--- a/configure.in
+++ b/configure.in
@@ -652,12 +652,11 @@
 warn_freetype=""
 warn_ftgl=""
 
-GL_RENDER_SRC=
 GRAPHICS_OPENGL=
 OCTAVE_OPENGL
 if test -n "$OPENGL_LIBS"; then
   GRAPHICS_OPENGL="opengl"
-  GL_RENDER_SRC="gl-render.cc"
+  AC_DEFINE(HAVE_OPENGL, 1, [Define if OpenGL is available])
 
 ## ftgl (needs freetype 2)
   AC_CHECK_FT2([9.0.3],[],
@@ -710,7 +709,6 @@
 
 GRAPHICS_LIBS=
 GRAPHICS_CFLAGS=
-FLTK_BACKEND_SRC=
 
 ## fltk (www.fltk.org)
 AC_ARG_WITH(fltk-prefix,
@@ -757,10 +755,10 @@
 
   if test -z "$warn_fltk_opengl"; then
     AC_MSG_RESULT(yes)
+    AC_DEFINE(HAVE_FLTK, 1, [Define if FLTK is available])
     GRAPHICS_CFLAGS="$FLTK_CFLAGS"
     GRAPHICS_LIBS="$FLTK_LDFLAGS"
     GRAPHICS_OPENGL="$GRAPHICS_OPENGL fltk_backend"
-    FLTK_BACKEND_SRC="fltk_backend.cc"
   else
     AC_MSG_RESULT(no)
   fi
@@ -769,8 +767,6 @@
 AC_SUBST(GRAPHICS_CFLAGS)
 AC_SUBST(GRAPHICS_LIBS)
 AC_SUBST(GRAPHICS_OPENGL)
-AC_SUBST(GL_RENDER_SRC)
-AC_SUBST(FLTK_BACKEND_SRC)
 
 OCTAVE_IEEE754_DATA_FORMAT