+# specify the plib location
+AC_ARG_WITH(plib, [ --with-plib=PREFIX Specify the prefix path to plib])
+
+if test "x$with_plib" != "x" ; then
+ echo "plib prefix is $with_plib"
+ EXTRA_DIRS="${EXTRA_DIRS} $with_plib"
+fi
+
+# specify the osg location
+AC_ARG_WITH(osg, [ --with-osg=PREFIX Specify the prefix path to osg])
+
+if test "x$with_osg" != "x" ; then
+ echo "osg prefix is $with_osg"
+ EXTRA_DIRS="${EXTRA_DIRS} $with_osg"
+fi
+
+dnl Determine an extra directories to add to include/lib search paths
+case "${host}" in
+*-apple-darwin* | *-*-mingw32*)
+ echo no EXTRA_DIRS for $host
+ ;;
+
+*-*-cygwin*)
+ if test -d /usr/local ; then
+ EXTRA_DIRS="${EXTRA_DIRS} /usr/local"
+ fi
+ ;;
+
+*)
+ if test -d /usr/X11R6 ; then
+ EXTRA_DIR1="/usr/X11R6"
+ fi
+ if test -d /opt/X11R6 ; then
+ EXTRA_DIR2="/opt/X11R6"
+ fi
+ EXTRA_DIRS="${EXTRA_DIRS} $EXTRA_DIR1 $EXTRA_DIR2 /usr/local"
+ ;;
+
+esac
+wi_EXTRA_DIRS(no, ${EXTRA_DIRS})
+
+