check for unsupported red passthrough

diff --git a/layout/layout b/layout/layout
index 391d7c6a6204cfaee05a0619f22c6f6b32d302d9..f50d33d94093a8f3ac499c6d62661ae4d71c6d63 100755 (executable)
--- a/layout/layout
+++ b/layout/layout
@@ -73,6 +73,9 @@ while (@ARGV && $ARGV[0] =~ m/^\-/) {
                    die "angbits varies" if $subsegcmapangscale != 1<<$angbits;
                }
                $datum= hex($datum);
+               if ($datum & 0x0ff) {
+                   die "sorry, cannot put any movfeatpos or segment in red";
+               }
                $subsegcmap{$csss}= sprintf("%.6f %.6f",
                                            (($datum >> 8) & 0xff)/255.0,
                                            (($datum >> 16) & 0xff)/255.0);