From 0eb382400cde2057cedda1cd0c6037375473db58 Mon Sep 17 00:00:00 2001
From: Alex Jordan <alex.jordan@pcc.edu>
Date: Tue, 30 Jul 2024 14:29:55 -0700
Subject: [PATCH] attempt to parse display math for proper PTX md/mrow
 structure when applicable

---
 macros/core/PGbasicmacros.pl | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/macros/core/PGbasicmacros.pl b/macros/core/PGbasicmacros.pl
index 536e86f5f..d7df61686 100644
--- a/macros/core/PGbasicmacros.pl
+++ b/macros/core/PGbasicmacros.pl
@@ -1968,11 +1968,26 @@ sub general_math_ev3 {
 		$out = "`$in`"                                   if $mode eq "inline";
 		$out = '<DIV ALIGN="CENTER">`' . $in . '`</DIV>' if $mode eq "display";
 	} elsif ($displayMode eq "PTX") {
-		#protect XML control characters
+		# protect XML control characters
 		$in =~ s/\&(?!([\w#]+;))/\\amp /g;
 		$in =~ s/</\\lt /g;
-		$out = '<m>' . "$in" . '</m>'   if $mode eq "inline";
-		$out = '<me>' . "$in" . '</me>' if $mode eq "display";
+		# attempt to parse align|alignat|gather into complete md/mrow structure, otherwise use me
+		if ($mode eq 'inline') {
+			$out = "<m>$in</m>";
+		} elsif ($mode eq 'display' && $in =~ /^\s*\\begin\{(align|alignat|gather)}((?!\\end\{\1}).)*\\end\{\1}\s*$/s) {
+			my $alignment = $1;
+			my $lines =
+				($in =~ s/^\s*\\begin\{$alignment}\s*(((?!\\end\{$alignment}).)*)\s*\\end\{$alignment}\s*$/$1/sr);
+			$lines =~ s/^\{\d+\}// if ($alignment eq 'alignat');
+			my @lines = split(/\\\\\n?/, $lines);
+			@lines = map { $_ =~ s/^\s+|\s+$//r } @lines;
+			my @rows = map {"<mrow>$_</mrow>"} @lines;
+			my $rows = join("\n", @rows);
+			$alignment = ($alignment eq 'align') ? '' : " alignment=\"$alignment\"";
+			$out       = "<md${alignment}>\n$rows\n</md>";
+		} elsif ($mode eq 'display') {
+			$out = "<me>$in</me>";
+		}
 	} elsif ($displayMode eq "HTML_LaTeXMathML") {
 		$in = HTML::Entities::encode_entities($in);
 		$in = '{' . $in . '}';