build: Add --with(out)-cairo configure option

Some builders (e.g. GNOME and jhbuild) hard depend on pangocairo,
and we really don't want to emit a build of pango without support
for it.  So jhbuild can specify --with-cairo, and we'll get
a hard error.

diff --git a/configure.ac b/configure.ac
index e34c7f3..358a428 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -355,7 +355,12 @@ have_cairo_win32=false
 have_cairo_quartz=false
 cairo_required=1.12.10
 
-PKG_CHECK_MODULES(CAIRO, cairo >= $cairo_required, have_cairo=true, AC_MSG_RESULT([no]))
+AC_ARG_WITH(cairo,
+           AS_HELP_STRING([--without-cairo], [Do not use cairo]),
+           :, with_cairo=auto)
+AS_IF([test x$with_cairo != xno], [
+  PKG_CHECK_MODULES(CAIRO, cairo >= $cairo_required, have_cairo=true, AC_MSG_RESULT([no]))
+])
 
 if $have_cairo ; then
   pango_save_libs=$LIBS
@@ -397,6 +402,9 @@ if $have_cairo ; then
   if $have_cairo ; then
     AC_MSG_RESULT([$cairo_font_backends])
   else
+    if test x${with_cairo} != xauto; then
+      AC_MSG_ERROR([cairo support requested, but not present])
+    fi
     AC_MSG_RESULT([none])
     AC_MSG_NOTICE([Disabling cairo support])
   fi