dbus-launch: add --exit-with-x11 option

This is more suitable for distributions' Xsession scripts: it verifies
that X is already available, and so never results in an attempt to poll
stdin.

Reviewed-by: Will Thompson <will.thompson@collabora.co.uk>
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=39197

2 files changed, 47 insertions, 12 deletions

diff --git a/doc/dbus-launch.1 b/doc/dbus-launch.1
index a7687cad..53d69f6d 100644
--- a/doc/dbus-launch.1
+++ b/doc/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] [\-\-autolaunch=MACHINEID] [\-\-config\-file=FILENAME] [PROGRAM] [ARGS...]
+.B dbus\-launch [\-\-version] [\-\-sh\-syntax] [\-\-csh\-syntax] [\-\-auto\-syntax] [\-\-exit\-with\-session] [\-\-exit\-with\-x11] [\-\-autolaunch=MACHINEID] [\-\-config\-file=FILENAME] [PROGRAM] [ARGS...]
 
 .SH DESCRIPTION
 
@@ -152,11 +152,25 @@ the \-\-session argument. See the man page for dbus\-daemon
 Emit csh compatible code to set up environment variables.
 
 .TP
-.I "\-\-exit\-with\-session"
-If this option is provided, a persistent "babysitter" process will be 
-created that watches stdin for HUP and tries to connect to the X
-server. If this process gets a HUP on stdin or loses its X connection,
-it kills the message bus daemon.
+.I \-\-exit\-with\-x11
+If this option is provided, a persistent "babysitter" process will be
+created, and will connect to the X server. If it cannot do so, launching
+fails. If the "babysitter" process loses its X connection,
+it kills the message bus daemon, disconnecting all of its clients (which
+should exit in response). This avoids having leftover daemon
+processes from a user X session, after the X session has ended.
+
+.TP
+.I \-\-exit\-with\-session
+If this option is provided, a persistent "babysitter" process will be
+created, as if for
+.BR \-\-exit\-with\-x11 .
+If it cannot connect to the X server, it will monitor the terminal from which
+.B dbus-launch
+was started instead, and if it gets a HUP on stdin, the message bus daemon
+will be killed. This option is not recommended, since it will consume input
+from the terminal where it was started; it is mainly provided for
+backwards compatibility.
 
 .TP
 .I "\-\-autolaunch=MACHINEID"
diff --git a/tools/dbus-launch.c b/tools/dbus-launch.c
index 1ec9ae59..dcce646e 100644
--- a/tools/dbus-launch.c
+++ b/tools/dbus-launch.c
@@ -181,7 +181,7 @@ verbose (const char *format,
 static void
 usage (int ecode)
 {
-  fprintf (stderr, "dbus-launch [--version] [--help] [--sh-syntax] [--csh-syntax] [--auto-syntax] [--exit-with-session]\n");
+  fprintf (stderr, "dbus-launch [--version] [--help] [--sh-syntax] [--csh-syntax] [--auto-syntax] [--exit-with-session] [--exit-with-x11]\n");
   exit (ecode);
 }
 
@@ -809,6 +809,7 @@ main (int argc, char **argv)
   const char *runprog = NULL;
   int remaining_args = 0;
   int exit_with_session;
+  int exit_with_x11 = FALSE;
   int binary_syntax = FALSE;
   int c_shell_syntax = FALSE;
   int bourne_shell_syntax = FALSE;
@@ -850,6 +851,8 @@ main (int argc, char **argv)
         version ();
       else if (strcmp (arg, "--exit-with-session") == 0)
         exit_with_session = TRUE;
+      else if (strcmp (arg, "--exit-with-x11") == 0)
+        exit_with_x11 = TRUE;
       else if (strcmp (arg, "--close-stderr") == 0)
         close_stderr = TRUE;
       else if (strstr (arg, "--autolaunch=") == arg)
@@ -961,6 +964,9 @@ main (int argc, char **argv)
   if (exit_with_session)
     verbose ("--exit-with-session enabled\n");
 
+  if (exit_with_x11)
+    verbose ("--exit-with-x11 enabled\n");
+
   if (autolaunch)
     {      
 #ifndef DBUS_BUILD_X11
@@ -983,10 +989,10 @@ main (int argc, char **argv)
         }
 
       verbose ("Autolaunch enabled (using X11).\n");
-      if (!exit_with_session)
+      if (!exit_with_x11)
 	{
-	  verbose ("--exit-with-session automatically enabled\n");
-	  exit_with_session = TRUE;
+          verbose ("--exit-with-x11 automatically enabled\n");
+          exit_with_x11 = TRUE;
 	}
 
       if (!x11_init ())
@@ -1009,12 +1015,27 @@ main (int argc, char **argv)
 	  exit (0);
 	}
 #endif /* DBUS_ENABLE_X11_AUTOLAUNCH */
+#endif /* DBUS_BUILD_X11 */
+    }
+  else if (exit_with_x11)
+    {
+#ifndef DBUS_BUILD_X11
+      fprintf (stderr, "Session lifetime based on X11 requested, but X11 support not compiled in.\n");
+      exit (1);
+#else /* DBUS_BUILD_X11 */
+      if (!x11_init ())
+        {
+          fprintf (stderr, "Session lifetime based on X11 requested, but X11 initialization failed.\n");
+          exit (1);
+        }
+#endif /* DBUS_BUILD_X11 */
     }
+#ifdef DBUS_BUILD_X11
   else if (read_machine_uuid_if_needed())
     {
       x11_init();
-#endif /* DBUS_BUILD_X11 */
     }
+#endif /* DBUS_BUILD_X11 */
 
 
   if (pipe (bus_pid_to_launcher_pipe) < 0 ||
@@ -1076,7 +1097,7 @@ main (int argc, char **argv)
            * and will also reap the pre-forked bus
            * daemon
            */
-          babysit (exit_with_session, ret,
+          babysit (exit_with_session || exit_with_x11, ret,
                    bus_pid_to_babysitter_pipe[READ_END]);
           exit (0);
         }