From 4e051d54eec34ed62a4fa8982c2b34493a61e016 Mon Sep 17 00:00:00 2001
From: Mischa POSLAWSKY <perl@shiar.org>
Date: Thu, 6 Apr 2017 01:48:37 +0200
Subject: [PATCH] charset: divide and append row offset label

---
 base.css    |  6 +++---
 charset.plp | 17 +++++++++++++++--
 2 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/base.css b/base.css
index d014b61..f3c0355 100644
--- a/base.css
+++ b/base.css
@@ -354,18 +354,18 @@ table.dimap {
 	padding-bottom: 1.1ex; /* reserve space for label */
 	vertical-align: bottom;
 }
-.glyphs small {
+.glyphs.dilabel small {
 	font-size: 50%;
 	display: block;
 	margin-top: 0.2ex;
 	margin-bottom: -2.2ex; /* take cell padding */
 }
-.glyphs small.digraph {
+.glyphs.dilabel small.digraph {
 	background: #000;
 	color: #FFF;
 	opacity: 0.3;
 }
-.glyphs small.value {
+.glyphs.dilabel small.value {
 	background: #600;
 	color: #FFF;
 	opacity: 0.3;
diff --git a/charset.plp b/charset.plp
index 1186585..73b3740 100644
--- a/charset.plp
+++ b/charset.plp
@@ -158,12 +158,14 @@ sub range_cell {
 
 for my $row (@request) {
 	my $colsize = $row->{cell} && $row->{cell}->{colsize} || 1;
+	my $coldigits = ceil(log($colsize * $cols) / log(16));  # uniform length of hexadecimal header
+	my $rowdiv = 16 ** $coldigits;  # divider of row headers
+
 	printf '<div class="section"><table class="glyphs%s">', !$row->{cell} && ' charmap';
 	my $title = $row->{set};
 	$title .= " <aside>($_)</aside>" for $row->{setnote} // ();
 	printf '<caption>%s</caption>', $title;
 	print '<col>' x ($cols + 1);
-	my $coldigits = ceil(log($colsize * $cols) / log(16));  # uniform length of hexadecimal header
 	for my $section (qw{thead}) {
 		print "<$section><tr><th>↱";
 		printf '<th>%0*X', $coldigits, $_ * $colsize for 0 .. $cols - 1;
@@ -171,7 +173,18 @@ for my $row (@request) {
 	}
 	print '<tbody>';
 	for my $msb (0 .. ((length($row->{table}) || 256) - 1) / $cols) {
-		printf '<tr><th>%X', ($msb + int($row->{offset} / $cols)) * $cols * $colsize;
+		print '<tr><th>';
+		{
+			my $rowlabel = ($msb + int($row->{offset} / $cols)) * $cols * $colsize;
+			if (my $rowmod = $rowlabel % $rowdiv) {
+				# offset in column units
+				printf '<small>+%X</small>', $rowmod;
+			}
+			else {
+				# divided row offset
+				printf '%X', $rowlabel / $rowdiv;
+			}
+		}
 		for my $lsb (0 .. $cols - 1) {
 			my $val = ( ($msb * $cols) + $lsb ) * $colsize;
 			if ($row->{cell}) {
-- 
2.30.0