = %d, child_pid = %ld, read_bus_pid_fd = %d\n",
+           exit_with_session, (long) child_pid, read_bus_pid_fd);
   
   /* We chdir ("/") since we are persistent and daemon-like, and fork
    * again so dbus-launch can reap the parent.  However, we don't
@@ -536,41 +529,26 @@ babysit (int   exit_with_session,
   /* Child continues */
   verbose ("=== Babysitter process created\n");
 
-  verbose ("Reading PID from daemon\n");
-  /* Now read data */
-  switch (read_line (read_bus_pid_fd, buf, MAX_PID_LEN))
+  verbose ("Reading PID from bus\n");
+      
+  switch (read_pid (read_bus_pid_fd, &bus_pid_to_kill))
     {
     case READ_STATUS_OK:
       break;
     case READ_STATUS_EOF:
-      fprintf (stderr, "EOF reading PID from bus daemon\n");
+      fprintf (stderr, "EOF in dbus-launch reading PID from bus daemon\n");
       exit (1);
       break;
     case READ_STATUS_ERROR:
-      fprintf (stderr, "Error reading PID from bus daemon: %s\n",
-               strerror (errno));
+      fprintf (stderr, "Error in dbus-launch reading PID from bus daemon: %s\n",
+	       strerror (errno));
       exit (1);
       break;
     }
 
-  end = NULL;
-  val = strtol (buf, &end, 0);
-  if (buf == end || end == NULL)
-    {
-      fprintf (stderr, "Failed to parse bus PID \"%s\": %s\n",
-               buf, strerror (errno));
-      exit (1);
-    }
-
-  bus_pid_to_kill = val;
-
   verbose ("Got PID %ld from daemon\n",
            (long) bus_pid_to_kill);
   
-  /* Write data to launcher */
-  write_pid (write_bus_pid_fd, bus_pid_to_kill);
-  close (write_bus_pid_fd);
-  
   if (exit_with_session)
     {
       /* Bus is now started and launcher has needed info;
@@ -597,9 +575,11 @@ main (int argc, char **argv)
   const char *runprog = NULL;
   int remaining_args = 0;
   int exit_with_session;
+  int binary_syntax = FALSE;
   int c_shell_syntax = FALSE;
   int bourne_shell_syntax = FALSE;
   int auto_shell_syntax = FALSE;
+  int autolaunch = FALSE;
   int i;  
   int ret;
   int bus_pid_to_launcher_pipe[2];
@@ -628,10 +608,14 @@ main (int argc, char **argv)
       else if (strcmp (arg, "-s") == 0 ||
 	       strcmp (arg, "--sh-syntax") == 0)
         bourne_shell_syntax = TRUE;
+      else if (strcmp (arg, "--binary-syntax") == 0)
+	binary_syntax = TRUE;
       else if (strcmp (arg, "--version") == 0)
         version ();
       else if (strcmp (arg, "--exit-with-session") == 0)
         exit_with_session = TRUE;
+      else if (strcmp (arg, "--autolaunch") == 0)
+	autolaunch = TRUE;
       else if (strstr (arg, "--config-file=") == arg)
         {
           const char *file;
@@ -672,9 +656,6 @@ main (int argc, char **argv)
       ++i;
     }
 
-  if (exit_with_session)
-    verbose ("--exit-with-session enabled\n");
-
   if (auto_shell_syntax)
     {
       if ((shname = getenv ("SHELL")) != NULL)
@@ -688,8 +669,52 @@ main (int argc, char **argv)
        bourne_shell_syntax = TRUE;
     }  
 
+  if (exit_with_session)
+    verbose ("--exit-with-session enabled\n");
+
+  if (autolaunch)
+    {
+#ifndef DBUS_BUILD_X11
+      fprintf (stderr, "Autolaunch requested, but X11 support not compiled in.\n"
+	       "Cannot continue.\n");
+      exit (1);
+#else
+      char *address;
+      pid_t pid;
+      long wid;
+
+      verbose ("Autolaunch enabled (using X11).\n");
+      if (!exit_with_session)
+	{
+	  verbose ("--exit-with-session automatically enabled\n");
+	  exit_with_session = TRUE;
+	}
+
+      if (!x11_init ())
+	{
+	  fprintf (stderr, "Autolaunch error: X11 initialization failed.\n");
+	  exit (1);
+	}
+
+      if (!x11_get_address (&address, &pid, &wid))
+	{
+	  fprintf (stderr, "Autolaunch error: X11 communication error.\n");
+	  exit (1);
+	}
+
+      if (address != NULL)
+	{
+	  verbose ("dbus-daemon is already running. Returning existing parameters.\n");
+	  print_variables (address, pid, wid, c_shell_syntax,
+			   bourne_shell_syntax, binary_syntax);
+	  exit (0);
+	}
+#endif
+    }
+
   if (pipe (bus_pid_to_launcher_pipe) < 0 ||
-      pipe (bus_address_to_launcher_pipe) < 0)
+      pipe (bus_address_to_launcher_pipe) < 0 ||
+      pipe (bus_pid_to_babysitter_pipe) < 0)
     {
       fprintf (stderr,
                "Failed to create pipe: %s\n",
@@ -697,9 +722,6 @@ main (int argc, char **argv)
       exit (1);
     }
 
-  bus_pid_to_babysitter_pipe[READ_END] = -1;
-  bus_pid_to_babysitter_pipe[WRITE_END] = -1;
-  
   ret = fork ();
   if (ret < 0)
     {
@@ -716,17 +738,9 @@ main (int argc, char **argv)
       char write_address_fd_as_string[MAX_FD_LEN];
 
       verbose ("=== Babysitter's intermediate parent created\n");
-      
+
       /* Fork once more to create babysitter */
       
-      if (pipe (bus_pid_to_babysitter_pipe) < 0)
-        {
-          fprintf (stderr,
-                   "Failed to create pipe: %s\n",
-                   strerror (errno));
-          exit (1);              
-        }
-      
       ret = fork ();
       if (ret < 0)
         {
@@ -741,6 +755,7 @@ main (int argc, char **argv)
           verbose ("=== Babysitter's intermediate parent continues\n");
           
           close (bus_pid_to_launcher_pipe[READ_END]);
+	  close (bus_pid_to_launcher_pipe[WRITE_END]);
           close (bus_address_to_launcher_pipe[READ_END]);
           close (bus_address_to_launcher_pipe[WRITE_END]);
           close (bus_pid_to_babysitter_pipe[WRITE_END]);
@@ -750,8 +765,7 @@ main (int argc, char **argv)
            * daemon
            */
           babysit (exit_with_session, ret,
-                   bus_pid_to_babysitter_pipe[READ_END],
-                   bus_pid_to_launcher_pipe[WRITE_END]);
+                   bus_pid_to_babysitter_pipe[READ_END]);
           exit (0);
         }
 
@@ -763,10 +777,10 @@ main (int argc, char **argv)
       close (bus_pid_to_launcher_pipe[READ_END]);
       close (bus_address_to_launcher_pipe[READ_END]);
       close (bus_pid_to_babysitter_pipe[READ_END]);
-      close (bus_pid_to_launcher_pipe[WRITE_END]);
+      close (bus_pid_to_babysitter_pipe[WRITE_END]);
 
       sprintf (write_pid_fd_as_string,
-               "%d", bus_pid_to_babysitter_pipe[WRITE_END]);
+               "%d", bus_pid_to_launcher_pipe[WRITE_END]);
 
       sprintf (write_address_fd_as_string,
                "%d", bus_address_to_launcher_pipe[WRITE_END]);
@@ -809,14 +823,20 @@ main (int argc, char **argv)
   else
     {
       /* Parent */
-#define MAX_ADDR_LEN 512
+#define MAX_PID_LEN 64
       pid_t bus_pid;  
       char bus_address[MAX_ADDR_LEN];
+      char buf[MAX_PID_LEN];
+      char *end;
+      long wid = 0;
+      long val;
+      int ret2;
 
       verbose ("=== Parent dbus-launch continues\n");
       
       close (bus_pid_to_launcher_pipe[WRITE_END]);
       close (bus_address_to_launcher_pipe[WRITE_END]);
+      close (bus_pid_to_babysitter_pipe[READ_END]);
 
       verbose ("Waiting for babysitter's intermediate parent\n");
       
@@ -851,25 +871,70 @@ main (int argc, char **argv)
         
       close (bus_address_to_launcher_pipe[READ_END]);
 
-      verbose ("Reading PID from babysitter\n");
-      
-      switch (read_pid (bus_pid_to_launcher_pipe[READ_END], &bus_pid))
-        {
-        case READ_STATUS_OK:
-          break;
-        case READ_STATUS_EOF:
-          fprintf (stderr, "EOF in dbus-launch reading address from bus daemon\n");
-          exit (1);
-          break;
-        case READ_STATUS_ERROR:
-          fprintf (stderr, "Error in dbus-launch reading address from bus daemon: %s\n",
-                   strerror (errno));
-          exit (1);
-          break;
-        }
+      verbose ("Reading PID from daemon\n");
+      /* Now read data */
+      switch (read_line (bus_pid_to_launcher_pipe[READ_END], buf, MAX_PID_LEN))
+	{
+	case READ_STATUS_OK:
+	  break;
+	case READ_STATUS_EOF:
+	  fprintf (stderr, "EOF reading PID from bus daemon\n");
+	  exit (1);
+	  break;
+	case READ_STATUS_ERROR:
+	  fprintf (stderr, "Error reading PID from bus daemon: %s\n",
+		   strerror (errno));
+	  exit (1);
+	  break;
+	}
+
+      end = NULL;
+      val = strtol (buf, &end, 0);
+      if (buf == end || end == NULL)
+	{
+	  fprintf (stderr, "Failed to parse bus PID \"%s\": %s\n",
+		   buf, strerror (errno));
+	  exit (1);
+	}
+
+      bus_pid = val;
 
       close (bus_pid_to_launcher_pipe[READ_END]);
-      
+
+#ifdef DBUS_BUILD_X11
+      ret2 = x11_save_address (bus_address, bus_pid, &wid);
+      if (ret2 == 0)
+	{
+	  /* another window got added. Return its address */
+	  char *address;
+	  pid_t pid;
+	  long wid;
+
+	  if (x11_get_address (&address, &pid, &wid) && address != NULL)
+	    {
+	      verbose ("dbus-daemon is already running. Returning existing parameters.\n");
+	      print_variables (address, pid, wid, c_shell_syntax,
+			       bourne_shell_syntax, binary_syntax);
+	      free (address);
+
+	      bus_pid_to_kill = bus_pid;
+	      kill_bus_and_exit (0);
+	    }
+
+	  /* if failed, fall through */
+	}
+      if (ret2 <= 0)
+	{
+	  fprintf (stderr, "Error saving bus information.\n");
+	  bus_pid_to_kill = bus_pid;
+	  kill_bus_and_exit (1);
+	}
+#endif
+
+      /* Forward the pid to the babysitter */
+      write_pid (bus_pid_to_babysitter_pipe[WRITE_END], bus_pid);
+      close (bus_pid_to_babysitter_pipe[WRITE_END]);
+
       if (runprog)
 	{
 	  char *envvar;
@@ -904,18 +969,8 @@ main (int argc, char **argv)
 	}
       else
 	{
-	  if (c_shell_syntax)
-	    printf ("setenv DBUS_SESSION_BUS_ADDRESS '%s';\n", bus_address);	
-	  else
-	    {
-	      printf ("DBUS_SESSION_BUS_ADDRESS='%s';\n", bus_address);
-	      if (bourne_shell_syntax)
-		printf ("export DBUS_SESSION_BUS_ADDRESS;\n");
-	    }
-	  if (c_shell_syntax)
-	    printf ("set DBUS_SESSION_BUS_PID=%ld;\n", (long) bus_pid);
-	  else
-	    printf ("DBUS_SESSION_BUS_PID=%ld;\n", (long) bus_pid);
+	  print_variables (bus_address, bus_pid, wid, c_shell_syntax,
+			   bourne_shell_syntax, binary_syntax);
 	}
 	  
       verbose ("dbus-launch exiting\n");
diff --git a/tools/dbus-launch.h b/tools/dbus-launch.h
new file mode 100644
index 00000000..1b22f3df
--- /dev/null
+++ b/tools/dbus-launch.h
@@ -0,0 +1,56 @@
+/* -*- mode: C; c-file-style: "gnu" -*- */
+/* dbus-launch.h  dbus-launch utility
+ *
+ * Copyright (C) 2006 Thiago Macieira <thiago@kde.org>
+ *
+ * Licensed under the Academic Free License version 2.1
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * 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
+ *
+ */
+
+#ifndef DBUS_LAUNCH_H
+#define DBUS_LAUNCH_H
+
+#include <config.h>
+#include <sys/types.h>
+
+#ifndef TRUE
+#define TRUE (1)
+#endif
+
+#ifndef FALSE
+#define FALSE (0)
+#endif
+
+#undef  MAX
+#define MAX(a, b)  (((a) > (b)) ? (a) : (b))
+
+#define MAX_ADDR_LEN 512
+
+/* defined in dbus-launch.c */
+void verbose (const char *format, ...);
+char *xstrdup (const char *str);
+void kill_bus_and_exit (int exitcode);
+
+#ifdef DBUS_BUILD_X11
+/* defined in dbus-launch-x11.c */
+int x11_init (void);
+int x11_get_address (char **paddress, pid_t *pid, long *wid);
+int x11_save_address (char *address, pid_t pid, long *wid);
+void x11_handle_event (void);
+#endif
+
+#endif