vis: experimental support for lua/lpeg based syntax highlighting

The lua based lexers are searched in the following order:

 $VIS_PATH/lexers
 $HOME/.vis/lexers
 /usr/share/vis/lexers

followed by the standard lua package.path

11 files changed, 499 insertions, 48 deletions

diff --git a/lexers/diff.lua b/lexers/diff.lua
index 53b7f17..ee680aa 100644
--- a/lexers/diff.lua
+++ b/lexers/diff.lua
@@ -34,9 +34,9 @@ M._rules = {
 
 M._tokenstyles = {
   header = l.STYLE_COMMENT,
-  addition = 'fore:$(color.green)',
-  deletion = 'fore:$(color.red)',
-  change = 'fore:$(color.yellow)'
+  addition = 'fore:'..l.colors.green,
+  deletion = 'fore:'..l.colors.red,
+  change = 'fore:'..l.colors.yellow,
 }
 
 M._LEXBYLINE = true
diff --git a/lexers/lexer.lua b/lexers/lexer.lua
index 0dc9674..4d7eb60 100644
--- a/lexers/lexer.lua
+++ b/lexers/lexer.lua
@@ -974,7 +974,10 @@ local default = {
   'function', 'class', 'type', 'label', 'regex', 'embedded'
 }
 for _, v in ipairs(default) do
-  M[string_upper(v)], M['STYLE_'..string_upper(v)] = v, '$(style.'..v..')'
+  M[string_upper(v)] = v
+  if not M['STYLE_'..string_upper(v)] then
+    M['STYLE_'..string_upper(v)] = ''
+  end
 end
 -- Predefined styles.
 local predefined = {
@@ -982,7 +985,10 @@ local predefined = {
   'indentguide', 'calltip'
 }
 for _, v in ipairs(predefined) do
-  M[string_upper(v)], M['STYLE_'..string_upper(v)] = v, '$(style.'..v..')'
+  M[string_upper(v)] = v
+  if not M['STYLE_'..string_upper(v)] then
+    M['STYLE_'..string_upper(v)] = ''
+  end
 end
 
 ---
@@ -1584,4 +1590,122 @@ M.property_expanded = setmetatable({}, {
 local lexer
 ]]
 
+function M.get_style(lexer, lang, token_name)
+  return lexer['STYLE_'..string_upper(token_name)] or lang._EXTRASTYLES[token_name]
+end
+
+local files = {
+	[".as|.asc"] = "actionscript",
+	[".adb|.ads"] = "ada",
+	[".g|.g4"] = "antlr",
+	[".ans|.inp|.mac"] = "apdl",
+	[".applescript"] = "applescript",
+	[".asm|.ASM|.s|.S"] = "asm",
+	[".asa|.asp|.hta"] = "asp",
+	[".awk"] = "awk",
+	[".bat|.cmd"] = "batch",
+	[".bib"] = "bibtex",
+	[".boo"] = "boo",
+	[".cs"] = "csharp",
+	[".c|.cc|.C"] = "ansi_c",
+	[".cpp|.cxx|.c++|.h|.hh|.hpp|.hxx|.h++"] = "cpp",
+	[".ck"] = "chuck",
+	[".cmake|.cmake.in|.ctest|.ctest.in"] = "cmake",
+	[".coffee"] = "coffeescript",
+	[".css"] = "css",
+	[".cu|.cuh"] = "cuda",
+	[".d|.di"] = "dmd",
+	[".dart"] = "dart",
+	[".desktop"] = "desktop",
+	[".diff|.patch"] = "diff",
+	[".dot"] = "dot",
+	[".e|.eif"] = "eiffel",
+	[".ex|.exs"] = "elixir",
+	[".erl|.hrl"] = "erlang",
+	[".fs"] = "fsharp",
+	[".fish"] = "fish",
+	[".forth|.frt|.fs"] = "forth",
+	[".f|.for|.ftn|.fpp|.f77|.f90|.f95|.f03|.f08"] = "fortran",
+	[".g|.gd|.gi|.gap"] = "gap",
+	[".po|.pot"] = "gettext",
+	[".glslf|.glslv"] = "glsl",
+	[".dem|.plt"] = "gnuplot",
+	[".go"] = "go",
+	[".groovy|.gvy"] = "groovy",
+	[".gtkrc"] = "gtkrc",
+	[".hs"] = "haskell",
+	[".htm|.html|.shtm|.shtml|.xhtml"] = "html",
+	[".idl|.odl"] = "idl",
+	[".inf|.ni"] = "inform",
+	[".cfg|.cnf|.inf|.ini|.reg"] = "ini",
+	[".io"] = "io_lang",
+	[".bsh|.java"] = "java",
+	[".js|.jsfl"] = "javascript",
+	[".json"] = "json",
+	[".jsp"] = "jsp",
+	[".bbl|.dtx|.ins|.ltx|.tex|.sty"] = "latex",
+	[".less"] = "less",
+	[".lily|.ly"] = "lilypond",
+	[".cl|.el|.lisp|.lsp"] = "lisp",
+	[".litcoffee"] = "litcoffee",
+	[".lua"] = "lua",
+	["GNUmakefile|.iface|.mak|.mk|makefile|Makefile"] = "makefile",
+	[".md"] = "markdown",
+	[".n"] = "nemerle",
+	[".nim"] = "nim",
+	[".nsh|.nsi|.nsis"] = "nsis",
+	[".m|.mm|.objc"] = "objective_c",
+	[".caml|.ml|.mli|.mll|.mly"] = "caml",
+	[".dpk|.dpr|.p|.pas"] = "pascal",
+	[".al|.perl|.pl|.pm|.pod"] = "perl",
+	[".inc|.php|.php3|.php4|.phtml"] = "php",
+	[".pike|.pmod"] = "pike",
+	[".PKGBUILD"] = "pkgbuild",
+	[".ps1"] = "powershell",
+	[".eps|.ps"] = "ps",
+	[".prolog"] = "prolog",
+	[".props|.properties"] = "props",
+	[".sc|.py|.pyw"] = "python",
+	[".R|.Rout|.Rhistory|.Rt|Rout.save|Rout.fail"] = "rstats",
+	[".r|.reb"] = "rebol",
+	[".rst"] = "rest",
+	[".orx|.rex"] = "rexx",
+	[".erb|.rhtml"] = "rhtml",
+	[".Rakefile|.rake|.rb|.rbw"] = "ruby",
+	[".rs"] = "rust",
+	[".sass|.scss"] = "sass",
+	[".scala"] = "scala",
+	[".sch|.scm"] = "scheme",
+	[".bash|.bashrc|.bash_profile|.configure|.csh|.sh|.zsh"] = "bash",
+	[".changes|.st|.sources"] = "smalltalk",
+	[".ddl|.sql"] = "sql",
+	[".tcl|.tk"] = "tcl",
+	[".texi"] = "texinfo",
+	[".toml"] = "toml",
+	[".vala"] = "vala",
+	[".vcf|.vcard"] = "vcard",
+	[".v|.ver"] = "verilog",
+	[".vh|.vhd|.vhdl"] = "vhdl",
+	[".asa|.bas|.cls|.ctl|.dob|.dsm|.dsr|.frm|.pag|.vb|.vba|.vbs"] = "vb",
+	[".wsf"] = "wsf",
+	[".dtd|.svg|.xml|.xsd|.xsl|.xslt|.xul"] = "xml",
+	[".xtend"] = "xtend",
+	[".yaml"] = "yaml",
+}
+
+function M.lexer_name(filename)
+	-- filename = string.lower(filename)
+	for patterns, lang in pairs(files) do
+		for pattern in string.gmatch(patterns, '[^|]+') do
+			if #filename >= #pattern then
+				local s, e = string.find(filename, pattern, -#pattern, true)
+				if s ~= e and e == #filename then
+					return lang
+				end
+			end
+		end
+	end
+	return nil
+end
+
 return M
diff --git a/lexers/themes/default.lua b/lexers/themes/default.lua
new file mode 120000
index 0000000..8479b1b
--- /dev/null
+++ b/lexers/themes/default.lua
@@ -0,0 +1 @@
+solarized.lua
\ No newline at end of file
diff --git a/lexers/themes/solarized.lua b/lexers/themes/solarized.lua
new file mode 100644
index 0000000..0575056
--- /dev/null
+++ b/lexers/themes/solarized.lua
@@ -0,0 +1,54 @@
+-- Solarized color codes Copyright (c) 2011 Ethan Schoonover
+local colors = {
+	['base03'] = '#002b36',
+	['base02'] = '#073642',
+	['base01'] = '#586e75',
+	['base00'] = '#657b83',
+	['base0']  = '#839496',
+	['base1'] = '#93a1a1',
+	['base2'] = '#eee8d5',
+	['base3'] = '#fdf6e3',
+	['yellow'] = '#b58900',
+	['orange'] = '#cb4b16',
+	['red'] = '#dc322f',
+	['magenta'] = '#d33682',
+	['violet'] = '#6c71c4',
+	['blue'] = '#268bd2',
+	['cyan'] = '#2aa198',
+	['green'] = '#859900',
+} 
+
+lexers.colors = colors
+-- dark
+local fg = ',fore:'..colors.base0..','
+local bg = ',back:'..colors.base03..','
+-- light
+-- local fg = ',fore:'..colors.base03..','
+-- local bg = ',back:'..colors.base3..','
+
+lexers.STYLE_DEFAULT = bg..fg
+lexers.STYLE_NOTHING = bg
+lexers.STYLE_CLASS = 'fore:yellow'
+lexers.STYLE_COMMENT = 'fore:'..colors.base01
+lexers.STYLE_CONSTANT = 'fore:'..colors.cyan
+lexers.STYLE_DEFINITION = 'fore:'..colors.blue
+lexers.STYLE_ERROR = 'fore:'..colors.red..',italics'
+lexers.STYLE_FUNCTION = 'fore:'..colors.blue
+lexers.STYLE_KEYWORD = 'fore:'..colors.green
+lexers.STYLE_LABEL = 'fore:'..colors.green
+lexers.STYLE_NUMBER = 'fore:'..colors.cyan
+lexers.STYLE_OPERATOR = 'fore:'..colors.green
+lexers.STYLE_REGEX = 'fore:green'
+lexers.STYLE_STRING = 'fore:'..colors.cyan
+lexers.STYLE_PREPROCESSOR = 'fore:'..colors.orange
+lexers.STYLE_TAG = 'fore:'..colors.red
+lexers.STYLE_TYPE = 'fore:'..colors.yellow
+lexers.STYLE_VARIABLE = 'fore:'..colors.blue
+lexers.STYLE_WHITESPACE = ''
+lexers.STYLE_EMBEDDED = 'back:blue'
+lexers.STYLE_IDENTIFIER = fg
+
+lexers.STYLE_LINENUMBER = fg
+lexers.STYLE_CURSOR = 'fore:'..colors.base03..',back:'..colors.base0
+-- lexers.STYLE_SELECTION = 'back:'..colors.base02
+lexers.STYLE_SELECTION = 'back:white'
diff --git a/ui-curses.c b/ui-curses.c
index 7c1f5b3..d00dbf3 100644
--- a/ui-curses.c
+++ b/ui-curses.c
@@ -59,6 +59,11 @@ int ESCDELAY;
 } while (0);
 #endif
 
+typedef struct {
+	attr_t attr;
+	short fg, bg;
+} CellStyle;
+
 typedef struct UiCursesWin UiCursesWin;
 
 typedef struct {
@@ -88,7 +93,7 @@ struct UiCursesWin {
 	int sidebar_width;        /* width of the sidebar showing line numbers etc. */
 	UiCursesWin *next, *prev; /* pointers to neighbouring windows */
 	enum UiOption options;    /* display settings for this window */
-	attr_t styles[UI_STYLES_MAX];
+	CellStyle styles[UI_STYLE_MAX];
 };
 
 static volatile sig_atomic_t need_resize; /* TODO */
@@ -454,7 +459,7 @@ static int color_fromstring(const char *s)
 	return -1;
 }
 
-static unsigned int color_pair_hash(short fg, short bg) {
+static inline unsigned int color_pair_hash(short fg, short bg) {
 	if (fg == -1)
 		fg = COLORS;
 	if (bg == -1)
@@ -510,41 +515,47 @@ static short color_pair_get(short fg, short bg) {
 	return color2palette[index];
 }
 
+static inline attr_t style_to_attr(CellStyle *style) {
+	return style->attr | COLOR_PAIR(color_pair_get(style->fg, style->bg));
+}
+
 static bool ui_window_syntax_style(UiWin *w, int id, const char *style) {
 	UiCursesWin *win = (UiCursesWin*)w;
-	if (id >= UI_STYLES_MAX)
+	if (id >= UI_STYLE_MAX)
 		return false;
-	short fg = -1, bg = -1;
-	attr_t attr = A_NORMAL;
+	if (!style)
+		return true;
+	CellStyle cell_style = win->styles[UI_STYLE_DEFAULT];
 	char *style_copy = strdup(style), *option = style_copy, *next, *p;
 	while (option) {
 		if ((next = strchr(option, ',')))
 			*next++ = '\0';
 		if ((p = strchr(option, ':')))
 			*p++ = '\0';
-		if (!strcasecmp(option, "bold")) {
-			attr |= A_BOLD;
+		if (!strcasecmp(option, "reverse")) {
+			cell_style.attr |= A_REVERSE;
+		} else if (!strcasecmp(option, "bold")) {
+			cell_style.attr |= A_BOLD;
 		} else if (!strcasecmp(option, "notbold")) {
-			attr &= ~A_BOLD;
+			cell_style.attr &= ~A_BOLD;
 #ifdef A_ITALIC
 		} else if (!strcasecmp(option, "italics")) {
-			attr |= A_ITALIC;
+			cell_style.attr |= A_ITALIC;
 		} else if (!strcasecmp(option, "notitalics")) {
-			attr &= ~A_ITALIC;
+			cell_style.attr &= ~A_ITALIC;
 #endif
 		} else if (!strcasecmp(option, "underlined")) {
-			attr |= A_UNDERLINE;
+			cell_style.attr |= A_UNDERLINE;
 		} else if (!strcasecmp(option, "notunderlined")) {
-			attr &= ~A_UNDERLINE;
+			cell_style.attr &= ~A_UNDERLINE;
 		} else if (!strcasecmp(option, "fore")) {
-			fg = color_fromstring(p);
+			cell_style.fg = color_fromstring(p);
 		} else if (!strcasecmp(option, "back")) {
-			bg = color_fromstring(p);
+			cell_style.bg = color_fromstring(p);
 		}
 		option = next;
 	}
-	attr |= COLOR_PAIR(color_pair_get(fg, bg));
-	win->styles[id] = attr;
+	win->styles[id] = cell_style;
 	free(style_copy);
 	return true;
 }
@@ -585,6 +596,8 @@ static bool ui_window_draw_sidebar(UiCursesWin *win) {
 		size_t prev_lineno = 0;
 		size_t cursor_lineno = view_cursor_getpos(win->view).line;
 		werase(win->winside);
+		wbkgd(win->winside, style_to_attr(&win->styles[UI_STYLE_DEFAULT]));
+		wattrset(win->winside, style_to_attr(&win->styles[UI_STYLE_LINENUMBER]));
 		for (const Line *l = line; l; l = l->next, i++) {
 			if (l->lineno && l->lineno != prev_lineno) {
 				if (win->options & UI_OPTION_LINE_NUMBERS_ABSOLUTE) {
@@ -632,15 +645,25 @@ static void ui_window_draw(UiWin *w) {
 	UiCursesWin *win = (UiCursesWin*)w;
 	if (!ui_window_draw_sidebar(win))
 		return;
+	wbkgd(win->win, style_to_attr(&win->styles[UI_STYLE_DEFAULT]));
 	wmove(win->win, 0, 0);
 	int width = view_width_get(win->view);
+	CellStyle *prev_style = NULL;
+	short selection_bg = win->styles[UI_STYLE_SELECTION].bg;
+	attr_t attr;
 	for (const Line *l = view_lines_get(win->view); l; l = l->next) {
 		for (int x = 0; x < width; x++) {
-			int attr = win->styles[l->cells[x].attr];
-			if (l->cells[x].cursor && (win->ui->selwin == win || win->ui->prompt_win == win))
-				attr = A_NORMAL | A_REVERSE;
-			if (l->cells[x].selected)
-				attr |= A_REVERSE;
+			CellStyle *style = &win->styles[l->cells[x].attr];
+			if (l->cells[x].cursor && (win->ui->selwin == win || win->ui->prompt_win == win)) {
+				attr = style_to_attr(&win->styles[UI_STYLE_CURSOR]);
+				prev_style = NULL;
+			} else if (l->cells[x].selected) {
+				attr = style->attr | COLOR_PAIR(color_pair_get(style->fg, selection_bg));
+				prev_style = NULL;
+			} else if (style != prev_style) {
+				attr = style_to_attr(style);
+				prev_style = style;
+			}
 			wattrset(win->win, attr);
 			waddstr(win->win, l->cells[x].data);
 		}
@@ -841,6 +864,18 @@ static UiWin *ui_window_new(Ui *ui, View *view, File *file) {
 		return NULL;
 	}
 
+	CellStyle style = (CellStyle) {
+		.fg = -1, .bg = -1, .attr = A_NORMAL,
+	};
+
+	for (int i = 0; i < UI_STYLE_MAX; i++) {
+		win->styles[i] = style;
+	}
+
+	style.attr |= A_REVERSE;
+	win->styles[UI_STYLE_CURSOR] = style;
+	win->styles[UI_STYLE_SELECTION] = style;
+
 	win->ui = uic;
 	win->view = view;
 	win->file = file;
@@ -1071,4 +1106,3 @@ void ui_curses_free(Ui *ui) {
 		termkey_destroy(uic->termkey);
 	free(uic);
 }
-
diff --git a/ui.h b/ui.h
index 8c94d51..656f5a8 100644
--- a/ui.h
+++ b/ui.h
@@ -23,7 +23,14 @@ enum UiOption {
 	UI_OPTION_SYMBOL_EOF = 1 << 6,
 };
 
-#define UI_STYLES_MAX 64
+enum UiStyles {
+	UI_STYLE_LEXER_MAX = 64,
+	UI_STYLE_DEFAULT,
+	UI_STYLE_CURSOR,
+	UI_STYLE_SELECTION,
+	UI_STYLE_LINENUMBER,
+	UI_STYLE_MAX,
+};
 
 #include "text.h"
 #include "view.h"
diff --git a/view.c b/view.c
index 2f5aa47..80e940b 100644
--- a/view.c
+++ b/view.c
@@ -71,6 +71,8 @@ struct View {
 	int tabwidth;       /* how many spaces should be used to display a tab character */
 	Cursor *cursors;    /* all cursors currently active */
 	Selection *selections; /* all selected regions */
+	lua_State *lua;     /* lua state used for syntax highlighting */
+	char *lexer_name;
 };
 
 static const SyntaxSymbol symbols_none[] = {
@@ -333,20 +335,31 @@ void view_cursor_to(View *view, size_t pos) {
  * stop once the screen is full, update view->end, view->lastline */
 void view_draw(View *view) {
 	view_clear(view);
-	/* current absolute file position */
-	size_t pos = view->start;
+	/* absolute start of visible area */
+	size_t start = view->start;
+	/* maximal number of bytes to consider for syntax highlighting before
+	 * the visible area */
+	const size_t lexer_before_max = 4096;
+	/* absolute position to start syntax highlighting */
+	size_t lexer_start = start >= lexer_before_max ? start - lexer_before_max : 0;
+	/* number of bytes used for syntax highlighting before visible are */
+	size_t lexer_before = start - lexer_start;
 	/* number of bytes to read in one go */
-	size_t text_len = view->width * view->height;
+	const size_t text_size = lexer_before_max + (view->width * view->height);
 	/* current buffer to work with */
-	char text[text_len+1];
+	char text[text_size+1];
 	/* remaining bytes to process in buffer*/
-	size_t rem = text_bytes_get(view->text, pos, text_len, text);
-	/* NUL terminate because regex(3) function expect it */
-	text[rem] = '\0';
+	size_t text_len = text_bytes_get(view->text, lexer_start, text_size, text);
+	/* NUL terminate text section */
+	text[text_len] = '\0';
+	/* remaining bytes to process */
+	size_t rem = text_len;
+	if (rem >= lexer_before)
+		rem -= lexer_before;
+	/* absolute position of character currently being added to display */
+	size_t pos = start;
 	/* current position into buffer from which to interpret a character */
-	char *cur = text;
-	/* default and current curses attributes to use */
-	int default_attrs = 0, attrs = default_attrs;
+	char *cur = text + lexer_before;
 	/* start from known multibyte state */
 	mbstate_t mbstate = { 0 };
 
@@ -369,7 +382,7 @@ void view_draw(View *view) {
 			 * wide character. advance file position and read
 			 * another junk into buffer.
 			 */
-			rem = text_bytes_get(view->text, pos, text_len, text);
+			rem = text_bytes_get(view->text, pos, text_size, text);
 			text[rem] = '\0';
 			cur = text;
 			continue;
@@ -392,7 +405,6 @@ void view_draw(View *view) {
 			cell = (Cell){ .data = "\n", .len = 2, .width = 1, .istab = false };
 		}
 
-		cell.attr = attrs;
 		if (!view_addch(view, &cell))
 			break;
 
@@ -404,6 +416,70 @@ void view_draw(View *view) {
 	/* set end of vieviewg region */
 	view->end = pos;
 	view->lastline = view->line ? view->line : view->bottomline;
+
+	lua_State *L = view->lua;
+	if (L && view->lexer_name) {
+
+		lua_getglobal(L, "lexers");
+		lua_getfield(L, -1, "load");
+		lua_pushstring(L, view->lexer_name);
+		lua_pcall(L, 1, 1, 0);
+
+		lua_getfield(L, -1, "_TOKENSTYLES");
+		lua_getfield(L, -2, "lex");
+
+		lua_pushvalue(L, -3); /* lexer obj */
+
+		const char *lex_text = text;
+		if (lexer_start > 0) {
+			/* try to start lexing at a line boundry */
+			const char *newline = memchr(text, '\n', lexer_before);
+			if (newline)
+				lex_text = newline;
+		}
+
+		lua_pushlstring(L, lex_text, text_len - (lex_text - text));
+		lua_pushinteger(L, 1 /* inital style: whitespace */);
+
+		int token_count;
+
+		if (lua_isfunction(L, -4) &&  !lua_pcall(L, 3, 1, 0) && lua_istable(L, -1) &&
+		   (token_count = lua_objlen(L, -1)) > 0) {
+
+			size_t pos = lexer_before - (lex_text - text);
+			Line *line = view->topline;
+			int col = 0;
+
+			for (int i = 1; i < token_count; i += 2) {
+				lua_rawgeti(L, -1, i);
+				//const char *name = lua_tostring(L, -1);
+				lua_gettable(L, -3); /* _TOKENSTYLES[token] */
+				size_t token_style = lua_tointeger(L, -1);
+				lua_pop(L, 1); /* style */
+				lua_rawgeti(L, -1, i + 1);
+				size_t token_end = lua_tointeger(L, -1) - 1;
+				lua_pop(L, 1); /* pos */
+
+				for (bool token_next = false; line; line = line->next, col = 0) {
+					for (; col < line->width; col++) {
+						if (pos < token_end) {
+							line->cells[col].attr = token_style;
+							pos += line->cells[col].len;
+						} else {
+							token_next = true;
+							break;
+						}
+					}
+					if (token_next)
+						break;
+				}
+			}
+			lua_pop(L, 1);
+		}
+
+		lua_pop(L, 3); /* _TOKENSTYLES, language specific lexer, lexers globale */
+	}
+
 	if (view->line) {
 		for (int x = view->col; x < view->width; x++)
 			view->line->cells[x] = cell_blank;
@@ -507,6 +583,7 @@ void view_free(View *view) {
 	while (view->selections)
 		view_selections_free(view->selections);
 	free(view->lines);
+	free(view->lexer_name);
 	free(view);
 }
 
@@ -516,7 +593,7 @@ void view_reload(View *view, Text *text) {
 	view_cursor_to(view, 0);
 }
 
-View *view_new(Text *text, ViewEvent *events) {
+View *view_new(Text *text, lua_State *lua, ViewEvent *events) {
 	if (!text)
 		return NULL;
 	View *view = calloc(1, sizeof(View));
@@ -528,6 +605,7 @@ View *view_new(Text *text, ViewEvent *events) {
 	}
 		
 	view->text = text;
+	view->lua = lua;
 	view->events = events;
 	view->tabwidth = 8;
 	view_options_set(view, 0);
@@ -782,12 +860,85 @@ void view_scroll_to(View *view, size_t pos) {
 	view_cursors_scroll_to(view->cursor, pos);
 }
 
+#include <stdio.h>
+
+
 bool view_syntax_set(View *view, const char *name) {
-	return false;
+	if (!name) {
+		free(view->lexer_name);
+		view->lexer_name = NULL;
+		return true;
+	}
+
+	lua_State *L = view->lua;
+	if (!L)
+		return false;
+
+	/* Try to load the specified lexer and parse its token styles.
+	 * Roughly equivalent to the following lua code:
+	 *
+	 * lang = lexers.load(name)
+	 * for token_name, id in pairs(lang._TOKENSTYLES) do
+	 * 	ui->syntax_style(id, lexers:get_style(lang, token_name); 
+	 */
+	lua_getglobal(L, "lexers");
+
+	lua_getfield(L, -1, "STYLE_DEFAULT");
+	view->ui->syntax_style(view->ui, UI_STYLE_DEFAULT, lua_tostring(L, -1));
+	lua_pop(L, 1);
+	lua_getfield(L, -1, "STYLE_CURSOR");
+	view->ui->syntax_style(view->ui, UI_STYLE_CURSOR, lua_tostring(L, -1));
+	lua_pop(L, 1);
+	lua_getfield(L, -1, "STYLE_SELECTION");
+	view->ui->syntax_style(view->ui, UI_STYLE_SELECTION, lua_tostring(L, -1));
+	lua_pop(L, 1);
+	lua_getfield(L, -1, "STYLE_LINENUMBER");
+	view->ui->syntax_style(view->ui, UI_STYLE_LINENUMBER, lua_tostring(L, -1));
+	lua_pop(L, 1);
+
+
+	lua_getfield(L, -1, "load");
+	lua_pushstring(L, name);
+
+	if (lua_pcall(L, 1, 1, 0))
+		return false;
+
+	if (!lua_istable(L, -1)) {
+		lua_pop(L, 2);
+		return false;
+	}
+
+	view->lexer_name = strdup(name);
+	/* loop through all _TOKENSTYLES and parse them */
+	lua_getfield(L, -1, "_TOKENSTYLES");
+	lua_pushnil(L); /* first key */
+	
+	while (lua_next(L, -2)) {
+		size_t id = lua_tointeger(L, -1);
+		//const char *name = lua_tostring(L, -2);
+		lua_pop(L, 1); /* remove value (=id), keep key (=name) */
+		lua_getfield(L, -4, "get_style");
+		lua_pushvalue(L, -5); /* lexer */
+		lua_pushvalue(L, -5); /* lang */
+		lua_pushvalue(L, -4); /* token_name */
+		if (lua_pcall(L, 3, 1, 0))
+			return false;
+		const char *style = lua_tostring(L, -1);
+		//printf("%s\t%d\t%s\n", name, id, style);
+		view->ui->syntax_style(view->ui, id, style);
+		lua_pop(L, 1); /* style */
+	}
+
+	lua_pop(L, 1); /* _TOKENSTYLES */
+	lua_pop(L, 1); /* grammar */
+
+	lua_pop(L, 1); /* lexers */
+
+	return true;
 }
 
 const char *view_syntax_get(View *view) {
-	return NULL;
+	return view->lexer_name;
 }
 
 void view_options_set(View *view, enum UiOption options) {
diff --git a/view.h b/view.h
index a9f7ec9..facccb1 100644
--- a/view.h
+++ b/view.h
@@ -3,6 +3,7 @@
 
 #include <stddef.h>
 #include <stdbool.h>
+#include <lua.h>
 #include "register.h"
 #include "text.h"
 #include "ui.h"
@@ -45,7 +46,7 @@ typedef struct {
 	size_t col;
 } CursorPos;
 
-View *view_new(Text*, ViewEvent*);
+View *view_new(Text*, lua_State*, ViewEvent*);
 void view_ui(View*, UiWin*);
 /* change associated text displayed in this window */
 void view_reload(View*, Text*);
diff --git a/vis-cmds.c b/vis-cmds.c
index 8b4e805..b407e1d 100644
--- a/vis-cmds.c
+++ b/vis-cmds.c
@@ -336,7 +336,7 @@ static const char *file_open_dialog(Vis *vis, const char *pattern) {
 	Text *txt_orig = file->text;
 	View *view_orig = win->view;
 	Text *txt = text_load(NULL);
-	View *view = view_new(txt, NULL);
+	View *view = view_new(txt, NULL, NULL);
 	filename[0] = '\0';
 	snprintf(vis_open, sizeof(vis_open)-1, "vis-open %s", pattern ? pattern : "");
 
diff --git a/vis-core.h b/vis-core.h
index ceb1311..1333eab 100644
--- a/vis-core.h
+++ b/vis-core.h
@@ -156,6 +156,7 @@ struct Vis {
 	volatile sig_atomic_t sigbus;        /* one of the memory mapped region became unavailable (SIGBUS) */
 	sigjmp_buf sigbus_jmpbuf;            /* used to jump back to a known good state in the mainloop after (SIGBUS) */
 	Map *actions;                        /* registered editor actions / special keys commands */
+	lua_State *lua;                      /* lua context used for syntax highligthing */
 };
 
 /** stuff used by multiple of the vis-* files */
diff --git a/vis.c b/vis.c
index 377b6a9..9684fac 100644
--- a/vis.c
+++ b/vis.c
@@ -33,8 +33,12 @@
 #include <sys/stat.h>
 #include <sys/ioctl.h>
 #include <sys/mman.h>
-
+#include <pwd.h>
+#include <lauxlib.h>
+#include <lualib.h>
+#include <lua.h>
 #include <termkey.h>
+
 #include "vis.h"
 #include "text-util.h"
 #include "text-motions.h"
@@ -120,11 +124,25 @@ static File *file_new(Vis *vis, const char *filename) {
 }
 
 void vis_window_name(Win *win, const char *filename) {
+	lua_State *L = win->vis->lua;
 	File *file = win->file;
 	if (filename != file->name) {
 		free((char*)file->name);
 		file->name = filename ? strdup(filename) : NULL;
 	}
+
+	if (filename && L) {
+		lua_getglobal(L, "lexers");
+		lua_getfield(L, -1, "lexer_name");
+		lua_pushstring(L, filename);
+		lua_pcall(L, 1, 1, 0);
+		if (lua_isstring(L, -1)) {
+			const char *lexer_name = lua_tostring(L, -1);
+			if (lexer_name)
+				view_syntax_set(win->view, lexer_name);
+		}
+		lua_pop(L, 2); /* return value: lexer name, lexers variable */
+	}
 }
 
 static void windows_invalidate(Vis *vis, size_t start, size_t end) {
@@ -169,7 +187,7 @@ static Win *window_new_file(Vis *vis, File *file) {
 		.selection = window_selection_changed,
 	};
 	win->jumplist = ringbuf_alloc(31);
-	win->view = view_new(file->text, &win->events);
+	win->view = view_new(file->text, vis->lua, &win->events);
 	win->ui = vis->ui->window_new(vis->ui, win->view, file);
 	if (!win->jumplist || !win->view || !win->ui) {
 		window_free(win);
@@ -287,6 +305,64 @@ Vis *vis_new(Ui *ui) {
 	Vis *vis = calloc(1, sizeof(Vis));
 	if (!vis)
 		return NULL;
+	lua_State *L = lua_open();
+	if (!(vis->lua = L))
+		goto err;
+	luaL_openlibs(L);
+
+	/* try to get users home directory */
+	const char *home = getenv("HOME");
+	if (!home || !*home) {
+		struct passwd *pw = getpwuid(getuid());
+		if (pw)
+			home = pw->pw_dir;
+	}
+
+	/* extends lua's package.path with:
+	 * - $VIS_PATH/lexers
+	 * - $HOME/.vis/lexers
+	 * - /usr/local/share/vis/lexers
+	 * - /usr/share/vis/lexers
+	 * - package.path (standard lua search path)
+	 */
+	int paths = 3;
+	lua_getglobal(L, "package");
+
+	const char *vis_path = getenv("VIS_PATH");
+	if (vis_path) {
+		lua_pushstring(L, vis_path);
+		lua_pushstring(L, "/lexers/?.lua;");
+		lua_concat(L, 2);
+		paths++;
+	}
+
+	if (home && *home) {
+		lua_pushstring(L, home);
+		lua_pushstring(L, "/.vis/lexers/?.lua;");
+		lua_concat(L, 2);
+		paths++;
+	}
+
+	lua_pushstring(L, "/usr/local/share/vis/lexers/?.lua;");
+	lua_pushstring(L, "/usr/share/vis/lexers/?.lua;");
+	lua_getfield(L, -paths, "path");
+	lua_concat(L, paths);
+	lua_setfield(L, -2, "path");
+	lua_pop(L, 1); /* package */
+
+	/* try to load the lexer module */
+	lua_getglobal(L, "require");
+	lua_pushstring(L, "lexer");
+	if (lua_pcall(L, 1, 1, 0)) {
+		lua_close(L);
+		vis->lua = L = NULL;
+	} else {
+		lua_setglobal(L, "lexers");
+		lua_getglobal(L, "require");
+		lua_pushstring(L, "themes/default");
+		lua_pcall(L, 1, 0, 0);
+	}
+
 	vis->ui = ui;
 	vis->ui->init(vis->ui, vis);
 	vis->tabwidth = 8;
@@ -302,7 +378,7 @@ Vis *vis_new(Ui *ui) {
 		goto err;
 	if (!(vis->prompt->file->text = text_load(NULL)))
 		goto err;
-	if (!(vis->prompt->view = view_new(vis->prompt->file->text, NULL)))
+	if (!(vis->prompt->view = view_new(vis->prompt->file->text, NULL, NULL)))
 		goto err;
 	if (!(vis->prompt->ui = vis->ui->prompt_new(vis->ui, vis->prompt->view, vis->prompt->file)))
 		goto err;
@@ -318,6 +394,8 @@ err:
 void vis_free(Vis *vis) {
 	if (!vis)
 		return;
+	if (vis->lua)
+		lua_close(vis->lua);
 	while (vis->windows)
 		vis_window_close(vis->windows);
 	file_free(vis, vis->prompt->file);