From b135c965f6f33150f648a35607c12daeac1c360e Mon Sep 17 00:00:00 2001
From: Enrico Forestieri <forenr@lyx.org>
Date: Mon, 19 Jun 2023 18:17:31 +0200
Subject: [PATCH] Use \ifthenelse instead of relying on TeX primitives

This fixes the issue reported here:
https://www.mail-archive.com/lyx-users@lists.lyx.org/msg115156.html
---
 lib/scripts/legacy_lyxpreview2ppm.py | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/lib/scripts/legacy_lyxpreview2ppm.py b/lib/scripts/legacy_lyxpreview2ppm.py
index 6ee5870df6..fce5e91e92 100644
--- a/lib/scripts/legacy_lyxpreview2ppm.py
+++ b/lib/scripts/legacy_lyxpreview2ppm.py
@@ -252,11 +252,10 @@ def legacy_latex_file(latex_file, fg_color, bg_color):
 \\definecolor{lyxbg}{rgb}{%s}
 \\pagecolor{lyxbg}
 \\usepackage[%s,tightpage]{preview}
+\\usepackage{ifthen}
+\\ifthenelse{\equal{\f@family}{cmr}}{
+\\IfFileExists{lmodern.sty}{\\usepackage{lmodern}}{\\usepackage{ae,aecompl}}}{}
 \\makeatletter
-\\def\\t@a{cmr}
-\\if\\f@family\\t@a
-\\IfFileExists{lmodern.sty}{\\usepackage{lmodern}}{\\usepackage{ae,aecompl}}
-\\fi
 \\g@addto@macro\\preview{\\begingroup\\color{lyxbg}\\special{ps::clippath fill}\\color{lyxfg}}
 \\g@addto@macro\\endpreview{\\endgroup}
 \\makeatother