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<h1>Lua LPeg Lexers</h1>
<p>Scintilla's LPeg lexer adds dynamic <a href="http://lua.org">Lua</a>
<a href="http://www.inf.puc-rio.br/~roberto/lpeg/">LPeg</a> lexers to
Scintilla. It is the quickest way to add new or customized syntax
highlighting and code folding for programming languages to any
Scintilla-based text editor or IDE.</p>
<h2>Features</h2>
<ul>
<li>Support for <a href="#LexerList">over 100 programming languages</a>.</li>
<li>Easy lexer embedding for multi-language lexers.</li>
<li>Universal color themes.</li>
<li>Comparable speed to native Scintilla lexers.</li>
</ul>
<h2>Enabling and Configuring the LPeg Lexer</h2>
<p>Scintilla is <em>not</em> compiled with the LPeg lexer enabled by
default (it is present, but empty). You need to manually enable it with the
<code>LPEG_LEXER</code> flag when building Scintilla and its lexers. You
also need to build and link the Lua source files contained in Scintilla's
<code>lua/src/</code> directory to <code>lexers/LexLPeg.cxx</code>. If your
application has its own copy of Lua, you can ignore Scintilla's copy and
link to yours.
<p>At this time, only the GTK, curses, and MinGW32 (for win32) platform
makefiles facilitate enabling the LPeg lexer. For example, when building
Scintilla, run <code>make LPEG_LEXER=1</code>. User contributions to
facilitate this for the other platforms is encouraged.</p>
<p>When Scintilla is compiled with the LPeg lexer enabled, and after
selecting it as the lexer to use via
<a class="message" href="ScintillaDoc.html#SCI_SETLEXER">SCI_SETLEXER</a> or
<a class="message" href="ScintillaDoc.html#SCI_SETLEXERLANGUAGE">SCI_SETLEXERLANGUAGE</a>,
the following property <em>must</em> be set via
<a class="message" href="ScintillaDoc.html#SCI_SETPROPERTY">SCI_SETPROPERTY</a>:</p>
<table class="standard" summary="Search flags">
<tbody>
<tr>
<td><code>lexer.lpeg.home</code></td>
<td>The directory containing the Lua lexers. This is the path
where you included Scintilla's <code>lexlua/</code> directory in
your application's installation location.</td>
</tr>
</tbody>
</table>
<p>The following properties are optional and may or may not be set:</p>
<table class="standard" summary="Search flags">
<tbody>
<tr>
<td><code>lexer.lpeg.color.theme</code></td>
<td>The color theme to use. Color themes are located in the
<code>lexlua/themes/</code> directory. Currently supported themes
are <code>light</code>, <code>dark</code>, <code>scite</code>, and
<code>curses</code>. Your application can define colors and styles
manually through Scintilla properties. The theme files have
examples.</td>
</tr>
<tr>
<td><code>fold</code></td>
<td>For Lua lexers that have a folder, folding is turned on if
<code>fold</code> is set to <code>1</code>. The default is
<code>0</code>.</td>
</tr>
<tr>
<td><code>fold.by.indentation</code</td>
<td>For Lua lexers that do not have a folder, if
<code>fold.by.indentation</code> is set to <code>1</code>, folding is
done based on indentation level (like Python). The default is
<code>0</code>.</td>
</tr>
<tr>
<td><code>fold.line.comments</code></td>
<td>If <code>fold.line.comments</code> is set to <code>1</code>,
multiple, consecutive line comments are folded, and only the top-level
comment is shown. There is a small performance penalty for large
source files when this option and folding are enabled. The default is
<code>0</code>.</td>
</tr>
<tr>
<td><code>fold.on.zero.sum.lines</code></td>
<td>If <code>fold.on.zero.sum.lines</code> is set to <code>1</code>,
lines that contain both an ending and starting fold point are marked
as fold points. For example, the C line <code>} else {</code> would be
marked as a fold point. The default is <code>0</code>.</td>
</tr>
</tbody>
</table>
<h2>Using the LPeg Lexer</h2>
<p>Your application communicates with the LPeg lexer using Scintilla's
<a class="message" href="ScintillaDoc.html#SCI_PRIVATELEXERCALL"><code>SCI_PRIVATELEXERCALL</code></a>
API. The operation constants recognized by the LPeg lexer are based on
Scintilla's existing named constants. Note that some of the names of the
operations do not make perfect sense. This is a tradeoff in order to reuse
Scintilla's existing constants.</p>
<p>In the descriptions that follow,
<code>SCI_PRIVATELEXERCALL(int operation, void *pointer)</code> means you
would call Scintilla like
<code>SendScintilla(sci, SCI_PRIVATELEXERCALL, operation, pointer);</code></p>
<h3>Usage Example</h3>
<p>The curses platform demo, jinx, has a C-source example for using the LPeg
lexer. Additionally, here is a pseudo-code example:</p>
<pre><code>
init_app() {
sci = scintilla_new()
}
create_doc() {
doc = SendScintilla(sci, SCI_CREATEDOCUMENT, 0, 0)
SendScintilla(sci, SCI_SETDOCPOINTER, 0, doc)
SendScintilla(sci, SCI_SETLEXERLANGUAGE, 0, "lpeg")
home = "/home/mitchell/app/lua_lexers"
SendScintilla(sci, SCI_SETPROPERTY, "lexer.lpeg.home", home)
SendScintilla(sci, SCI_SETPROPERTY, "lexer.lpeg.color.theme", "light")
fn = SendScintilla(sci, SCI_GETDIRECTFUNCTION, 0, 0)
SendScintilla(sci, SCI_PRIVATELEXERCALL, SCI_GETDIRECTFUNCTION, fn)
psci = SendScintilla(sci, SCI_GETDIRECTPOINTER, 0, 0)
SendScintilla(sci, SCI_PRIVATELEXERCALL, SCI_SETDOCPOINTER, psci)
SendScintilla(sci, SCI_PRIVATELEXERCALL, SCI_SETLEXERLANGUAGE, "lua")
}
set_lexer(lang) {
psci = SendScintilla(sci, SCI_GETDIRECTPOINTER, 0, 0)
SendScintilla(sci, SCI_PRIVATELEXERCALL, SCI_SETDOCPOINTER, psci)
SendScintilla(sci, SCI_PRIVATELEXERCALL, SCI_SETLEXERLANGUAGE, lang)
}
</code></pre>
<code><a class="message" href="#SCI_CHANGELEXERSTATE">SCI_PRIVATELEXERCALL(SCI_CHANGELEXERSTATE, lua_State *L)</a><br/>
<a class="message" href="#SCI_GETDIRECTFUNCTION">SCI_PRIVATELEXERCALL(SCI_GETDIRECTFUNCTION, int SciFnDirect)</a><br/>
<a class="message" href="#SCI_GETLEXERLANGUAGE">SCI_PRIVATELEXERCALL(SCI_GETLEXERLANGUAGE, char *languageName) → int</a><br/>
<a class="message" href="#SCI_GETSTATUS">SCI_PRIVATELEXERCALL(SCI_GETSTATUS, char *errorMessage) → int</a><br/>
<a class="message" href="#styleNum">SCI_PRIVATELEXERCALL(int styleNum, char *styleName) → int</a><br/>
<a class="message" href="#SCI_SETDOCPOINTER">SCI_PRIVATELEXERCALL(SCI_SETDOCPOINTER, int sci)</a><br/>
<a class="message" href="#SCI_SETLEXERLANGUAGE">SCI_PRIVATELEXERCALL(SCI_SETLEXERLANGUAGE, languageName)</a><br/>
</code>
<p><b id="SCI_CHANGELEXERSTATE">SCI_PRIVATELEXERCALL(SCI_CHANGELEXERSTATE, lua_State *L)</b><br/>
Tells the LPeg lexer to use <code>L</code> as its Lua state instead of
creating a separate state.</p>
<p><code>L</code> must have already opened the "base", "string", "table",
"package", and "lpeg" libraries. If <code>L</code> is a Lua 5.1 state, it
must have also opened the "io" library.</p>
<p>The LPeg lexer will create a single <code>lexer</code> package (that can
be used with Lua's <code>require</code> function), as well as a number of
other variables in the <code>LUA_REGISTRYINDEX</code> table with the "sci_"
prefix.</p>
<p>Rather than including the path to Scintilla's Lua lexers in the
<code>package.path</code> of the given Lua state, set the "lexer.lpeg.home"
property instead. The LPeg lexer uses that property to find and load
lexers.</p>
<p>Usage:</p>
<pre><code>
lua = luaL_newstate()
SendScintilla(sci, SCI_PRIVATELEXERCALL, SCI_CHANGELEXERSTATE, lua)
</code></pre>
<p><b id="SCI_GETDIRECTFUNCTION">SCI_PRIVATELEXERCALL(SCI_GETDIRECTFUNCTION, SciFnDirect)</b><br/>
Tells the LPeg lexer the address of <code>SciFnDirect</code>, the function
that handles Scintilla messages.</p>
<p>Despite the name <code>SCI_GETDIRECTFUNCTION</code>, it only notifies the
LPeg lexer what the value of <code>SciFnDirect</code> obtained from
<a class="message" href="ScintillaDoc.html#SCI_GETDIRECTFUNCTION"><code>SCI_GETDIRECTFUNCTION</code></a>
is. It does not return anything. Use this if you would like to have the LPeg
lexer set all Lua lexer styles automatically. This is useful for maintaining
a consistent color theme. Do not use this if your application maintains its
own color theme.</p>
<p>If you use this call, it <em>must</em> be made <em>once</em> for each
Scintilla document that was created using Scintilla's
<a class="message" href="ScintillaDoc.html#SCI_CREATEDOCUMENT"><code>SCI_CREATEDOCUMENT</code></a>.
You must also use the
<a class="message" href="#SCI_SETDOCPOINTER"><code>SCI_SETDOCPOINTER</code></a> LPeg lexer
API call.</p>
<p>Usage:</p>
<pre><code>
fn = SendScintilla(sci, SCI_GETDIRECTFUNCTION, 0, 0)
SendScintilla(sci, SCI_PRIVATELEXERCALL, SCI_GETDIRECTFUNCTION, fn)
</code></pre>
<p>See also: <a class="message" href="#SCI_SETDOCPOINTER"><code>SCI_SETDOCPOINTER</code></a></p>
<p><b id="SCI_GETLEXERLANGUAGE">SCI_PRIVATELEXERCALL(SCI_GETLEXERLANGUAGE, char *languageName) → int</b><br/>
Returns the length of the string name of the current Lua lexer or stores the
name into the given buffer. If the buffer is long enough, the name is
terminated by a <code>0</code> character.</p>
<p>For parent lexers with embedded children or child lexers embedded into
parents, the name is in "lexer/current" format, where "lexer" is the actual
lexer's name and "current" is the parent or child lexer at the current caret
position. In order for this to work, you must have called
<a class="message" href="#SCI_GETDIRECTFUNCTION"><code>SCI_GETDIRECTFUNCTION</code></a>
and
<a class="message" href="#SCI_SETDOCPOINTER"><code>SCI_SETDOCPOINTER</code></a>.</p>
<p><b id="SCI_GETSTATUS">SCI_PRIVATELEXERCALL(SCI_GETSTATUS, char *errorMessage) → int</b><br/>
Returns the length of the error message of the LPeg lexer or Lua lexer error
that occurred (if any), or stores the error message into the given buffer.</p>
<p>If no error occurred, the returned message will be empty.</p>
<p>Since the LPeg lexer does not throw errors as they occur, errors can only
be handled passively. Note that the LPeg lexer does print all errors to
stderr.</p>
<p>Usage:</p>
<pre><code>
SendScintilla(sci, SCI_PRIVATELEXERCALL, SCI_GETSTATUS, errmsg)
if (strlen(errmsg) > 0) { /* handle error */ }
</code></pre>
<p><b id="SCI_PRIVATELEXERCALL">SCI_PRIVATELEXERCALL(int styleNum, char *styleName) → int</b><br/>
Returns the length of the token name associated with the given style number
or stores the style name into the given buffer. If the buffer is long
enough, the string is terminated by a <code>0</code> character.</p>
<p>Usage:</p>
<pre><code>
style = SendScintilla(sci, SCI_GETSTYLEAT, pos, 0)
SendScintilla(sci, SCI_PRIVATELEXERCALL, style, token)
// token now contains the name of the style at pos
</code></pre>
<p><b id="SCI_SETDOCPOINTER">SCI_PRIVATELEXERCALL(SCI_SETDOCPOINTER, int sci)</b><br/>
Tells the LPeg lexer the address of the Scintilla window (obtained via
Scintilla's
<a class="message" href="ScintillaDoc.html#SCI_GETDIRECTPOINTER"><code>SCI_GETDIRECTPOINTER</code></a>)
currently in use.</p>
<p>Despite the name <code>SCI_SETDOCPOINTER</code>, it has no relationship
to Scintilla documents.</p>
<p>Use this call only if you are using the
<a class="message" href="#SCI_GETDIRECTFUNCTION"><code>SCI_GETDIRECTFUNCTION</code></a>
LPeg lexer API call. It <em>must</em> be made <em>before</em> each call to
the <a class="message" href="#SCI_SETLEXERLANGUAGE"><code>SCI_SETLEXERLANGUAGE</code></a>
LPeg lexer API call.</p>
<p>Usage:</p>
<pre><code>
SendScintilla(sci, SCI_PRIVATELEXERCALL, SCI_SETDOCPOINTER, sci)
</code></pre>
<p>See also: <a class="message" href="#SCI_GETDIRECTFUNCTION"><code>SCI_GETDIRECTFUNCTION</code></a>,
<a class="message" href="#SCI_SETLEXERLANGUAGE"><code>SCI_SETLEXERLANGUAGE</code></a></p>
<p><b id="SCI_SETLEXERLANGUAGE">SCI_PRIVATELEXERCALL(SCI_SETLEXERLANGUAGE, const char *languageName)</b><br/>
Sets the current Lua lexer to <code>languageName</code>.</p>
<p>If you are having the LPeg lexer set the Lua lexer styles automatically,
make sure you call the
<a class="message" href="#SCI_SETDOCPOINTER"><code>SCI_SETDOCPOINTER</code></a>
LPeg lexer API <em>first</em>.</p>
<p>Usage:</p>
<pre><code>
SendScintilla(sci, SCI_PRIVATELEXERCALL, SCI_SETLEXERLANGUAGE, "lua")
</code></pre>
<p>See also: <a class="message" href="#SCI_SETDOCPOINTER"><code>SCI_SETDOCPOINTER</code></a></p>
<h2 id="lexer">Writing Lua Lexers</h2>
<p>Lexers highlight the syntax of source code. Scintilla (the editing component
behind <a href="http://foicica.com/textadept">Textadept</a>) traditionally uses static, compiled C++
lexers which are notoriously difficult to create and/or extend. On the other
hand, <a href="http://lua.org">Lua</a> makes it easy to to rapidly create new lexers, extend existing
ones, and embed lexers within one another. Lua lexers tend to be more
readable than C++ lexers too.</p>
<p>Lexers are Parsing Expression Grammars, or PEGs, composed with the Lua
<a href="http://www.inf.puc-rio.br/~roberto/lpeg/lpeg.html">LPeg library</a>. The following table comes from the LPeg documentation and
summarizes all you need to know about constructing basic LPeg patterns. This
module provides convenience functions for creating and working with other
more advanced patterns and concepts.</p>
<table class="standard">
<thead>
<tr>
<th>Operator </th>
<th> Description</th>
</tr>
</thead>
<tbody>
<tr>
<td><code>lpeg.P(string)</code> </td>
<td> Matches <code>string</code> literally.</td>
</tr>
<tr>
<td><code>lpeg.P(</code><em><code>n</code></em><code>)</code> </td>
<td> Matches exactly <em><code>n</code></em> characters.</td>
</tr>
<tr>
<td><code>lpeg.S(string)</code> </td>
<td> Matches any character in set <code>string</code>.</td>
</tr>
<tr>
<td><code>lpeg.R("</code><em><code>xy</code></em><code>")</code> </td>
<td> Matches any character between range <code>x</code> and <code>y</code>.</td>
</tr>
<tr>
<td><code>patt^</code><em><code>n</code></em> </td>
<td> Matches at least <em><code>n</code></em> repetitions of <code>patt</code>.</td>
</tr>
<tr>
<td><code>patt^-</code><em><code>n</code></em> </td>
<td> Matches at most <em><code>n</code></em> repetitions of <code>patt</code>.</td>
</tr>
<tr>
<td><code>patt1 * patt2</code> </td>
<td> Matches <code>patt1</code> followed by <code>patt2</code>.</td>
</tr>
<tr>
<td><code>patt1 + patt2</code> </td>
<td> Matches <code>patt1</code> or <code>patt2</code> (ordered choice).</td>
</tr>
<tr>
<td><code>patt1 - patt2</code> </td>
<td> Matches <code>patt1</code> if <code>patt2</code> does not match.</td>
</tr>
<tr>
<td><code>-patt</code> </td>
<td> Equivalent to <code>("" - patt)</code>.</td>
</tr>
<tr>
<td><code>#patt</code> </td>
<td> Matches <code>patt</code> but consumes no input.</td>
</tr>
</tbody>
</table>
<p>The first part of this document deals with rapidly constructing a simple
lexer. The next part deals with more advanced techniques, such as custom
coloring and embedding lexers within one another. Following that is a
discussion about code folding, or being able to tell Scintilla which code
blocks are "foldable" (temporarily hideable from view). After that are
instructions on how to use Lua lexers with the aforementioned Textadept
editor. Finally there are comments on lexer performance and limitations.</p>
<p><a id="lexer.Lexer.Basics"></a></p>
<h3>Lexer Basics</h3>
<p>The <em>lexlua/</em> directory contains all lexers, including your new one. Before
attempting to write one from scratch though, first determine if your
programming language is similar to any of the 100+ languages supported. If
so, you may be able to copy and modify that lexer, saving some time and
effort. The filename of your lexer should be the name of your programming
language in lower case followed by a <em>.lua</em> extension. For example, a new Lua
lexer has the name <em>lua.lua</em>.</p>
<p>Note: Try to refrain from using one-character language names like "c", "d",
or "r". For example, Lua lexers for those languages are named "ansi_c", "dmd", and "rstats",
respectively.</p>
<p><a id="lexer.New.Lexer.Template"></a></p>
<h4>New Lexer Template</h4>
<p>There is a <em>lexlua/template.txt</em> file that contains a simple template for a
new lexer. Feel free to use it, replacing the '?'s with the name of your
lexer. Consider this snippet from the template:</p>
<pre><code>
-- ? LPeg lexer.
local lexer = require('lexer')
local token, word_match = lexer.token, lexer.word_match
local P, R, S = lpeg.P, lpeg.R, lpeg.S
local lex = lexer.new('?')
-- Whitespace.
local ws = token(lexer.WHITESPACE, lexer.space^1)
lex:add_rule('whitespace', ws)
[...]
return lex
</code></pre>
<p>The first 3 lines of code simply define often used convenience variables. The
fourth and last lines <a href="#lexer.new">define</a> and return the lexer object
Scintilla uses; they are very important and must be part of every lexer. The
fifth line defines something called a "token", an essential building block of
lexers. You will learn about tokens shortly. The sixth line defines a lexer
grammar rule, which you will learn about later, as well as token styles. (Be
aware that it is common practice to combine these two lines for short rules.)
Note, however, the <code>local</code> prefix in front of variables, which is needed
so-as not to affect Lua's global environment. All in all, this is a minimal,
working lexer that you can build on.</p>
<p><a id="lexer.Tokens"></a></p>
<h4>Tokens</h4>
<p>Take a moment to think about your programming language's structure. What kind
of key elements does it have? In the template shown earlier, one predefined
element all languages have is whitespace. Your language probably also has
elements like comments, strings, and keywords. Lexers refer to these elements
as "tokens". Tokens are the fundamental "building blocks" of lexers. Lexers
break down source code into tokens for coloring, which results in the syntax
highlighting familiar to you. It is up to you how specific your lexer is when
it comes to tokens. Perhaps only distinguishing between keywords and
identifiers is necessary, or maybe recognizing constants and built-in
functions, methods, or libraries is desirable. The Lua lexer, for example,
defines 11 tokens: whitespace, keywords, built-in functions, constants,
built-in libraries, identifiers, strings, comments, numbers, labels, and
operators. Even though constants, built-in functions, and built-in libraries
are subsets of identifiers, Lua programmers find it helpful for the lexer to
distinguish between them all. It is perfectly acceptable to just recognize
keywords and identifiers.</p>
<p>In a lexer, tokens consist of a token name and an LPeg pattern that matches a
sequence of characters recognized as an instance of that token. Create tokens
using the <a href="#lexer.token"><code>lexer.token()</code></a> function. Let us examine the "whitespace" token
defined in the template shown earlier:</p>
<pre><code>
local ws = token(lexer.WHITESPACE, lexer.space^1)
</code></pre>
<p>At first glance, the first argument does not appear to be a string name and
the second argument does not appear to be an LPeg pattern. Perhaps you
expected something like:</p>
<pre><code>
local ws = token('whitespace', S('\t\v\f\n\r ')^1)
</code></pre>
<p>The <code>lexer</code> module actually provides a convenient list of common token names
and common LPeg patterns for you to use. Token names include
<a href="#lexer.DEFAULT"><code>lexer.DEFAULT</code></a>, <a href="#lexer.WHITESPACE"><code>lexer.WHITESPACE</code></a>, <a href="#lexer.COMMENT"><code>lexer.COMMENT</code></a>,
<a href="#lexer.STRING"><code>lexer.STRING</code></a>, <a href="#lexer.NUMBER"><code>lexer.NUMBER</code></a>, <a href="#lexer.KEYWORD"><code>lexer.KEYWORD</code></a>,
<a href="#lexer.IDENTIFIER"><code>lexer.IDENTIFIER</code></a>, <a href="#lexer.OPERATOR"><code>lexer.OPERATOR</code></a>, <a href="#lexer.ERROR"><code>lexer.ERROR</code></a>,
<a href="#lexer.PREPROCESSOR"><code>lexer.PREPROCESSOR</code></a>, <a href="#lexer.CONSTANT"><code>lexer.CONSTANT</code></a>, <a href="#lexer.VARIABLE"><code>lexer.VARIABLE</code></a>,
<a href="#lexer.FUNCTION"><code>lexer.FUNCTION</code></a>, <a href="#lexer.CLASS"><code>lexer.CLASS</code></a>, <a href="#lexer.TYPE"><code>lexer.TYPE</code></a>, <a href="#lexer.LABEL"><code>lexer.LABEL</code></a>,
<a href="#lexer.REGEX"><code>lexer.REGEX</code></a>, and <a href="#lexer.EMBEDDED"><code>lexer.EMBEDDED</code></a>. Patterns include
<a href="#lexer.any"><code>lexer.any</code></a>, <a href="#lexer.ascii"><code>lexer.ascii</code></a>, <a href="#lexer.extend"><code>lexer.extend</code></a>, <a href="#lexer.alpha"><code>lexer.alpha</code></a>,
<a href="#lexer.digit"><code>lexer.digit</code></a>, <a href="#lexer.alnum"><code>lexer.alnum</code></a>, <a href="#lexer.lower"><code>lexer.lower</code></a>, <a href="#lexer.upper"><code>lexer.upper</code></a>,
<a href="#lexer.xdigit"><code>lexer.xdigit</code></a>, <a href="#lexer.cntrl"><code>lexer.cntrl</code></a>, <a href="#lexer.graph"><code>lexer.graph</code></a>, <a href="#lexer.print"><code>lexer.print</code></a>,
<a href="#lexer.punct"><code>lexer.punct</code></a>, <a href="#lexer.space"><code>lexer.space</code></a>, <a href="#lexer.newline"><code>lexer.newline</code></a>,
<a href="#lexer.nonnewline"><code>lexer.nonnewline</code></a>, <a href="#lexer.nonnewline_esc"><code>lexer.nonnewline_esc</code></a>, <a href="#lexer.dec_num"><code>lexer.dec_num</code></a>,
<a href="#lexer.hex_num"><code>lexer.hex_num</code></a>, <a href="#lexer.oct_num"><code>lexer.oct_num</code></a>, <a href="#lexer.integer"><code>lexer.integer</code></a>,
<a href="#lexer.float"><code>lexer.float</code></a>, and <a href="#lexer.word"><code>lexer.word</code></a>. You may use your own token names if
none of the above fit your language, but an advantage to using predefined
token names is that your lexer's tokens will inherit the universal syntax
highlighting color theme used by your text editor.</p>
<p><a id="lexer.Example.Tokens"></a></p>
<h5>Example Tokens</h5>
<p>So, how might you define other tokens like keywords, comments, and strings?
Here are some examples.</p>
<p><strong>Keywords</strong></p>
<p>Instead of matching <em>n</em> keywords with <em>n</em> <code>P('keyword_</code><em><code>n</code></em><code>')</code> ordered
choices, use another convenience function: <a href="#lexer.word_match"><code>lexer.word_match()</code></a>. It is
much easier and more efficient to write word matches like:</p>
<pre><code>
local keyword = token(lexer.KEYWORD, lexer.word_match[[
keyword_1 keyword_2 ... keyword_n
]])
local case_insensitive_keyword = token(lexer.KEYWORD, lexer.word_match([[
KEYWORD_1 keyword_2 ... KEYword_n
]], true))
local hyphened_keyword = token(lexer.KEYWORD, lexer.word_match[[
keyword-1 keyword-2 ... keyword-n
]])
</code></pre>
<p>In order to more easily separate or categorize keyword sets, you can use Lua
line comments within keyword strings. Such comments will be ignored. For
example:</p>
<pre><code>
local keyword = token(lexer.KEYWORD, lexer.word_match[[
-- Version 1 keywords.
keyword_11, keyword_12 ... keyword_1n
-- Version 2 keywords.
keyword_21, keyword_22 ... keyword_2n
...
-- Version N keywords.
keyword_m1, keyword_m2 ... keyword_mn
]])
</code></pre>
<p><strong>Comments</strong></p>
<p>Line-style comments with a prefix character(s) are easy to express with LPeg:</p>
<pre><code>
local shell_comment = token(lexer.COMMENT, '#' * lexer.nonnewline^0)
local c_line_comment = token(lexer.COMMENT,
'//' * lexer.nonnewline_esc^0)
</code></pre>
<p>The comments above start with a '#' or "//" and go to the end of the line.
The second comment recognizes the next line also as a comment if the current
line ends with a '\' escape character.</p>
<p>C-style "block" comments with a start and end delimiter are also easy to
express:</p>
<pre><code>
local c_comment = token(lexer.COMMENT,
'/*' * (lexer.any - '*/')^0 * P('*/')^-1)
</code></pre>
<p>This comment starts with a "/*" sequence and contains anything up to and
including an ending "*/" sequence. The ending "*/" is optional so the lexer
can recognize unfinished comments as comments and highlight them properly.</p>
<p><strong>Strings</strong></p>
<p>It is tempting to think that a string is not much different from the block
comment shown above in that both have start and end delimiters:</p>
<pre><code>
local dq_str = '"' * (lexer.any - '"')^0 * P('"')^-1
local sq_str = "'" * (lexer.any - "'")^0 * P("'")^-1
local simple_string = token(lexer.STRING, dq_str + sq_str)
</code></pre>
<p>However, most programming languages allow escape sequences in strings such
that a sequence like "\"" in a double-quoted string indicates that the
'"' is not the end of the string. The above token incorrectly matches
such a string. Instead, use the <a href="#lexer.delimited_range"><code>lexer.delimited_range()</code></a> convenience
function.</p>
<pre><code>
local dq_str = lexer.delimited_range('"')
local sq_str = lexer.delimited_range("'")
local string = token(lexer.STRING, dq_str + sq_str)
</code></pre>
<p>In this case, the lexer treats '\' as an escape character in a string
sequence.</p>
<p><strong>Numbers</strong></p>
<p>Most programming languages have the same format for integer and float tokens,
so it might be as simple as using a couple of predefined LPeg patterns:</p>
<pre><code>
local number = token(lexer.NUMBER, lexer.float + lexer.integer)
</code></pre>
<p>However, some languages allow postfix characters on integers.</p>
<pre><code>
local integer = P('-')^-1 * (lexer.dec_num * S('lL')^-1)
local number = token(lexer.NUMBER, lexer.float + lexer.hex_num + integer)
</code></pre>
<p>Your language may need other tweaks, but it is up to you how fine-grained you
want your highlighting to be. After all, you are not writing a compiler or
interpreter!</p>
<p><a id="lexer.Rules"></a></p>
<h4>Rules</h4>
<p>Programming languages have grammars, which specify valid token structure. For
example, comments usually cannot appear within a string. Grammars consist of
rules, which are simply combinations of tokens. Recall from the lexer
template the <a href="#lexer.add_rule"><code>lexer.add_rule()</code></a> call, which adds a rule to the lexer's
grammar:</p>
<pre><code>
lex:add_rule('whitespace', ws)
</code></pre>
<p>Each rule has an associated name, but rule names are completely arbitrary and
serve only to identify and distinguish between different rules. Rule order is
important: if text does not match the first rule added to the grammar, the
lexer tries to match the second rule added, and so on. Right now this lexer
simply matches whitespace tokens under a rule named "whitespace".</p>
<p>To illustrate the importance of rule order, here is an example of a
simplified Lua lexer:</p>
<pre><code>
lex:add_rule('whitespace', token(lexer.WHITESPACE, ...))
lex:add_rule('keyword', token(lexer.KEYWORD, ...))
lex:add_rule('identifier', token(lexer.IDENTIFIER, ...))
lex:add_rule('string', token(lexer.STRING, ...))
lex:add_rule('comment', token(lexer.COMMENT, ...))
lex:add_rule('number', token(lexer.NUMBER, ...))
lex:add_rule('label', token(lexer.LABEL, ...))
lex:add_rule('operator', token(lexer.OPERATOR, ...))
</code></pre>
<p>Note how identifiers come after keywords. In Lua, as with most programming
languages, the characters allowed in keywords and identifiers are in the same
set (alphanumerics plus underscores). If the lexer added the "identifier"
rule before the "keyword" rule, all keywords would match identifiers and thus
incorrectly highlight as identifiers instead of keywords. The same idea
applies to function, constant, etc. tokens that you may want to distinguish
between: their rules should come before identifiers.</p>
<p>So what about text that does not match any rules? For example in Lua, the '!'
character is meaningless outside a string or comment. Normally the lexer
skips over such text. If instead you want to highlight these "syntax errors",
add an additional end rule:</p>
<pre><code>
lex:add_rule('whitespace', ws)
...
lex:add_rule('error', token(lexer.ERROR, lexer.any))
</code></pre>
<p>This identifies and highlights any character not matched by an existing
rule as a <code>lexer.ERROR</code> token.</p>
<p>Even though the rules defined in the examples above contain a single token,
rules may consist of multiple tokens. For example, a rule for an HTML tag
could consist of a tag token followed by an arbitrary number of attribute
tokens, allowing the lexer to highlight all tokens separately. That rule
might look something like this:</p>
<pre><code>
lex:add_rule('tag', tag_start * (ws * attributes)^0 * tag_end^-1)
</code></pre>
<p>Note however that lexers with complex rules like these are more prone to lose
track of their state, especially if they span multiple lines.</p>
<p><a id="lexer.Summary"></a></p>
<h4>Summary</h4>
<p>Lexers primarily consist of tokens and grammar rules. At your disposal are a
number of convenience patterns and functions for rapidly creating a lexer. If
you choose to use predefined token names for your tokens, you do not have to
define how the lexer highlights them. The tokens will inherit the default
syntax highlighting color theme your editor uses.</p>
<p><a id="lexer.Advanced.Techniques"></a></p>
<h3>Advanced Techniques</h3>
<p><a id="lexer.Styles.and.Styling"></a></p>
<h4>Styles and Styling</h4>
<p>The most basic form of syntax highlighting is assigning different colors to
different tokens. Instead of highlighting with just colors, Scintilla allows
for more rich highlighting, or "styling", with different fonts, font sizes,
font attributes, and foreground and background colors, just to name a few.
The unit of this rich highlighting is called a "style". Styles are simply
strings of comma-separated property settings. By default, lexers associate
predefined token names like <code>lexer.WHITESPACE</code>, <code>lexer.COMMENT</code>,
<code>lexer.STRING</code>, etc. with particular styles as part of a universal color
theme. These predefined styles include <a href="#lexer.STYLE_CLASS"><code>lexer.STYLE_CLASS</code></a>,
<a href="#lexer.STYLE_COMMENT"><code>lexer.STYLE_COMMENT</code></a>, <a href="#lexer.STYLE_CONSTANT"><code>lexer.STYLE_CONSTANT</code></a>,
<a href="#lexer.STYLE_ERROR"><code>lexer.STYLE_ERROR</code></a>, <a href="#lexer.STYLE_EMBEDDED"><code>lexer.STYLE_EMBEDDED</code></a>,
<a href="#lexer.STYLE_FUNCTION"><code>lexer.STYLE_FUNCTION</code></a>, <a href="#lexer.STYLE_IDENTIFIER"><code>lexer.STYLE_IDENTIFIER</code></a>,
<a href="#lexer.STYLE_KEYWORD"><code>lexer.STYLE_KEYWORD</code></a>, <a href="#lexer.STYLE_LABEL"><code>lexer.STYLE_LABEL</code></a>, <a href="#lexer.STYLE_NUMBER"><code>lexer.STYLE_NUMBER</code></a>,
<a href="#lexer.STYLE_OPERATOR"><code>lexer.STYLE_OPERATOR</code></a>, <a href="#lexer.STYLE_PREPROCESSOR"><code>lexer.STYLE_PREPROCESSOR</code></a>,
<a href="#lexer.STYLE_REGEX"><code>lexer.STYLE_REGEX</code></a>, <a href="#lexer.STYLE_STRING"><code>lexer.STYLE_STRING</code></a>, <a href="#lexer.STYLE_TYPE"><code>lexer.STYLE_TYPE</code></a>,
<a href="#lexer.STYLE_VARIABLE"><code>lexer.STYLE_VARIABLE</code></a>, and <a href="#lexer.STYLE_WHITESPACE"><code>lexer.STYLE_WHITESPACE</code></a>. Like with
predefined token names and LPeg patterns, you may define your own styles. At
their core, styles are just strings, so you may create new ones and/or modify
existing ones. Each style consists of the following comma-separated settings:</p>
<table class="standard">
<thead>
<tr>
<th>Setting </th>
<th> Description</th>
</tr>
</thead>
<tbody>
<tr>
<td>font:<em>name</em> </td>
<td> The name of the font the style uses.</td>
</tr>
<tr>
<td>size:<em>int</em> </td>
<td> The size of the font the style uses.</td>
</tr>
<tr>
<td>[not]bold </td>
<td> Whether or not the font face is bold.</td>
</tr>
<tr>
<td>weight:<em>int</em> </td>
<td> The weight or boldness of a font, between 1 and 999.</td>
</tr>
<tr>
<td>[not]italics </td>
<td> Whether or not the font face is italic.</td>
</tr>
<tr>
<td>[not]underlined</td>
<td> Whether or not the font face is underlined.</td>
</tr>
<tr>
<td>fore:<em>color</em> </td>
<td> The foreground color of the font face.</td>
</tr>
<tr>
<td>back:<em>color</em> </td>
<td> The background color of the font face.</td>
</tr>
<tr>
<td>[not]eolfilled </td>
<td> Does the background color extend to the end of the line?</td>
</tr>
<tr>
<td>case:<em>char</em> </td>
<td> The case of the font ('u': upper, 'l': lower, 'm': normal).</td>
</tr>
<tr>
<td>[not]visible </td>
<td> Whether or not the text is visible.</td>
</tr>
<tr>
<td>[not]changeable</td>
<td> Whether the text is changeable or read-only.</td>
</tr>
</tbody>
</table>
<p>Specify font colors in either "#RRGGBB" format, "0xBBGGRR" format, or the
decimal equivalent of the latter. As with token names, LPeg patterns, and
styles, there is a set of predefined color names, but they vary depending on
the current color theme in use. Therefore, it is generally not a good idea to
manually define colors within styles in your lexer since they might not fit
into a user's chosen color theme. Try to refrain from even using predefined
colors in a style because that color may be theme-specific. Instead, the best
practice is to either use predefined styles or derive new color-agnostic
styles from predefined ones. For example, Lua "longstring" tokens use the
existing <code>lexer.STYLE_STRING</code> style instead of defining a new one.</p>
<p><a id="lexer.Example.Styles"></a></p>
<h5>Example Styles</h5>
<p>Defining styles is pretty straightforward. An empty style that inherits the
default theme settings is simply an empty string:</p>
<pre><code>
local style_nothing = ''
</code></pre>
<p>A similar style but with a bold font face looks like this:</p>
<pre><code>
local style_bold = 'bold'
</code></pre>
<p>If you want the same style, but also with an italic font face, define the new
style in terms of the old one:</p>
<pre><code>
local style_bold_italic = style_bold..',italics'
</code></pre>
<p>This allows you to derive new styles from predefined ones without having to
rewrite them. This operation leaves the old style unchanged. Thus if you
had a "static variable" token whose style you wanted to base off of
<code>lexer.STYLE_VARIABLE</code>, it would probably look like:</p>
<pre><code>
local style_static_var = lexer.STYLE_VARIABLE..',italics'
</code></pre>
<p>The color theme files in the <em>lexlua/themes/</em> folder give more examples of
style definitions.</p>
<p><a id="lexer.Token.Styles"></a></p>
<h4>Token Styles</h4>
<p>Lexers use the <a href="#lexer.add_style"><code>lexer.add_style()</code></a> function to assign styles to
particular tokens. Recall the token definition and from the lexer template:</p>
<pre><code>
local ws = token(lexer.WHITESPACE, lexer.space^1)
lex:add_rule('whitespace', ws)
</code></pre>
<p>Why is a style not assigned to the <code>lexer.WHITESPACE</code> token? As mentioned
earlier, lexers automatically associate tokens that use predefined token
names with a particular style. Only tokens with custom token names need
manual style associations. As an example, consider a custom whitespace token:</p>
<pre><code>
local ws = token('custom_whitespace', lexer.space^1)
</code></pre>
<p>Assigning a style to this token looks like:</p>
<pre><code>
lex:add_style('custom_whitespace', lexer.STYLE_WHITESPACE)
</code></pre>
<p>Do not confuse token names with rule names. They are completely different
entities. In the example above, the lexer associates the "custom_whitespace"
token with the existing style for <code>lexer.WHITESPACE</code> tokens. If instead you
prefer to color the background of whitespace a shade of grey, it might look
like:</p>
<pre><code>
local custom_style = lexer.STYLE_WHITESPACE..',back:$(color.grey)'
lex:add_style('custom_whitespace', custom_style)
</code></pre>
<p>Notice that the lexer peforms Scintilla-style "$()" property expansion.
You may also use "%()". Remember to refrain from assigning specific colors in
styles, but in this case, all user color themes probably define the
"color.grey" property.</p>
<p><a id="lexer.Line.Lexers"></a></p>
<h4>Line Lexers</h4>
<p>By default, lexers match the arbitrary chunks of text passed to them by
Scintilla. These chunks may be a full document, only the visible part of a
document, or even just portions of lines. Some lexers need to match whole
lines. For example, a lexer for the output of a file "diff" needs to know if
the line started with a '+' or '-' and then style the entire line
accordingly. To indicate that your lexer matches by line, create the lexer
with an extra parameter:</p>
<pre><code>
local lex = lexer.new('?', {lex_by_line = true})
</code></pre>
<p>Now the input text for the lexer is a single line at a time. Keep in mind
that line lexers do not have the ability to look ahead at subsequent lines.</p>
<p><a id="lexer.Embedded.Lexers"></a></p>
<h4>Embedded Lexers</h4>
<p>Lexers embed within one another very easily, requiring minimal effort. In the
following sections, the lexer being embedded is called the "child" lexer and
the lexer a child is being embedded in is called the "parent". For example,
consider an HTML lexer and a CSS lexer. Either lexer stands alone for styling
their respective HTML and CSS files. However, CSS can be embedded inside
HTML. In this specific case, the CSS lexer is the "child" lexer with the HTML
lexer being the "parent". Now consider an HTML lexer and a PHP lexer. This
sounds a lot like the case with CSS, but there is a subtle difference: PHP
<em>embeds itself into</em> HTML while CSS is <em>embedded in</em> HTML. This fundamental
difference results in two types of embedded lexers: a parent lexer that
embeds other child lexers in it (like HTML embedding CSS), and a child lexer
that embeds itself into a parent lexer (like PHP embedding itself in HTML).</p>
<p><a id="lexer.Parent.Lexer"></a></p>
<h5>Parent Lexer</h5>
<p>Before embedding a child lexer into a parent lexer, the parent lexer needs to
load the child lexer. This is done with the <a href="#lexer.load"><code>lexer.load()</code></a> function. For
example, loading the CSS lexer within the HTML lexer looks like:</p>
<pre><code>
local css = lexer.load('css')
</code></pre>
<p>The next part of the embedding process is telling the parent lexer when to
switch over to the child lexer and when to switch back. The lexer refers to
these indications as the "start rule" and "end rule", respectively, and are
just LPeg patterns. Continuing with the HTML/CSS example, the transition from
HTML to CSS is when the lexer encounters a "style" tag with a "type"
attribute whose value is "text/css":</p>
<pre><code>
local css_tag = P('<style') * P(function(input, index)
if input:find('^[^>]+type="text/css"', index) then
return index
end
end)
</code></pre>
<p>This pattern looks for the beginning of a "style" tag and searches its
attribute list for the text "<code>type="text/css"</code>". (In this simplified example,
the Lua pattern does not consider whitespace between the '=' nor does it
consider that using single quotes is valid.) If there is a match, the
functional pattern returns a value instead of <code>nil</code>. In this case, the value
returned does not matter because we ultimately want to style the "style" tag
as an HTML tag, so the actual start rule looks like this:</p>
<pre><code>
local css_start_rule = #css_tag * tag
</code></pre>
<p>Now that the parent knows when to switch to the child, it needs to know when
to switch back. In the case of HTML/CSS, the switch back occurs when the
lexer encounters an ending "style" tag, though the lexer should still style
the tag as an HTML tag:</p>
<pre><code>
local css_end_rule = #P('</style>') * tag
</code></pre>
<p>Once the parent loads the child lexer and defines the child's start and end
rules, it embeds the child with the <a href="#lexer.embed"><code>lexer.embed()</code></a> function:</p>
<pre><code>
lex:embed(css, css_start_rule, css_end_rule)
</code></pre>
<p><a id="lexer.Child.Lexer"></a></p>
<h5>Child Lexer</h5>
<p>The process for instructing a child lexer to embed itself into a parent is
very similar to embedding a child into a parent: first, load the parent lexer
into the child lexer with the <a href="#lexer.load"><code>lexer.load()</code></a> function and then create
start and end rules for the child lexer. However, in this case, call
<a href="#lexer.embed"><code>lexer.embed()</code></a> with switched arguments. For example, in the PHP lexer:</p>
<pre><code>
local html = lexer.load('html')
local php_start_rule = token('php_tag', '<?php ')
local php_end_rule = token('php_tag', '?>')
lex:add_style('php_tag', lexer.STYLE_EMBEDDED)
html:embed(lex, php_start_rule, php_end_rule)
</code></pre>
<p><a id="lexer.Lexers.with.Complex.State"></a></p>
<h4>Lexers with Complex State</h4>
<p>A vast majority of lexers are not stateful and can operate on any chunk of
text in a document. However, there may be rare cases where a lexer does need
to keep track of some sort of persistent state. Rather than using <code>lpeg.P</code>
function patterns that set state variables, it is recommended to make use of
Scintilla's built-in, per-line state integers via <a href="#lexer.line_state"><code>lexer.line_state</code></a>. It
was designed to accommodate up to 32 bit flags for tracking state.
<a href="#lexer.line_from_position"><code>lexer.line_from_position()</code></a> will return the line for any position given
to an <code>lpeg.P</code> function pattern. (Any positions derived from that position
argument will also work.)</p>
<p>Writing stateful lexers is beyond the scope of this document.</p>
<p><a id="lexer.Code.Folding"></a></p>
<h3>Code Folding</h3>
<p>When reading source code, it is occasionally helpful to temporarily hide
blocks of code like functions, classes, comments, etc. This is the concept of
"folding". In many Scintilla-based editors, such as Textadept, little indicators
in the editor margins appear next to code that can be folded at places called
"fold points". When the user clicks an indicator, the editor hides the code
associated with the indicator until the user clicks the indicator again. The
lexer specifies these fold points and what code exactly to fold.</p>
<p>The fold points for most languages occur on keywords or character sequences.
Examples of fold keywords are "if" and "end" in Lua and examples of fold
character sequences are '{', '}', "/*", and "*/" in C for code block and
comment delimiters, respectively. However, these fold points cannot occur
just anywhere. For example, lexers should not recognize fold keywords that
appear within strings or comments. The <a href="#lexer.add_fold_point"><code>lexer.add_fold_point()</code></a> function
allows you to conveniently define fold points with such granularity. For
example, consider C:</p>
<pre><code>
lex:add_fold_point(lexer.OPERATOR, '{', '}')
lex:add_fold_point(lexer.COMMENT, '/*', '*/')
</code></pre>
<p>The first assignment states that any '{' or '}' that the lexer recognized as
an <code>lexer.OPERATOR</code> token is a fold point. Likewise, the second assignment
states that any "/*" or "*/" that the lexer recognizes as part of a
<code>lexer.COMMENT</code> token is a fold point. The lexer does not consider any
occurrences of these characters outside their defined tokens (such as in a
string) as fold points. How do you specify fold keywords? Here is an example
for Lua:</p>
<pre><code>
lex:add_fold_point(lexer.KEYWORD, 'if', 'end')
lex:add_fold_point(lexer.KEYWORD, 'do', 'end')
lex:add_fold_point(lexer.KEYWORD, 'function', 'end')
lex:add_fold_point(lexer.KEYWORD, 'repeat', 'until')
</code></pre>
<p>If your lexer has case-insensitive keywords as fold points, simply add a
<code>case_insensitive_fold_points = true</code> option to <a href="#lexer.new"><code>lexer.new()</code></a>, and
specify keywords in lower case.</p>
<p>If your lexer needs to do some additional processing in order to determine if
a token is a fold point, pass a function that returns an integer to
<code>lex:add_fold_point()</code>. Returning <code>1</code> indicates the token is a beginning fold
point and returning <code>-1</code> indicates the token is an ending fold point.
Returning <code>0</code> indicates the token is not a fold point. For example:</p>
<pre><code>
local function fold_strange_token(text, pos, line, s, symbol)
if ... then
return 1 -- beginning fold point
elseif ... then
return -1 -- ending fold point
end
return 0
end
lex:add_fold_point('strange_token', '|', fold_strange_token)
</code></pre>
<p>Any time the lexer encounters a '|' that is a "strange_token", it calls the
<code>fold_strange_token</code> function to determine if '|' is a fold point. The lexer
calls these functions with the following arguments: the text to identify fold
points in, the beginning position of the current line in the text to fold,
the current line's text, the position in the current line the fold point text
starts at, and the fold point text itself.</p>
<p><a id="lexer.Fold.by.Indentation"></a></p>
<h4>Fold by Indentation</h4>
<p>Some languages have significant whitespace and/or no delimiters that indicate
fold points. If your lexer falls into this category and you would like to
mark fold points based on changes in indentation, create the lexer with a
<code>fold_by_indentation = true</code> option:</p>
<pre><code>
local lex = lexer.new('?', {fold_by_indentation = true})
</code></pre>
<p><a id="lexer.Using.Lexers"></a></p>
<h3>Using Lexers</h3>
<p><a id="lexer.Textadept"></a></p>
<h4>Textadept</h4>
<p>Put your lexer in your <em>~/.textadept/lexers/</em> directory so you do not
overwrite it when upgrading Textadept. Also, lexers in this directory
override default lexers. Thus, Textadept loads a user <em>lua</em> lexer instead of
the default <em>lua</em> lexer. This is convenient for tweaking a default lexer to
your liking. Then add a <a href="https://foicica.com/textadept/api.html#textadept.file_types">file type</a> for your lexer if necessary.</p>
<p><a id="lexer.Migrating.Legacy.Lexers"></a></p>
<h3>Migrating Legacy Lexers</h3>
<p>Legacy lexers are of the form:</p>
<pre><code>
local l = require('lexer')
local token, word_match = l.token, l.word_match
local P, R, S = lpeg.P, lpeg.R, lpeg.S
local M = {_NAME = '?'}
[... token and pattern definitions ...]
M._rules = {
{'rule', pattern},
[...]
}
M._tokenstyles = {
'token' = 'style',
[...]
}
M._foldsymbols = {
_patterns = {...},
['token'] = {['start'] = 1, ['end'] = -1},
[...]
}
return M
</code></pre>
<p>While such legacy lexers will be handled just fine without any
changes, it is recommended that you migrate yours. The migration process is
fairly straightforward:</p>
<ol>
<li>Replace all instances of <code>l</code> with <code>lexer</code>, as it's better practice and
results in less confusion.</li>
<li>Replace <code>local M = {_NAME = '?'}</code> with <code>local lex = lexer.new('?')</code>, where
<code>?</code> is the name of your legacy lexer. At the end of the lexer, change
<code>return M</code> to <code>return lex</code>.</li>
<li>Instead of defining rules towards the end of your lexer, define your rules
as you define your tokens and patterns using
<a href="#lexer.add_rule"><code>lex:add_rule()</code></a>.</li>
<li>Similarly, any custom token names should have their styles immediately
defined using <a href="#lexer.add_style"><code>lex:add_style()</code></a>.</li>
<li>Convert any table arguments passed to <a href="#lexer.word_match"><code>lexer.word_match()</code></a> to a
space-separated string of words.</li>
<li>Replace any calls to <code>lexer.embed(M, child, ...)</code> and
<code>lexer.embed(parent, M, ...)</code> with
<a href="#lexer.embed"><code>lex:embed</code></a><code>(child, ...)</code> and <code>parent:embed(lex, ...)</code>,
respectively.</li>
<li>Define fold points with simple calls to
<a href="#lexer.add_fold_point"><code>lex:add_fold_point()</code></a>. No need to mess with Lua
patterns anymore.</li>
<li>Any legacy lexer options such as <code>M._FOLDBYINDENTATION</code>, <code>M._LEXBYLINE</code>,
<code>M._lexer</code>, etc. should be added as table options to <a href="#lexer.new"><code>lexer.new()</code></a>.</li>
<li>Any external lexer rule fetching and/or modifications via <code>lexer._RULES</code>
should be changed to use <a href="#lexer.get_rule"><code>lexer.get_rule()</code></a> and
<a href="#lexer.modify_rule"><code>lexer.modify_rule()</code></a>.</li>
</ol>
<p>As an example, consider the following sample legacy lexer:</p>
<pre><code>
local l = require('lexer')
local token, word_match = l.token, l.word_match
local P, R, S = lpeg.P, lpeg.R, lpeg.S
local M = {_NAME = 'legacy'}
local ws = token(l.WHITESPACE, l.space^1)
local comment = token(l.COMMENT, '#' * l.nonnewline^0)
local string = token(l.STRING, l.delimited_range('"'))
local number = token(l.NUMBER, l.float + l.integer)
local keyword = token(l.KEYWORD, word_match{'foo', 'bar', 'baz'})
local custom = token('custom', P('quux'))
local identifier = token(l.IDENTIFIER, l.word)
local operator = token(l.OPERATOR, S('+-*/%^=<>,.()[]{}'))
M._rules = {
{'whitespace', ws},
{'keyword', keyword},
{'custom', custom},
{'identifier', identifier},
{'string', string},
{'comment', comment},
{'number', number},
{'operator', operator}
}
M._tokenstyles = {
'custom' = l.STYLE_KEYWORD..',bold'
}
M._foldsymbols = {
_patterns = {'[{}]'},
[l.OPERATOR] = {['{'] = 1, ['}'] = -1}
}
return M
</code></pre>
<p>Following the migration steps would yield:</p>
<pre><code>
local lexer = require('lexer')
local token, word_match = lexer.token, lexer.word_match
local P, R, S = lpeg.P, lpeg.R, lpeg.S
local lex = lexer.new('legacy')
lex:add_rule('whitespace', token(lexer.WHITESPACE, lexer.space^1))
lex:add_rule('keyword', token(lexer.KEYWORD, word_match[[foo bar baz]]))
lex:add_rule('custom', token('custom', P('quux')))
lex:add_style('custom', lexer.STYLE_KEYWORD..',bold')
lex:add_rule('identifier', token(lexer.IDENTIFIER, lexer.word))
lex:add_rule('string', token(lexer.STRING, lexer.delimited_range('"')))
lex:add_rule('comment', token(lexer.COMMENT, '#' * lexer.nonnewline^0))
lex:add_rule('number', token(lexer.NUMBER, lexer.float + lexer.integer))
lex:add_rule('operator', token(lexer.OPERATOR, S('+-*/%^=<>,.()[]{}')))
lex:add_fold_point(lexer.OPERATOR, '{', '}')
return lex
</code></pre>
<p><a id="lexer.Considerations"></a></p>
<h3>Considerations</h3>
<p><a id="lexer.Performance"></a></p>
<h4>Performance</h4>
<p>There might be some slight overhead when initializing a lexer, but loading a
file from disk into Scintilla is usually more expensive. On modern computer
systems, I see no difference in speed between Lua lexers and Scintilla's C++
ones. Optimize lexers for speed by re-arranging <code>lexer.add_rule()</code> calls so
that the most common rules match first. Do keep in mind that order matters
for similar rules.</p>
<p>In some cases, folding may be far more expensive than lexing, particularly
in lexers with a lot of potential fold points. If your lexer is exhibiting
signs of slowness, try disabling folding your text editor first. If that
speeds things up, you can try reducing the number of fold points you added,
overriding <code>lexer.fold()</code> with your own implementation, or simply eliminating
folding support from your lexer.</p>
<p><a id="lexer.Limitations"></a></p>
<h4>Limitations</h4>
<p>Embedded preprocessor languages like PHP cannot completely embed in their
parent languages in that the parent's tokens do not support start and end
rules. This mostly goes unnoticed, but code like</p>
<pre><code>
<div id="<?php echo $id; ?>">
</code></pre>
<p>will not style correctly.</p>
<p><a id="lexer.Troubleshooting"></a></p>
<h4>Troubleshooting</h4>
<p>Errors in lexers can be tricky to debug. Lexers print Lua errors to
<code>io.stderr</code> and <code>_G.print()</code> statements to <code>io.stdout</code>. Running your editor
from a terminal is the easiest way to see errors as they occur.</p>
<p><a id="lexer.Risks"></a></p>
<h4>Risks</h4>
<p>Poorly written lexers have the ability to crash Scintilla (and thus its
containing application), so unsaved data might be lost. However, I have only
observed these crashes in early lexer development, when syntax errors or
pattern errors are present. Once the lexer actually starts styling text
(either correctly or incorrectly, it does not matter), I have not observed
any crashes.</p>
<p><a id="lexer.Acknowledgements"></a></p>
<h4>Acknowledgements</h4>
<p>Thanks to Peter Odding for his <a href="http://lua-users.org/lists/lua-l/2007-04/msg00116.html">lexer post</a> on the Lua mailing list
that inspired me, and thanks to Roberto Ierusalimschy for LPeg.</p>
<h2>Lua <code>lexer</code> module API fields</h2>
<p><a id="lexer.CLASS"></a></p>
<h3><code>lexer.CLASS</code> (string)</h3>
<p>The token name for class tokens.</p>
<p><a id="lexer.COMMENT"></a></p>
<h3><code>lexer.COMMENT</code> (string)</h3>
<p>The token name for comment tokens.</p>
<p><a id="lexer.CONSTANT"></a></p>
<h3><code>lexer.CONSTANT</code> (string)</h3>
<p>The token name for constant tokens.</p>
<p><a id="lexer.DEFAULT"></a></p>
<h3><code>lexer.DEFAULT</code> (string)</h3>
<p>The token name for default tokens.</p>
<p><a id="lexer.ERROR"></a></p>
<h3><code>lexer.ERROR</code> (string)</h3>
<p>The token name for error tokens.</p>
<p><a id="lexer.FOLD_BASE"></a></p>
<h3><code>lexer.FOLD_BASE</code> (number)</h3>
<p>The initial (root) fold level.</p>
<p><a id="lexer.FOLD_BLANK"></a></p>
<h3><code>lexer.FOLD_BLANK</code> (number)</h3>
<p>Flag indicating that the line is blank.</p>
<p><a id="lexer.FOLD_HEADER"></a></p>
<h3><code>lexer.FOLD_HEADER</code> (number)</h3>
<p>Flag indicating the line is fold point.</p>
<p><a id="lexer.FUNCTION"></a></p>
<h3><code>lexer.FUNCTION</code> (string)</h3>
<p>The token name for function tokens.</p>
<p><a id="lexer.IDENTIFIER"></a></p>
<h3><code>lexer.IDENTIFIER</code> (string)</h3>
<p>The token name for identifier tokens.</p>
<p><a id="lexer.KEYWORD"></a></p>
<h3><code>lexer.KEYWORD</code> (string)</h3>
<p>The token name for keyword tokens.</p>
<p><a id="lexer.LABEL"></a></p>
<h3><code>lexer.LABEL</code> (string)</h3>
<p>The token name for label tokens.</p>
<p><a id="lexer.NUMBER"></a></p>
<h3><code>lexer.NUMBER</code> (string)</h3>
<p>The token name for number tokens.</p>
<p><a id="lexer.OPERATOR"></a></p>
<h3><code>lexer.OPERATOR</code> (string)</h3>
<p>The token name for operator tokens.</p>
<p><a id="lexer.PREPROCESSOR"></a></p>
<h3><code>lexer.PREPROCESSOR</code> (string)</h3>
<p>The token name for preprocessor tokens.</p>
<p><a id="lexer.REGEX"></a></p>
<h3><code>lexer.REGEX</code> (string)</h3>
<p>The token name for regex tokens.</p>
<p><a id="lexer.STRING"></a></p>
<h3><code>lexer.STRING</code> (string)</h3>
<p>The token name for string tokens.</p>
<p><a id="lexer.STYLE_BRACEBAD"></a></p>
<h3><code>lexer.STYLE_BRACEBAD</code> (string)</h3>
<p>The style used for unmatched brace characters.</p>
<p><a id="lexer.STYLE_BRACELIGHT"></a></p>
<h3><code>lexer.STYLE_BRACELIGHT</code> (string)</h3>
<p>The style used for highlighted brace characters.</p>
<p><a id="lexer.STYLE_CALLTIP"></a></p>
<h3><code>lexer.STYLE_CALLTIP</code> (string)</h3>
<p>The style used by call tips if <a href="#buffer.call_tip_use_style"><code>buffer.call_tip_use_style</code></a> is set.
Only the font name, size, and color attributes are used.</p>
<p><a id="lexer.STYLE_CLASS"></a></p>
<h3><code>lexer.STYLE_CLASS</code> (string)</h3>
<p>The style typically used for class definitions.</p>
<p><a id="lexer.STYLE_COMMENT"></a></p>
<h3><code>lexer.STYLE_COMMENT</code> (string)</h3>
<p>The style typically used for code comments.</p>
<p><a id="lexer.STYLE_CONSTANT"></a></p>
<h3><code>lexer.STYLE_CONSTANT</code> (string)</h3>
<p>The style typically used for constants.</p>
<p><a id="lexer.STYLE_CONTROLCHAR"></a></p>
<h3><code>lexer.STYLE_CONTROLCHAR</code> (string)</h3>
<p>The style used for control characters.
Color attributes are ignored.</p>
<p><a id="lexer.STYLE_DEFAULT"></a></p>
<h3><code>lexer.STYLE_DEFAULT</code> (string)</h3>
<p>The style all styles are based off of.</p>
<p><a id="lexer.STYLE_EMBEDDED"></a></p>
<h3><code>lexer.STYLE_EMBEDDED</code> (string)</h3>
<p>The style typically used for embedded code.</p>
<p><a id="lexer.STYLE_ERROR"></a></p>
<h3><code>lexer.STYLE_ERROR</code> (string)</h3>
<p>The style typically used for erroneous syntax.</p>
<p><a id="lexer.STYLE_FOLDDISPLAYTEXT"></a></p>
<h3><code>lexer.STYLE_FOLDDISPLAYTEXT</code> (string)</h3>
<p>The style used for fold display text.</p>
<p><a id="lexer.STYLE_FUNCTION"></a></p>
<h3><code>lexer.STYLE_FUNCTION</code> (string)</h3>
<p>The style typically used for function definitions.</p>
<p><a id="lexer.STYLE_IDENTIFIER"></a></p>
<h3><code>lexer.STYLE_IDENTIFIER</code> (string)</h3>
<p>The style typically used for identifier words.</p>
<p><a id="lexer.STYLE_INDENTGUIDE"></a></p>
<h3><code>lexer.STYLE_INDENTGUIDE</code> (string)</h3>
<p>The style used for indentation guides.</p>
<p><a id="lexer.STYLE_KEYWORD"></a></p>
<h3><code>lexer.STYLE_KEYWORD</code> (string)</h3>
<p>The style typically used for language keywords.</p>
<p><a id="lexer.STYLE_LABEL"></a></p>
<h3><code>lexer.STYLE_LABEL</code> (string)</h3>
<p>The style typically used for labels.</p>
<p><a id="lexer.STYLE_LINENUMBER"></a></p>
<h3><code>lexer.STYLE_LINENUMBER</code> (string)</h3>
<p>The style used for all margins except fold margins.</p>
<p><a id="lexer.STYLE_NUMBER"></a></p>
<h3><code>lexer.STYLE_NUMBER</code> (string)</h3>
<p>The style typically used for numbers.</p>
<p><a id="lexer.STYLE_OPERATOR"></a></p>
<h3><code>lexer.STYLE_OPERATOR</code> (string)</h3>
<p>The style typically used for operators.</p>
<p><a id="lexer.STYLE_PREPROCESSOR"></a></p>
<h3><code>lexer.STYLE_PREPROCESSOR</code> (string)</h3>
<p>The style typically used for preprocessor statements.</p>
<p><a id="lexer.STYLE_REGEX"></a></p>
<h3><code>lexer.STYLE_REGEX</code> (string)</h3>
<p>The style typically used for regular expression strings.</p>
<p><a id="lexer.STYLE_STRING"></a></p>
<h3><code>lexer.STYLE_STRING</code> (string)</h3>
<p>The style typically used for strings.</p>
<p><a id="lexer.STYLE_TYPE"></a></p>
<h3><code>lexer.STYLE_TYPE</code> (string)</h3>
<p>The style typically used for static types.</p>
<p><a id="lexer.STYLE_VARIABLE"></a></p>
<h3><code>lexer.STYLE_VARIABLE</code> (string)</h3>
<p>The style typically used for variables.</p>
<p><a id="lexer.STYLE_WHITESPACE"></a></p>
<h3><code>lexer.STYLE_WHITESPACE</code> (string)</h3>
<p>The style typically used for whitespace.</p>
<p><a id="lexer.TYPE"></a></p>
<h3><code>lexer.TYPE</code> (string)</h3>
<p>The token name for type tokens.</p>
<p><a id="lexer.VARIABLE"></a></p>
<h3><code>lexer.VARIABLE</code> (string)</h3>
<p>The token name for variable tokens.</p>
<p><a id="lexer.WHITESPACE"></a></p>
<h3><code>lexer.WHITESPACE</code> (string)</h3>
<p>The token name for whitespace tokens.</p>
<p><a id="lexer.alnum"></a></p>
<h3><code>lexer.alnum</code> (pattern)</h3>
<p>A pattern that matches any alphanumeric character ('A'-'Z', 'a'-'z',
'0'-'9').</p>
<p><a id="lexer.alpha"></a></p>
<h3><code>lexer.alpha</code> (pattern)</h3>
<p>A pattern that matches any alphabetic character ('A'-'Z', 'a'-'z').</p>
<p><a id="lexer.any"></a></p>
<h3><code>lexer.any</code> (pattern)</h3>
<p>A pattern that matches any single character.</p>
<p><a id="lexer.ascii"></a></p>
<h3><code>lexer.ascii</code> (pattern)</h3>
<p>A pattern that matches any ASCII character (codes 0 to 127).</p>
<p><a id="lexer.cntrl"></a></p>
<h3><code>lexer.cntrl</code> (pattern)</h3>
<p>A pattern that matches any control character (ASCII codes 0 to 31).</p>
<p><a id="lexer.dec_num"></a></p>
<h3><code>lexer.dec_num</code> (pattern)</h3>
<p>A pattern that matches a decimal number.</p>
<p><a id="lexer.digit"></a></p>
<h3><code>lexer.digit</code> (pattern)</h3>
<p>A pattern that matches any digit ('0'-'9').</p>
<p><a id="lexer.extend"></a></p>
<h3><code>lexer.extend</code> (pattern)</h3>
<p>A pattern that matches any ASCII extended character (codes 0 to 255).</p>
<p><a id="lexer.float"></a></p>
<h3><code>lexer.float</code> (pattern)</h3>
<p>A pattern that matches a floating point number.</p>
<p><a id="lexer.fold_level"></a></p>
<h3><code>lexer.fold_level</code> (table, Read-only)</h3>
<p>Table of fold level bit-masks for line numbers starting from zero.
Fold level masks are composed of an integer level combined with any of the
following bits:</p>
<ul>
<li><code>lexer.FOLD_BASE</code>
The initial fold level.</li>
<li><code>lexer.FOLD_BLANK</code>
The line is blank.</li>
<li><code>lexer.FOLD_HEADER</code>
The line is a header, or fold point.</li>
</ul>
<p><a id="lexer.graph"></a></p>
<h3><code>lexer.graph</code> (pattern)</h3>
<p>A pattern that matches any graphical character ('!' to '~').</p>
<p><a id="lexer.hex_num"></a></p>
<h3><code>lexer.hex_num</code> (pattern)</h3>
<p>A pattern that matches a hexadecimal number.</p>
<p><a id="lexer.indent_amount"></a></p>
<h3><code>lexer.indent_amount</code> (table, Read-only)</h3>
<p>Table of indentation amounts in character columns, for line numbers
starting from zero.</p>
<p><a id="lexer.integer"></a></p>
<h3><code>lexer.integer</code> (pattern)</h3>
<p>A pattern that matches either a decimal, hexadecimal, or octal number.</p>
<p><a id="lexer.line_state"></a></p>
<h3><code>lexer.line_state</code> (table)</h3>
<p>Table of integer line states for line numbers starting from zero.
Line states can be used by lexers for keeping track of persistent states.</p>
<p><a id="lexer.lower"></a></p>
<h3><code>lexer.lower</code> (pattern)</h3>
<p>A pattern that matches any lower case character ('a'-'z').</p>
<p><a id="lexer.newline"></a></p>
<h3><code>lexer.newline</code> (pattern)</h3>
<p>A pattern that matches any set of end of line characters.</p>
<p><a id="lexer.nonnewline"></a></p>
<h3><code>lexer.nonnewline</code> (pattern)</h3>
<p>A pattern that matches any single, non-newline character.</p>
<p><a id="lexer.nonnewline_esc"></a></p>
<h3><code>lexer.nonnewline_esc</code> (pattern)</h3>
<p>A pattern that matches any single, non-newline character or any set of end
of line characters escaped with '\'.</p>
<p><a id="lexer.oct_num"></a></p>
<h3><code>lexer.oct_num</code> (pattern)</h3>
<p>A pattern that matches an octal number.</p>
<p><a id="lexer.path"></a></p>
<h3><code>lexer.path</code> (string)</h3>
<p>The path used to search for a lexer to load.
Identical in format to Lua's <code>package.path</code> string.
The default value is <code>package.path</code>.</p>
<p><a id="lexer.print"></a></p>
<h3><code>lexer.print</code> (pattern)</h3>
<p>A pattern that matches any printable character (' ' to '~').</p>
<p><a id="lexer.property"></a></p>
<h3><code>lexer.property</code> (table)</h3>
<p>Map of key-value string pairs.</p>
<p><a id="lexer.property_expanded"></a></p>
<h3><code>lexer.property_expanded</code> (table, Read-only)</h3>
<p>Map of key-value string pairs with <code>$()</code> and <code>%()</code> variable replacement
performed in values.</p>
<p><a id="lexer.property_int"></a></p>
<h3><code>lexer.property_int</code> (table, Read-only)</h3>
<p>Map of key-value pairs with values interpreted as numbers, or <code>0</code> if not
found.</p>
<p><a id="lexer.punct"></a></p>
<h3><code>lexer.punct</code> (pattern)</h3>
<p>A pattern that matches any punctuation character ('!' to '/', ':' to '@',
'[' to ''', '{' to '~').</p>
<p><a id="lexer.space"></a></p>
<h3><code>lexer.space</code> (pattern)</h3>
<p>A pattern that matches any whitespace character ('\t', '\v', '\f', '\n',
'\r', space).</p>
<p><a id="lexer.style_at"></a></p>
<h3><code>lexer.style_at</code> (table, Read-only)</h3>
<p>Table of style names at positions in the buffer starting from 1.</p>
<p><a id="lexer.upper"></a></p>
<h3><code>lexer.upper</code> (pattern)</h3>
<p>A pattern that matches any upper case character ('A'-'Z').</p>
<p><a id="lexer.word"></a></p>
<h3><code>lexer.word</code> (pattern)</h3>
<p>A pattern that matches a typical word. Words begin with a letter or
underscore and consist of alphanumeric and underscore characters.</p>
<p><a id="lexer.xdigit"></a></p>
<h3><code>lexer.xdigit</code> (pattern)</h3>
<p>A pattern that matches any hexadecimal digit ('0'-'9', 'A'-'F', 'a'-'f').</p>
<h2>Lua <code>lexer</code> module API functions</h2>
<p><a id="lexer.add_fold_point"></a></p>
<h3><code>lexer.add_fold_point</code> (lexer, token_name, start_symbol, end_symbol)</h3>
<p>Adds to lexer <em>lexer</em> a fold point whose beginning and end tokens are string
<em>token_name</em> tokens with string content <em>start_symbol</em> and <em>end_symbol</em>,
respectively.
In the event that <em>start_symbol</em> may or may not be a fold point depending on
context, and that additional processing is required, <em>end_symbol</em> may be a
function that ultimately returns <code>1</code> (indicating a beginning fold point),
<code>-1</code> (indicating an ending fold point), or <code>0</code> (indicating no fold point).
That function is passed the following arguments:</p>
<ul>
<li><code>text</code>: The text being processed for fold points.</li>
<li><code>pos</code>: The position in <em>text</em> of the beginning of the line currently
being processed.</li>
<li><code>line</code>: The text of the line currently being processed.</li>
<li><code>s</code>: The position of <em>start_symbol</em> in <em>line</em>.</li>
<li><code>symbol</code>: <em>start_symbol</em> itself.</li>
</ul>
<p>Fields:</p>
<ul>
<li><code>lexer</code>: The lexer to add a fold point to.</li>
<li><code>token_name</code>: The token name of text that indicates a fold point.</li>
<li><code>start_symbol</code>: The text that indicates the beginning of a fold point.</li>
<li><code>end_symbol</code>: Either the text that indicates the end of a fold point, or
a function that returns whether or not <em>start_symbol</em> is a beginning fold
point (1), an ending fold point (-1), or not a fold point at all (0).</li>
</ul>
<p>Usage:</p>
<ul>
<li><code>lex:add_fold_point(lexer.OPERATOR, '{', '}')</code></li>
<li><code>lex:add_fold_point(lexer.KEYWORD, 'if', 'end')</code></li>
<li><code>lex:add_fold_point(lexer.COMMENT, '#', lexer.fold_line_comments('#'))</code></li>
<li><code>lex:add_fold_point('custom', function(text, pos, line, s, symbol)
... end)</code></li>
</ul>
<p><a id="lexer.add_rule"></a></p>
<h3><code>lexer.add_rule</code> (lexer, id, rule)</h3>
<p>Adds pattern <em>rule</em> identified by string <em>id</em> to the ordered list of rules
for lexer <em>lexer</em>.</p>
<p>Fields:</p>
<ul>
<li><code>lexer</code>: The lexer to add the given rule to.</li>
<li><code>id</code>: The id associated with this rule. It does not have to be the same
as the name passed to <code>token()</code>.</li>
<li><code>rule</code>: The LPeg pattern of the rule.</li>
</ul>
<p>See also:</p>
<ul>
<li><a href="#lexer.modify_rule"><code>lexer.modify_rule</code></a></li>
</ul>
<p><a id="lexer.add_style"></a></p>
<h3><code>lexer.add_style</code> (lexer, token_name, style)</h3>
<p>Associates string <em>token_name</em> in lexer <em>lexer</em> with Scintilla style string
<em>style</em>.
Style strings are comma-separated property settings. Available property
settings are:</p>
<ul>
<li><code>font:name</code>: Font name.</li>
<li><code>size:int</code>: Font size.</li>
<li><code>bold</code> or <code>notbold</code>: Whether or not the font face is bold.</li>
<li><code>weight:int</code>: Font weight (between 1 and 999).</li>
<li><code>italics</code> or <code>notitalics</code>: Whether or not the font face is italic.</li>
<li><code>underlined</code> or <code>notunderlined</code>: Whether or not the font face is
underlined.</li>
<li><code>fore:color</code>: Font face foreground color in "#RRGGBB" or 0xBBGGRR format.</li>
<li><code>back:color</code>: Font face background color in "#RRGGBB" or 0xBBGGRR format.</li>
<li><code>eolfilled</code> or <code>noteolfilled</code>: Whether or not the background color
extends to the end of the line.</li>
<li><code>case:char</code>: Font case ('u' for uppercase, 'l' for lowercase, and 'm' for
mixed case).</li>
<li><code>visible</code> or <code>notvisible</code>: Whether or not the text is visible.</li>
<li><code>changeable</code> or <code>notchangeable</code>: Whether or not the text is changeable or
read-only.</li>
</ul>
<p>Property settings may also contain "$(property.name)" expansions for
properties defined in Scintilla, theme files, etc.</p>
<p>Fields:</p>
<ul>
<li><code>lexer</code>: The lexer to add a style to.</li>
<li><code>token_name</code>: The name of the token to associated with the style.</li>
<li><code>style</code>: A style string for Scintilla.</li>
</ul>
<p>Usage:</p>
<ul>
<li><code>lex:add_style('longstring', lexer.STYLE_STRING)</code></li>
<li><code>lex:add_style('deprecated_function', lexer.STYLE_FUNCTION..',italics')</code></li>
<li><code>lex:add_style('visible_ws',
lexer.STYLE_WHITESPACE..',back:$(color.grey)')</code></li>
</ul>
<p><a id="lexer.delimited_range"></a></p>
<h3><code>lexer.delimited_range</code> (chars, single_line, no_escape, balanced)</h3>
<p>Creates and returns a pattern that matches a range of text bounded by
<em>chars</em> characters.
This is a convenience function for matching more complicated delimited ranges
like strings with escape characters and balanced parentheses. <em>single_line</em>
indicates whether or not the range must be on a single line, <em>no_escape</em>
indicates whether or not to ignore '\' as an escape character, and <em>balanced</em>
indicates whether or not to handle balanced ranges like parentheses and
requires <em>chars</em> to be composed of two characters.</p>
<p>Fields:</p>
<ul>
<li><code>chars</code>: The character(s) that bound the matched range.</li>
<li><code>single_line</code>: Optional flag indicating whether or not the range must be
on a single line.</li>
<li><code>no_escape</code>: Optional flag indicating whether or not the range end
character may be escaped by a '\' character.</li>
<li><code>balanced</code>: Optional flag indicating whether or not to match a balanced
range, like the "%b" Lua pattern. This flag only applies if <em>chars</em>
consists of two different characters (e.g. "()").</li>
</ul>
<p>Usage:</p>
<ul>
<li><code>local dq_str_escapes = lexer.delimited_range('"')</code></li>
<li><code>local dq_str_noescapes = lexer.delimited_range('"', false, true)</code></li>
<li><code>local unbalanced_parens = lexer.delimited_range('()')</code></li>
<li><code>local balanced_parens = lexer.delimited_range('()', false, false,
true)</code></li>
</ul>
<p>Return:</p>
<ul>
<li>pattern</li>
</ul>
<p>See also:</p>
<ul>
<li><a href="#lexer.nested_pair"><code>lexer.nested_pair</code></a></li>
</ul>
<p><a id="lexer.embed"></a></p>
<h3><code>lexer.embed</code> (lexer, child, start_rule, end_rule)</h3>
<p>Embeds child lexer <em>child</em> in parent lexer <em>lexer</em> using patterns
<em>start_rule</em> and <em>end_rule</em>, which signal the beginning and end of the
embedded lexer, respectively.</p>
<p>Fields:</p>
<ul>
<li><code>lexer</code>: The parent lexer.</li>
<li><code>child</code>: The child lexer.</li>
<li><code>start_rule</code>: The pattern that signals the beginning of the embedded
lexer.</li>
<li><code>end_rule</code>: The pattern that signals the end of the embedded lexer.</li>
</ul>
<p>Usage:</p>
<ul>
<li><code>html:embed(css, css_start_rule, css_end_rule)</code></li>
<li><code>html:embed(lex, php_start_rule, php_end_rule) -- from php lexer</code></li>
</ul>
<p><a id="lexer.fold"></a></p>
<h3><code>lexer.fold</code> (lexer, text, start_pos, start_line, start_level)</h3>
<p>Determines fold points in a chunk of text <em>text</em> using lexer <em>lexer</em>,
returning a table of fold levels associated with line numbers.
<em>text</em> starts at position <em>start_pos</em> on line number <em>start_line</em> with a
beginning fold level of <em>start_level</em> in the buffer.</p>
<p>Fields:</p>
<ul>
<li><code>lexer</code>: The lexer to fold text with.</li>
<li><code>text</code>: The text in the buffer to fold.</li>
<li><code>start_pos</code>: The position in the buffer <em>text</em> starts at, starting at
zero.</li>
<li><code>start_line</code>: The line number <em>text</em> starts on.</li>
<li><code>start_level</code>: The fold level <em>text</em> starts on.</li>
</ul>
<p>Return:</p>
<ul>
<li>table of fold levels associated with line numbers.</li>
</ul>
<p><a id="lexer.fold_line_comments"></a></p>
<h3><code>lexer.fold_line_comments</code> (prefix)</h3>
<p>Returns a fold function (to be passed to <code>lexer.add_fold_point()</code>) that folds
consecutive line comments that start with string <em>prefix</em>.</p>
<p>Fields:</p>
<ul>
<li><code>prefix</code>: The prefix string defining a line comment.</li>
</ul>
<p>Usage:</p>
<ul>
<li><code>lex:add_fold_point(lexer.COMMENT, '--',
lexer.fold_line_comments('--'))</code></li>
<li><code>lex:add_fold_point(lexer.COMMENT, '//',
lexer.fold_line_comments('//'))</code></li>
</ul>
<p><a id="lexer.get_rule"></a></p>
<h3><code>lexer.get_rule</code> (lexer, id)</h3>
<p>Returns the rule identified by string <em>id</em>.</p>
<p>Fields:</p>
<ul>
<li><code>lexer</code>: The lexer to fetch a rule from.</li>
<li><code>id</code>: The id of the rule to fetch.</li>
</ul>
<p>Return:</p>
<ul>
<li>pattern</li>
</ul>
<p><a id="lexer.last_char_includes"></a></p>
<h3><code>lexer.last_char_includes</code> (s)</h3>
<p>Creates and returns a pattern that verifies that string set <em>s</em> contains the
first non-whitespace character behind the current match position.</p>
<p>Fields:</p>
<ul>
<li><code>s</code>: String character set like one passed to <code>lpeg.S()</code>.</li>
</ul>
<p>Usage:</p>
<ul>
<li><code>local regex = lexer.last_char_includes('+-*!%^&|=,([{') *
lexer.delimited_range('/')</code></li>
</ul>
<p>Return:</p>
<ul>
<li>pattern</li>
</ul>
<p><a id="lexer.lex"></a></p>
<h3><code>lexer.lex</code> (lexer, text, init_style)</h3>
<p>Lexes a chunk of text <em>text</em> (that has an initial style number of
<em>init_style</em>) using lexer <em>lexer</em>, returning a table of token names and
positions.</p>
<p>Fields:</p>
<ul>
<li><code>lexer</code>: The lexer to lex text with.</li>
<li><code>text</code>: The text in the buffer to lex.</li>
<li><code>init_style</code>: The current style. Multiple-language lexers use this to
determine which language to start lexing in.</li>
</ul>
<p>Return:</p>
<ul>
<li>table of token names and positions.</li>
</ul>
<p><a id="lexer.line_from_position"></a></p>
<h3><code>lexer.line_from_position</code> (pos)</h3>
<p>Returns the line number of the line that contains position <em>pos</em>, which
starts from 1.</p>
<p>Fields:</p>
<ul>
<li><code>pos</code>: The position to get the line number of.</li>
</ul>
<p>Return:</p>
<ul>
<li>number</li>
</ul>
<p><a id="lexer.load"></a></p>
<h3><code>lexer.load</code> (name, alt_name, cache)</h3>
<p>Initializes or loads and returns the lexer of string name <em>name</em>.
Scintilla calls this function in order to load a lexer. Parent lexers also
call this function in order to load child lexers and vice-versa. The user
calls this function in order to load a lexer when using this module as a Lua
library.</p>
<p>Fields:</p>
<ul>
<li><code>name</code>: The name of the lexing language.</li>
<li><code>alt_name</code>: The alternate name of the lexing language. This is useful for
embedding the same child lexer with multiple sets of start and end tokens.</li>
<li><code>cache</code>: Flag indicating whether or not to load lexers from the cache.
This should only be <code>true</code> when initially loading a lexer (e.g. not from
within another lexer for embedding purposes).
The default value is <code>false</code>.</li>
</ul>
<p>Return:</p>
<ul>
<li>lexer object</li>
</ul>
<p><a id="lexer.modify_rule"></a></p>
<h3><code>lexer.modify_rule</code> (lexer, id, rule)</h3>
<p>Replaces in lexer <em>lexer</em> the existing rule identified by string <em>id</em> with
pattern <em>rule</em>.</p>
<p>Fields:</p>
<ul>
<li><code>lexer</code>: The lexer to modify.</li>
<li><code>id</code>: The id associated with this rule.</li>
<li><code>rule</code>: The LPeg pattern of the rule.</li>
</ul>
<p><a id="lexer.nested_pair"></a></p>
<h3><code>lexer.nested_pair</code> (start_chars, end_chars)</h3>
<p>Returns a pattern that matches a balanced range of text that starts with
string <em>start_chars</em> and ends with string <em>end_chars</em>.
With single-character delimiters, this function is identical to
<code>delimited_range(start_chars..end_chars, false, true, true)</code>.</p>
<p>Fields:</p>
<ul>
<li><code>start_chars</code>: The string starting a nested sequence.</li>
<li><code>end_chars</code>: The string ending a nested sequence.</li>
</ul>
<p>Usage:</p>
<ul>
<li><code>local nested_comment = lexer.nested_pair('/*', '*/')</code></li>
</ul>
<p>Return:</p>
<ul>
<li>pattern</li>
</ul>
<p>See also:</p>
<ul>
<li><a href="#lexer.delimited_range"><code>lexer.delimited_range</code></a></li>
</ul>
<p><a id="lexer.new"></a></p>
<h3><code>lexer.new</code> (name, opts)</h3>
<p>Creates a returns a new lexer with the given name.</p>
<p>Fields:</p>
<ul>
<li><code>name</code>: The lexer's name.</li>
<li><code>opts</code>: Table of lexer options. Options currently supported:
<ul>
<li><code>lex_by_line</code>: Whether or not the lexer only processes whole lines of
text (instead of arbitrary chunks of text) at a time.
Line lexers cannot look ahead to subsequent lines.
The default value is <code>false</code>.</li>
<li><code>fold_by_indentation</code>: Whether or not the lexer does not define any fold
points and that fold points should be calculated based on changes in line
indentation.
The default value is <code>false</code>.</li>
<li><code>case_insensitive_fold_points</code>: Whether or not fold points added via
<code>lexer.add_fold_point()</code> ignore case.
The default value is <code>false</code>.</li>
<li><code>inherit</code>: Lexer to inherit from.
The default value is <code>nil</code>.</li>
</ul>
</li>
</ul>
<p>Usage:</p>
<ul>
<li><code>lexer.new('rhtml', {inherit = lexer.load('html')})</code></li>
</ul>
<p><a id="lexer.starts_line"></a></p>
<h3><code>lexer.starts_line</code> (patt)</h3>
<p>Creates and returns a pattern that matches pattern <em>patt</em> only at the
beginning of a line.</p>
<p>Fields:</p>
<ul>
<li><code>patt</code>: The LPeg pattern to match on the beginning of a line.</li>
</ul>
<p>Usage:</p>
<ul>
<li><code>local preproc = token(lexer.PREPROCESSOR, lexer.starts_line('#') *
lexer.nonnewline^0)</code></li>
</ul>
<p>Return:</p>
<ul>
<li>pattern</li>
</ul>
<p><a id="lexer.token"></a></p>
<h3><code>lexer.token</code> (name, patt)</h3>
<p>Creates and returns a token pattern with token name <em>name</em> and pattern
<em>patt</em>.
If <em>name</em> is not a predefined token name, its style must be defined via
<code>lexer.add_style()</code>.</p>
<p>Fields:</p>
<ul>
<li><code>name</code>: The name of token. If this name is not a predefined token name,
then a style needs to be assiciated with it via <code>lexer.add_style()</code>.</li>
<li><code>patt</code>: The LPeg pattern associated with the token.</li>
</ul>
<p>Usage:</p>
<ul>
<li><code>local ws = token(lexer.WHITESPACE, lexer.space^1)</code></li>
<li><code>local annotation = token('annotation', '@' * lexer.word)</code></li>
</ul>
<p>Return:</p>
<ul>
<li>pattern</li>
</ul>
<p><a id="lexer.word_match"></a></p>
<h3><code>lexer.word_match</code> (words, case_insensitive, word_chars)</h3>
<p>Creates and returns a pattern that matches any single word in string <em>words</em>.
<em>case_insensitive</em> indicates whether or not to ignore case when matching
words.
This is a convenience function for simplifying a set of ordered choice word
patterns.
If <em>words</em> is a multi-line string, it may contain Lua line comments (<code>--</code>)
that will ultimately be ignored.</p>
<p>Fields:</p>
<ul>
<li><code>words</code>: A string list of words separated by spaces.</li>
<li><code>case_insensitive</code>: Optional boolean flag indicating whether or not the
word match is case-insensitive. The default value is <code>false</code>.</li>
<li><code>word_chars</code>: Unused legacy parameter.</li>
</ul>
<p>Usage:</p>
<ul>
<li><code>local keyword = token(lexer.KEYWORD, word_match[[foo bar baz]])</code></li>
<li><code>local keyword = token(lexer.KEYWORD, word_match([[foo-bar foo-baz
bar-foo bar-baz baz-foo baz-bar]], true))</code></li>
</ul>
<p>Return:</p>
<ul>
<li>pattern</li>
</ul>
<h2 id="LexerList">Supported Languages</h2>
<p>Scintilla has Lua lexers for all of the languages below. Languages
denoted by a <code>*</code> have native
<a href="#lexer.Code.Folding">folders</a>. For languages without
native folding support, folding based on indentation can be used if
<code>fold.by.indentation</code> is enabled.</p>
<ol>
<li>Actionscript<code>*</code></li>
<li>Ada</li>
<li>ANTLR<code>*</code></li>
<li>APDL<code>*</code></li>
<li>APL</li>
<li>Applescript</li>
<li>ASM<code>*</code> (NASM)</li>
<li>ASP<code>*</code></li>
<li>AutoIt</li>
<li>AWK<code>*</code></li>
<li>Batch<code>*</code></li>
<li>BibTeX<code>*</code></li>
<li>Boo</li>
<li>C<code>*</code></li>
<li>C++<code>*</code></li>
<li>C#<code>*</code></li>
<li>ChucK</li>
<li>CMake<code>*</code></li>
<li>Coffeescript</li>
<li>ConTeXt<code>*</code></li>
<li>CSS<code>*</code></li>
<li>CUDA<code>*</code></li>
<li>D<code>*</code></li>
<li>Dart<code>*</code></li>
<li>Desktop Entry</li>
<li>Diff</li>
<li>Django<code>*</code></li>
<li>Dockerfile</li>
<li>Dot<code>*</code></li>
<li>Eiffel<code>*</code></li>
<li>Elixir</li>
<li>Erlang<code>*</code></li>
<li>F#</li>
<li>Faust</li>
<li>Fish<code>*</code></li>
<li>Forth</li>
<li>Fortran</li>
<li>GAP<code>*</code></li>
<li>gettext</li>
<li>Gherkin</li>
<li>GLSL<code>*</code></li>
<li>Gnuplot</li>
<li>Go<code>*</code></li>
<li>Groovy<code>*</code></li>
<li>Gtkrc<code>*</code></li>
<li>Haskell</li>
<li>HTML<code>*</code></li>
<li>Icon<code>*</code></li>
<li>IDL</li>
<li>Inform</li>
<li>ini</li>
<li>Io<code>*</code></li>
<li>Java<code>*</code></li>
<li>Javascript<code>*</code></li>
<li>JSON<code>*</code></li>
<li>JSP<code>*</code></li>
<li>LaTeX<code>*</code></li>
<li>Ledger</li>
<li>LESS<code>*</code></li>
<li>LilyPond</li>
<li>Lisp<code>*</code></li>
<li>Literate Coffeescript</li>
<li>Logtalk</li>
<li>Lua<code>*</code></li>
<li>Makefile</li>
<li>Man Page</li>
<li>Markdown</li>
<li>MATLAB<code>*</code></li>
<li>MoonScript</li>
<li>Myrddin</li>
<li>Nemerle<code>*</code></li>
<li>Nim</li>
<li>NSIS</li>
<li>Objective-C<code>*</code></li>
<li>OCaml</li>
<li>Pascal</li>
<li>Perl<code>*</code></li>
<li>PHP<code>*</code></li>
<li>PICO-8<code>*</code></li>
<li>Pike<code>*</code></li>
<li>PKGBUILD<code>*</code></li>
<li>Postscript</li>
<li>PowerShell<code>*</code></li>
<li>Prolog</li>
<li>Properties</li>
<li>Pure</li>
<li>Python</li>
<li>R</li>
<li>rc<code>*</code></li>
<li>REBOL<code>*</code></li>
<li>Rexx<code>*</code></li>
<li>ReStructuredText<code>*</code></li>
<li>RHTML<code>*</code></li>
<li>Ruby<code>*</code></li>
<li>Ruby on Rails<code>*</code></li>
<li>Rust<code>*</code></li>
<li>Sass<code>*</code></li>
<li>Scala<code>*</code></li>
<li>Scheme<code>*</code></li>
<li>Shell<code>*</code></li>
<li>Smalltalk<code>*</code></li>
<li>Standard ML</li>
<li>SNOBOL4</li>
<li>SQL</li>
<li>TaskPaper</li>
<li>Tcl<code>*</code></li>
<li>TeX<code>*</code></li>
<li>Texinfo<code>*</code></li>
<li>TOML</li>
<li>Vala<code>*</code></li>
<li>VBScript</li>
<li>vCard<code>*</code></li>
<li>Verilog<code>*</code></li>
<li>VHDL</li>
<li>Visual Basic</li>
<li>Windows Script File<code>*</code></li>
<li>XML<code>*</code></li>
<li>Xtend<code>*</code></li>
<li>YAML</li>
</ol>
<h2>Code Contributors</h2>
<ul>
<li>Alejandro Baez</li>
<li>Alex Saraci</li>
<li>Brian Schott</li>
<li>Carl Sturtivant</li>
<li>Chris Emerson</li>
<li>Christian Hesse</li>
<li>David B. Lamkins</li>
<li>Heck Fy</li>
<li>Jason Schindler</li>
<li>Jeff Stone</li>
<li>Joseph Eib</li>
<li>Joshua Krämer</li>
<li>Klaus Borges</li>
<li>Larry Hynes</li>
<li>M Rawash</li>
<li>Marc André Tanner</li>
<li>Markus F.X.J. Oberhumer</li>
<li>Martin Morawetz</li>
<li>Michael Forney</li>
<li>Michael T. Richter</li>
<li>Michel Martens</li>
<li>Murray Calavera</li>
<li>Neil Hodgson</li>
<li>Olivier Guibé</li>
<li>Peter Odding</li>
<li>Piotr Orzechowski</li>
<li>Richard Philips</li>
<li>Robert Gieseke</li>
<li>Roberto Ierusalimschy</li>
<li>S. Gilles</li>
<li>Stéphane Rivière</li>
<li>Tymur Gubayev</li>
<li>Wolfgang Seeberg</li>
</ul>
</body>
</html>
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