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

@@ -202,6 +202,7 @@ def extract_resolution(log_file, dpi):
 
 def legacy_latex_file(latex_file, fg_color, bg_color):
     use_preview_re = re.compile(r"\s*\\usepackage\[([^]]+)\]{preview}")
+    use_polyglossia_re = re.compile(r"\s*\\usepackage{polyglossia}")
     fg_color_gr = make_texcolor(fg_color, True)
     bg_color_gr = make_texcolor(bg_color, True)
 
@@ -216,17 +217,35 @@ def legacy_latex_file(latex_file, fg_color, bg_color):
         warning('Warning in legacy_latex_file! Unable to open "%s"' % latex_file)
         warning(`sys.exc_type` + ',' + `sys.exc_value`)
 
+    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:
+            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
+        previewopts = match.group(1)
+        if not polyglossia:
             tmp.write(r"""
 \usepackage{color}
 \definecolor{fg}{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(r"""
+\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)
 

status.22x

@@ -57,6 +57,9 @@ What's new
 - Do not let the natbibapa module overwrite what the class or other packages
   add to the preamble.
 
+- Assure the color package is loaded before polyglossia in preview snippets
+  This fixes preview image generation with polyglossia and bidi (bug 10716).
+
 
 * LYX2LYX