-# Define odd RSL install location
-AC_CHECK_LIB(rsl, RSL_wsr88d_to_radar, RSL_LIBS="-lrsl")
-AM_CONDITIONAL(HAVE_RSL, test "$RSL_LIBS" != "")
-AC_SUBST(RSL_LIBS)
+# Test for windowing system
+case "${host}" in
+ *mingw32*) SYS="WIN" ;;
+ *cygwin*) SYS="WIN" ;;
+ *apple*) SYS="MAC" ;;
+ *) SYS="X11" ;;
+esac
+AM_CONDITIONAL([SYS_WIN], test "$SYS" = "WIN")
+AM_CONDITIONAL([SYS_MAC], test "$SYS" = "MAC")
+AM_CONDITIONAL([SYS_X11], test "$SYS" = "X11")
+if test "$WIN32" = yes; then
+ ac_default_prefix="/"
+fi
+
+# OpenGL flags
+GL_CFLAGS="-DSYS_$SYS"
+case "$SYS" in
+ "WIN") GL_LIBS="-lglu32 -lopengl32" ;;
+ "MAC") GL_LIBS="-framework OpenGL" ;;
+ "X11") GL_LIBS="-lGL -lGLU" ;;
+esac
+AC_SUBST([GL_CFLAGS])
+AC_SUBST([GL_LIBS])