[LyX/master] tex2lyx: fix import of umlauts and ß in math (#12739)

[Juergen Spitzmueller]

commit 9ec80456feed688440360e0a493cbf537c4fe5f9
Author: Juergen Spitzmueller <spitz at lyx.org>
Date:   Fri Apr 14 19:13:23 2023 +0200

    tex2lyx: fix import of umlauts and ß in math (#12739)
---
 src/tex2lyx/math.cpp |   24 ++++++++++++++++--------
 1 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/src/tex2lyx/math.cpp b/src/tex2lyx/math.cpp
index 616b616..adda26d 100644
--- a/src/tex2lyx/math.cpp
+++ b/src/tex2lyx/math.cpp
@@ -213,17 +213,25 @@ void parse_math(Parser & p, ostream & os, unsigned flags, const mode_type mode)
 
 		else if (t.cs() == "\"") {
 			string const name = p.verbatim_item();
-			     if (name == "a") os << '\xe4';
-			else if (name == "o") os << '\xf6';
-			else if (name == "u") os << '\xfc';
-			else if (name == "A") os << '\xc4';
-			else if (name == "O") os << '\xd6';
-			else if (name == "U") os << '\xdc';
-			else os << "\"{" << name << "}";
+			LYXERR0("name: " << name);
+			if (name == "a")
+				os << "ä";
+			else if (name == "o")
+				os << "ö";
+			else if (name == "u")
+				os << "ü";
+			else if (name == "A")
+				os << "Ä";
+			else if (name == "O")
+				os << "Ö";
+			else if (name == "U")
+				os << "Ü";
+			else
+				os << "\"{" << name << "}";
 		}
 
 		else if (t.cs() == "ss")
-			os << "\xdf";
+			os << "ß";
 
 		else if (t.cs() == "cr") {
 			// lyx can't handle \\cr