--- a
+++ b/lexers/LexLaTeX.cxx
@@ -0,0 +1,539 @@
+// Scintilla source code edit control
+/** @file LexLaTeX.cxx
+ ** Lexer for LaTeX2e.
+  **/
+// Copyright 1998-2001 by Neil Hodgson <neilh@scintilla.org>
+// The License.txt file describes the conditions under which this software may be distributed.
+
+// Modified by G. HU in 2013. Added folding, syntax highting inside math environments, and changed some minor behaviors.
+
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdarg.h>
+#include <assert.h>
+#include <ctype.h>
+#include <vector>
+
+#include "ILexer.h"
+#include "Scintilla.h"
+#include "SciLexer.h"
+
+#include "PropSetSimple.h"
+#include "WordList.h"
+#include "LexAccessor.h"
+#include "Accessor.h"
+#include "StyleContext.h"
+#include "CharacterSet.h"
+#include "LexerModule.h"
+#include "LexerBase.h"
+
+#ifdef SCI_NAMESPACE
+using namespace Scintilla;
+#endif
+
+using namespace std;
+
+struct latexFoldSave {
+	latexFoldSave() : structLev(0) {
+		for (int i = 0; i < 8; ++i) openBegins[i] = 0;
+	}
+	latexFoldSave(const latexFoldSave &save) : structLev(save.structLev) {
+		for (int i = 0; i < 8; ++i) openBegins[i] = save.openBegins[i];
+	}
+	int openBegins[8];
+	int structLev;
+};
+
+class LexerLaTeX : public LexerBase {
+private:
+	vector<int> modes;
+	void setMode(int line, int mode) {
+		if (line >= static_cast<int>(modes.size())) modes.resize(line + 1, 0);
+		modes[line] = mode;
+	}
+	int getMode(int line) {
+		if (line >= 0 && line < static_cast<int>(modes.size())) return modes[line];
+		return 0;
+	}
+	void truncModes(int numLines) {
+		if (static_cast<int>(modes.size()) > numLines * 2 + 256)
+			modes.resize(numLines + 128);
+	}
+	
+	vector<latexFoldSave> saves;
+	void setSave(int line, const latexFoldSave &save) {
+		if (line >= static_cast<int>(saves.size())) saves.resize(line + 1);
+		saves[line] = save;
+	}
+	void getSave(int line, latexFoldSave &save) {
+		if (line >= 0 && line < static_cast<int>(saves.size())) save = saves[line];
+		else {
+			save.structLev = 0;
+			for (int i = 0; i < 8; ++i) save.openBegins[i] = 0;
+		}
+	}
+	void truncSaves(int numLines) {
+		if (static_cast<int>(saves.size()) > numLines * 2 + 256)
+			saves.resize(numLines + 128);
+	}
+public:
+	static ILexer *LexerFactoryLaTeX() {
+		return new LexerLaTeX();
+	}
+	void SCI_METHOD Lex(unsigned int startPos, int length, int initStyle, IDocument *pAccess);
+	void SCI_METHOD Fold(unsigned int startPos, int length, int initStyle, IDocument *pAccess);
+};
+
+static bool latexIsSpecial(int ch) {
+	return (ch == '#') || (ch == '$') || (ch == '%') || (ch == '&') || (ch == '_') ||
+		   (ch == '{') || (ch == '}') || (ch == ' ');
+}
+
+static bool latexIsBlank(int ch) {
+	return (ch == ' ') || (ch == '\t');
+}
+
+static bool latexIsBlankAndNL(int ch) {
+	return (ch == ' ') || (ch == '\t') || (ch == '\r') || (ch == '\n');
+}
+
+static bool latexIsLetter(int ch) {
+	return isascii(ch) && isalpha(ch);
+}
+
+static bool latexIsTagValid(int &i, int l, Accessor &styler) {
+	while (i < l) {
+		if (styler.SafeGetCharAt(i) == '{') {
+			while (i < l) {
+				i++;
+				if (styler.SafeGetCharAt(i) == '}') {
+					return true;
+				}	else if (!latexIsLetter(styler.SafeGetCharAt(i)) &&
+                   styler.SafeGetCharAt(i)!='*') {
+					return false;
+				}
+			}
+		} else if (!latexIsBlank(styler.SafeGetCharAt(i))) {
+			return false;
+		}
+		i++;
+	}
+	return false;
+}
+
+static bool latexNextNotBlankIs(int i, Accessor &styler, char needle) {
+  char ch;
+	while (i < styler.Length()) {
+    ch = styler.SafeGetCharAt(i);
+		if (!latexIsBlankAndNL(ch) && ch != '*') {
+      if (ch == needle)
+        return true;
+      else
+        return false;
+		}
+		i++;
+	}
+	return false;
+}
+
+static bool latexLastWordIs(int start, Accessor &styler, const char *needle) {
+	unsigned int i = 0;
+	unsigned int l = static_cast<unsigned int>(strlen(needle));
+	int ini = start-l+1;
+	char s[32];
+
+	while (i < l && i < 31) {
+		s[i] = styler.SafeGetCharAt(ini + i);
+		i++;
+	}
+	s[i] = '\0';
+
+	return (strcmp(s, needle) == 0);
+}
+
+static bool latexLastWordIsMathEnv(int pos, Accessor &styler) {
+	int i, j;
+	char s[32];
+	const char *mathEnvs[] = { "align", "alignat", "flalign", "gather",
+		"multiline", "displaymath", "eqnarray", "equation" };
+	if (styler.SafeGetCharAt(pos) != '}') return false;
+	for (i = pos - 1; i >= 0; --i) {
+		if (styler.SafeGetCharAt(i) == '{') break;
+		if (pos - i >= 20) return false;
+	}
+	if (i < 0 || i == pos - 1) return false;
+	++i;
+	for (j = 0; i + j < pos; ++j)
+		s[j] = styler.SafeGetCharAt(i + j);
+	s[j] = '\0';
+	if (j == 0) return false;
+	if (s[j - 1] == '*') s[--j] = '\0';
+	for (i = 0; i < static_cast<int>(sizeof(mathEnvs) / sizeof(const char *)); ++i)
+		if (strcmp(s, mathEnvs[i]) == 0) return true;
+	return false;
+}
+
+static inline void latexStateReset(int &mode, int &state) {
+	switch (mode) {
+	case 1:     state = SCE_L_MATH; break;
+	case 2:     state = SCE_L_MATH2; break;
+	default:    state = SCE_L_DEFAULT; break;
+	}
+}
+
+// There are cases not handled correctly, like $abcd\textrm{what is $x+y$}z+w$.
+// But I think it's already good enough.
+void SCI_METHOD LexerLaTeX::Lex(unsigned int startPos, int length, int initStyle, IDocument *pAccess) {
+	// startPos is assumed to be the first character of a line
+	Accessor styler(pAccess, &props);
+	styler.StartAt(startPos);
+	int mode = getMode(styler.GetLine(startPos) - 1);
+	int state = initStyle;
+	if (state == SCE_L_ERROR || state == SCE_L_SHORTCMD || state == SCE_L_SPECIAL)   // should not happen
+		latexStateReset(mode, state);
+	
+	char chNext = styler.SafeGetCharAt(startPos);
+	char chVerbatimDelim = '\0';
+	styler.StartSegment(startPos);
+	int lengthDoc = startPos + length;
+
+	for (int i = startPos; i < lengthDoc; i++) {
+		char ch = chNext;
+		chNext = styler.SafeGetCharAt(i + 1);
+
+		if (styler.IsLeadByte(ch)) {
+			i++;
+			chNext = styler.SafeGetCharAt(i + 1);
+			continue;
+		}
+		
+		if (ch == '\r' || ch == '\n')
+			setMode(styler.GetLine(i), mode);
+
+		switch (state) {
+		case SCE_L_DEFAULT :
+			switch (ch) {
+			case '\\' :
+				styler.ColourTo(i - 1, state);
+				if (latexIsLetter(chNext)) {
+					state = SCE_L_COMMAND;
+				} else if (latexIsSpecial(chNext)) {
+					styler.ColourTo(i + 1, SCE_L_SPECIAL);
+					i++;
+					chNext = styler.SafeGetCharAt(i + 1);
+				} else if (chNext == '\r' || chNext == '\n') {
+					styler.ColourTo(i, SCE_L_ERROR);
+				} else {
+					styler.ColourTo(i + 1, SCE_L_SHORTCMD);
+					if (chNext == '(') {
+						mode = 1;
+						state = SCE_L_MATH;
+					} else if (chNext == '[') {
+						mode = 2;
+						state = SCE_L_MATH2;
+					}
+					i++;
+					chNext = styler.SafeGetCharAt(i + 1);
+				}
+				break;
+			case '$' :
+				styler.ColourTo(i - 1, state);
+				if (chNext == '$') {
+					styler.ColourTo(i + 1, SCE_L_SHORTCMD);
+					mode = 2;
+					state = SCE_L_MATH2;
+					i++;
+					chNext = styler.SafeGetCharAt(i + 1);
+				} else {
+					styler.ColourTo(i, SCE_L_SHORTCMD);
+					mode = 1;
+					state = SCE_L_MATH;
+				}
+				break;
+			case '%' :
+				styler.ColourTo(i - 1, state);
+				state = SCE_L_COMMENT;
+				break;
+			}
+			break;	
+		// These 3 will never be reached.
+		case SCE_L_ERROR:
+		case SCE_L_SPECIAL:
+		case SCE_L_SHORTCMD:
+			break;
+		case SCE_L_COMMAND :
+			if (!latexIsLetter(chNext)) {
+				styler.ColourTo(i, state);
+				if (latexNextNotBlankIs(i + 1, styler, '[' )) {
+					state = SCE_L_CMDOPT;
+				} else if (latexLastWordIs(i, styler, "\\begin")) {
+					state = SCE_L_TAG;
+				} else if (latexLastWordIs(i, styler, "\\end")) {
+					state = SCE_L_TAG2;
+				} else if (latexLastWordIs(i, styler, "\\verb") && chNext != '*' && chNext != ' ') {
+					chVerbatimDelim = chNext;
+					state = SCE_L_VERBATIM;
+				} else {
+					latexStateReset(mode, state);
+				}
+			}
+			break;
+		case SCE_L_CMDOPT :
+			if (ch == ']') {
+				styler.ColourTo(i, state);
+				latexStateReset(mode, state);
+			}
+			break;
+		case SCE_L_TAG :
+			if (latexIsTagValid(i, lengthDoc, styler)) {
+				styler.ColourTo(i, state);
+				latexStateReset(mode, state);
+				if (latexLastWordIs(i, styler, "{verbatim}")) {
+					state = SCE_L_VERBATIM;
+				} else if (latexLastWordIs(i, styler, "{comment}")) {
+					state = SCE_L_COMMENT2;
+				} else if (latexLastWordIs(i, styler, "{math}") && mode == 0) {
+					mode = 1;
+					state = SCE_L_MATH;
+				} else if (latexLastWordIsMathEnv(i, styler) && mode == 0) {
+					mode = 2;
+					state = SCE_L_MATH2;
+				}
+			} else {
+				styler.ColourTo(i, SCE_L_ERROR);
+				latexStateReset(mode, state);
+				ch = styler.SafeGetCharAt(i);
+				if (ch == '\r' || ch == '\n') setMode(styler.GetLine(i), mode);
+			}
+			chNext = styler.SafeGetCharAt(i+1);
+			break;
+		case SCE_L_TAG2 :
+			if (latexIsTagValid(i, lengthDoc, styler)) {
+				styler.ColourTo(i, state);
+				latexStateReset(mode, state);
+			} else {
+				styler.ColourTo(i, SCE_L_ERROR);
+				latexStateReset(mode, state);
+				ch = styler.SafeGetCharAt(i);
+				if (ch == '\r' || ch == '\n') setMode(styler.GetLine(i), mode);
+			}
+			chNext = styler.SafeGetCharAt(i+1);
+			break;
+		case SCE_L_MATH :
+			switch (ch) {
+			case '\\' :
+				styler.ColourTo(i - 1, state);
+				if (latexIsLetter(chNext)) {
+					int match = i + 3;
+					if (latexLastWordIs(match, styler, "\\end")) {
+						match++;
+						if (latexIsTagValid(match, lengthDoc, styler)) {
+							if (latexLastWordIs(match, styler, "{math}"))
+								mode = 0;
+						}
+					}
+					state = SCE_L_COMMAND;
+				} else if (latexIsSpecial(chNext)) {
+					styler.ColourTo(i + 1, SCE_L_SPECIAL);
+					i++;
+					chNext = styler.SafeGetCharAt(i + 1);
+				} else if (chNext == '\r' || chNext == '\n') {
+					styler.ColourTo(i, SCE_L_ERROR);
+				} else {
+					if (chNext == ')') {
+						mode = 0;
+						state = SCE_L_DEFAULT;
+					}
+					styler.ColourTo(i + 1, SCE_L_SHORTCMD);
+					i++;
+					chNext = styler.SafeGetCharAt(i + 1);
+				}
+				break;
+			case '$' :
+				styler.ColourTo(i - 1, state);
+				styler.ColourTo(i, SCE_L_SHORTCMD);
+				mode = 0;
+				state = SCE_L_DEFAULT;
+				break;
+			case '%' :
+				styler.ColourTo(i - 1, state);
+				state = SCE_L_COMMENT;
+				break;
+			}
+			break;
+		case SCE_L_MATH2 :
+			switch (ch) {
+			case '\\' :
+				styler.ColourTo(i - 1, state);
+				if (latexIsLetter(chNext)) {
+					int match = i + 3;
+					if (latexLastWordIs(match, styler, "\\end")) {
+						match++;
+						if (latexIsTagValid(match, lengthDoc, styler)) {
+							if (latexLastWordIsMathEnv(match, styler))
+								mode = 0;
+						}
+					}
+					state = SCE_L_COMMAND;
+				} else if (latexIsSpecial(chNext)) {
+					styler.ColourTo(i + 1, SCE_L_SPECIAL);
+					i++;
+					chNext = styler.SafeGetCharAt(i + 1);
+				} else if (chNext == '\r' || chNext == '\n') {
+					styler.ColourTo(i, SCE_L_ERROR);
+				} else {
+					if (chNext == ']') {
+						mode = 0;
+						state = SCE_L_DEFAULT;
+					}
+					styler.ColourTo(i + 1, SCE_L_SHORTCMD);
+					i++;
+					chNext = styler.SafeGetCharAt(i + 1);
+				}
+				break;
+			case '$' :
+				styler.ColourTo(i - 1, state);
+				if (chNext == '$') {
+					styler.ColourTo(i + 1, SCE_L_SHORTCMD);
+					i++;
+					chNext = styler.SafeGetCharAt(i + 1);
+					mode = 0;
+					state = SCE_L_DEFAULT;
+				} else { // This may not be an error, e.g. \begin{equation}\text{$a$}\end{equation}	
+					styler.ColourTo(i, SCE_L_SHORTCMD);
+				}
+				break;
+			case '%' :
+				styler.ColourTo(i - 1, state);
+				state = SCE_L_COMMENT;
+				break;
+			}
+			break;
+		case SCE_L_COMMENT :
+			if (ch == '\r' || ch == '\n') {
+				styler.ColourTo(i - 1, state);
+				latexStateReset(mode, state);
+			}
+			break;
+		case SCE_L_COMMENT2 :
+			if (ch == '\\') {
+				int match = i + 3;
+				if (latexLastWordIs(match, styler, "\\end")) {
+					match++;
+					if (latexIsTagValid(match, lengthDoc, styler)) {
+						if (latexLastWordIs(match, styler, "{comment}")) {
+							styler.ColourTo(i - 1, state);
+							state = SCE_L_COMMAND;
+						}
+					}
+				}
+			}
+			break;
+		case SCE_L_VERBATIM :
+			if (ch == '\\') {
+				int match = i + 3;
+				if (latexLastWordIs(match, styler, "\\end")) {
+					match++;
+					if (latexIsTagValid(match, lengthDoc, styler)) {
+						if (latexLastWordIs(match, styler, "{verbatim}")) {
+							styler.ColourTo(i - 1, state);
+							state = SCE_L_COMMAND;
+						}
+					}
+				}
+			} else if (chNext == chVerbatimDelim) {
+				styler.ColourTo(i + 1, state);
+				latexStateReset(mode, state);
+				chVerbatimDelim = '\0';
+				i++;
+				chNext = styler.SafeGetCharAt(i + 1);
+			} else if (chVerbatimDelim != '\0' && (ch == '\n' || ch == '\r')) {
+				styler.ColourTo(i, SCE_L_ERROR);
+				latexStateReset(mode, state);
+				chVerbatimDelim = '\0';
+			}
+			break;
+		}
+	}
+	if (lengthDoc == styler.Length()) truncModes(styler.GetLine(lengthDoc - 1));
+	styler.ColourTo(lengthDoc - 1, state);
+	styler.Flush();
+}
+
+static int latexFoldSaveToInt(const latexFoldSave &save) {
+	int sum = 0;
+	for (int i = 0; i <= save.structLev; ++i)
+		sum += save.openBegins[i];
+	return ((sum + save.structLev + SC_FOLDLEVELBASE) & SC_FOLDLEVELNUMBERMASK);
+}
+
+// Change folding state while processing a line
+// Return the level before the first relevant command
+void SCI_METHOD LexerLaTeX::Fold(unsigned int startPos, int length, int, IDocument *pAccess) {
+	const char *structWords[7] = {"part", "chapter", "section", "subsection",
+		"subsubsection", "paragraph", "subparagraph"};
+	Accessor styler(pAccess, &props);
+	unsigned int endPos = startPos + length;
+	int curLine = styler.GetLine(startPos);
+	latexFoldSave save;
+	getSave(curLine - 1, save);
+	do {
+		char ch, buf[16];
+		int i, j, lev = -1;
+		bool needFold = false;
+		for (i = static_cast<int>(startPos); i < static_cast<int>(endPos); ++i) {
+			ch = styler.SafeGetCharAt(i);
+			if (ch == '\r' || ch == '\n') break;
+			if (ch != '\\' || styler.StyleAt(i) != SCE_L_COMMAND) continue;
+			for (j = 0; j < 15 && i + 1 < static_cast<int>(endPos); ++j, ++i) {
+				buf[j] = styler.SafeGetCharAt(i + 1);
+				if (!latexIsLetter(buf[j])) break;
+			}
+			buf[j] = '\0';
+			if (strcmp(buf, "begin") == 0) {
+				if (lev < 0) lev = latexFoldSaveToInt(save);
+				++save.openBegins[save.structLev];
+				needFold = true;
+			}
+			else if (strcmp(buf, "end") == 0) {
+				while (save.structLev > 0 && save.openBegins[save.structLev] == 0)
+					--save.structLev;
+				if (lev < 0) lev = latexFoldSaveToInt(save);
+				if (save.openBegins[save.structLev] > 0) --save.openBegins[save.structLev];
+			}
+			else {
+				for (j = 0; j < 7; ++j)
+					if (strcmp(buf, structWords[j]) == 0) break;
+				if (j >= 7) continue;
+				save.structLev = j;   // level before the command
+				for (j = save.structLev + 1; j < 8; ++j) {
+					save.openBegins[save.structLev] += save.openBegins[j];
+					save.openBegins[j] = 0;
+				}
+				if (lev < 0) lev = latexFoldSaveToInt(save);
+				++save.structLev;   // level after the command
+				needFold = true;
+			}
+		}
+		if (lev < 0) lev = latexFoldSaveToInt(save);
+		if (needFold) lev |= SC_FOLDLEVELHEADERFLAG;
+		styler.SetLevel(curLine, lev);
+		setSave(curLine, save);
+		++curLine;
+		startPos = styler.LineStart(curLine);
+		if (static_cast<int>(startPos) == styler.Length()) {
+			lev = latexFoldSaveToInt(save);
+			styler.SetLevel(curLine, lev);
+			setSave(curLine, save);
+			truncSaves(curLine);
+		}
+	} while (startPos < endPos);
+	styler.Flush();
+}
+
+static const char *const emptyWordListDesc[] = {
+	0
+};
+
+LexerModule lmLatex(SCLEX_LATEX, LexerLaTeX::LexerFactoryLaTeX, "latex", emptyWordListDesc);