client/x11: Add support for XFixes ClientDisconnectMode

The Xserver itself is capable of terminating itself once all X11 clients
are gone, yet in a typical full session, there are a number of X11
clients such as ibus-x11 running continuously.

Those always-running clients will prevent the Xserver from terminating,
because the actual number of X11 clients will never drop to 0.

Use XFixes ClientDisconnectMode to inform the X11 server that it can
terminate even if ibus-x11 is still running.

That will allow Xwayland from terminating automatically when regular
clients have quit.

On plain Xorg servers, the lifetime of the session is usually tied to
the session manager or window manager, and this change will have no
effect.

BUG=#2314

client/x11/Makefile.am

@@ -49,11 +49,13 @@ ibus_x11_LDADD = \
 	$(libibus) \
 	@X11_LIBS@ \
 	$(GTK_LIBS) \
+	$(XFIXES_LIBS) \
 	$(NULL)
 
 ibus_x11_CFLAGS = \
 	@X11_CFLAGS@ \
 	$(GTK_CFLAGS) \
+	$(XFIXES_CFLAGS) \
 	@DBUS_CFLAGS@ \
 	-I$(top_srcdir)/util/IMdkit \
 	-I$(top_srcdir)/src \

client/x11/main.c

@@ -24,10 +24,15 @@
  */
 #define _GNU_SOURCE
 
+#include "config.h"
+
 #include <X11/Xproto.h>
 #include <X11/Xlib.h>
 #include <X11/keysym.h>
 #include <X11/Xutil.h>
+#ifdef HAVE_XFIXES
+#include <X11/extensions/Xfixes.h>
+#endif
 #include <XimProto.h>
 #include <IMdkit.h>
 #include <Xi18n.h>
@@ -1174,6 +1179,11 @@ main (int argc, char **argv)
     XSetErrorHandler (_xerror_handler);
     XSetIOErrorHandler (_xerror_io_handler);
 
+#ifdef HAVE_XFIXES
+    XFixesSetClientDisconnectMode(GDK_DISPLAY_XDISPLAY (gdk_display_get_default ()),
+                                  XFixesClientDisconnectFlagTerminate);
+#endif
+
     while (1) {
         static struct option long_options [] = {
             { "debug", 1, 0, 0},

configure.ac

@@ -618,6 +618,13 @@ PKG_CHECK_MODULES(XTEST,
 )
 AM_CONDITIONAL([ENABLE_XTEST], [test x"$enable_xtest" = x"yes"])
 
+PKG_CHECK_MODULES(XFIXES,
+    [x11 xfixes >= 6],
+    [AC_DEFINE([HAVE_XFIXES], [1], [Define to enable XFixes])
+     have_xfixes=yes],
+    [have_xfixes="no (libXfixes version is lower than 6)"]
+)
+
 # --enable-install-tests
 AC_ARG_ENABLE(install-tests,
     AS_HELP_STRING([--enable-install-tests],
@@ -843,6 +850,7 @@ Build options:
   Enable Unicode dict           $enable_unicode_dict
   UCD directory                 $UCD_DIR
   Socket directory              "$IBUS_SOCKET_DIR"
+  XFixes client disconnect      $have_xfixes
   Run test cases                $enable_tests
   Install tests                 $enable_install_tests
 ])