From 414f2bc754363a3052954e45a92c76db6bfc9c06 Mon Sep 17 00:00:00 2001
From: Mischa POSLAWSKY <perl@shiar.org>
Date: Sat, 8 Apr 2017 23:33:37 +0200
Subject: [PATCH] charset: support partial cp437 glyph replacement

---
 charset.plp | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/charset.plp b/charset.plp
index e82e3d7..5e50004 100644
--- a/charset.plp
+++ b/charset.plp
@@ -297,14 +297,21 @@ sub tabinput {
 			}
 			$row{endpoint} -= $row{offset};
 
-			if ($row{set} eq 'cp437' and !$row{offset}) {
-				substr($row{table}, 237, 1) = pack 'U*', 0x3D5; # phi sign
-				substr($row{table}, 0, 32) = pack 'U*', map {hex} qw(
-					2007 263A 263B 2665 2666 2663 2660 2022
-					25D8 25CB 25D9 2642 2640 266A 266B 263C
-					25BA 25C4 2195 203C 00B6 00A7 25AC 21A8
-					2191 2193 2192 2190 221F 2194 25B2 25BC
-				);
+			if ($row{set} eq 'cp437') {
+				for my $phipos (237 - $row{offset}) {
+					next if $phipos < 0 or $phipos > $row{endpoint};
+					# replace phi glyph
+					substr($row{table}, $phipos, 1) = pack 'U*', 0x3D5;
+				}
+				if ($row{offset} == 0) {
+					# replace control characters by visible variants
+					substr($row{table}, 0, 32) = pack 'U*', map {hex} qw(
+						2007 263A 263B 2665 2666 2663 2660 2022
+						25D8 25CB 25D9 2642 2640 266A 266B 263C
+						25BA 25C4 2195 203C 00B6 00A7 25AC 21A8
+						2191 2193 2192 2190 221F 2194 25B2 25BC
+					);
+				}
 			}
 
 			$visible->{ascii} =  # assume common base
-- 
2.30.0