[PATCH][weston] build: Require dbus for systemd-login

[Manuel Bachmann]

systemd-login support requires dbus (see "dbus.h" header in
"launcher-logind.c") but the configure script was only
checking libsystemd-login availability to define the
HAVE_SYSTEMD_LOGIN macro, which results in undefined
symbols in launcher-unit.

Put the systemd-login checks after the dbus ones, and only
run the checks if it is present. Also mention dbus in the
error message if "--enable-systemd-login" was forced.

Signed-off-by: Manuel Bachmann <manuel.bachmann at iot.bzh>
---
 configure.ac | 66 +++++++++++++++++++++++++++++++-----------------------------
 1 file changed, 34 insertions(+), 32 deletions(-)

diff --git a/configure.ac b/configure.ac
index e5afbc0..9e29098 100644
--- a/configure.ac
+++ b/configure.ac
@@ -380,38 +380,6 @@ AC_ARG_ENABLE(resize-optimization,
 AS_IF([test "x$enable_resize_optimization" = "xyes"],
       [AC_DEFINE([USE_RESIZE_POOL], [1], [Use resize memory pool as a performance optimization])])
 
-AC_ARG_ENABLE(systemd-login,
-              AS_HELP_STRING([--enable-systemd-login],
-                             [Enable logind support]),,
-              enable_systemd_login=auto)
-if test x$enable_systemd_login != xno; then
-  PKG_CHECK_MODULES(SYSTEMD_LOGIN,
-                    [libsystemd >= 209],
-                    [have_systemd_login_209=yes;have_systemd_login=yes],
-                    [have_systemd_login_209=no;have_systemd_login=no])
-
-  # Older versions of systemd package systemd-login separately. Fall back on that
-  AS_IF([test x$have_systemd_login != xyes],[
-        PKG_CHECK_MODULES(SYSTEMD_LOGIN,
-                          [libsystemd-login >= 198],
-                          [have_systemd_login=yes],
-                          [have_systemd_login=no])
-        ])
-else
-  have_systemd_login=no
-fi
-
-if test "x$have_systemd_login" = "xno" -a "x$enable_systemd_login" = "xyes"; then
-  AC_MSG_ERROR([systemd-login support explicitly enabled, but can't find libsystemd>=209 or libsystemd-login])
-fi
-
-AS_IF([test "x$have_systemd_login" = "xyes"],
-      [AC_DEFINE([HAVE_SYSTEMD_LOGIN], [1], [Have systemd-login])])
-AM_CONDITIONAL(HAVE_SYSTEMD_LOGIN, test "x$have_systemd_login" = "xyes")
-
-AS_IF([test "x$have_systemd_login_209" = "xyes"],
-      [AC_DEFINE([HAVE_SYSTEMD_LOGIN_209], [1], [Have systemd-login >= 209])])
-
 AC_ARG_ENABLE(weston-launch, [  --enable-weston-launch],, enable_weston_launch=yes)
 AM_CONDITIONAL(BUILD_WESTON_LAUNCH, test x$enable_weston_launch == xyes)
 if test x$enable_weston_launch == xyes; then
@@ -484,6 +452,40 @@ if test "x$enable_dbus" != "xno"; then
 fi
 AM_CONDITIONAL(ENABLE_DBUS, test "x$enable_dbus" = "xyes")
 
+# systemd-login support
+AC_ARG_ENABLE(systemd-login,
+              AS_HELP_STRING([--enable-systemd-login],
+                             [Enable logind support]),,
+              enable_systemd_login=auto)
+if test x$enable_systemd_login != xno -a x$have_dbus != xno; then
+  PKG_CHECK_MODULES(SYSTEMD_LOGIN,
+                    [libsystemd >= 209],
+                    [have_systemd_login_209=yes;have_systemd_login=yes],
+                    [have_systemd_login_209=no;have_systemd_login=no])
+
+  # Older versions of systemd package systemd-login separately. Fall back on that
+  AS_IF([test x$have_systemd_login != xyes],[
+        PKG_CHECK_MODULES(SYSTEMD_LOGIN,
+                          [libsystemd-login >= 198],
+                          [have_systemd_login=yes],
+                          [have_systemd_login=no])
+        ])
+else
+  have_systemd_login=no
+fi
+
+if test "x$have_systemd_login" = "xno" -a "x$enable_systemd_login" = "xyes"; then
+  AC_MSG_ERROR([systemd-login support explicitly enabled, but can't find libsystemd>=209, libsystemd-login or dbus])
+fi
+
+AS_IF([test "x$have_systemd_login" = "xyes"],
+      [AC_DEFINE([HAVE_SYSTEMD_LOGIN], [1], [Have systemd-login])])
+AM_CONDITIONAL(HAVE_SYSTEMD_LOGIN, test "x$have_systemd_login" = "xyes")
+
+AS_IF([test "x$have_systemd_login_209" = "xyes"],
+      [AC_DEFINE([HAVE_SYSTEMD_LOGIN_209], [1], [Have systemd-login >= 209])])
+
+
 # Note that other features might want libxml2, or this feature might use
 # alternative xml libraries at some point. Therefore the feature and
 # pre-requisite concepts are split.
-- 
1.8.3.1