\foreignlanguage leads to wrong font used for amsthm theorem environments and headers

[chpech]

When the following MWE is compiled in xelatex, Theorem 1 is set in arial while it should be set in palatino If the command \foreignlanguage is replaced by \textenglish, then it is set properly.

The same is true for headings. On the first page, because of \forreignlanguage, the header is set in arial. On the second page, after \textenglish, it is set in palatino, as it should.

When not including amsthm, then the faulty behaviour goes away for theorems but remains for headers.

When not using \foreignlanguage at all, then everything works well.

\documentclass{article}
\usepackage{amsthm}
 \newtheorem{THM}{Теорема}

\usepackage{fontspec}
\setmainfont{Arial}
\newfontfamily{\cyrillicfont}{Palatino}

\usepackage{polyglossia}
\setdefaultlanguage[script=Cyrillic]{serbian}
\setotherlanguage{english}

\begin{document}

\pagestyle{headings}

\section{Тест}

\foreignlanguage{english}{This is a test}

\begin{THM}
    То је тест 
\end{THM}
    То је тест 

\newpage
\textenglish{This is a test}

\begin{THM}
    То је тест 
\end{THM}
    То је тест 

\end{document}

[jspitz]

Fixed for 1.66

[chpech]

I tried it and it works fine. Thank you very much for this quick fix!

[jspitz]

Thanks for testing and confirming.

[Udi-Fogiel]

@jspitz It looks like the following patch also solves the problem, with simpler and faster code. Can you test it? I'm not sure it won't cause any regressions, so I don't want to push yet.

diff --git a/tex/polyglossia.sty b/tex/polyglossia.sty
index 92ce14e3..bbc70500 100644
--- a/tex/polyglossia.sty
+++ b/tex/polyglossia.sty
@@ -1662,7 +1662,7 @@
 }

 % This saves the normalfont for the latin script since we may change normalfont in other scripts
-\cs_gset_eq:cc { normalfontlatin } { normalfont }
+\cs_set_eq:cc { normalfontlatin } { normalfont }

 % Provide default fonts (as set with \setmainfont, \setsansfont and \setmonofont)
 % for Latin scripts and as a fallback for non-Latin scripts.
@@ -1694,9 +1694,9 @@
 {
   % This robustifies the redefinitions of \<xx>family (suggestion by Enrico Gregorio)
   % e.g. to prevent expansion of the \familytype redefinition in auxiliary files
-  \tl_gput_right:cn {rmfamily~} {\tl_set:Nn \familytype {rm}}
-  \tl_gput_right:cn {sffamily~} {\tl_set:Nn \familytype {sf}}
-  \tl_gput_right:cn {ttfamily~} {\tl_set:Nn \familytype {tt}}
+  \tl_put_right:cn {rmfamily~} {\tl_set:Nn \familytype {rm}}
+  \tl_put_right:cn {sffamily~} {\tl_set:Nn \familytype {sf}}
+  \tl_put_right:cn {ttfamily~} {\tl_set:Nn \familytype {tt}}
 }

 % These switches activate the default fonts
@@ -1720,11 +1720,11 @@
   \__xpg_patch_fontfamilies:
   % This (re-)saves the normalfont for the latin script since we may
   % change normalfont in other scripts
-  \cs_gset_eq:cc{ normalfontlatin }{ normalfont }
+  \cs_set_eq:cc{ normalfontlatin }{ normalfont }
   % And for all cases, we also reset \<xx>familylatin
-  \cs_gset_eq:cc{ rmfamilylatin }{ xpg_defaultfont_rm: }
-  \cs_gset_eq:cc{ sffamilylatin }{ xpg_defaultfont_sf: }
-  \cs_gset_eq:cc{ ttfamilylatin }{ xpg_defaultfont_tt: }
+  \cs_set_eq:cc{ rmfamilylatin }{ xpg_defaultfont_rm: }
+  \cs_set_eq:cc{ sffamilylatin }{ xpg_defaultfont_sf: }
+  \cs_set_eq:cc{ ttfamilylatin }{ xpg_defaultfont_tt: }
 }

 \cs_set_nopar:Npn \resetfontlatin
@@ -1733,7 +1733,7 @@
   \cs_set_protected:Npn \sffamily { \xpg_defaultfont_sf: }
   \cs_set_protected:Npn \ttfamily { \xpg_defaultfont_tt: }
   \__xpg_patch_fontfamilies:
-  \cs_gset_eq:cc { normalfont } { normalfontlatin }
+  \cs_set_eq:cc { normalfont } { normalfontlatin }
 }

 \cs_set_nopar:Npn \selectfontfamilylatin
@@ -1758,17 +1758,17 @@

 \cs_new_nopar:Nn \xpg_set_normalfont:n
 {
-  \cs_gset_eq:cc { rmfamily } { #1@font@rm }
-  \cs_gset_eq:cc { sffamily } { #1@font@sf }
-  \cs_gset_eq:cc { ttfamily } { #1@font@tt }
-  \cs_gset_nopar:Npn \normalfont 
+  \cs_set_eq:cc { rmfamily } { #1@font@rm }
+  \cs_set_eq:cc { sffamily } { #1@font@sf }
+  \cs_set_eq:cc { ttfamily } { #1@font@tt }
+  \cs_set_nopar:Npn \normalfont 
       { \protect \xpg_select_fontfamily:n {#1}
         \fontseries{\seriesdefault}\selectfont
         \fontshape{\shapedefault}
         \cs_if_exist_use:NT \UseHook { {normalfont} }
         \selectfont
       }
-  \cs_gset_nopar:Npn \reset@font {\protect\normalfont}
+  \cs_set_nopar:Npn \reset@font {\protect\normalfont}
 }

 \cs_gset_eq:cc { @@fterindentfalse } { @afterindentfalse }
@@ -1932,30 +1932,6 @@
   \xpg_set_foreign_language:nn { #1 } { #2 }
 }

-% Stack to store matrix languages
-\seq_new:N \__xpg_current_matrixlang_stack
-
-% Store embedding language when an embedded language is switched to
-\cs_new_nopar:Nn \__xpg_store_matrixlang:
-{
-   \seq_gput_left:Nn \__xpg_current_matrixlang_stack \languagename
-}
-
-% When an embedded language is closed, reset to the embedding language
-% and remove stored matrix language from stack
-\cs_new_nopar:Nn \__xpg_reset_to_matrixlang:
-{
-  % if stack is empty, use main language
-  \seq_gpop_left:NNTF \__xpg_current_matrixlang_stack \l_tmpa_tl
-     { \cs_set_eq:NN \__xpg_current_matrixlang \l_tmpa_tl }
-     { \cs_set_eq:NN \__xpg_current_matrixlang \mainlanguagename }
-  % Reset the language's/script's font families if the embedding script is latin
-  \str_if_eq:eeT{\prop_item:Ne{\g_xpg_langsetup_prop}{\__xpg_current_matrixlang/lcscript}}{latin}
-       {\resetfontlatin}
-  % In case a \<lang>font is defined, re-activate that
-  \exp_args:Ne \xpg_set_normalfont:n{\__xpg_current_matrixlang}
-}
-
 % internal wrapper for foreign language
 % #1 option
 % #2 alias
@@ -1967,12 +1943,10 @@
   {
     \msg_show:nnn { polyglossia } { languagenotloaded } {#2}
   }{
-    \__xpg_store_matrixlang:
     \group_begin:
       \xpg_otherlanguage:nn{ \xpg_alias_add_to_option_i:nn{#2}{#1} }{ #3 }
       \__xpg_lang_set_text_direction:nn{#3}{#4}
     \group_end:
-    \__xpg_reset_to_matrixlang:
   }
 }
 \cs_generate_variant:Nn \__xpg_foreignlanguage:nnnn {eeen}
@@ -1981,11 +1955,9 @@
 % otherlanguage* is the environment equivalent of \foreignlanguage
 \DeclareDocumentEnvironment { otherlanguage* } { O{} m }
   {
-   \__xpg_store_matrixlang:
    \__xpg_otherlanguage:eee { #1 } { #2 } { \xpg_alias_base_lang:n { #2 } }
   }{
    \c_group_end_token% \group_end: does not work here!
-   \__xpg_reset_to_matrixlang:
   }

 % internal wrapper
@@ -2032,7 +2004,6 @@
     \msg_show:nnn { polyglossia } { languagenotloaded } {#2}
   }
   {
-    \__xpg_store_matrixlang:
     \group_begin:
       \bool_set_true:N \l__xpg_inline_lang_bool
       \xpg_otherlanguage:nn{#1}{#3}
@@ -2042,7 +2013,6 @@
       \cs_if_exist_use:c{date@bbl@\babelname}
       \__xpg_lang_set_text_direction:nn{#3}{#4}
     \group_end:
-    \__xpg_reset_to_matrixlang:
   }
 }
 \cs_generate_variant:Nn \__xpg_textlanguage:nnnn {nnen}

Note that I'm not sure why the assignments there are global in the first place. I first noticed it in 035be4e, but it seems strange.

[Udi-Fogiel]

Oh, actually the speed gain was from something else. Still might be worth considering as it is simpler...

[Udi-Fogiel]

Also tested with the examples given in #603

[Udi-Fogiel]

In fact, with this patch it seems like \resetfontlatin is not needed

diff --git a/tex/polyglossia.sty b/tex/polyglossia.sty
index 1df4b59d..19c05ce9 100644
--- a/tex/polyglossia.sty
+++ b/tex/polyglossia.sty
@@ -1662,7 +1662,7 @@
 }

 % This saves the normalfont for the latin script since we may change normalfont in other scripts
-\cs_gset_eq:cc { normalfontlatin } { normalfont }
+\cs_set_eq:cc { normalfontlatin } { normalfont }

 % Provide default fonts (as set with \setmainfont, \setsansfont and \setmonofont)
 % for Latin scripts and as a fallback for non-Latin scripts.
@@ -1694,17 +1694,17 @@
 {
   % This robustifies the redefinitions of \<xx>family (suggestion by Enrico Gregorio)
   % e.g. to prevent expansion of the \familytype redefinition in auxiliary files
-  \tl_gput_right:cn {rmfamily~} {\tl_set:Nn \familytype {rm}}
-  \tl_gput_right:cn {sffamily~} {\tl_set:Nn \familytype {sf}}
-  \tl_gput_right:cn {ttfamily~} {\tl_set:Nn \familytype {tt}}
+  \tl_put_right:cn {rmfamily~} {\tl_set:Nn \familytype {rm}}
+  \tl_put_right:cn {sffamily~} {\tl_set:Nn \familytype {sf}}
+  \tl_put_right:cn {ttfamily~} {\tl_set:Nn \familytype {tt}}
 }

 % These switches activate the default fonts
 % Note that a simple \let\rmfamilylatin=\rmfamily
 % does not work reliably (see #24)
-\cs_gset_eq:cc{rmfamilylatin}{xpg_defaultfont_rm:}
-\cs_gset_eq:cc{sffamilylatin}{xpg_defaultfont_sf:}
-\cs_gset_eq:cc{ttfamilylatin}{xpg_defaultfont_tt:}
+\cs_set_eq:cc{rmfamilylatin}{xpg_defaultfont_rm:}
+\cs_set_eq:cc{sffamilylatin}{xpg_defaultfont_sf:}
+\cs_set_eq:cc{ttfamilylatin}{xpg_defaultfont_tt:}

 \cs_new:Nn \xpg_set_familydefault:
 {
@@ -1720,30 +1720,11 @@
   \__xpg_patch_fontfamilies:
   % This (re-)saves the normalfont for the latin script since we may
   % change normalfont in other scripts
-  \cs_gset_eq:cc{ normalfontlatin }{ normalfont }
+  \cs_set_eq:cc{ normalfontlatin }{ normalfont }
   % And for all cases, we also reset \<xx>familylatin
-  \cs_gset_eq:cc{ rmfamilylatin }{ xpg_defaultfont_rm: }
-  \cs_gset_eq:cc{ sffamilylatin }{ xpg_defaultfont_sf: }
-  \cs_gset_eq:cc{ ttfamilylatin }{ xpg_defaultfont_tt: }
-}
-
-\cs_set_nopar:Npn \resetfontlatin
-{
-  \cs_set_protected:Npn \rmfamily { \xpg_defaultfont_rm: }
-  \cs_set_protected:Npn \sffamily { \xpg_defaultfont_sf: }
-  \cs_set_protected:Npn \ttfamily { \xpg_defaultfont_tt: }
-  \__xpg_patch_fontfamilies:
-  \cs_gset_eq:cc { normalfont } { normalfontlatin }
-}
-
-\cs_set_nopar:Npn \selectfontfamilylatin
-{
-  \str_if_eq:nnTF \familytype { tt }
-    { \ttfamilylatin }
-    { \str_if_eq:nnTF \familytype { sf }
-        { \sffamilylatin }
-        { \rmfamilylatin }
-    }
+  \cs_set_eq:cc{ rmfamilylatin }{ xpg_defaultfont_rm: }
+  \cs_set_eq:cc{ sffamilylatin }{ xpg_defaultfont_sf: }
+  \cs_set_eq:cc{ ttfamilylatin }{ xpg_defaultfont_tt: }
 }

 \cs_set_nopar:Nn \xpg_select_fontfamily:n
@@ -1758,17 +1739,17 @@

 \cs_new_nopar:Nn \xpg_set_normalfont:n
 {
-  \cs_gset_eq:cc { rmfamily } { #1@font@rm }
-  \cs_gset_eq:cc { sffamily } { #1@font@sf }
-  \cs_gset_eq:cc { ttfamily } { #1@font@tt }
-  \cs_gset_nopar:Npn \normalfont 
+  \cs_set_eq:cc { rmfamily } { #1@font@rm }
+  \cs_set_eq:cc { sffamily } { #1@font@sf }
+  \cs_set_eq:cc { ttfamily } { #1@font@tt }
+  \cs_set_nopar:Npn \normalfont 
       { \protect \xpg_select_fontfamily:n {#1}
         \fontseries{\seriesdefault}\selectfont
         \fontshape{\shapedefault}
         \cs_if_exist_use:NT \UseHook { {normalfont} }
         \selectfont
       }
-  \cs_gset_nopar:Npn \reset@font {\protect\normalfont}
+  \cs_set_nopar:Npn \reset@font {\protect\normalfont}
 }

 \cs_gset_eq:cc { @@fterindentfalse } { @afterindentfalse }
@@ -1935,30 +1916,6 @@
   \xpg_set_foreign_language:nn { #1 } { #2 }
 }

-% Stack to store matrix languages
-\seq_new:N \__xpg_current_matrixlang_stack
-
-% Store embedding language when an embedded language is switched to
-\cs_new_nopar:Nn \__xpg_store_matrixlang:
-{
-   \seq_gput_left:Nn \__xpg_current_matrixlang_stack \languagename
-}
-
-% When an embedded language is closed, reset to the embedding language
-% and remove stored matrix language from stack
-\cs_new_nopar:Nn \__xpg_reset_to_matrixlang:
-{
-  % if stack is empty, use main language
-  \seq_gpop_left:NNTF \__xpg_current_matrixlang_stack \l_tmpa_tl
-     { \cs_set_eq:NN \__xpg_current_matrixlang \l_tmpa_tl }
-     { \cs_set_eq:NN \__xpg_current_matrixlang \mainlanguagename }
-  % Reset the language's/script's font families if the embedding script is latin
-  \str_if_eq:eeT{\prop_item:Ne{\g_xpg_langsetup_prop}{\__xpg_current_matrixlang/lcscript}}{latin}
-       {\resetfontlatin}
-  % In case a \<lang>font is defined, re-activate that
-  \exp_args:Ne \xpg_set_normalfont:n{\__xpg_current_matrixlang}
-}
-
 % internal wrapper for foreign language
 % #1 option
 % #2 alias
@@ -1970,12 +1927,10 @@
   {
     \msg_show:nnn { polyglossia } { languagenotloaded } {#2}
   }{
-    \__xpg_store_matrixlang:
     \group_begin:
       \xpg_otherlanguage:nn{ \xpg_alias_add_to_option_i:nn{#2}{#1} }{ #3 }
       \__xpg_lang_set_text_direction:nn{#3}{#4}
     \group_end:
-    \__xpg_reset_to_matrixlang:
   }
 }
 \cs_generate_variant:Nn \__xpg_foreignlanguage:nnnn {eeen}
@@ -1984,11 +1939,9 @@
 % otherlanguage* is the environment equivalent of \foreignlanguage
 \DeclareDocumentEnvironment { otherlanguage* } { O{} m }
   {
-   \__xpg_store_matrixlang:
    \__xpg_otherlanguage:eee { #1 } { #2 } { \xpg_alias_base_lang:n { #2 } }
   }{
    \c_group_end_token% \group_end: does not work here!
-   \__xpg_reset_to_matrixlang:
   }

 % internal wrapper
@@ -2035,7 +1988,6 @@
     \msg_show:nnn { polyglossia } { languagenotloaded } {#2}
   }
   {
-    \__xpg_store_matrixlang:
     \group_begin:
       \bool_set_true:N \l__xpg_inline_lang_bool
       \xpg_otherlanguage:nn{#1}{#3}
@@ -2045,7 +1997,6 @@
       \cs_if_exist_use:c{date@bbl@\babelname}
       \__xpg_lang_set_text_direction:nn{#3}{#4}
     \group_end:
-    \__xpg_reset_to_matrixlang:
   }
 }
 \cs_generate_variant:Nn \__xpg_textlanguage:nnnn {nnen}
@@ -2495,11 +2446,6 @@
     }
   }
   \xpg_set_language_name:nn { #1 } { #2 }
-  % Set the language's/script's font families
-  \str_if_eq:eeT{\prop_item:Nn{\g_xpg_langsetup_prop}{#2/lcscript}} {latin}
-  {
-    \resetfontlatin
-  }
   \bool_if:NF \l__xpg_inline_lang_bool
   { % This for non-inline font switches
     % in case a \<lang>font is defined

[Udi-Fogiel]

Also tested with the example in #164

[Udi-Fogiel]

committed at 75cbd77