Fix switch of language and line spacing in InTitle commands.

Fixes: #9332, #10849
(cherry picked from commit 49e3f8e830)

src/Paragraph.cpp

@@ -2426,7 +2426,9 @@ void Paragraph::latex(BufferParams const & bparams,
 
 	// if the paragraph is empty, the loop will not be entered at all
 	if (empty()) {
-		if (style.isCommand()) {
+		// For InTitle commands, we have already opened a group
+		// in output_latex::TeXOnePar.
+		if (style.isCommand() && style.intitle) {
 			os << '{';
 			++column;
 		}
@@ -2464,7 +2466,9 @@ void Paragraph::latex(BufferParams const & bparams,
 				os << "}] ";
 				column +=3;
 			}
-			if (style.isCommand()) {
+			// For InTitle commands, we have already opened a group
+			// in output_latex::TeXOnePar.
+			if (style.isCommand() && !style.intitle) {
 				os << '{';
 				++column;
 			}

src/Spacing.cpp

@@ -99,6 +99,18 @@ string envName(Spacing::Space space, bool useSetSpace)
 	return useSetSpace ? name : support::ascii_lowercase(name);
 }
 
+string cmdName(Spacing::Space space, bool useSetSpace)
+{
+	static char const * const cmd_names[]
+		= { "SingleSpacing", "OnehalfSpacing", "DoubleSpacing", "SetStretch", ""};
+	string const name = cmd_names[space];
+
+	if (useSetSpace && name == "SetStretch")
+		return "setSpacing";
+
+	return useSetSpace ? name : support::ascii_lowercase(name);
+}
+
 } // namespace
 
 string const Spacing::writeEnvirBegin(bool useSetSpace) const
@@ -118,6 +130,16 @@ string const Spacing::writeEnvirEnd(bool useSetSpace) const
 }
 
 
+string const Spacing::writeCmd(bool useSetSpace) const
+{
+	string const name = cmdName(space, useSetSpace);
+	if (space == Other)
+		return "\\" + name + "{" + getValueAsString() + '}';
+	else
+		return name.empty() ? string() : "\\" + name + "{}";
+}
+
+
 string const Spacing::writePreamble(bool useSetSpace) const
 {
 	string preamble;

src/Spacing.h

@@ -62,6 +62,9 @@ public:
 	std::string const writeEnvirEnd(bool useSetSpace) const;
 	/// useSetSpace is true when using the variant supported by
 	/// the memoir class.
+	std::string const writeCmd(bool useSetSpace) const;
+	/// useSetSpace is true when using the variant supported by
+	/// the memoir class.
 	std::string const writePreamble(bool useSetSpace) const;
 
 private:

src/output_latex.cpp

@@ -812,6 +812,14 @@ void TeXOnePar(Buffer const & buf,
 	bool const using_begin_end = use_polyglossia ||
 					!lang_end_command.empty();
 
+	// For InTitle commands, we need to switch the language inside the command
+	// (see #10849); thus open the command here.
+	bool const intitle_command = style.intitle && style.latextype == LATEX_COMMAND;
+	if (intitle_command) {
+		parStartCommand(par, os, runparams, style);
+		os << '{';
+	}
+
 	// In some insets (such as Arguments), we cannot use \selectlanguage
 	bool const localswitch = text.inset().forceLocalFontSwitch()
 			|| (using_begin_end && text.inset().forcePlainLayout());
@@ -975,19 +983,34 @@ void TeXOnePar(Buffer const & buf,
 			os << "\n\\appendix\n";
 		}
 
-		if (!par.params().spacing().isDefault()
-			&& (pit == 0 || !priorpar->hasSameLayout(par)))
-		{
-			os << from_ascii(par.params().spacing().writeEnvirBegin(useSetSpace))
-			    << '\n';
-		}
+		// InTitle commands must use switches (not environments)
+		// inside the commands (see #9332)
+		if (style.intitle) {
+			if (!par.params().spacing().isDefault())
+			{
+				if (runparams.moving_arg)
+					os << "\\protect";
+				os << from_ascii(par.params().spacing().writeCmd(useSetSpace));
+			}
+		} else {
+			if (!par.params().spacing().isDefault()
+				&& (pit == 0 || !priorpar->hasSameLayout(par)))
+			{
+				os << from_ascii(par.params().spacing().writeEnvirBegin(useSetSpace))
+				    << '\n';
+			}
 
-		if (style.isCommand()) {
-			os << '\n';
+			if (style.isCommand()) {
+				os << '\n';
+			}
 		}
 	}
 
-	parStartCommand(par, os, runparams, style);
+	// For InTitle commands, we already started the command before
+	// the language switch
+	if (!intitle_command)
+		parStartCommand(par, os, runparams, style);
+
 	Font const outerfont = text.outerFont(pit);
 
 	// FIXME UNICODE
@@ -1000,13 +1023,16 @@ void TeXOnePar(Buffer const & buf,
 
 	bool const is_command = style.isCommand();
 
-	if (is_command) {
-		os << '}';
-		if (!style.postcommandargs().empty())
-			latexArgInsets(par, os, runparams, style.postcommandargs(), "post:");
-		if (runparams.encoding != prev_encoding) {
-			runparams.encoding = prev_encoding;
-			os << setEncoding(prev_encoding->iconvName());
+	// InTitle commands need to be closed after the language has been closed.
+	if (!intitle_command) {
+		if (is_command) {
+			os << '}';
+			if (!style.postcommandargs().empty())
+				latexArgInsets(par, os, runparams, style.postcommandargs(), "post:");
+			if (runparams.encoding != prev_encoding) {
+				runparams.encoding = prev_encoding;
+				os << setEncoding(prev_encoding->iconvName());
+			}
 		}
 	}
 
@@ -1039,12 +1065,13 @@ void TeXOnePar(Buffer const & buf,
 	// possible
 	// fall through
 	default:
-		// we don't need it for the last paragraph!!!
-		if (nextpar)
+		// we don't need it for the last paragraph and in InTitle commands!!!
+		if (nextpar && !intitle_command)
 			pending_newline = true;
 	}
 
-	if (par.allowParagraphCustomization()) {
+	// InTitle commands use switches (not environments) for space settings
+	if (par.allowParagraphCustomization() && !style.intitle) {
 		if (!par.params().spacing().isDefault()
 			&& (runparams.isLastPar || !nextpar->hasSameLayout(par))) {
 			if (pending_newline)
@@ -1060,9 +1087,10 @@ void TeXOnePar(Buffer const & buf,
 		}
 	}
 
-	// Closing the language is needed for the last paragraph; it is also
-	// needed if we're within an \L or \R that we may have opened above (not
-	// necessarily in this paragraph) and are about to close.
+	// Closing the language is needed for the last paragraph in a given language
+	// as well as for any InTitleCommand (since these set the language locally);
+	// it is also needed if we're within an \L or \R that we may have opened above
+	// (not necessarily in this paragraph) and are about to close.
 	bool closing_rtl_ltr_environment = !using_begin_end
 		// not for ArabTeX
 		&& (par_language->lang() != "arabic_arabtex"
@@ -1074,7 +1102,8 @@ void TeXOnePar(Buffer const & buf,
 		&&((nextpar && par_lang != nextpar_lang)
 		   || (runparams.isLastPar && par_lang != outer_lang));
 
-	if (closing_rtl_ltr_environment
+	if ((intitle_command && using_begin_end)
+	    || closing_rtl_ltr_environment
 	    || ((runparams.isLastPar || close_lang_switch)
 	        && (par_lang != outer_lang || (using_begin_end
 						&& style.isEnvironment()
@@ -1145,6 +1174,19 @@ void TeXOnePar(Buffer const & buf,
 	if (closing_rtl_ltr_environment)
 		os << "}";
 
+	// InTitle commands need to be closed after the language has been closed.
+	if (intitle_command) {
+		if (is_command) {
+			os << '}';
+			if (!style.postcommandargs().empty())
+				latexArgInsets(par, os, runparams, style.postcommandargs(), "post:");
+			if (runparams.encoding != prev_encoding) {
+				runparams.encoding = prev_encoding;
+				os << setEncoding(prev_encoding->iconvName());
+			}
+		}
+	}
+
 	bool const last_was_separator =
 		par.size() > 0 && par.isEnvSeparator(par.size() - 1);