Disable x11 plugin if X11 headers are not found.

configure

@@ -3521,7 +3521,48 @@ if test "${enable_x11+set}" = set; then
   :
 fi
 
-if test x$enable_x11 != xno; then PLUGINS=${PLUGINS}"x11 "; fi
+if test x$enable_x11 != xno; then
+  for ac_hdr in X11/Xlib.h
+do
+ac_safe=`echo "$ac_hdr" | sed 'y%./+-%__p_%'`
+echo $ac_n "checking for $ac_hdr""... $ac_c" 1>&6
+echo "configure:3530: checking for $ac_hdr" >&5
+if eval "test \"`echo '$''{'ac_cv_header_$ac_safe'+set}'`\" = set"; then
+  echo $ac_n "(cached) $ac_c" 1>&6
+else
+  cat > conftest.$ac_ext <<EOF
+#line 3535 "configure"
+#include "confdefs.h"
+#include <$ac_hdr>
+EOF
+ac_try="$ac_cpp conftest.$ac_ext >/dev/null 2>conftest.out"
+{ (eval echo configure:3540: \"$ac_try\") 1>&5; (eval $ac_try) 2>&5; }
+ac_err=`grep -v '^ *+' conftest.out | grep -v "^conftest.${ac_ext}\$"`
+if test -z "$ac_err"; then
+  rm -rf conftest*
+  eval "ac_cv_header_$ac_safe=yes"
+else
+  echo "$ac_err" >&5
+  echo "configure: failed program was:" >&5
+  cat conftest.$ac_ext >&5
+  rm -rf conftest*
+  eval "ac_cv_header_$ac_safe=no"
+fi
+rm -f conftest*
+fi
+if eval "test \"`echo '$ac_cv_header_'$ac_safe`\" = yes"; then
+  echo "$ac_t""yes" 1>&6
+    ac_tr_hdr=HAVE_`echo $ac_hdr | sed 'y%abcdefghijklmnopqrstuvwxyz./-%ABCDEFGHIJKLMNOPQRSTUVWXYZ___%'`
+  cat >> confdefs.h <<EOF
+#define $ac_tr_hdr 1
+EOF
+ PLUGINS=${PLUGINS}"x11 "
+else
+  echo "$ac_t""no" 1>&6
+fi
+done
+
+fi
 # Check whether --enable-xvideo or --disable-xvideo was given.
 if test "${enable_xvideo+set}" = set; then
   enableval="$enable_xvideo"
@@ -3534,17 +3575,17 @@ if test "${enable_alsa+set}" = set; then
   enableval="$enable_alsa"
   if test x$enable_alsa = xyes; then ac_safe=`echo "sys/asoundlib.h" | sed 'y%./+-%__p_%'`
 echo $ac_n "checking for sys/asoundlib.h""... $ac_c" 1>&6
-echo "configure:3538: checking for sys/asoundlib.h" >&5
+echo "configure:3579: checking for sys/asoundlib.h" >&5
 if eval "test \"`echo '$''{'ac_cv_header_$ac_safe'+set}'`\" = set"; then
   echo $ac_n "(cached) $ac_c" 1>&6
 else
   cat > conftest.$ac_ext <<EOF
-#line 3543 "configure"
+#line 3584 "configure"
 #include "confdefs.h"
 #include <sys/asoundlib.h>
 EOF
 ac_try="$ac_cpp conftest.$ac_ext >/dev/null 2>conftest.out"
-{ (eval echo configure:3548: \"$ac_try\") 1>&5; (eval $ac_try) 2>&5; }
+{ (eval echo configure:3589: \"$ac_try\") 1>&5; (eval $ac_try) 2>&5; }
 ac_err=`grep -v '^ *+' conftest.out | grep -v "^conftest.${ac_ext}\$"`
 if test -z "$ac_err"; then
   rm -rf conftest*
@@ -3561,7 +3602,7 @@ fi
 if eval "test \"`echo '$ac_cv_header_'$ac_safe`\" = yes"; then
   echo "$ac_t""yes" 1>&6
   echo $ac_n "checking for main in -lasound""... $ac_c" 1>&6
-echo "configure:3565: checking for main in -lasound" >&5
+echo "configure:3606: checking for main in -lasound" >&5
 ac_lib_var=`echo asound'_'main | sed 'y%./+-%__p_%'`
 if eval "test \"`echo '$''{'ac_cv_lib_$ac_lib_var'+set}'`\" = set"; then
   echo $ac_n "(cached) $ac_c" 1>&6
@@ -3569,14 +3610,14 @@ else
   ac_save_LIBS="$LIBS"
 LIBS="-lasound  $LIBS"
 cat > conftest.$ac_ext <<EOF
-#line 3573 "configure"
+#line 3614 "configure"
 #include "confdefs.h"
 
 int main() {
 main()
 ; return 0; }
 EOF
-if { (eval echo configure:3580: \"$ac_link\") 1>&5; (eval $ac_link) 2>&5; } && test -s conftest${ac_exeext}; then
+if { (eval echo configure:3621: \"$ac_link\") 1>&5; (eval $ac_link) 2>&5; } && test -s conftest${ac_exeext}; then
   rm -rf conftest*
   eval "ac_cv_lib_$ac_lib_var=yes"
 else

configure.in

@@ -246,7 +246,9 @@ if test x$enable_gtk != xno; then
 fi
 AC_ARG_ENABLE(x11,
   [  --disable-x11           X11 support (default enabled)])
-if test x$enable_x11 != xno; then PLUGINS=${PLUGINS}"x11 "; fi
+if test x$enable_x11 != xno; then
+  AC_CHECK_HEADERS(X11/Xlib.h, [PLUGINS=${PLUGINS}"x11 "])
+fi
 AC_ARG_ENABLE(xvideo,
   [  --enable-xvideo         XVideo interface support (default disabled)],
   [if test x$enable_xvideo = xyes; then PLUGINS=${PLUGINS}"xvideo "; fi])