Scintilla |
Scintilla's LPeg lexer adds dynamic Lua LPeg 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.
Scintilla is not compiled with the LPeg lexer enabled by
default (it is present, but empty). You need to manually enable it with the
LPEG_LEXER
flag when building Scintilla and its lexers. You
also need to build and link the Lua source files contained in Scintilla's
lua/src/
directory to lexers/LexLPeg.cxx
. If your
application has its own copy of Lua, you can ignore Scintilla's copy and
link to yours.
At this time, only the GTK, curses, and MinGW32 (for win32) platform
makefiles facilitate enabling the LPeg lexer. For example, when building
Scintilla, run make LPEG_LEXER=1
. User contributions to
facilitate this for the other platforms is encouraged.
When Scintilla is compiled with the LPeg lexer enabled, and after
selecting it as the lexer to use via
lexlua/
directory in your application's installation location. If you prefer not to
use SCI_PRIVATELEXERCALL
, you may instead set via
the lexer.lpeg.home
lexer property to the location of
lexlua/
.
The following properties are recognized by the LPeg lexer and can be set via
:lexer.lpeg.home |
The directory containing the Lua lexers. This is the path
where you included Scintilla's lexlua/ directory in
your application's installation location. It is automatically set when
calling
with
.
Lexers across multiple directories can be used by separating
directories with a ; character. |
lexer.lpeg.color.theme |
The color theme to use. Color themes are located in the
lexlua/themes/ directory. (They can also be located in
any themes subdirectories of additional paths specified
in lexer.lpeg.home .) Currently supported themes are
light , dark , scite , and
curses . Your application can define colors and styles
manually through Scintilla properties. The theme files have
examples. |
fold |
For Lua lexers that have a folder, folding is turned on if
fold is set to 1 . The default is
0 . |
fold.by.indentation
| For Lua lexers that do not have a folder, if
fold.by.indentation is set to 1 , folding is
done based on indentation level (like Python). The default is
0 . |
fold.line.comments |
If fold.line.comments is set to 1 ,
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
0 . |
fold.on.zero.sum.lines |
If fold.on.zero.sum.lines is set to 1 ,
lines that contain both an ending and starting fold point are marked
as fold points. For example, the C line } else { would be
marked as a fold point. The default is 0 . |
fold.compact |
If fold.compact is set to 1 , blank lines
after an ending fold point are included in that fold.
|
Your application primarily communicates with the LPeg lexer using Scintilla's
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.In the descriptions that follow,
SCI_PRIVATELEXERCALL(int operation, void *pointer)
means you
would call Scintilla like
SendScintilla(sci, SCI_PRIVATELEXERCALL, operation, pointer);
The curses platform demo, jinx, has a C-source example for using the LPeg lexer. Additionally, here is a pseudo-code example:
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")
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)
home = "/home/mitchell/app/lua_lexers"
SendScintilla(sci, SCI_PRIVATELEXERCALL, SCI_LOADLEXERLIBRARY, home);
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)
}
SCI_PRIVATELEXERCALL(SCI_CHANGELEXERSTATE, lua_State *L)
SCI_PRIVATELEXERCALL(SCI_GETDIRECTFUNCTION, int SciFnDirect)
SCI_PRIVATELEXERCALL(SCI_GETLEXERLANGUAGE, char *languageName) → int
SCI_PRIVATELEXERCALL(SCI_GETSTATUS, char *errorMessage) → int
SCI_PRIVATELEXERCALL(SCI_LOADLEXERLIBRARY, const char *path)
SCI_PRIVATELEXERCALL(SCI_PROPERTYNAMES, char *names) → int
SCI_PRIVATELEXERCALL(SCI_SETDOCPOINTER, int sci)
SCI_PRIVATELEXERCALL(SCI_SETLEXERLANGUAGE, char *languageName)
SCI_PRIVATELEXERCALL(SCI_GETNAMEDSTYLES, char *styleName) → int
SCI_NAMEOFSTYLE(int style, char *name) → int
SCI_PRIVATELEXERCALL(SCI_CHANGELEXERSTATE, lua_State *L)
Tells the LPeg lexer to use L
as its Lua state instead of
creating a separate state.
L
must have already opened the "base", "string", "table",
"package", and "lpeg" libraries. If L
is a Lua 5.1 state, it
must have also opened the "io" library.
The LPeg lexer will create a single lexer
package (that can
be used with Lua's require
function), as well as a number of
other variables in the LUA_REGISTRYINDEX
table with the "sci_"
prefix.
Rather than including the path to Scintilla's Lua lexers in the
package.path
of the given Lua state, set the "lexer.lpeg.home"
property instead. The LPeg lexer uses that property to find and load
lexers.
Usage:
lua = luaL_newstate()
SendScintilla(sci, SCI_PRIVATELEXERCALL, SCI_CHANGELEXERSTATE, lua)
SCI_PRIVATELEXERCALL(SCI_GETDIRECTFUNCTION, SciFnDirect)
Tells the LPeg lexer the address of SciFnDirect
, the function
that handles Scintilla messages.
Despite the name SCI_GETDIRECTFUNCTION
, it only notifies the
LPeg lexer what the value of SciFnDirect
obtained from
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.
If you use this call, it must be made once for each Scintilla document that was created using Scintilla's
. You must also use the LPeg lexer API call.Usage:
fn = SendScintilla(sci, SCI_GETDIRECTFUNCTION, 0, 0)
SendScintilla(sci, SCI_PRIVATELEXERCALL, SCI_GETDIRECTFUNCTION, fn)
See also:
SCI_PRIVATELEXERCALL(SCI_GETLEXERLANGUAGE, char *languageName) → int
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 0
character.
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
and .SCI_PRIVATELEXERCALL(SCI_GETSTATUS, char *errorMessage) → int
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.
If no error occurred, the returned message will be empty.
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.
Usage:
SendScintilla(sci, SCI_PRIVATELEXERCALL, SCI_GETSTATUS, errmsg)
if (strlen(errmsg) > 0) { /* handle error */ }
SCI_PRIVATELEXERCALL(SCI_LOADLEXERLIBRARY, const char *path)
Tells the LPeg lexer that the given path is where a copy of Scintilla's
lexlua/
is located, or is a path that contains additional
lexers and/or themes to load (e.g. user-defined lexers/themes).
This call may be made multiple times in order to support lexers and themes across multiple directories.
Usage:
SendScintilla(sci, SCI_PRIVATELEXERCALL, SCI_LOADLEXERLIBRARY, "path/to/lexlua")
SCI_PRIVATELEXERCALL(SCI_PRIVATELEXERCALL, char *names) → int
Returns the length of a '\n'-separated list of known lexer names, or stores
the lexer list into the given buffer. If the buffer is long enough, the
string is terminated by a 0
character.
The lexers in this list can be passed to the
LPeg Lexer API call.Usage:
SendScintilla(sci, SCI_PRIVATELEXERCALL, SCI_PROPERTYNAMES, lexers)
// lexers now contains a '\n'-separated list of known lexer names
See also:
SCI_PRIVATELEXERCALL(SCI_SETDOCPOINTER, int sci)
Tells the LPeg lexer the address of the Scintilla window (obtained via
Scintilla's
)
currently in use.
Despite the name SCI_SETDOCPOINTER
, it has no relationship
to Scintilla documents.
Use this call only if you are using the
LPeg lexer API call. It must be made before each call to the LPeg lexer API call.Usage:
SendScintilla(sci, SCI_PRIVATELEXERCALL, SCI_SETDOCPOINTER, sci)
See also:
,SCI_PRIVATELEXERCALL(SCI_SETLEXERLANGUAGE, const char *languageName)
Sets the current Lua lexer to languageName
.
If you are having the LPeg lexer set the Lua lexer styles automatically, make sure you call the
LPeg lexer API first.Usage:
SendScintilla(sci, SCI_PRIVATELEXERCALL, SCI_SETLEXERLANGUAGE, "lua")
See also:
,SCI_PRIVATELEXERCALL(SCI_GETNAMEDSTYLES, const char *styleName)
Returns the style number associated with styleName
, or STYLE_DEFAULT
if styleName
is not in use.
Usage:
style = SendScintilla(sci, SCI_PRIVATELEXERCALL, SCI_GETNAMEDSTYLES, "error")
SendScintilla(sci, SCI_ANNOTATIONSETSTYLE, line, style) // match error style
SCI_NAMEOFSTYLE(int style, char *name) → int
Retrieves the name of a style. Note this is not a
SCI_PRIVATELEXERCALL
.
Usage:
style = SendScintilla(sci, SCI_GETSTYLEAT, pos, 0)
SendScintilla(sci, SCI_NAMEOFSTYLE, style, token)
// token now contains the name of the style at pos
In order to use Scintilla as a Lua library, simply place the lexlua/
directory in your Lua path (or modify Lua’s package.path
accordingly),
require()
the library and load()
a lexer, and call that lexer’s
lex()
function. Here is an example interactive Lua session doing this:
$> lua
Lua 5.1.4 Copyright (C) 1994-2008 Lua.org, PUC-Rio
> lexer_path = '/home/mitchell/code/scintilla/lexlua/?.lua'
> package.path = package.path..';'..lexer_path
> c = require('lexer').load('ansi_c')
> tokens = c:lex('int void main() { return 0; }')
> for i = 1, #tokens, 2 do print(tokens[i], tokens[i+1]) end
type 4
ansi_c_whitespace 5
type 9
ansi_c_whitespace 10
identifier 14
operator 15
operator 16
ansi_c_whitespace 17
operator 18
ansi_c_whitespace 19
keyword 25
ansi_c_whitespace 26
number 27
operator 28
ansi_c_whitespace 29
operator 30
Lexers highlight the syntax of source code. Scintilla (the editing component behind Textadept) traditionally uses static, compiled C++ lexers which are notoriously difficult to create and/or extend. On the other hand, Lua 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.
Lexers are Parsing Expression Grammars, or PEGs, composed with the Lua LPeg library. 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.
Operator | Description |
---|---|
lpeg.P(string) |
Matches string literally. |
lpeg.P( n ) |
Matches exactly n number of characters. |
lpeg.S(string) |
Matches any character in set string . |
lpeg.R(" xy ") |
Matches any character between range x and y . |
patt^ n |
Matches at least n repetitions of patt . |
patt^- n |
Matches at most n repetitions of patt . |
patt1 * patt2 |
Matches patt1 followed by patt2 . |
patt1 + patt2 |
Matches patt1 or patt2 (ordered choice). |
patt1 - patt2 |
Matches patt1 if patt2 does not also match. |
-patt |
Equivalent to ("" - patt) . |
#patt |
Matches patt but consumes no input. |
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.
The lexlua/ 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 .lua extension. For example, a new Lua lexer has the name lua.lua.
Note: Try to refrain from using one-character language names like “c”, “d”, or “r”. For example, Lua lexers for those language names are named “ansi_c”, “dmd”, and “rstats”, respectively.
There is a lexlua/template.txt 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:
-- ? 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
The first 3 lines of code simply define often used convenience variables. The
fourth and last lines define 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 local
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.
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.
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 lexer.token()
function. Let us examine the “whitespace” token
defined in the template shown earlier:
local ws = token(lexer.WHITESPACE, lexer.space^1)
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:
local ws = token('whitespace', S('\t\v\f\n\r ')^1)
The lexer
module actually provides a convenient list of common token names
and common LPeg patterns for you to use. Token names include
lexer.DEFAULT
, lexer.WHITESPACE
, lexer.COMMENT
,
lexer.STRING
, lexer.NUMBER
, lexer.KEYWORD
,
lexer.IDENTIFIER
, lexer.OPERATOR
, lexer.ERROR
,
lexer.PREPROCESSOR
, lexer.CONSTANT
, lexer.VARIABLE
,
lexer.FUNCTION
, lexer.CLASS
, lexer.TYPE
, lexer.LABEL
,
lexer.REGEX
, and lexer.EMBEDDED
. Patterns include
lexer.any
, lexer.alpha
,
lexer.digit
, lexer.alnum
, lexer.lower
, lexer.upper
,
lexer.xdigit
, lexer.graph
,
lexer.punct
, lexer.space
, lexer.newline
,
lexer.nonnewline
, lexer.dec_num
,
lexer.hex_num
, lexer.oct_num
, lexer.integer
,
lexer.float
, lexer.number
, and lexer.word
. 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.
So, how might you define other tokens like keywords, comments, and strings? Here are some examples.
Keywords
Instead of matching n keywords with n P('keyword_
n
')
ordered
choices, use another convenience function: lexer.word_match()
. It is
much easier and more efficient to write word matches like:
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
]])
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:
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
]])
Comments
Line-style comments with a prefix character(s) are easy to express with LPeg:
local shell_comment = token(lexer.COMMENT, lexer.to_eol('#'))
local c_line_comment = token(lexer.COMMENT, lexer.to_eol('//', true))
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.
C-style “block” comments with a start and end delimiter are also easy to express:
local c_comment = token(lexer.COMMENT, lexer.range('/*', '*/'))
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.
Strings
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. lexer.range()
handles escapes
inherently.
local dq_str = lexer.range('"')
local sq_str = lexer.range("'")
local string = token(lexer.STRING, dq_str + sq_str)
In this case, the lexer treats ‘\’ as an escape character in a string sequence.
Numbers
Most programming languages have the same format for integer and float tokens, so it might be as simple as using a predefined LPeg pattern:
local number = token(lexer.NUMBER, lexer.number)
However, some languages allow postfix characters on integers.
local integer = P('-')^-1 * (lexer.dec_num * S('lL')^-1)
local number = token(lexer.NUMBER, lexer.float + lexer.hex_num + integer)
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!
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 lexer.add_rule()
call, which adds a rule to the lexer’s
grammar:
lex:add_rule('whitespace', ws)
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”.
To illustrate the importance of rule order, here is an example of a simplified Lua lexer:
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, ...))
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.
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:
lex:add_rule('whitespace', ws)
...
lex:add_rule('error', token(lexer.ERROR, lexer.any))
This identifies and highlights any character not matched by an existing
rule as a lexer.ERROR
token.
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:
lex:add_rule('tag', tag_start * (ws * attributes)^0 * tag_end^-1)
Note however that lexers with complex rules like these are more prone to lose track of their state, especially if they span multiple lines.
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.
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 Lua
tables of properties. By default, lexers associate predefined token names
like lexer.WHITESPACE
, lexer.COMMENT
, lexer.STRING
, etc. with
particular styles as part of a universal color theme. These predefined styles
are contained in lexer.styles
, and you may define your own styles. See
that table’s documentation for more information. 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 lexer.styles.string
style instead of defining a new
one.
Defining styles is pretty straightforward. An empty style that inherits the default theme settings is simply an empty table:
local style_nothing = {}
A similar style but with a bold font face looks like this:
local style_bold = {bold = true}
You can derive new styles from predefined ones without having to rewrite
them. This operation leaves the old style unchanged. For example, if you had
a “static variable” token whose style you wanted to base off of
lexer.styles.variable
, it would probably look like:
local style_static_var = lexer.styles.variable .. {italics = true}
The color theme files in the lexlua/themes/ folder give more examples of style definitions.
Lexers use the lexer.add_style()
function to assign styles to
particular tokens. Recall the token definition and from the lexer template:
local ws = token(lexer.WHITESPACE, lexer.space^1)
lex:add_rule('whitespace', ws)
Why is a style not assigned to the lexer.WHITESPACE
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:
local ws = token('custom_whitespace', lexer.space^1)
Assigning a style to this token looks like:
lex:add_style('custom_whitespace', lexer.styles.whitespace)
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 lexer.WHITESPACE
tokens. If instead you
prefer to color the background of whitespace a shade of grey, it might look
like:
lex:add_style('custom_whitespace',
lexer.styles.whitespace .. {back = lexer.colors.grey})
Remember to refrain from assigning specific colors in styles, but in this
case, all user color themes probably define colors.grey
.
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:
local lex = lexer.new('?', {lex_by_line = true})
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.
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 embeds itself into HTML while CSS is embedded in 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).
Before embedding a child lexer into a parent lexer, the parent lexer needs to
load the child lexer. This is done with the lexer.load()
function. For
example, loading the CSS lexer within the HTML lexer looks like:
local css = lexer.load('css')
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”:
local css_tag = P('<style') * P(function(input, index)
if input:find('^[^>]+type="text/css"', index) then
return index
end
end)
This pattern looks for the beginning of a “style” tag and searches its
attribute list for the text “type="text/css"
”. (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 nil
. 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:
local css_start_rule = #css_tag * tag
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:
local css_end_rule = #P('</style>') * tag
Once the parent loads the child lexer and defines the child’s start and end
rules, it embeds the child with the lexer.embed()
function:
lex:embed(css, css_start_rule, css_end_rule)
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 lexer.load()
function and then create
start and end rules for the child lexer. However, in this case, call
lexer.embed()
with switched arguments. For example, in the PHP lexer:
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.styles.embedded)
html:embed(lex, php_start_rule, php_end_rule)
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 lpeg.P
function patterns that set state variables, it is recommended to make use of
Scintilla’s built-in, per-line state integers via lexer.line_state
. It
was designed to accommodate up to 32 bit flags for tracking state.
lexer.line_from_position()
will return the line for any position given
to an lpeg.P
function pattern. (Any positions derived from that position
argument will also work.)
Writing stateful lexers is beyond the scope of this document.
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.
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 lexer.add_fold_point()
function
allows you to conveniently define fold points with such granularity. For
example, consider C:
lex:add_fold_point(lexer.OPERATOR, '{', '}')
lex:add_fold_point(lexer.COMMENT, '/*', '*/')
The first assignment states that any ‘{’ or ‘}’ that the lexer recognized as
an lexer.OPERATOR
token is a fold point. Likewise, the second assignment
states that any “/*” or “*/” that the lexer recognizes as part of a
lexer.COMMENT
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:
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')
If your lexer has case-insensitive keywords as fold points, simply add a
case_insensitive_fold_points = true
option to lexer.new()
, and
specify keywords in lower case.
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
lex:add_fold_point()
. Returning 1
indicates the token is a beginning fold
point and returning -1
indicates the token is an ending fold point.
Returning 0
indicates the token is not a fold point. For example:
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)
Any time the lexer encounters a ‘|’ that is a “strange_token”, it calls the
fold_strange_token
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.
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
fold_by_indentation = true
option:
local lex = lexer.new('?', {fold_by_indentation = true})
Put your lexer in your ~/.textadept/lexers/ directory so you do not overwrite it when upgrading Textadept. Also, lexers in this directory override default lexers. Thus, Textadept loads a user lua lexer instead of the default lua lexer. This is convenient for tweaking a default lexer to your liking. Then add a file type for your lexer if necessary.
Legacy lexers are of the form:
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
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:
l
with lexer
, as it’s better practice and
results in less confusion.local M = {_NAME = '?'}
with local lex = lexer.new('?')
, where
?
is the name of your legacy lexer. At the end of the lexer, change
return M
to return lex
.lex:add_rule()
.lex:add_style()
.lexer.word_match()
to a
space-separated string of words.lexer.embed(M, child, ...)
and
lexer.embed(parent, M, ...)
with
lex:embed
(child, ...)
and parent:embed(lex, ...)
,
respectively.lex:add_fold_point()
. No need to mess with Lua
patterns anymore.M._FOLDBYINDENTATION
, M._LEXBYLINE
,
M._lexer
, etc. should be added as table options to lexer.new()
.lexer._RULES
should be changed to use lexer.get_rule()
and
lexer.modify_rule()
.As an example, consider the following sample legacy lexer:
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
Following the migration steps would yield:
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.styles.keyword .. {bold = true})
lex:add_rule('identifier', token(lexer.IDENTIFIER, lexer.word))
lex:add_rule('string', token(lexer.STRING, lexer.range('"')))
lex:add_rule('comment', token(lexer.COMMENT, lexer.to_eol('#')))
lex:add_rule('number', token(lexer.NUMBER, lexer.number))
lex:add_rule('operator', token(lexer.OPERATOR, S('+-*/%^=<>,.()[]{}')))
lex:add_fold_point(lexer.OPERATOR, '{', '}')
return lex
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 lexer.add_rule()
calls so
that the most common rules match first. Do keep in mind that order matters
for similar rules.
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 in your text editor first. If that
speeds things up, you can try reducing the number of fold points you added,
overriding lexer.fold()
with your own implementation, or simply eliminating
folding support from your lexer.
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
<div id="<?php echo $id; ?>">
will not style correctly.
Errors in lexers can be tricky to debug. Lexers print Lua errors to
io.stderr
and _G.print()
statements to io.stdout
. Running your editor
from a terminal is the easiest way to see errors as they occur.
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.
Thanks to Peter Odding for his lexer post on the Lua mailing list that provided inspiration, and thanks to Roberto Ierusalimschy for LPeg.
lexer
module API fieldslexer.CLASS
(string)The token name for class tokens.
lexer.COMMENT
(string)The token name for comment tokens.
lexer.CONSTANT
(string)The token name for constant tokens.
lexer.DEFAULT
(string)The token name for default tokens.
lexer.ERROR
(string)The token name for error tokens.
lexer.FOLD_BASE
(number)The initial (root) fold level.
lexer.FOLD_BLANK
(number)Flag indicating that the line is blank.
lexer.FOLD_HEADER
(number)Flag indicating the line is fold point.
lexer.FUNCTION
(string)The token name for function tokens.
lexer.IDENTIFIER
(string)The token name for identifier tokens.
lexer.KEYWORD
(string)The token name for keyword tokens.
lexer.LABEL
(string)The token name for label tokens.
lexer.NUMBER
(string)The token name for number tokens.
lexer.OPERATOR
(string)The token name for operator tokens.
lexer.PREPROCESSOR
(string)The token name for preprocessor tokens.
lexer.REGEX
(string)The token name for regex tokens.
lexer.STRING
(string)The token name for string tokens.
lexer.TYPE
(string)The token name for type tokens.
lexer.VARIABLE
(string)The token name for variable tokens.
lexer.WHITESPACE
(string)The token name for whitespace tokens.
lexer.alnum
(pattern)A pattern that matches any alphanumeric character (‘A’-‘Z’, ‘a’-‘z’, ‘0’-‘9’).
lexer.alpha
(pattern)A pattern that matches any alphabetic character (‘A’-‘Z’, ‘a’-‘z’).
lexer.any
(pattern)A pattern that matches any single character.
lexer.ascii
(pattern)A pattern that matches any ASCII character (codes 0 to 127).
lexer.cntrl
(pattern)A pattern that matches any control character (ASCII codes 0 to 31).
lexer.dec_num
(pattern)A pattern that matches a decimal number.
lexer.digit
(pattern)A pattern that matches any digit (‘0’-‘9’).
lexer.extend
(pattern)A pattern that matches any ASCII extended character (codes 0 to 255).
lexer.float
(pattern)A pattern that matches a floating point number.
lexer.fold_by_indentation
(boolean)Whether or not to fold based on indentation level if a lexer does not have
a folder.
Some lexers automatically enable this option. It is disabled by default.
This is an alias for lexer.property['fold.by.indentation'] = '1|0'
.
lexer.fold_compact
(boolean)Whether or not blank lines after an ending fold point are included in that
fold.
This option is disabled by default.
This is an alias for lexer.property['fold.compact'] = '1|0'
.
lexer.fold_level
(table, Read-only)Table of fold level bit-masks for line numbers starting from 1. Fold level masks are composed of an integer level combined with any of the following bits:
lexer.FOLD_BASE
The initial fold level.lexer.FOLD_BLANK
The line is blank.lexer.FOLD_HEADER
The line is a header, or fold point.lexer.fold_line_groups
(boolean)Whether or not to fold multiple, consecutive line groups (such as line
comments or import statements) and only show the top line.
This option is disabled by default.
This is an alias for lexer.property['fold.line.groups'] = '1|0'
.
lexer.fold_on_zero_sum_lines
(boolean)Whether or not to mark as a fold point lines that contain both an ending
and starting fold point. For example, } else {
would be marked as a fold
point.
This option is disabled by default.
This is an alias for lexer.property['fold.on.zero.sum.lines'] = '1|0'
.
lexer.folding
(boolean)Whether or not folding is enabled.
This option is disabled by default.
This is an alias for lexer.property['fold'] = '1|0'
.
lexer.graph
(pattern)A pattern that matches any graphical character (‘!’ to ‘~’).
lexer.hex_num
(pattern)A pattern that matches a hexadecimal number.
lexer.indent_amount
(table, Read-only)Table of indentation amounts in character columns, for line numbers starting from 1.
lexer.integer
(pattern)A pattern that matches either a decimal, hexadecimal, or octal number.
lexer.line_state
(table)Table of integer line states for line numbers starting from 1. Line states can be used by lexers for keeping track of persistent states.
lexer.lower
(pattern)A pattern that matches any lower case character (‘a’-‘z’).
lexer.newline
(pattern)A pattern that matches a sequence of end of line characters.
lexer.nonnewline
(pattern)A pattern that matches any single, non-newline character.
lexer.nonnewline_esc
(pattern)A pattern that matches any single, non-newline character or any set of end of line characters escaped with ‘\’.
lexer.number
(pattern)A pattern that matches a typical number, either a floating point, decimal, hexadecimal, or octal number.
lexer.oct_num
(pattern)A pattern that matches an octal number.
lexer.print
(pattern)A pattern that matches any printable character (‘ ’ to ‘~’).
lexer.property
(table)Map of key-value string pairs.
lexer.property_expanded
(table, Read-only)Map of key-value string pairs with $()
and %()
variable replacement
performed in values.
lexer.property_int
(table, Read-only)Map of key-value pairs with values interpreted as numbers, or 0
if not
found.
lexer.punct
(pattern)A pattern that matches any punctuation character (‘!’ to ‘/’, ‘:’ to ‘@’, ‘[’ to ‘’‘, ’{‘ to ’~‘).
lexer.space
(pattern)A pattern that matches any whitespace character (‘\t’, ‘\v’, ‘\f’, ‘\n’, ‘\r’, space).
lexer.style_at
(table, Read-only)Table of style names at positions in the buffer starting from 1.
lexer.upper
(pattern)A pattern that matches any upper case character (‘A’-‘Z’).
lexer.word
(pattern)A pattern that matches a typical word. Words begin with a letter or underscore and consist of alphanumeric and underscore characters.
lexer.xdigit
(pattern)A pattern that matches any hexadecimal digit (‘0’-‘9’, ‘A’-‘F’, ‘a’-‘f’).
lexer
module API functionslexer.add_fold_point
(lexer, token_name, start_symbol, end_symbol)Adds to lexer lexer a fold point whose beginning and end tokens are string
token_name tokens with string content start_symbol and end_symbol,
respectively.
In the event that start_symbol may or may not be a fold point depending on
context, and that additional processing is required, end_symbol may be a
function that ultimately returns 1
(indicating a beginning fold point),
-1
(indicating an ending fold point), or 0
(indicating no fold point).
That function is passed the following arguments:
text
: The text being processed for fold points.pos
: The position in text of the beginning of the line currently
being processed.line
: The text of the line currently being processed.s
: The position of start_symbol in line.symbol
: start_symbol itself.Parameters:
lexer
: The lexer to add a fold point to.token_name
: The token name of text that indicates a fold point.start_symbol
: The text that indicates the beginning of a fold point.end_symbol
: Either the text that indicates the end of a fold point, or
a function that returns whether or not start_symbol is a beginning fold
point (1), an ending fold point (-1), or not a fold point at all (0).Usage:
lex:add_fold_point(lexer.OPERATOR, '{', '}')
lex:add_fold_point(lexer.KEYWORD, 'if', 'end')
lex:add_fold_point(lexer.COMMENT, '#', lexer.fold_line_comments('#'))
lex:add_fold_point('custom', function(text, pos, line, s, symbol)
... end)
lexer.add_rule
(lexer, id, rule)Adds pattern rule identified by string id to the ordered list of rules for lexer lexer.
Parameters:
lexer
: The lexer to add the given rule to.id
: The id associated with this rule. It does not have to be the same
as the name passed to token()
.rule
: The LPeg pattern of the rule.See also:
lexer.add_style
(lexer, token_name, style)Associates string token_name in lexer lexer with style table style.
Parameters:
lexer
: The lexer to add a style to.token_name
: The name of the token to associated with the style.style
: A style table.Usage:
lex:add_style('longstring', lexer.styles.string)
lex:add_style('deprecated_func', lexer.styles['function'] ..
{italics = true}
lex:add_style('visible_ws', lexer.styles.whitespace ..
{back = lexer.colors.grey}
See also:
lexer.embed
(lexer, child, start_rule, end_rule)Embeds child lexer child in parent lexer lexer using patterns start_rule and end_rule, which signal the beginning and end of the embedded lexer, respectively.
Parameters:
lexer
: The parent lexer.child
: The child lexer.start_rule
: The pattern that signals the beginning of the embedded
lexer.end_rule
: The pattern that signals the end of the embedded lexer.Usage:
html:embed(css, css_start_rule, css_end_rule)
html:embed(lex, php_start_rule, php_end_rule) -- from php lexer
lexer.fold
(lexer, text, start_pos, start_line, start_level)Determines fold points in a chunk of text text using lexer lexer, returning a table of fold levels associated with line numbers. text starts at position start_pos on line number start_line with a beginning fold level of start_level in the buffer.
Parameters:
lexer
: The lexer to fold text with.text
: The text in the buffer to fold.start_pos
: The position in the buffer text starts at, counting from
1.start_line
: The line number text starts on, counting from 1.start_level
: The fold level text starts on.Return:
lexer.fold_consecutive_lines
(prefix)Returns for lexer.add_fold_point()
the parameters needed to fold
consecutive lines that start with string prefix.
Parameters:
prefix
: The prefix string (e.g. a line comment).Usage:
lex:add_fold_point(lexer.COMMENT, lexer.fold_consecutive_lines('--'))
lex:add_fold_point(lexer.COMMENT, lexer.fold_consecutive_lines('//'))
lex:add_fold_point(lexer.KEYWORD, lexer.fold_consecutive_lines('import'))
lexer.get_rule
(lexer, id)Returns the rule identified by string id.
Parameters:
lexer
: The lexer to fetch a rule from.id
: The id of the rule to fetch.Return:
lexer.last_char_includes
(s)Creates and returns a pattern that verifies the first non-whitespace character behind the current match position is in string set s.
Parameters:
s
: String character set like one passed to lpeg.S()
.Usage:
local regex = lexer.last_char_includes('+-*!%^&|=,([{') *
lexer.range('/')
Return:
lexer.lex
(lexer, text, init_style)Lexes a chunk of text text (that has an initial style number of init_style) using lexer lexer, returning a table of token names and positions.
Parameters:
lexer
: The lexer to lex text with.text
: The text in the buffer to lex.init_style
: The current style. Multiple-language lexers use this to
determine which language to start lexing in.Return:
lexer.line_from_position
(pos)Returns the line number (starting from 1) of the line that contains position pos, which starts from 1.
Parameters:
pos
: The position to get the line number of.Return:
lexer.load
(name, alt_name, cache)Initializes or loads and returns the lexer of string name name. 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.
Parameters:
name
: The name of the lexing language.alt_name
: The alternate name of the lexing language. This is useful for
embedding the same child lexer with multiple sets of start and end tokens.cache
: Flag indicating whether or not to load lexers from the cache.
This should only be true
when initially loading a lexer (e.g. not from
within another lexer for embedding purposes).
The default value is false
.Return:
lexer.modify_rule
(lexer, id, rule)Replaces in lexer lexer the existing rule identified by string id with pattern rule.
Parameters:
lexer
: The lexer to modify.id
: The id associated with this rule.rule
: The LPeg pattern of the rule.lexer.new
(name, opts)Creates a returns a new lexer with the given name.
Parameters:
name
: The lexer’s name.opts
: Table of lexer options. Options currently supported:
lex_by_line
: 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 false
.fold_by_indentation
: 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 false
.case_insensitive_fold_points
: Whether or not fold points added via
lexer.add_fold_point()
ignore case.
The default value is false
.inherit
: Lexer to inherit from.
The default value is nil
.Usage:
lexer.new('rhtml', {inherit = lexer.load('html')})
lexer.range
(s, e, single_line, escapes, balanced)Creates and returns a pattern that matches a range of text bounded by strings or patterns s and e. This is a convenience function for matching more complicated ranges like strings with escape characters, balanced parentheses, and block comments (nested or not). e is optional and defaults to s. single_line indicates whether or not the range must be on a single line; escapes indicates whether or not to allow ‘\’ as an escape character; and balanced indicates whether or not to handle balanced ranges like parentheses, and requires s and e to be different.
Parameters:
s
: String or pattern start of a range.e
: Optional string or pattern end of a range. The default value is s.single_line
: Optional flag indicating whether or not the range must be
on a single line.escapes
: Optional flag indicating whether or not the range end may
be escaped by a ‘\’ character.
The default value is false
unless s and e are identical,
single-character strings. In that case, the default value is true
.balanced
: Optional flag indicating whether or not to match a balanced
range, like the “%b” Lua pattern. This flag only applies if s and e are
different.Usage:
local dq_str_escapes = lexer.range('"')
local dq_str_noescapes = lexer.range('"', false, false)
local unbalanced_parens = lexer.range('(', ')')
local balanced_parens = lexer.range('(', ')', false, false, true)
Return:
lexer.starts_line
(patt)Creates and returns a pattern that matches pattern patt only at the beginning of a line.
Parameters:
patt
: The LPeg pattern to match on the beginning of a line.Usage:
local preproc = token(lexer.PREPROCESSOR, lexer.starts_line('#') *
lexer.nonnewline^0)
Return:
lexer.to_eol
(prefix, escape)Creates and returns a pattern that matches from string or pattern prefix until the end of the line. escape indicates whether the end of the line can be escaped with a ‘\’ character.
Parameters:
prefix
: String or pattern prefix to start matching at.escape
: Optional flag indicating whether or not newlines can be escaped
by a ‘\’ character. The default value is false
.Usage:
local line_comment = lexer.to_eol('//')
local line_comment = lexer.to_eol(P('#') + ';')
Return:
lexer.token
(name, patt)Creates and returns a token pattern with token name name and pattern
patt.
If name is not a predefined token name, its style must be defined via
lexer.add_style()
.
Parameters:
name
: The name of token. If this name is not a predefined token name,
then a style needs to be assiciated with it via lexer.add_style()
.patt
: The LPeg pattern associated with the token.Usage:
local ws = token(lexer.WHITESPACE, lexer.space^1)
local annotation = token('annotation', '@' * lexer.word)
Return:
lexer.word_match
(words, case_insensitive, word_chars)Creates and returns a pattern that matches any single word in string words.
case_insensitive 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 words is a multi-line string, it may contain Lua line comments (--
)
that will ultimately be ignored.
Parameters:
words
: A string list of words separated by spaces.case_insensitive
: Optional boolean flag indicating whether or not the
word match is case-insensitive. The default value is false
.word_chars
: Unused legacy parameter.Usage:
local keyword = token(lexer.KEYWORD, word_match[[foo bar baz]])
local keyword = token(lexer.KEYWORD, word_match([[foo-bar foo-baz
bar-foo bar-baz baz-foo baz-bar]], true))
Return:
lexer
module API tableslexer.colors
Map of color name strings to color values in 0xBBGGRR
or "#RRGGBB"
format.
Note: for applications running within a terminal emulator, only 16 color
values are recognized, regardless of how many colors a user’s terminal
actually supports. (A terminal emulator’s settings determines how to actually
display these recognized color values, which may end up being mapped to a
completely different color set.) In order to use the light variant of a
color, some terminals require a style’s bold
attribute must be set along
with that normal color. Recognized color values are black (0x000000), red
(0x000080), green (0x008000), yellow (0x008080), blue (0x800000), magenta
(0x800080), cyan (0x808000), white (0xC0C0C0), light black (0x404040), light
red (0x0000FF), light green (0x00FF00), light yellow (0x00FFFF), light blue
(0xFF0000), light magenta (0xFF00FF), light cyan (0xFFFF00), and light white
(0xFFFFFF).
lexer.styles
Map of style names to style definition tables.
Style names consist of the following default names as well as the token names defined by lexers.
default
: The default style all others are based on.line_number
: The line number margin style.control_char
: The style of control character blocks.indent_guide
: The style of indentation guides.call_tip
: The style of call tip text. Only the font
, size
, fore
,
and back
style definition fields are supported.fold_display_text
: The style of text displayed next to folded lines.class
, comment
, constant
, embedded
, error
, function
,
identifier
, keyword
, label
, number
, operator
, preprocessor
,
regex
, string
, type
, variable
, whitespace
: Some token names used
by lexers. Some lexers may define more token names, so this list is not
exhaustive.Style definition tables may contain the following fields:
font
: String font name.size
: Integer font size.bold
: Whether or not the font face is bold. The default value is false
.weight
: Integer weight or boldness of a font, between 1 and 999.italics
: Whether or not the font face is italic. The default value is
false
.underlined
: Whether or not the font face is underlined. The default value
is false
.fore
: Font face foreground color in 0xBBGGRR
or "#RRGGBB"
format.back
: Font face background color in 0xBBGGRR
or "#RRGGBB"
format.eolfilled
: Whether or not the background color extends to the end of the
line. The default value is false
.case
: Font case, 'u'
for upper, 'l'
for lower, 'm'
for normal,
mixed case, and 'c'
for camel case. The default value is 'm'
.visible
: Whether or not the text is visible. The default value is true
.changeable
: Whether the text is changeable instead of read-only. The
default value is true
.Scintilla has Lua lexers for all of the languages below. Languages
denoted by a *
have native
folders. For languages without
native folding support, folding based on indentation can be used if
fold.by.indentation
is enabled.
*
*
*
*
(NASM)*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*