/**
 * \file output_latex.cpp
 * This file is part of LyX, the document processor.
 * Licence details can be found in the file COPYING.
 *
 * \author Lars Gullik Bjønnes
 *
 * Full author contact details are available in file CREDITS.
 */

#include <config.h>

#include "output_latex.h"

#include "BiblioInfo.h"
#include "Buffer.h"
#include "BufferParams.h"
#include "Encoding.h"
#include "Font.h"
#include "InsetList.h"
#include "Language.h"
#include "LyXRC.h"
#include "OutputParams.h"
#include "Paragraph.h"
#include "ParagraphParameters.h"
#include "texstream.h"
#include "TextClass.h"

#include "insets/InsetBibitem.h"
#include "insets/InsetArgument.h"

#include "frontends/alert.h"

#include "support/lassert.h"
#include "support/convert.h"
#include "support/debug.h"
#include "support/lstrings.h"
#include "support/textutils.h"
#include "support/gettext.h"

#include <QThreadStorage>

#include <list>
#include <stack>

using namespace std;
using namespace lyx::support;


namespace lyx {

namespace {

enum OpenEncoding {
	none,
	inputenc,
	CJK
};


struct OutputState
{
	OutputState() : prev_env_language_(nullptr), open_encoding_(none),
		cjk_inherited_(0), nest_level_(0)
	{
	}
	Language const * prev_env_language_;
	stack<int> lang_switch_depth_;          // Both are always empty when
	stack<string> open_polyglossia_lang_;   // not using polyglossia
	OpenEncoding open_encoding_;
	int cjk_inherited_;
	int nest_level_;
};


OutputState * getOutputState()
{
	// FIXME An instance of OutputState should be kept around for each export
	//       instead of using local thread storage
	static QThreadStorage<OutputState *> outputstate;
	if (!outputstate.hasLocalData())
		outputstate.setLocalData(new OutputState);
	return outputstate.localData();
}


string const & openLanguageName(OutputState const * state)
{
	// Return a reference to the last active language opened with
	// polyglossia or when using begin/end commands. If none or when
	// using babel with only a begin command, return a reference to
	// an empty string.

	static string const empty;

	return state->open_polyglossia_lang_.empty()
		? empty
		: state->open_polyglossia_lang_.top();
}


bool atSameLastLangSwitchDepth(OutputState const * state)
{
	// Return true if the actual nest level is the same at which the
	// language was switched when using polyglossia or begin/end
	// commands. Instead, return always true when using babel with
	// only a begin command.

	return state->lang_switch_depth_.empty()
			? true
			: abs(state->lang_switch_depth_.top()) == state->nest_level_;
}


bool isLocalSwitch(OutputState const * state)
{
	// Return true if the language was opened by a local command switch.

	return !state->lang_switch_depth_.empty()
		&& state->lang_switch_depth_.top() < 0;
}


bool langOpenedAtThisLevel(OutputState const * state)
{
	// Return true if the language was opened at the current nesting level.

	return !state->lang_switch_depth_.empty()
		&& abs(state->lang_switch_depth_.top()) == state->nest_level_;
}


string const getPolyglossiaEnvName(Language const * lang)
{
	string result = lang->polyglossia();
	if (result == "arabic")
		// exceptional spelling; see polyglossia docs.
		result = "Arabic";
	return result;
}


string const getPolyglossiaBegin(string const & lang_begin_command,
				 string const & lang, string const & opts,
				 bool const localswitch = false)
{
	string result;
	if (!lang.empty()) {
		// we need to revert the upcasing done in getPolyglossiaEnvName()
		// in case we have a local polyglossia command (\textarabic).
		string language = localswitch ? ascii_lowercase(lang) : lang;
		result = subst(lang_begin_command, "$$lang", language);
	}
	string options = opts.empty() ?
		    string() : "[" + opts + "]";
	result = subst(result, "$$opts", options);

	return result;
}


struct TeXEnvironmentData
{
	Layout const * style;
	Language const * par_language;
	Encoding const * prev_encoding;
	bool cjk_nested;
	bool leftindent_open;
};


static TeXEnvironmentData prepareEnvironment(Buffer const & buf,
					Text const & text,
					ParagraphList::const_iterator pit,
					otexstream & os,
					OutputParams const & runparams)
{
	TeXEnvironmentData data;

	BufferParams const & bparams = buf.params();

	// FIXME This test should not be necessary.
	// We should perhaps issue an error if it is.
	Layout const & style = text.inset().forcePlainLayout() ?
		bparams.documentClass().plainLayout() : pit->layout();

	ParagraphList const & paragraphs = text.paragraphs();
	bool const firstpar = pit == paragraphs.begin();
	ParagraphList::const_iterator const priorpit =
		firstpar ? pit : prev(pit, 1);

	OutputState * state = getOutputState();
	bool const use_prev_env_language = state->prev_env_language_ != nullptr
			&& priorpit->layout().isEnvironment()
			&& (priorpit->getDepth() > pit->getDepth()
			    || (priorpit->getDepth() == pit->getDepth()
				&& priorpit->layout() != pit->layout()));

	data.prev_encoding = runparams.encoding;
	data.par_language = pit->getParLanguage(bparams);
	Language const * const doc_language = bparams.language;
	Language const * const prev_par_language =
		// use font at inset or document language in first paragraph
		firstpar ? (runparams.local_font ?
				    runparams.local_font->language()
				  : doc_language)
			 : (use_prev_env_language ?
				    state->prev_env_language_
				  : priorpit->getParLanguage(bparams));

	bool const use_polyglossia = runparams.use_polyglossia;
	string const par_lang = use_polyglossia ?
		getPolyglossiaEnvName(data.par_language) : data.par_language->babel();
	string const prev_par_lang = use_polyglossia ?
		getPolyglossiaEnvName(prev_par_language) : prev_par_language->babel();
	string const doc_lang = use_polyglossia ?
		getPolyglossiaEnvName(doc_language) : doc_language->babel();
	string const lang_begin_command = use_polyglossia ?
		"\\begin{$$lang}" : lyxrc.language_command_begin;
	string const lang_end_command = use_polyglossia ?
		"\\end{$$lang}" : lyxrc.language_command_end;
	bool const using_begin_end = use_polyglossia ||
					!lang_end_command.empty();

	// For polyglossia, switch language outside of environment, if possible.
	// However, if we are at the start of an inset, do not close languages
	// opened outside.
	if (par_lang != prev_par_lang) {
		if (!firstpar
		    && (!using_begin_end || langOpenedAtThisLevel(state))
		    && !lang_end_command.empty()
		    && prev_par_lang != doc_lang
		    && !prev_par_lang.empty()) {
			os << from_ascii(subst(
				lang_end_command,
				"$$lang",
				prev_par_lang))
			  // the '%' is necessary to prevent unwanted whitespace
			  << "%\n";
			if (using_begin_end)
				popLanguageName();
		}

		// If no language was explicitly opened and we are using
		// polyglossia or begin/end commands, then the current
		// language is the document language.
		string const & cur_lang = using_begin_end
					  && !state->lang_switch_depth_.empty()
						  ? openLanguageName(state)
						  : doc_lang;

		if ((lang_end_command.empty() ||
		    par_lang != doc_lang ||
		    par_lang != cur_lang) &&
		    !par_lang.empty()) {
			    string bc = use_polyglossia ?
					getPolyglossiaBegin(lang_begin_command, par_lang,
							    data.par_language->polyglossiaOpts())
				      : subst(lang_begin_command, "$$lang", par_lang);
			    os << bc;
			    // the '%' is necessary to prevent unwanted whitespace
			    os << "%\n";
			    if (using_begin_end)
				    pushLanguageName(par_lang);
		}
	}

	data.leftindent_open = false;
	if (!pit->params().leftIndent().zero()) {
		os << "\\begin{LyXParagraphLeftIndent}{"
		   << from_ascii(pit->params().leftIndent().asLatexString())
		   << "}\n";
		data.leftindent_open = true;
	}

	if (style.isEnvironment())
		state->nest_level_ += 1;

	if (style.isEnvironment() && !style.latexname().empty()) {
		os << "\\begin{" << from_ascii(style.latexname()) << '}';
		if (!style.latexargs().empty()) {
			OutputParams rp = runparams;
			rp.local_font = &pit->getFirstFontSettings(bparams);
			latexArgInsets(paragraphs, pit, os, rp, style.latexargs());
		}
		if (style.latextype == LATEX_LIST_ENVIRONMENT) {
			os << '{'
			   << pit->params().labelWidthString()
			   << "}\n";
		} else if (style.labeltype == LABEL_BIBLIO) {
			if (pit->params().labelWidthString().empty())
				os << '{' << bibitemWidest(buf, runparams) << "}\n";
			else
				os << '{'
				  << pit->params().labelWidthString()
				  << "}\n";
		} else
			os << from_ascii(style.latexparam()) << '\n';
		if (style.latextype == LATEX_BIB_ENVIRONMENT
		    || style.latextype == LATEX_ITEM_ENVIRONMENT
		    || style.latextype ==  LATEX_LIST_ENVIRONMENT) {
			OutputParams rp = runparams;
			rp.local_font = &pit->getFirstFontSettings(bparams);
			latexArgInsets(paragraphs, pit, os, rp, style.listpreamble(),
				       "listpreamble:");
		}
	}
	data.style = &style;

	// in multilingual environments, the CJK tags have to be nested properly
	data.cjk_nested = false;
	if (!bparams.useNonTeXFonts
	    && (bparams.inputenc == "auto-legacy"
			|| bparams.inputenc == "auto-legacy-plain")
	    && data.par_language->encoding()->package() == Encoding::CJK
	    && state->open_encoding_ != CJK && pit->isMultiLingual(bparams)) {
		if (prev_par_language->encoding()->package() == Encoding::CJK) {
			os << "\\begin{CJK}{"
			   << from_ascii(data.par_language->encoding()->latexName())
			   << "}{" << from_ascii(bparams.fonts_cjk) << "}%\n";
		}
		state->open_encoding_ = CJK;
		data.cjk_nested = true;
	}
	return data;
}


static void finishEnvironment(otexstream & os, OutputParams const & runparams,
			      TeXEnvironmentData const & data, bool const maintext,
			      bool const lastpar)
{
	OutputState * state = getOutputState();
	// BufferParams const & bparams = buf.params();
	// FIXME: for speedup shortcut below, would require passing of "buf" as argument
	if (state->open_encoding_ == CJK && data.cjk_nested) {
		// We need to close the encoding even if it does not change
		// to do correct environment nesting
		os << "\\end{CJK}\n";
		state->open_encoding_ = none;
	}

	if (data.style->isEnvironment()) {
		os << breakln;
		bool const using_begin_end =
			runparams.use_polyglossia ||
				!lyxrc.language_command_end.empty();
		// Close any language opened at this nest level
		if (using_begin_end) {
			while (langOpenedAtThisLevel(state)) {
				if (isLocalSwitch(state)) {
					os << "}";
				} else {
					os << "\\end{"
					   << openLanguageName(state)
					   << "}%\n";
				}
				popLanguageName();
			}
		}
		if (data.style->latextype == LATEX_BIB_ENVIRONMENT)
			// bibliography needs a blank line after
			// each item for backref to function properly
			// (see #12041)
			os << '\n';
		state->nest_level_ -= 1;
		string const & name = data.style->latexname();
		if (!name.empty())
			os << "\\end{" << from_ascii(name) << "}\n";
		state->prev_env_language_ = data.par_language;
		if (runparams.encoding != data.prev_encoding) {
			runparams.encoding = data.prev_encoding;
			os << setEncoding(data.prev_encoding->iconvName());
		}
		// If this is the last par of an inset, the language needs
		// to be closed after the environment
		if (lastpar && !maintext) {
			if (using_begin_end && langOpenedAtThisLevel(state)) {
				if (isLocalSwitch(state)) {
					os << "}";
				} else {
					os << "\\end{"
					   << openLanguageName(state)
					   << "}%\n";
				}
				popLanguageName();
			}
		}
	}

	if (data.leftindent_open) {
		os << breakln << "\\end{LyXParagraphLeftIndent}\n";
		state->prev_env_language_ = data.par_language;
		if (runparams.encoding != data.prev_encoding) {
			runparams.encoding = data.prev_encoding;
			os << setEncoding(data.prev_encoding->iconvName());
		}
	}

	// Check whether we should output a blank line after the environment
	if (!data.style->nextnoindent)
		os << '\n';
}


void TeXEnvironment(Buffer const & buf, Text const & text,
		    OutputParams const & runparams,
		    pit_type & pit, otexstream & os)
{
	ParagraphList const & paragraphs = text.paragraphs();
	ParagraphList::const_iterator ipar = paragraphs.iterator_at(pit);
	LYXERR(Debug::OUTFILE, "TeXEnvironment for paragraph " << pit);

	Layout const & current_layout = ipar->layout();
	depth_type const current_depth = ipar->params().depth();
	Length const & current_left_indent = ipar->params().leftIndent();

	// This is for debugging purpose at the end.
	pit_type const par_begin = pit;
	for (; pit < runparams.par_end; ++pit) {
		ParagraphList::const_iterator par = paragraphs.iterator_at(pit);

		// check first if this is an higher depth paragraph.
		bool go_out = (par->params().depth() < current_depth);
		if (par->params().depth() == current_depth) {
			// This environment is finished.
			go_out |= (par->layout() != current_layout);
			go_out |= (par->params().leftIndent() != current_left_indent);
		}
		if (go_out) {
			// nothing to do here, restore pit and go out.
			pit--;
			break;
		}

		if (par->layout() == current_layout
			&& par->params().depth() == current_depth
			&& par->params().leftIndent() == current_left_indent) {
			// We are still in the same environment so TeXOnePar and continue;
			TeXOnePar(buf, text, pit, os, runparams);
			continue;
		}

		// We are now in a deeper environment.
		// Either par->layout() != current_layout
		// Or     par->params().depth() > current_depth
		// Or     par->params().leftIndent() != current_left_indent)

		// FIXME This test should not be necessary.
		// We should perhaps issue an error if it is.
		bool const force_plain_layout = text.inset().forcePlainLayout();
		Layout const & style = force_plain_layout
			? buf.params().documentClass().plainLayout()
			: par->layout();

		if (!style.isEnvironment()) {
			// This is a standard paragraph, no need to call TeXEnvironment.
			TeXOnePar(buf, text, pit, os, runparams);
			continue;
		}

		// Do not output empty environments if the whole paragraph has
		// been deleted with ct and changes are not output.
		bool output_changes;
		if (!runparams.find_effective())
			output_changes = buf.params().output_changes;
		else
			output_changes = runparams.find_with_deleted();
		if (size_t(pit + 1) < paragraphs.size()) {
			ParagraphList::const_iterator nextpar = paragraphs.iterator_at(pit + 1);
			Paragraph const & cpar = paragraphs.at(pit);
			if ((par->layout() != nextpar->layout()
			     || par->params().depth() == nextpar->params().depth()
			     || par->params().leftIndent() == nextpar->params().leftIndent())
			    && !cpar.empty()
			    && cpar.isDeleted(0, cpar.size()) && !output_changes) {
				if (!output_changes && !cpar.parEndChange().deleted())
					os << '\n' << '\n';
				continue;
			}
		}

		// This is a new environment.
		TeXEnvironmentData const data =
			prepareEnvironment(buf, text, par, os, runparams);
		// Recursive call to TeXEnvironment!
		TeXEnvironment(buf, text, runparams, pit, os);
		bool const lastpar = size_t(pit + 1) >= paragraphs.size();
		finishEnvironment(os, runparams, data, text.isMainText(), lastpar);
	}

	if (pit != runparams.par_end)
		LYXERR(Debug::OUTFILE, "TeXEnvironment for paragraph " << par_begin << " done.");
}


// FIXME: pass the \c required vector by reference and add the stuff
// from \c latexargs to a different vector. This avoids a copy and
// (more importantly?) a coverity defect.
void getArgInsets(otexstream & os, OutputParams const & runparams,
                  Layout::LaTeXArgMap const & latexargs,
                  map<size_t, lyx::InsetArgument const *> const & ilist,
                  vector<string> required, string const & prefix)
{
	size_t const argnr = latexargs.size();
	if (argnr == 0)
		return;

	// Default and preset args are always output, so if they require
	// other arguments, consider this.
	for (auto const & larg : latexargs) {
		Layout::latexarg const & arg = larg.second;
		if ((!arg.presetarg.empty() || !arg.defaultarg.empty()) && !arg.required.empty()) {
				vector<string> req = getVectorFromString(arg.required);
				required.insert(required.end(), req.begin(), req.end());
			}
	}

	for (size_t i = 1; i <= argnr; ++i) {
		map<size_t, InsetArgument const *>::const_iterator lit = ilist.find(i);
		bool inserted = false;
		if (lit != ilist.end()) {
			InsetArgument const * ins = lit->second;
			if (ins) {
				Layout::LaTeXArgMap::const_iterator const lait =
						latexargs.find(ins->name());
				if (lait != latexargs.end()) {
					Layout::latexarg arg = lait->second;
					docstring ldelim;
					docstring rdelim;
					if (!arg.nodelims) {
						ldelim = arg.mandatory ?
							from_ascii("{") : from_ascii("[");
						rdelim = arg.mandatory ?
							from_ascii("}") : from_ascii("]");
					}
					if (!arg.ldelim.empty())
						ldelim = arg.ldelim;
					if (!arg.rdelim.empty())
						rdelim = arg.rdelim;
					ins->latexArgument(os, runparams, ldelim, rdelim, arg.presetarg);
					if (prefix == "listpreamble:")
						os << breakln;
					inserted = true;
				}
			}
		}
		if (!inserted) {
			Layout::LaTeXArgMap::const_iterator lait = latexargs.begin();
			Layout::LaTeXArgMap::const_iterator const laend = latexargs.end();
			for (; lait != laend; ++lait) {
				string const name = prefix + convert<string>(i);
				if ((*lait).first == name) {
					Layout::latexarg arg = (*lait).second;
					docstring preset = arg.presetarg;
					if (!arg.defaultarg.empty()) {
						if (!preset.empty())
							preset += ",";
						preset += arg.defaultarg;
					}
					if (arg.mandatory) {
						docstring ldelim = arg.ldelim.empty() ?
								from_ascii("{") : arg.ldelim;
						docstring rdelim = arg.rdelim.empty() ?
								from_ascii("}") : arg.rdelim;
						os << ldelim << preset << rdelim;
					} else if (!preset.empty()) {
						docstring ldelim = arg.ldelim.empty() ?
								from_ascii("[") : arg.ldelim;
						docstring rdelim = arg.rdelim.empty() ?
								from_ascii("]") : arg.rdelim;
						os << ldelim << preset << rdelim;
					} else if (find(required.begin(), required.end(),
						   (*lait).first) != required.end()) {
						docstring ldelim = arg.ldelim.empty() ?
								from_ascii("[") : arg.ldelim;
						docstring rdelim = arg.rdelim.empty() ?
								from_ascii("]") : arg.rdelim;
						os << ldelim << rdelim;
					} else
						break;
				}
			}
		}
	}
	if (runparams.find_effective() && argnr > 1) {
		// Mark end of arguments for findadv() only
		os << "\\endarguments{}";
	}
}


} // namespace


void pushLanguageName(string const & lang_name, bool localswitch)
{
	OutputState * state = getOutputState();

	int nest_level = localswitch ? -state->nest_level_ : state->nest_level_;
	state->lang_switch_depth_.push(nest_level);
	state->open_polyglossia_lang_.push(lang_name);
}


void popLanguageName()
{
	OutputState * state = getOutputState();

	state->lang_switch_depth_.pop();
	state->open_polyglossia_lang_.pop();
}


bool languageStackEmpty()
{
	OutputState * state = getOutputState();

	return state->lang_switch_depth_.empty();
}


string const & openLanguageName()
{
	OutputState * state = getOutputState();

	return openLanguageName(state);
}


namespace {

void addArgInsets(Paragraph const & par, string const & prefix,
                 Layout::LaTeXArgMap const & latexargs,
                 map<size_t, InsetArgument const *> & ilist,
                 vector<string> & required)
{
	for (auto const & table : par.insetList()) {
		InsetArgument const * arg = table.inset->asInsetArgument();
		if (!arg)
			continue;
		if (arg->name().empty()) {
			LYXERR0("Error: Unnamed argument inset!");
			continue;
		}
		string const name = prefix.empty() ?
			arg->name() : split(arg->name(), ':');
		size_t const nr = convert<size_t>(name);
		ilist.insert({nr, arg});
		Layout::LaTeXArgMap::const_iterator const lit =
			latexargs.find(arg->name());
		if (lit != latexargs.end()) {
			Layout::latexarg const & larg = lit->second;
			vector<string> req = getVectorFromString(larg.required);
			move(req.begin(), req.end(), back_inserter(required));
		}
	}
}

} // namespace


void latexArgInsets(Paragraph const & par, otexstream & os,
                    OutputParams const & runparams,
                    Layout::LaTeXArgMap const & latexargs,
                    string const & prefix)
{
	map<size_t, InsetArgument const *> ilist;
	vector<string> required;
	addArgInsets(par, prefix, latexargs, ilist, required);
	getArgInsets(os, runparams, latexargs, ilist, required, prefix);
}


void latexArgInsets(ParagraphList const & pars,
                    ParagraphList::const_iterator pit,
                    otexstream & os, OutputParams const & runparams,
                    Layout::LaTeXArgMap const & latexargs,
                    string const & prefix)
{
	map<size_t, InsetArgument const *> ilist;
	vector<string> required;

	depth_type const current_depth = pit->params().depth();
	Layout const current_layout = pit->layout();

	// get the first paragraph in sequence with this layout and depth
	ptrdiff_t offset = 0;
	while (true) {
		if (prev(pit, offset) == pars.begin())
			break;
		ParagraphList::const_iterator priorpit = prev(pit, offset + 1);
		if (priorpit->layout() == current_layout
		    && priorpit->params().depth() == current_depth)
			++offset;
		else
			break;
	}

	ParagraphList::const_iterator spit = prev(pit, offset);
	for (; spit != pars.end(); ++spit) {
		if (spit->layout() != current_layout ||
		    spit->params().depth() < current_depth)
			break;
		if (spit->params().depth() > current_depth)
			continue;
		addArgInsets(*spit, prefix, latexargs, ilist, required);
	}
	getArgInsets(os, runparams, latexargs, ilist, required, prefix);
}


void latexArgInsetsForParent(ParagraphList const & pars, otexstream & os,
                             OutputParams const & runparams,
                             Layout::LaTeXArgMap const & latexargs,
                             string const & prefix)
{
	map<size_t, InsetArgument const *> ilist;
	vector<string> required;

	for (Paragraph const & par : pars) {
		if (par.layout().hasArgs())
			// The InsetArguments inside this paragraph refer to this paragraph
			continue;
		addArgInsets(par, prefix, latexargs, ilist, required);
	}
	getArgInsets(os, runparams, latexargs, ilist, required, prefix);
}


namespace {

// output the proper paragraph start according to latextype.
void parStartCommand(Paragraph const & par, otexstream & os,
		     OutputParams const & runparams, Layout const & style)
{
	switch (style.latextype) {
	case LATEX_COMMAND:
		if (par.needsCProtection(runparams.moving_arg)) {
			if (contains(runparams.active_chars, '^'))
				// cprotect relies on ^ being on catcode 7
				os << "\\begingroup\\catcode`\\^=7";
			os << "\\cprotect";
		}
		os << '\\' << from_ascii(style.latexname());

		// Command arguments
		if (!style.latexargs().empty())
			latexArgInsets(par, os, runparams, style.latexargs());
		os << from_ascii(style.latexparam());
		break;
	case LATEX_ITEM_ENVIRONMENT:
	case LATEX_LIST_ENVIRONMENT:
		if (runparams.find_effective()) {
			os << "\\" + style.itemcommand() << "{" << style.latexname() << "}";
		}
		else {
			os << "\\" + style.itemcommand();
			// Item arguments
			if (!style.itemargs().empty())
				latexArgInsets(par, os, runparams, style.itemargs(), "item:");
			os << " ";
		}
		break;
	case LATEX_ENVIRONMENT:
		if (runparams.find_effective()) {
			os << "\\latexenvironment{" << style.latexname() << "}{";
		}
		break;
	case LATEX_BIB_ENVIRONMENT:
		// ignore this, the inset will write itself
		break;
	default:
		break;
	}
}

} // namespace

// FIXME: this should be anonymous
void TeXOnePar(Buffer const & buf,
	       Text const & text,
	       pit_type pit,
	       otexstream & os,
	       OutputParams const & runparams_in,
	       string const & everypar,
	       int start_pos, int end_pos,
	       bool const force)
{
	BufferParams const & bparams = runparams_in.is_child
		? buf.masterParams() : buf.params();
	ParagraphList const & paragraphs = text.paragraphs();
	Paragraph const & par = paragraphs.at(pit);
	// FIXME This check should not really be needed.
	// Perhaps we should issue an error if it is.
	Layout const & style = text.inset().forcePlainLayout() ?
		bparams.documentClass().plainLayout() : par.layout();

	if (style.inpreamble && !force)
		return;

	// Do not output empty commands if the whole paragraph has
	// been deleted with ct and changes are not output.
	if (!runparams_in.find_with_deleted() && style.latextype != LATEX_ENVIRONMENT
	    && !par.empty() && par.isDeleted(0, par.size()) && !bparams.output_changes)
		return;

	LYXERR(Debug::OUTFILE, "TeXOnePar for paragraph " << pit << " ptr " << &par << " '"
	                                                  << everypar << "'");

	OutputParams runparams = runparams_in;
	runparams.isLastPar = (pit == pit_type(paragraphs.size() - 1));
	// We reinitialize par begin and end to be on the safe side
	// with embedded inset as we don't know if they set those
	// value correctly.
	runparams.par_begin = 0;
	runparams.par_end = 0;

	bool const maintext = text.isMainText();
	// we are at the beginning of an inset and CJK is already open;
	// we count inheritation levels to get the inset nesting right.
	OutputState * state = getOutputState();
	if (pit == 0 && !maintext
	    && (state->cjk_inherited_ > 0 || state->open_encoding_ == CJK)) {
		state->cjk_inherited_ += 1;
		state->open_encoding_ = none;
	}

	// This paragraph is merged and we do not show changes in the output
	bool const merged_par = !bparams.output_changes && par.parEndChange().deleted();

	if (text.inset().isPassThru()) {
		Font const outerfont = text.outerFont(pit);

		// No newline before first paragraph in this lyxtext
		if (pit > 0 && !text.inset().getLayout().parbreakIgnored() && !merged_par) {
			os << '\n';
			if (!text.inset().getLayout().parbreakIsNewline())
				os << '\n';
		}

		par.latex(bparams, outerfont, os, runparams, start_pos, end_pos, force);
		return;
	}

	Paragraph const * nextpar = runparams.isLastPar
		? nullptr : &paragraphs.at(pit + 1);

	bool const intitle_command = style.intitle && style.isCommand();
	// Intitle commands switch languages locally, thus increase
	// language nesting level
	if (intitle_command)
		state->nest_level_ += 1;

	if (style.pass_thru) {
		Font const outerfont = text.outerFont(pit);
		parStartCommand(par, os, runparams, style);
		if (style.isCommand() && style.needprotect)
			// Due to the moving argument, some fragile
			// commands (labels, index entries)
			// are output after this command (#2154)
			runparams.postpone_fragile_stuff =
				bparams.postpone_fragile_content;
		if (intitle_command)
			os << '{';

		par.latex(bparams, outerfont, os, runparams, start_pos, end_pos, force);

		// I did not create a parEndCommand for this minuscule
		// task because in the other user of parStartCommand
		// the code is different (JMarc)
		if (style.isCommand()) {
			os << "}";
			if (par.needsCProtection(runparams.moving_arg)
			    && contains(runparams.active_chars, '^'))
				os << "\\endgroup";
			if (merged_par)
				os << "{}";
			else
				os << "\n";
		}
		else if (!merged_par)
			os << '\n';
		if (!style.parbreak_is_newline && !merged_par) {
			os << '\n';
		} else if (nextpar && !style.isEnvironment()) {
			Layout const nextstyle = text.inset().forcePlainLayout()
				? bparams.documentClass().plainLayout()
				: nextpar->layout();
			if (nextstyle.name() != style.name() && !merged_par)
				os << '\n';
		}

		return;
	}

	// This paragraph's language
	Language const * const par_language = par.getParLanguage(bparams);
	Language const * const nextpar_language = nextpar ?
		nextpar->getParLanguage(bparams) : nullptr;
	// The document's language
	Language const * const doc_language = bparams.language;
	// The language that was in effect when the environment this paragraph is
	// inside of was opened
	Language const * const outer_language =
		(runparams.local_font != nullptr) ?
			runparams.local_font->language() : doc_language;

	Paragraph const * priorpar = (pit == 0) ? nullptr : &paragraphs.at(pit - 1);

	// 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.
	// Note further that we take the outer language also if the prior par
	// is PassThru, since in that case it has latex_language, and all secondary
	// languages have been closed (#10793).
	bool const use_prev_env_language = state->prev_env_language_ != nullptr
			&& priorpar
			&& priorpar->layout().isEnvironment()
			&& (priorpar->getDepth() > par.getDepth()
			    || (priorpar->getDepth() == par.getDepth()
				&& priorpar->layout() != par.layout()));

	// We need to ignore previous intitle commands since languages
	// are switched locally there (# 11514)
	// There might be paragraphs before the title, so we check this.
	Paragraph * prior_nontitle_par = nullptr;
	if (!intitle_command) {
		pit_type ppit = pit;
		while (ppit > 0) {
			--ppit;
			Paragraph const * tmppar = &paragraphs.at(ppit);
			if (tmppar->layout().intitle && tmppar->layout().isCommand())
				continue;
			prior_nontitle_par = const_cast<Paragraph*>(tmppar);
			break;
		}
	}
	bool const have_prior_nptpar =
			prior_nontitle_par && !prior_nontitle_par->isPassThru();
	Language const * const prev_language =
		runparams_in.find_effective()
			? languages.getLanguage("ignore")
			: (have_prior_nptpar)
				? (use_prev_env_language 
					? state->prev_env_language_
					: prior_nontitle_par->getParLanguage(bparams))
				: outer_language;

	bool const use_polyglossia = runparams.use_polyglossia;
	string const par_lang = use_polyglossia ?
		getPolyglossiaEnvName(par_language): par_language->babel();
	string const prev_lang = use_polyglossia ?
		getPolyglossiaEnvName(prev_language) : prev_language->babel();
	string const outer_lang = use_polyglossia ?
		getPolyglossiaEnvName(outer_language) : outer_language->babel();
	string const nextpar_lang = nextpar_language ? (use_polyglossia ?
		getPolyglossiaEnvName(nextpar_language) :
		nextpar_language->babel()) : string();
	string lang_begin_command = use_polyglossia ?
		"\\begin{$$lang}$$opts" : lyxrc.language_command_begin;
	string lang_end_command = use_polyglossia ?
		"\\end{$$lang}" : lyxrc.language_command_end;
	// the '%' is necessary to prevent unwanted whitespace
	string lang_command_termination = "%\n";
	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.
	if (intitle_command) {
		parStartCommand(par, os, runparams, style);
		if (style.isCommand() && style.needprotect)
			// Due to the moving argument, some fragile
			// commands (labels, index entries)
			// are output after this command (#2154)
			runparams.postpone_fragile_stuff =
				bparams.postpone_fragile_content;
		os << '{';
	}

	// In some insets (such as Arguments), we cannot use \selectlanguage.
	// Also, if an RTL language is set via environment in polyglossia,
	// only a nested \\text<lang> command will reset the direction for LTR
	// languages (see # 10111).
	bool const in_polyglossia_rtl_env =
		use_polyglossia
		&& runparams.local_font != nullptr
		&& outer_language->rightToLeft()
		&& !par_language->rightToLeft()
		&& !(have_prior_nptpar
		     && (prev_language->rightToLeft() != par_language->rightToLeft()));
	bool const localswitch =
			(runparams_in.find_effective()
			|| text.inset().forceLocalFontSwitch()
			|| (using_begin_end && text.inset().forcePlainLayout())
			|| in_polyglossia_rtl_env)
			&& !text.inset().forceParDirectionSwitch();
	if (localswitch) {
		lang_begin_command = use_polyglossia ?
			    "\\text$$lang$$opts{" : lyxrc.language_command_local;
		lang_end_command = "}";
		lang_command_termination.clear();
	}

	bool const localswitch_needed = localswitch && par_lang != outer_lang;

	// localswitches need to be closed and reopened at each par
	if (runparams_in.find_effective() || ((par_lang != prev_lang || localswitch_needed)
	     // check if we already put language command in TeXEnvironment()
	     && !(style.isEnvironment()
		  && (pit == 0 || (priorpar->layout() != par.layout()
			           && priorpar->getDepth() <= par.getDepth())
		      || priorpar->getDepth() < par.getDepth())))) {
		if (!localswitch
		    && (!using_begin_end || langOpenedAtThisLevel(state))
		    && !lang_end_command.empty()
		    && prev_lang != outer_lang
		    && !prev_lang.empty()
		    && (!using_begin_end || !style.isEnvironment())) {
			os << from_ascii(subst(lang_end_command,
					       "$$lang",
					       prev_lang))
			   << lang_command_termination;
			if (using_begin_end)
				popLanguageName();
		}

		// We need to open a new language if we couldn't close the previous
		// one (because there's no language_command_end); and even if we closed
		// the previous one, if the current language is different than the
		// outer_language (which is currently in effect once the previous one
		// is closed).
		if ((lang_end_command.empty() || par_lang != outer_lang
		     || (!using_begin_end
			 || (style.isEnvironment() && par_lang != prev_lang)))
			&& !par_lang.empty()) {
			// If we're inside an inset, and that inset is within an \L or \R
			// (or equivalents), then within the inset, too, any opposite
			// language paragraph should appear within an \L or \R (in addition
			// to, outside of, the normal language switch commands).
			// This behavior is not correct for ArabTeX, though.
			if (!using_begin_end
			    // not for ArabTeX
			    && par_language->lang() != "arabic_arabtex"
			    && outer_language->lang() != "arabic_arabtex"
			    // are we in an inset?
			    && runparams.local_font != nullptr
			    // is the inset within an \L or \R?
			    //
			    // FIXME: currently, we don't check this; this means that
			    // we'll have unnnecessary \L and \R commands, but that
			    // doesn't seem to hurt (though latex will complain)
			    //
			    // is this paragraph in the opposite direction?
			    && runparams.local_font->isRightToLeft() != par_language->rightToLeft()) {
				// FIXME: I don't have a working copy of the Arabi package, so
				// I'm not sure if the farsi and arabic_arabi stuff is correct
				// or not...
				if (par_language->lang() == "farsi")
					os << "\\textFR{";
				else if (outer_language->lang() == "farsi")
					os << "\\textLR{";
				else if (par_language->lang() == "arabic_arabi")
					os << "\\textAR{";
				else if (outer_language->lang() == "arabic_arabi")
					os << "\\textLR{";
				// remaining RTL languages currently is hebrew
				else if (par_language->rightToLeft() && !runparams.isFullUnicode())
					os << "\\R{";
				else
					os << "\\L{";
			}
			// With CJK, the CJK tag has to be closed first (see below)
			if ((runparams.encoding->package() != Encoding::CJK
				 || bparams.useNonTeXFonts
				 || runparams.find_effective())
			    && (par_lang != openLanguageName(state) || localswitch || intitle_command)
			    && !par_lang.empty()) {
				string bc = use_polyglossia ?
					  getPolyglossiaBegin(lang_begin_command, par_lang,
					  		      par_language->polyglossiaOpts(),
					  		      localswitch)
					  : subst(lang_begin_command, "$$lang", par_lang);
				os << bc;
				os << lang_command_termination;
				if (using_begin_end)
					pushLanguageName(par_lang, localswitch);
			}
		}
	}

	// Switch file encoding if necessary; no need to do this for "auto-legacy-plain"
	// encoding, since this only affects the position of the outputted
	// \inputencoding command; the encoding switch will occur when necessary
	if (bparams.inputenc == "auto-legacy"
		&& !runparams.isFullUnicode() // Xe/LuaTeX use one document-wide encoding  (see also switchEncoding())
		&& runparams.encoding->package() != Encoding::japanese
		&& runparams.encoding->package() != Encoding::none) {
		// Look ahead for future encoding changes.
		// We try to output them at the beginning of the paragraph,
		// since the \inputencoding command is not allowed e.g. in
		// sections. For this reason we only set runparams.moving_arg
		// after checking for the encoding change, otherwise the
		// change would be always avoided by switchEncoding().
		for (pos_type i = 0; i < par.size(); ++i) {
			char_type const c = par.getChar(i);
			Encoding const * const encoding =
				par.getFontSettings(bparams, i).language()->encoding();
			if (encoding->package() != Encoding::CJK
				&& runparams.encoding->package() == Encoding::inputenc
				&& isASCII(c))
				continue;
			if (par.isInset(i))
				break;
			// All characters before c are in the ASCII range, and
			// c is non-ASCII (but no inset), so change the
			// encoding to that required by the language of c.
			// With CJK, only add switch if we have CJK content at the beginning
			// of the paragraph
			if (i != 0 && encoding->package() == Encoding::CJK)
				continue;

			pair<bool, int> enc_switch = switchEncoding(os.os(),
						bparams, runparams, *encoding);
			// the following is necessary after a CJK environment in a multilingual
			// context (nesting issue).
			if (par_language->encoding()->package() == Encoding::CJK
				&& state->open_encoding_ != CJK && state->cjk_inherited_ == 0) {
				os << "\\begin{CJK}{"
				   << from_ascii(par_language->encoding()->latexName())
				   << "}{" << from_ascii(bparams.fonts_cjk) << "}%\n";
				state->open_encoding_ = CJK;
			}
			if (encoding->package() != Encoding::none && enc_switch.first) {
				if (enc_switch.second > 0) {
					// the '%' is necessary to prevent unwanted whitespace
					os << "%\n";
				}
				// With CJK, the CJK tag had to be closed first (see above)
				if (runparams.encoding->package() == Encoding::CJK
				    && par_lang != openLanguageName(state)
				    && !par_lang.empty()) {
					os << subst(lang_begin_command, "$$lang", par_lang)
					   << lang_command_termination;
					if (using_begin_end)
						pushLanguageName(par_lang, localswitch);
				}
				runparams.encoding = encoding;
			}
			break;
		}
	}

	runparams.moving_arg |= style.needprotect;
	if (style.needmboxprotect)
		++runparams.inulemcmd;
	Encoding const * const prev_encoding = runparams.encoding;

	bool const useSetSpace = bparams.documentClass().provides("SetSpace");
	if (par.allowParagraphCustomization()) {
		if (par.params().startOfAppendix()) {
			os << "\n\\appendix\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';
			}
		}
	}

	// For InTitle commands, we already started the command before
	// the language switch
	if (!intitle_command) {
		parStartCommand(par, os, runparams, style);
		if (style.isCommand() && style.needprotect)
			// Due to the moving argument, some fragile
			// commands (labels, index entries)
			// are output after this command (#2154)
			runparams.postpone_fragile_stuff =
				bparams.postpone_fragile_content;
	}

	Font const outerfont = text.outerFont(pit);

	// FIXME UNICODE
	os << from_utf8(everypar);
	par.latex(bparams, outerfont, os, runparams, start_pos, end_pos, force);

	Font const font = par.empty()
		 ? par.getLayoutFont(bparams, outerfont)
		 : par.getFont(bparams, par.size() - 1, outerfont);

	bool const is_command = style.isCommand();

	bool const last_was_separator =
		!par.empty() && par.isEnvSeparator(par.size() - 1);

	// InTitle commands need to be closed after the language has been closed.
	if (!intitle_command) {
		if (is_command) {
			// Signify added/deleted par break in output if show changes in output
			if (nextpar && !os.afterParbreak() && !last_was_separator
			    && bparams.output_changes && par.parEndChange().changed()) {
				Changes::latexMarkChange(os, bparams, Change(Change::UNCHANGED),
							 par.parEndChange(), runparams);
				os << bparams.encoding().latexString(docstring(1, 0x00b6)).first << "}";
			}
			os << '}';
			if (!style.postcommandargs().empty())
				latexArgInsets(par, os, runparams, style.postcommandargs(), "post:");
			if (!runparams.post_macro.empty()) {
				// Output the stored fragile commands (labels, indices etc.)
				// that need to be output after the command with moving argument.
				os << runparams.post_macro;
				runparams.post_macro.clear();
			}
			if (par.needsCProtection(runparams.moving_arg)
			    && contains(runparams.active_chars, '^'))
				os << "\\endgroup";
			if (runparams.encoding != prev_encoding) {
				runparams.encoding = prev_encoding;
				os << setEncoding(prev_encoding->iconvName());
			}
		}
	}

	bool pending_newline = false;
	bool unskip_newline = false;
	bool close_lang_switch = false;
	switch (style.latextype) {
	case LATEX_ITEM_ENVIRONMENT:
	case LATEX_LIST_ENVIRONMENT:
		if ((nextpar && par_lang != nextpar_lang
			     && nextpar->getDepth() == par.getDepth())
		    || (atSameLastLangSwitchDepth(state) && nextpar
			    && nextpar->getDepth() < par.getDepth()))
			close_lang_switch = using_begin_end;
		if (nextpar && par.params().depth() < nextpar->params().depth())
			pending_newline = !text.inset().getLayout().parbreakIgnored() && !merged_par;
		break;
	case LATEX_ENVIRONMENT: {
		// if it's the last paragraph of the current environment
		// skip it otherwise fall through
		if (nextpar
		    && ((nextpar->layout() != par.layout()
			   || nextpar->params().depth() != par.params().depth())
			|| (!using_begin_end || par_lang != nextpar_lang)))
		{
			close_lang_switch = using_begin_end;
			break;
		}
	}
	// possible
	// fall through
	default:
		// we don't need it for the last paragraph and in InTitle commands!!!
		if (nextpar && !intitle_command)
			pending_newline = !text.inset().getLayout().parbreakIgnored() && !merged_par;
	}

	// 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)
				os << '\n';

			string const endtag =
				par.params().spacing().writeEnvirEnd(useSetSpace);
			if (prefixIs(endtag, "\\end{"))
				os << breakln;

			os << from_ascii(endtag);
			pending_newline = true;
		}
	}

	// 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"
		    && outer_language->lang() != "arabic_arabtex")
		// have we opened an \L or \R environment?
		&& runparams.local_font != nullptr
		&& runparams.local_font->isRightToLeft() != par_language->rightToLeft()
		// are we about to close the language?
		&&((nextpar && par_lang != nextpar_lang)
		   || (runparams.isLastPar && par_lang != outer_lang));

	if (localswitch_needed
	    || (intitle_command && using_begin_end)
	    || closing_rtl_ltr_environment
	    || (((runparams.isLastPar
		  && (using_begin_end
		      // Since \selectlanguage write the language to the aux file,
		      // we need to reset the language at the end of footnote or
		      // float.
		      || runparams.inFloat != OutputParams::NONFLOAT || runparams.inFootnote
		      // Same for maintext in children (see below)
		      || maintext))
		 || close_lang_switch)
	        && (par_lang != outer_lang || (using_begin_end
						&& style.isEnvironment()
						&& par_lang != nextpar_lang)))) {

		if (!localswitch && (pending_newline || close_lang_switch))
			os << '\n';

		// when the paragraph uses CJK, the language has to be closed earlier
		if ((font.language()->encoding()->package() != Encoding::CJK)
			|| bparams.useNonTeXFonts
			|| runparams_in.find_effective()) {
			if (lang_end_command.empty()) {
				// If this is a child, we should restore the
				// master language after the last paragraph.
				Language const * const current_language =
					(runparams.isLastPar && runparams.master_language)
						? runparams.master_language
						: outer_language;
				string const current_lang = use_polyglossia
					? getPolyglossiaEnvName(current_language)
					: current_language->babel();
				if (!current_lang.empty()
				    && current_lang != openLanguageName(state)) {
					string bc = use_polyglossia ?
						    getPolyglossiaBegin(lang_begin_command, current_lang,
									current_language->polyglossiaOpts(),
									localswitch)
						  : subst(lang_begin_command, "$$lang", current_lang);
					os << bc;
					pending_newline = !localswitch
							&& !text.inset().getLayout().parbreakIgnored();
					unskip_newline = !localswitch;
					if (using_begin_end)
						pushLanguageName(current_lang, localswitch);
				}
			} else if ((!using_begin_end ||
				    langOpenedAtThisLevel(state)) &&
				   !par_lang.empty()) {
				// If we are in an environment, we have to
				// close the "outer" language afterwards
				string const & cur_lang = openLanguageName(state);
				if (!style.isEnvironment()
				    || (close_lang_switch
					&& atSameLastLangSwitchDepth(state)
					&& par_lang != outer_lang
					&& (par_lang != cur_lang
					    || (cur_lang != outer_lang
						&& nextpar
						&& style != nextpar->layout())))
				    || (atSameLastLangSwitchDepth(state)
					&& !state->lang_switch_depth_.empty()
					&& cur_lang != par_lang)
				    || in_polyglossia_rtl_env)
				{
					if (using_begin_end && !localswitch)
						os << breakln;
					os << from_ascii(subst(
						lang_end_command,
						"$$lang",
						par_lang));
					pending_newline = !localswitch
							&& !text.inset().getLayout().parbreakIgnored();
					unskip_newline = !localswitch;
					if (using_begin_end)
						popLanguageName();
				}
			}
		}
	}
	if (closing_rtl_ltr_environment)
		os << "}";

	// InTitle commands need to be closed after the language has been closed.
	if (intitle_command) {
		os << '}';
		if (!style.postcommandargs().empty())
			latexArgInsets(par, os, runparams, style.postcommandargs(), "post:");
		if (!runparams.post_macro.empty()) {
			// Output the stored fragile commands (labels, indices etc.)
			// that need to be output after the command with moving argument.
			os << runparams.post_macro;
			runparams.post_macro.clear();
		}
		if (par.needsCProtection(runparams.moving_arg)
		    && contains(runparams.active_chars, '^'))
			os << "\\endgroup";
		if (runparams.encoding != prev_encoding) {
			runparams.encoding = prev_encoding;
			os << setEncoding(prev_encoding->iconvName());
		}
	}

	// Signify added/deleted par break in output if show changes in output
	if ((intitle_command || !is_command) && nextpar && !os.afterParbreak() && !last_was_separator
	    && bparams.output_changes && par.parEndChange().changed()) {
		Changes::latexMarkChange(os, bparams, Change(Change::UNCHANGED),
					 par.parEndChange(), runparams);
		os << bparams.encoding().latexString(docstring(1, 0x00b6)).first << "}";
	}

	if (pending_newline) {
		if (unskip_newline)
			// prevent unwanted whitespace
			os << '%';
		if (!os.afterParbreak() && !last_was_separator)
			os << '\n';
	}

	// if this is a CJK-paragraph and the next isn't, close CJK
	// also if the next paragraph is a multilingual environment (because of nesting)
	if (nextpar && state->open_encoding_ == CJK
		&& bparams.encoding().iconvName() != "UTF-8"
		&& bparams.encoding().package() != Encoding::CJK
		&& ((nextpar_language &&
			nextpar_language->encoding()->package() != Encoding::CJK)
			|| (nextpar->layout().isEnvironment() && nextpar->isMultiLingual(bparams)))
		// inbetween environments, CJK has to be closed later (nesting!)
		&& (!style.isEnvironment() || !nextpar->layout().isEnvironment())) {
		os << "\\end{CJK}\n";
		state->open_encoding_ = none;
	}

	// If this is the last paragraph, close the CJK environment
	// if necessary. If it's an environment or nested in an environment,
	// we'll have to \end that first.
	if (runparams.isLastPar && !style.isEnvironment()
		&& par.params().depth() < 1) {
		switch (state->open_encoding_) {
			case CJK: {
				// do nothing at the end of child documents
				if (maintext && buf.masterBuffer() != &buf)
					break;
				// end of main text: also insert a \clearpage (see #5386)
				if (maintext) {
					os << "\n\\clearpage\n\\end{CJK}\n";
				// end of an inset
				} else
					os << "\\end{CJK}";
				state->open_encoding_ = none;
				break;
			}
			case inputenc: {
				// FIXME: If we are in an inset and the switch happened outside this inset,
				// do not switch back at the end of the inset (bug #8479)
				// The following attempt does not help with listings-caption in a CJK document:
				// if (runparams_in.local_font != 0
				//    && runparams_in.encoding == runparams_in.local_font->language()->encoding())
				//	break;
				os << "\\egroup";
				state->open_encoding_ = none;
				break;
			}
			case none:
			default:
				// do nothing
				break;
		}
	}

	// Information about local language is stored as a font feature.
	// If this is the last paragraph of the inset and a local_font was set upon entering
	// and we are mixing encodings ("auto-legacy" or "auto-legacy-plain" and no XeTeX or LuaTeX),
	// ensure the encoding is set back to the default encoding of the local language.
	if (runparams.isLastPar && runparams_in.local_font != nullptr
	    && runparams_in.encoding != runparams_in.local_font->language()->encoding()
	    && (bparams.inputenc == "auto-legacy" || bparams.inputenc == "auto-legacy-plain")
		&& !runparams.isFullUnicode()
	   ) {
		runparams_in.encoding = runparams_in.local_font->language()->encoding();
		os << setEncoding(runparams_in.encoding->iconvName());
	}
	// Otherwise, the current encoding should be set for the next paragraph.
	else
		runparams_in.encoding = runparams.encoding;

	// Also pass the post_macros upstream
	runparams_in.post_macro = runparams.post_macro;
	// These need to be passed upstream as well
	runparams_in.need_maketitle = runparams.need_maketitle;
	runparams_in.have_maketitle = runparams.have_maketitle;


	// we don't need a newline for the last paragraph!!!
	// Note from JMarc: we will re-add a \n explicitly in
	// TeXEnvironment, because it is needed in this case
	if (nextpar && !os.afterParbreak() && !last_was_separator) {
		if (!text.inset().getLayout().parbreakIgnored() && !merged_par)
			// Make sure to start a new line
			os << breakln;
		// A newline '\n' is always output before a command,
		// so avoid doubling it.
		Layout const & next_layout = nextpar->layout();
		if (!next_layout.isCommand()) {
			// Here we now try to avoid spurious empty lines by
			// outputting a paragraph break only if: 
			// (case 1) the paragraph style allows parbreaks and
			// no \begin, \end or \item tags are going to follow
			// (i.e., if the next isn't the first or the current
			// isn't the last paragraph of an environment or itemize)
			// and the depth and alignment of the following paragraph is
			// unchanged, or 
			// (case 2) the following is a non-environment paragraph
			// whose depth is increased but whose alignment is unchanged, or
			// (case 3) the paragraph is not an environment and the next one
			// is a non-itemize-like env at lower depth, or
			// (case 4) the paragraph is a command not followed by an
			// environment and the alignment of the current and next
			// paragraph is unchanged, or
			// (case 5) the current alignment is changed and a
			// standard paragraph follows.
			DocumentClass const & tclass = bparams.documentClass();
			if ((style == next_layout
			     && !style.parbreak_is_newline
			     && !text.inset().getLayout().parbreakIsNewline()
			     && !text.inset().getLayout().parbreakIgnored()
			     && style.latextype != LATEX_ITEM_ENVIRONMENT
			     && style.latextype != LATEX_LIST_ENVIRONMENT
			     && style.align == par.getAlign(bparams)
			     && nextpar->getDepth() == par.getDepth()
			     && (nextpar->getAlign(bparams) == par.getAlign(bparams)
			         || par.params().spacing() != nextpar->params().spacing()))
			    || (!next_layout.isEnvironment()
				&& nextpar->getDepth() > par.getDepth()
				&& nextpar->getAlign(bparams) == next_layout.align)
			    || (!style.isEnvironment()
				&& next_layout.latextype == LATEX_ENVIRONMENT
				&& nextpar->getDepth() < par.getDepth())
			    || (style.isCommand()
				&& !next_layout.isEnvironment()
				&& style.align == par.getAlign(bparams)
				&& next_layout.align == nextpar->getAlign(bparams))
			    || (style.align != par.getAlign(bparams)
				&& tclass.isDefaultLayout(next_layout))) {
				// and omit paragraph break if it has been deleted with ct
				// and changes are not shown in output
				if (!merged_par) {
					if (runparams.isNonLong)
						// This is to allow parbreak in multirow
						// It could also be used for other non-long
						// contexts
						os << "\\endgraf\n";
					else
						os << '\n';
				}
			}
		}
	}

	// Reset language nesting level after intitle command
	if (intitle_command)
		state->nest_level_ -= 1;

	LYXERR(Debug::OUTFILE, "TeXOnePar for paragraph " << pit << " done; ptr "
	                                                  << &par << " next " << nextpar);

	return;
}


// LaTeX all paragraphs
void latexParagraphs(Buffer const & buf,
		     Text const & text,
		     otexstream & os,
		     OutputParams const & runparams,
		     string const & everypar)
{
	LASSERT(runparams.par_begin <= runparams.par_end,
		{ os << "% LaTeX Output Error\n"; return; } );

	BufferParams const & bparams = buf.params();
	BufferParams const & mparams = buf.masterParams();

	bool const maintext = text.isMainText();
	bool const is_child = buf.masterBuffer() != &buf;
	bool const multibib_child = maintext && is_child
			&& mparams.multibib == "child";

	if (multibib_child && mparams.useBiblatex())
		os << "\\newrefsection";
	else if (multibib_child && mparams.useBibtopic()
		 && !buf.masterBibInfo().empty()) {
		os << "\\begin{btUnit}\n";
		runparams.openbtUnit = true;
	}

	// Open a CJK environment at the beginning of the main buffer
	// if the document's main encoding requires the CJK package
	// or the document encoding is utf8 and the CJK package is required
	// (but not in child documents or documents using system fonts):
	OutputState * state = getOutputState();
	if (maintext && !is_child && !bparams.useNonTeXFonts
	    && (bparams.encoding().package() == Encoding::CJK
			|| (bparams.encoding().name() == "utf8"
				&& runparams.use_CJK))
	   ) {
		docstring const cjkenc = bparams.encoding().iconvName() == "UTF-8"
								 ? from_ascii("UTF8")
								 : from_ascii(bparams.encoding().latexName());
		os << "\\begin{CJK}{" << cjkenc
		   << "}{" << from_ascii(bparams.fonts_cjk) << "}%\n";
		state->open_encoding_ = CJK;
	}
	// if "auto begin" is switched off, explicitly switch the
	// language on at start
	string const mainlang = runparams.use_polyglossia
		? getPolyglossiaEnvName(bparams.language)
		: bparams.language->babel();
	string const lang_begin_command = runparams.use_polyglossia ?
		"\\begin{$$lang}$$opts" : lyxrc.language_command_begin;
	string const lang_end_command = runparams.use_polyglossia ?
		"\\end{$$lang}" : lyxrc.language_command_end;
	bool const using_begin_end = runparams.use_polyglossia ||
					!lang_end_command.empty();

	if (maintext && !lyxrc.language_auto_begin &&
	    !mainlang.empty()) {
		// FIXME UNICODE
		string bc = runparams.use_polyglossia ?
			    getPolyglossiaBegin(lang_begin_command, mainlang,
						bparams.language->polyglossiaOpts())
			  : subst(lang_begin_command, "$$lang", mainlang);
		os << bc;
		os << '\n';
		if (using_begin_end)
			pushLanguageName(mainlang);
	}

	ParagraphList const & paragraphs = text.paragraphs();

	if (runparams.par_begin == runparams.par_end) {
		// The full doc will be exported but it is easier to just rely on
		// runparams range parameters that will be passed TeXEnvironment.
		runparams.par_begin = 0;
		runparams.par_end = static_cast<int>(paragraphs.size());
	}

	pit_type pit = runparams.par_begin;
	// lastpit is for the language check after the loop.
	pit_type lastpit = pit;
	DocumentClass const & tclass = bparams.documentClass();

	// Did we already warn about inTitle layout mixing? (we only warn once)
	bool gave_layout_warning = false;
	for (; pit < runparams.par_end; ++pit) {
		lastpit = pit;
		ParagraphList::const_iterator par = paragraphs.iterator_at(pit);

		// FIXME This check should not be needed. We should
		// perhaps issue an error if it is.
		Layout const & layout = text.inset().forcePlainLayout() ?
				tclass.plainLayout() : par->layout();

		if (layout.intitle) {
			if (runparams.have_maketitle) {
				if (!gave_layout_warning && !runparams.dryrun) {
					gave_layout_warning = true;
					frontend::Alert::warning(_("Error in latexParagraphs"),
							bformat(_("You are using at least one "
							  "layout (%1$s) intended for the title, "
							  "after using non-title layouts. This "
							  "could lead to missing or incorrect output."
							  ), layout.name()));
				}
			} else if (!runparams.need_maketitle) {
				runparams.need_maketitle = true;
				if (tclass.titletype() == TITLE_ENVIRONMENT) {
					os << "\\begin{"
							<< from_ascii(tclass.titlename())
							<< "}\n";
				}
			}
		} else if (runparams.need_maketitle && !runparams.have_maketitle
			   && !layout.inpreamble && !text.inset().isInTitle()) {
			if (tclass.titletype() == TITLE_ENVIRONMENT) {
				os << "\\end{" << from_ascii(tclass.titlename())
						<< "}\n";
			}
			else {
				os << "\\" << from_ascii(tclass.titlename())
						<< "\n";
			}
			runparams.have_maketitle = true;
			runparams.need_maketitle = false;
		}

		if (layout.isCommand() && !layout.latexname().empty()
		    && layout.latexname() == bparams.multibib) {
			if (runparams.openbtUnit)
				os << "\\end{btUnit}\n";
			if (!bparams.useBiblatex()
			    && !buf.masterBibInfo().empty()) {
				os << '\n' << "\\begin{btUnit}\n";
				runparams.openbtUnit = true;
			}
		}

		if (!layout.isEnvironment() && par->params().leftIndent().zero()) {
			// This is a standard top level paragraph, TeX it and continue.
			TeXOnePar(buf, text, pit, os, runparams, everypar);
			continue;
		}

		// Do not output empty environments if the whole paragraph has
		// been deleted with ct and changes are not output.
		bool output_changes;
		if (!runparams.find_effective())
			output_changes = bparams.output_changes;
		else
			output_changes = runparams.find_with_deleted();
		bool const lastpar = size_t(pit + 1) >= paragraphs.size();
		if (!lastpar) {
			ParagraphList::const_iterator nextpar = paragraphs.iterator_at(pit + 1);
			Paragraph const & cpar = paragraphs.at(pit);
			if ((par->layout() != nextpar->layout()
			     || par->params().depth() == nextpar->params().depth()
			     || par->params().leftIndent() == nextpar->params().leftIndent())
			    && !cpar.empty()
			    && cpar.isDeleted(0, cpar.size()) && !output_changes) {
				if (!cpar.parEndChange().deleted())
					os << '\n' << '\n';
				continue;
			}
		} else {
			// This is the last par
			Paragraph const & cpar = paragraphs.at(pit);
			if ( !cpar.empty()
			    && cpar.isDeleted(0, cpar.size()) && !output_changes) {
				if (!cpar.parEndChange().deleted())
					os << '\n' << '\n';
				continue;
			}
		}

		TeXEnvironmentData const data =
			prepareEnvironment(buf, text, par, os, runparams);
		// pit can be changed in TeXEnvironment.
		TeXEnvironment(buf, text, runparams, pit, os);
		finishEnvironment(os, runparams, data, maintext, lastpar);
	}

	// FIXME: uncomment the content or remove this block
	if (pit == runparams.par_end) {
			// Make sure that the last paragraph is
			// correctly terminated (because TeXOnePar does
			// not add a \n in this case)
			//os << '\n';
	}

	// It might be that we only have a title in this document.
	// But if we're in an inset, this is not the end of
	// the document. (There may be some other checks of this
	// kind that are needed.)
	if (runparams.need_maketitle && !runparams.have_maketitle && maintext) {
		if (tclass.titletype() == TITLE_ENVIRONMENT) {
			os << "\\end{" << from_ascii(tclass.titlename())
			   << "}\n";
		} else {
			os << "\\" << from_ascii(tclass.titlename())
			   << "\n";
		}
	}

	if (maintext && !is_child && runparams.openbtUnit)
		os << "\\end{btUnit}\n";

	// if "auto end" is switched off, explicitly close the language at the end
	// but only if the last par is in a babel or polyglossia language
	Language const * const lastpar_language =
			paragraphs.at(lastpit).getParLanguage(bparams);
	if (maintext && !lyxrc.language_auto_end && !mainlang.empty() &&
		lastpar_language->encoding()->package() != Encoding::CJK) {
		os << from_utf8(subst(lang_end_command,
					"$$lang",
					mainlang))
			<< '\n';
		// If we have language_auto_begin, the stack will
		// already be empty, nothing to pop()
		if (using_begin_end && langOpenedAtThisLevel(state))
			popLanguageName();
	}

	// If the last paragraph is an environment, we'll have to close
	// CJK at the very end to do proper nesting.
	if (maintext && !is_child && state->open_encoding_ == CJK) {
		os << "\\clearpage\n\\end{CJK}\n";
		state->open_encoding_ = none;
	}
	// Likewise for polyglossia or when using begin/end commands
	// or at the very end of an active branch inset with a language switch
	Language const * const outer_language = (runparams.local_font != nullptr)
			? runparams.local_font->language() : bparams.language;
	string const & prev_lang = runparams.use_polyglossia
			? getPolyglossiaEnvName(outer_language)
			: outer_language->babel();
	string const lastpar_lang = runparams.use_polyglossia ?
		getPolyglossiaEnvName(lastpar_language): lastpar_language->babel();
	string const & cur_lang = openLanguageName(state);
	if (((runparams.inbranch && langOpenedAtThisLevel(state) && prev_lang != cur_lang)
	     || (maintext && !is_child)) && !cur_lang.empty()) {
		os << from_utf8(subst(lang_end_command,
					"$$lang",
					cur_lang))
		   << '\n';
		if (using_begin_end)
			popLanguageName();
	} else if (runparams.inbranch && !using_begin_end
		   && prev_lang != lastpar_lang && !lastpar_lang.empty()) {
		// with !using_begin_end, cur_lang is empty, so we need to
		// compare against the paragraph language (and we are in the
		// last paragraph at this point)
		os << subst(lang_begin_command, "$$lang", prev_lang) << '\n';
	}

	// reset inherited encoding
	if (state->cjk_inherited_ > 0) {
		state->cjk_inherited_ -= 1;
		if (state->cjk_inherited_ == 0)
			state->open_encoding_ = CJK;
	}

	if (multibib_child && mparams.useBibtopic()) {
		os << "\\end{btUnit}\n";
		runparams.openbtUnit = false;
	}
}

// Switch the input encoding for some part(s) of the document.
pair<bool, int> switchEncoding(odocstream & os, BufferParams const & bparams,
		   OutputParams const & runparams, Encoding const & newEnc,
		   bool force, bool noswitchmacro)
{
	// Never switch encoding with XeTeX/LuaTeX
	// or if we're in a moving argument or inherit the outer encoding.
	if (runparams.isFullUnicode() || newEnc.name() == "inherit")
		return make_pair(false, 0);	

	// Only switch for auto-selected legacy encodings (inputenc setting
	// "auto-legacy" or "auto-legacy-plain").
	// The "listings" environment can force a switch also with other
	// encoding settings (it does not support variable width encodings
	// (utf8, jis, ...) under 8-bit latex engines).
	if (!force && ((bparams.inputenc != "auto-legacy" && bparams.inputenc != "auto-legacy-plain")
				   || runparams.moving_arg))
		return make_pair(false, 0);

	Encoding const & oldEnc = *runparams.encoding;
	// Do not switch, if the encoding is unchanged or switching is not supported.
	if (oldEnc.name() == newEnc.name()
		|| oldEnc.package() == Encoding::japanese
		|| oldEnc.package() == Encoding::none
		|| newEnc.package() == Encoding::none
		|| runparams.find_effective())
		return make_pair(false, 0);
	// FIXME We ignore encoding switches from/to encodings that do
	// neither support the inputenc package nor the CJK package here.
	// This may fail for characters not supported by "unicodesymbols"
	// or for non-ASCII characters in "listings"
	// but it is the best we can do.

	// change encoding
	LYXERR(Debug::OUTFILE, "Changing LaTeX encoding from "
		   << oldEnc.name() << " to " << newEnc.name());
	os << setEncoding(newEnc.iconvName());
	if (bparams.inputenc == "auto-legacy-plain")
	  return make_pair(true, 0);

	docstring const inputenc_arg(from_ascii(newEnc.latexName()));
	OutputState * state = getOutputState();
	switch (newEnc.package()) {
		case Encoding::none:
		case Encoding::japanese:
			// shouldn't ever reach here (see above) but avoids warning.
			return make_pair(true, 0);
		case Encoding::inputenc: {
			size_t count = inputenc_arg.length();
			if (oldEnc.package() == Encoding::CJK &&
			    state->open_encoding_ == CJK) {
				os << "\\end{CJK}";
				state->open_encoding_ = none;
				count += 9;
			}
			else if (oldEnc.package() == Encoding::inputenc &&
				 state->open_encoding_ == inputenc) {
				os << "\\egroup";
				state->open_encoding_ = none;
				count += 7;
			}
			if (runparams.local_font != nullptr
			    && 	oldEnc.package() == Encoding::CJK) {
				// within insets, \inputenc switches need
				// to be embraced within \bgroup...\egroup;
				// else CJK fails.
				os << "\\bgroup";
				count += 7;
				state->open_encoding_ = inputenc;
			}
			if (noswitchmacro)
				return make_pair(true, count);
			os << "\\inputencoding{" << inputenc_arg << '}';
			return make_pair(true, count + 16);
		}
		case Encoding::CJK: {
			size_t count = inputenc_arg.length();
			if (oldEnc.package() == Encoding::CJK &&
			    state->open_encoding_ == CJK) {
				os << "\\end{CJK}";
				count += 9;
			}
			if (oldEnc.package() == Encoding::inputenc &&
			    state->open_encoding_ == inputenc) {
				os << "\\egroup";
				count += 7;
			}
			os << "\\begin{CJK}{"
			   << from_ascii(newEnc.latexName()) << "}{"
			   << from_ascii(bparams.fonts_cjk) << "}";
			state->open_encoding_ = CJK;
			return make_pair(true, count + 15);
		}
	}
	// Dead code to avoid a warning:
	return make_pair(true, 0);
}

} // namespace lyx
