configure.ac: Add an --enable-libpng option

Now there is a way to not link against libpng even if it's available.

Signed-off-by: Jeremy Huddleston <jeremyhu@apple.com>

diff --git a/configure.ac b/configure.ac
index 9f81b11..233d3dc 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -855,7 +855,14 @@ AC_SUBST(TOOLCHAIN_SUPPORTS_ATTRIBUTE_CONSTRUCTOR)
 dnl ==================
 dnl libpng
 
-PKG_CHECK_MODULES(PNG, [libpng], have_libpng=yes, have_libpng=no)
+AC_ARG_ENABLE(libpng, AS_HELP_STRING([--enable-libpng], [Build support for libpng (default: auto)]),
+                      [have_libpng=$enableval], [have_libpng=auto])
+
+case x$have_libpng in
+       xyes) PKG_CHECK_MODULES(PNG, [libpng]) ;;
+       xno) ;;
+       *) PKG_CHECK_MODULES(PNG, [libpng], have_libpng=yes, have_libpng=no) ;;
+esac
 
 if test x$have_libpng = xyes; then
     AC_DEFINE([HAVE_LIBPNG], [1], [Whether we have libpng])