From 700dd75d5eaeab28997b2ba6f40aedbd3e440ba5 Mon Sep 17 00:00:00 2001
From: Enrico Forestieri <forenr@lyx.org>
Date: Thu, 30 Jul 2009 01:13:11 +0000
Subject: [PATCH] Better fix for bug #5096: Language switch fails in
 environments.

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/branches/BRANCH_1_6_X@30804 a592a061-630c-0410-9148-cb99ea01b6c8
---
 src/output_latex.cpp | 55 +++++++++++++++++++++-----------------------
 1 file changed, 26 insertions(+), 29 deletions(-)

diff --git a/src/output_latex.cpp b/src/output_latex.cpp
index a6abd25aee..fed63b566d 100644
--- a/src/output_latex.cpp
+++ b/src/output_latex.cpp
@@ -52,6 +52,7 @@ enum OpenEncoding {
 
 static int open_encoding_ = none;
 static int cjk_inherited_ = 0;
+Language const * prev_env_language_ = 0;
 
 
 ParagraphList::const_iterator
@@ -119,12 +120,20 @@ TeXEnvironment(Buffer const & buf,
 		bparams.documentClass().plainLayout() : pit->layout();
 
 	ParagraphList const & paragraphs = text.paragraphs();
+	ParagraphList::const_iterator const priorpit =
+		pit == paragraphs.begin() ? pit : boost::prior(pit);
+
+	bool const use_prev_env_language = priorpit->layout().isEnvironment()
+			&& (priorpit->getDepth() > pit->getDepth()
+			    || (priorpit->getDepth() == pit->getDepth()
+				&& priorpit->layout() != pit->layout()));
 
 	Language const * const par_language = pit->getParLanguage(bparams);
 	Language const * const doc_language = bparams.language;
 	Language const * const prev_par_language =
 		(pit != paragraphs.begin())
-		? boost::prior(pit)->getParLanguage(bparams)
+		? (use_prev_env_language ? prev_env_language_
+					 : priorpit->getParLanguage(bparams))
 		: doc_language;
 	if (par_language->babel() != prev_par_language->babel()) {
 
@@ -244,6 +253,7 @@ TeXEnvironment(Buffer const & buf,
 	if (style.isEnvironment()) {
 		os << "\\end{" << from_ascii(style.latexname()) << "}\n";
 		texrow.newline();
+		prev_env_language_ = par_language;
 	}
 
 	if (leftindent_open) {
@@ -342,36 +352,23 @@ TeXOnePar(Buffer const & buf,
 	Language const * const outer_language =
 		(runparams.local_font != 0) ?
 			runparams.local_font->language() : doc_language;
-	// The previous language that was in effect is either the language of
-	// the previous paragraph, if there is one, or else the outer language
-	// if there is no previous paragraph
-	Language const * prev_language =
-		(pit != paragraphs.begin()) ?
-			priorpit->getParLanguage(bparams) : outer_language;
 
-	// When the language is changed at the very start of a LyX environment,
-	// the language switch in the LaTeX code occurs just before switching to
-	// the corresponding LaTeX environment. So, when the environment ends,
-	// we have to restore the language that was in effect.
-	bool env_lang_switch = false;
-	if (!priorpit->hasSameLayout(*pit)) {
-		ParagraphList::const_iterator outpit = priorpit;
-		while (outpit != paragraphs.begin()
-			&& (outpit->hasSameLayout(*priorpit)
-				|| outpit->getDepth() > priorpit->getDepth()))
-			outpit = boost::prior(outpit);
-		ParagraphList::const_iterator const inpit = boost::next(outpit);
-		Language const * const outenv_language
-					= outpit->getParLanguage(bparams);
-		Language const * const inenv_language
-					= inpit->getParLanguage(bparams);
-		if (outenv_language->babel() != inenv_language->babel())
-			env_lang_switch = true;
-		if (outenv_language->babel() != par_language->babel())
-			prev_language = outenv_language;
-	}
+	// The previous language that was in effect is the language of the
+	// previous paragraph, unless the previous paragraph is inside an
+	// environment with nesting depth greater than (or equal to, but with
+	// a different layout) the current one. If there is no previous
+	// paragraph, the previous language is the outer language.
+	bool const use_prev_env_language = priorpit->layout().isEnvironment()
+			&& (priorpit->getDepth() > pit->getDepth()
+			    || (priorpit->getDepth() == pit->getDepth()
+				&& priorpit->layout() != pit->layout()));
+	Language const * const prev_language =
+		(pit != paragraphs.begin())
+		? (use_prev_env_language ? prev_env_language_
+					 : priorpit->getParLanguage(bparams))
+		: outer_language;
 
-	if ((par_language->babel() != prev_language->babel() || env_lang_switch)
+	if (par_language->babel() != prev_language->babel()
 	    // check if we already put language command in TeXEnvironment()
 	    && !(style.isEnvironment()
 		 && (pit == paragraphs.begin() ||