From 7945ba0cb002995233491b5e861df6b07c2140ff Mon Sep 17 00:00:00 2001
From: Juergen Spitzmueller <spitz@lyx.org>
Date: Tue, 11 Jul 2017 10:03:03 +0200
Subject: [PATCH] Load color before polyglossia also in preview snippets

This fixes an error in the preview generation with polyglossia
and bidi that prevents snippet generation (and consequently also
"math as image" xhtml output).

Fixes: #10716.
---
 lib/scripts/legacy_lyxpreview2ppm.py | 38 +++++++++++++++++++++++-----
 1 file changed, 32 insertions(+), 6 deletions(-)

diff --git a/lib/scripts/legacy_lyxpreview2ppm.py b/lib/scripts/legacy_lyxpreview2ppm.py
index c40cd8962c..a5eb05a129 100644
--- a/lib/scripts/legacy_lyxpreview2ppm.py
+++ b/lib/scripts/legacy_lyxpreview2ppm.py
@@ -201,6 +201,7 @@ def extract_resolution(log_file, dpi):
 
 
 def legacy_latex_file(latex_file, fg_color, bg_color):
+    use_polyglossia_re = re.compile(b"\\s*\\\\usepackage{polyglossia}")
     use_preview_re = re.compile(b"\\s*\\\\usepackage\\[([^]]+)\\]{preview}")
     fg_color_gr = make_texcolor(fg_color, True)
     bg_color_gr = make_texcolor(bg_color, True)
@@ -216,18 +217,36 @@ def legacy_latex_file(latex_file, fg_color, bg_color):
         warning('Warning in legacy_latex_file! Unable to open "%s"' % latex_file)
         warning(repr(sys.exc_info()[0]) + ',' + repr(sys.exc_info()[1]))
 
+    polyglossia = False
     for line in f.readlines():
         if success:
             tmp.write(line)
             continue
         match = use_preview_re.match(line)
+        polymatch = use_polyglossia_re.match(line)
+        # Package order:
+        # * if polyglossia is used, we need to load color before that
+        #   (also, we do not have to load lmodern)
+        # * else, color should be loaded before preview
         if match == None:
-            tmp.write(line)
-            continue
+            if polymatch == None:
+                tmp.write(line)
+                continue
+            else:
+                tmp.write(b"""
+\\usepackage{color}
+\\definecolor{fg}{rgb}{%s}
+\\definecolor{bg}{rgb}{%s}
+\\pagecolor{bg}
+\\usepackage{polyglossia}
+""" % (fg_color_gr, bg_color_gr))
+                polyglossia = True
+                continue
         success = 1
-        # Package order: color should be loaded before preview
         # Preview options: add the options lyx and tightpage
-        tmp.write(b"""
+        previewopts = match.group(1)
+        if not polyglossia:
+            tmp.write(b"""
 \\usepackage{color}
 \\definecolor{fg}{rgb}{%s}
 \\definecolor{bg}{rgb}{%s}
@@ -241,8 +260,15 @@ def legacy_latex_file(latex_file, fg_color, bg_color):
 \\g@addto@macro\\preview{\\begingroup\\color{bg}\\special{ps::clippath fill}\\color{fg}}
 \\g@addto@macro\\endpreview{\\endgroup}
 \\makeatother
-""" % (fg_color_gr, bg_color_gr, match.group(1)))
-
+""" % (fg_color_gr, bg_color_gr, previewopts))
+        else:
+            tmp.write(b"""
+\\usepackage[%s,tightpage]{preview}
+\\makeatletter
+\\g@addto@macro\\preview{\\begingroup\\color{bg}\\special{ps::clippath fill}\\color{fg}}
+\\g@addto@macro\\endpreview{\\endgroup}
+\\makeatother
+""" % previewopts)
     if success:
         copyfileobj(tmp, open(latex_file,"wb"), 1)