From e70cdfd3a222f12ab25a8c7296b180018bc06381 Mon Sep 17 00:00:00 2001
From: Thibaut Cuvelier <tcuvelier@lyx.org>
Date: Sun, 8 Jan 2023 02:27:36 +0100
Subject: [PATCH] InsetMathBox: split the boxed text into <mtext> and other
 tags, while boxing the whole inset within an <mrow>.

Rationales:
- previously, <mstyle> was used, but it's being deprecated for MathML 4 Core in favour of CSS and <mrow> (not a big deal in itself)
- the whole box cannot be hosted within the same tag, because neither <mstyle> nor <mrow> can have text, they need an intermediate container, <mtext> (which cannot hold anything else that pure text)
- new behaviour: always output a container for the whole box that has the right attributes, i.e. an <mrow>; split the content of the cell to have text and other tags set apart (text in <mtext>, other tags left as they were)

Old behaviour, invalid MathML (2 to 4):
<mstyle XXX>text<mn>.</mn></mstyle>

New behaviour, valid MathML:
<mrow XXX><mtext>text</mtext><mn>.</mn></mrow>
---
 src/mathed/InsetMathBox.cpp | 89 ++++++++++++++++++++++++++++++-------
 1 file changed, 74 insertions(+), 15 deletions(-)

diff --git a/src/mathed/InsetMathBox.cpp b/src/mathed/InsetMathBox.cpp
index f3ba7a7cb5..30cbd14356 100644
--- a/src/mathed/InsetMathBox.cpp
+++ b/src/mathed/InsetMathBox.cpp
@@ -25,6 +25,7 @@
 #include "frontends/Painter.h"
 
 #include <algorithm>
+#include <iostream>
 #include <ostream>
 
 using namespace lyx::support;
@@ -57,16 +58,82 @@ void InsetMathBox::normalize(NormalStream & os) const
 }
 
 
+namespace {
+void splitAndWrapInMText(MathMLStream & ms, MathData const & cell,
+						 const std::string & attributes)
+{
+	// First, generate the inset into a string of its own.
+	docstring inset_contents;
+	{
+		odocstringstream ostmp;
+		MathMLStream mstmp(ostmp, ms.xmlns());
+
+		SetMode textmode(mstmp, true);
+		mstmp << cell;
+
+		inset_contents = ostmp.str();
+	}
+
+	std::cout << '"' << to_ascii(inset_contents) << '"' << std::endl;
+
+	// No tags are allowed within <m:mtext>: split the string if there are tags.
+	std::vector<docstring> parts;
+	while (true) {
+		std::size_t angle_pos = inset_contents.find('<');
+		if (angle_pos == docstring::npos)
+			break;
+
+		// String structure:
+		// - prefix: pure text, no tag
+		// - tag to split: something like <m:mn>1</m:mn> or more complicated
+		//   (like nested tags), with or without name space
+		// - rest to be taken care of in the next iteration
+
+		// Push the part before the tag.
+		parts.emplace_back(inset_contents.substr(0, angle_pos));
+		inset_contents = inset_contents.substr(angle_pos);
+		// Now, inset_contents starts with the tag to isolate, so that
+		//     inset_contents[0] == '<'
+
+		// Push the tag, up to its end. Process: find the tag name (either
+		// before > or the first attribute of the tag), then the matching end
+		// tag, then proceed with pushing.
+		const std::size_t tag_name_end =
+				std::min(inset_contents.find(' ', 1), inset_contents.find('>', 1));
+		const std::size_t tag_name_length = tag_name_end - 1;
+		const docstring tag_name = inset_contents.substr(1, tag_name_length);
+
+		const std::size_t end_tag_start =
+				inset_contents.find(tag_name, tag_name_end + 1);
+		const std::size_t end_tag = inset_contents.find('>', end_tag_start);
+
+		parts.emplace_back(inset_contents.substr(0, end_tag + 1));
+		inset_contents = inset_contents.substr(end_tag + 1);
+	}
+	parts.emplace_back(inset_contents);
+
+	// Finally, output the complete inset: escape the test in <m:mtext>, leave
+	// the other tags untouched.
+	ms << MTag("mrow", attributes);
+	for (int i = 0; i < parts.size(); i += 2) {
+		ms << MTag("mtext")
+		   << parts[i]
+		   << ETag("mtext");
+		if (parts.size() > i + 1)
+			ms << parts[i + 1];
+	}
+	ms << ETag("mrow");
+}
+}
+
+
 void InsetMathBox::mathmlize(MathMLStream & ms) const
 {
 	// FIXME XHTML
 	// Need to do something special for tags here.
 	// Probably will have to involve deferring them, which
 	// means returning something from this routine.
-	SetMode textmode(ms, true);
-	ms << MTag("mtext", "class='mathbox'")
-	   << cell(0)
-	   << ETag("mtext");
+	splitAndWrapInMText(ms, cell(0), "class='mathbox'");
 }
 
 
@@ -165,10 +232,7 @@ void InsetMathFBox::normalize(NormalStream & os) const
 
 void InsetMathFBox::mathmlize(MathMLStream & ms) const
 {
-	SetMode textmode(ms, true);
-	ms << MTag("mtext", "class='fbox'")
-	   << cell(0)
-	   << ETag("mtext");
+	splitAndWrapInMText(ms, cell(0), "class='fbox'");
 }
 
 
@@ -311,10 +375,7 @@ void InsetMathMakebox::mathmlize(MathMLStream & ms) const
 {
 	// FIXME We could do something with the other arguments.
 	std::string const cssclass = framebox_ ? "framebox" : "makebox";
-	SetMode textmode(ms, true);
-	ms << MTag("mtext", "class='" + cssclass + "'")
-	   << cell(2)
-	   << ETag("mtext");
+	splitAndWrapInMText(ms, cell(2), "class='" + cssclass + "'");
 }
 
 
@@ -393,9 +454,7 @@ void InsetMathBoxed::infoize(odocstream & os) const
 
 void InsetMathBoxed::mathmlize(MathMLStream & ms) const
 {
-	ms << MTag("mtext", "class='boxed'")
-	   << cell(0)
-	   << ETag("mtext");
+	splitAndWrapInMText(ms, cell(0), "class='boxed'");
 }
 
 
-- 
2.39.5