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Published: Jan 12, 2022 License: MIT Imports: 15 Imported by: 760


Chroma — A general purpose syntax highlighter in pure Go

Golang Documentation CI Slack chat

NOTE: As Chroma has just been released, its API is still in flux. That said, the high-level interface should not change significantly.

Chroma takes source code and other structured text and converts it into syntax highlighted HTML, ANSI-coloured text, etc.

Chroma is based heavily on Pygments, and includes translators for Pygments lexers and styles.

Table of Contents

  1. Table of Contents
  2. Supported languages
  3. Try it
  4. Using the library
    1. Quick start
    2. Identifying the language
    3. Formatting the output
    4. The HTML formatter
  5. More detail
    1. Lexers
    2. Formatters
    3. Styles
  6. Command-line interface
  7. What's missing compared to Pygments?

Supported languages

Prefix Language
A ABAP, ABNF, ActionScript, ActionScript 3, Ada, Angular2, ANTLR, ApacheConf, APL, AppleScript, Arduino, Awk
B Ballerina, Base Makefile, Bash, Batchfile, BibTeX, Bicep, BlitzBasic, BNF, Brainfuck
C C, C#, C++, Caddyfile, Caddyfile Directives, Cap'n Proto, Cassandra CQL, Ceylon, CFEngine3, cfstatement, ChaiScript, Cheetah, Clojure, CMake, COBOL, CoffeeScript, Common Lisp, Coq, Crystal, CSS, Cython
D D, Dart, Diff, Django/Jinja, Docker, DTD, Dylan
E EBNF, Elixir, Elm, EmacsLisp, Erlang
F Factor, Fish, Forth, Fortran, FSharp
G GAS, GDScript, Genshi, Genshi HTML, Genshi Text, Gherkin, GLSL, Gnuplot, Go, Go HTML Template, Go Text Template, GraphQL, Groff, Groovy
H Handlebars, Haskell, Haxe, HCL, Hexdump, HLB, HTML, HTTP, Hy
I Idris, Igor, INI, Io
J J, Java, JavaScript, JSON, Julia, Jungle
K Kotlin
L Lighttpd configuration file, LLVM, Lua
M Mako, markdown, Mason, Mathematica, Matlab, MiniZinc, MLIR, Modula-2, MonkeyC, MorrowindScript, Myghty, MySQL
N NASM, Newspeak, Nginx configuration file, Nim, Nix
O Objective-C, OCaml, Octave, OnesEnterprise, OpenEdge ABL, OpenSCAD, Org Mode
P PacmanConf, Perl, PHP, PHTML, Pig, PkgConfig, PL/pgSQL, plaintext, Pony, PostgreSQL SQL dialect, PostScript, POVRay, PowerShell, Prolog, PromQL, Protocol Buffer, Puppet, Python 2, Python
Q QBasic
R R, Racket, Ragel, Raku, react, ReasonML, reg, reStructuredText, Rexx, Ruby, Rust
S SAS, Sass, Scala, Scheme, Scilab, SCSS, Smalltalk, Smarty, Snobol, Solidity, SPARQL, SQL, SquidConf, Standard ML, Stylus, Svelte, Swift, SYSTEMD, systemverilog
T TableGen, TASM, Tcl, Tcsh, Termcap, Terminfo, Terraform, TeX, Thrift, TOML, TradingView, Transact-SQL, Turing, Turtle, Twig, TypeScript, TypoScript, TypoScriptCssData, TypoScriptHtmlData
V, verilog, VHDL, VimL, vue
X XML, Xorg
Z Zig

I will attempt to keep this section up to date, but an authoritative list can be displayed with chroma --list.

Try it

Try out various languages and styles on the Chroma Playground.

Using the library

Chroma, like Pygments, has the concepts of lexers, formatters and styles.

Lexers convert source text into a stream of tokens, styles specify how token types are mapped to colours, and formatters convert tokens and styles into formatted output.

A package exists for each of these, containing a global Registry variable with all of the registered implementations. There are also helper functions for using the registry in each package, such as looking up lexers by name or matching filenames, etc.

In all cases, if a lexer, formatter or style can not be determined, nil will be returned. In this situation you may want to default to the Fallback value in each respective package, which provides sane defaults.

Quick start

A convenience function exists that can be used to simply format some source text, without any effort:

err := quick.Highlight(os.Stdout, someSourceCode, "go", "html", "monokai")

Identifying the language

To highlight code, you'll first have to identify what language the code is written in. There are three primary ways to do that:

  1. Detect the language from its filename.

    lexer := lexers.Match("foo.go")
  2. Explicitly specify the language by its Chroma syntax ID (a full list is available from lexers.Names()).

    lexer := lexers.Get("go")
  3. Detect the language from its content.

    lexer := lexers.Analyse("package main\n\nfunc main()\n{\n}\n")

In all cases, nil will be returned if the language can not be identified.

if lexer == nil {
  lexer = lexers.Fallback

At this point, it should be noted that some lexers can be extremely chatty. To mitigate this, you can use the coalescing lexer to coalesce runs of identical token types into a single token:

lexer = chroma.Coalesce(lexer)

Formatting the output

Once a language is identified you will need to pick a formatter and a style (theme).

style := styles.Get("swapoff")
if style == nil {
  style = styles.Fallback
formatter := formatters.Get("html")
if formatter == nil {
  formatter = formatters.Fallback

Then obtain an iterator over the tokens:

contents, err := ioutil.ReadAll(r)
iterator, err := lexer.Tokenise(nil, string(contents))

And finally, format the tokens from the iterator:

err := formatter.Format(w, style, iterator)

The HTML formatter

By default the html registered formatter generates standalone HTML with embedded CSS. More flexibility is available through the formatters/html package.

Firstly, the output generated by the formatter can be customised with the following constructor options:

  • Standalone() - generate standalone HTML with embedded CSS.
  • WithClasses() - use classes rather than inlined style attributes.
  • ClassPrefix(prefix) - prefix each generated CSS class.
  • TabWidth(width) - Set the rendered tab width, in characters.
  • WithLineNumbers() - Render line numbers (style with LineNumbers).
  • LinkableLineNumbers() - Make the line numbers linkable and be a link to themselves.
  • HighlightLines(ranges) - Highlight lines in these ranges (style with LineHighlight).
  • LineNumbersInTable() - Use a table for formatting line numbers and code, rather than spans.

If WithClasses() is used, the corresponding CSS can be obtained from the formatter with:

formatter := html.New(html.WithClasses())
err := formatter.WriteCSS(w, style)

More detail


See the Pygments documentation for details on implementing lexers. Most concepts apply directly to Chroma, but see existing lexer implementations for real examples.

In many cases lexers can be automatically converted directly from Pygments by using the included Python 3 script I use something like the following:

python3 _tools/ \
  pygments.lexers.jvm.KotlinLexer \
  > lexers/k/kotlin.go \
  && gofmt -s -w lexers/k/kotlin.go

See notes in pygments-lexers.txt for a list of lexers, and notes on some of the issues importing them.


Chroma supports HTML output, as well as terminal output in 8 colour, 256 colour, and true-colour.

A noop formatter is included that outputs the token text only, and a tokens formatter outputs raw tokens. The latter is useful for debugging lexers.


Chroma styles use the same syntax as Pygments.

All Pygments styles have been converted to Chroma using the _tools/ script.

When you work with one of Chroma's styles, know that the chroma.Background token type provides the default style for tokens. It does so by defining a foreground color and background color.

For example, this gives each token name not defined in the style a default color of #f8f8f8 and uses #000000 for the highlighted code block's background:

chroma.Background: "#f8f8f2 bg:#000000",

Also, token types in a style file are hierarchical. For instance, when CommentSpecial is not defined, Chroma uses the token style from Comment. So when several comment tokens use the same color, you'll only need to define Comment and override the one that has a different color.

For a quick overview of the available styles and how they look, check out the Chroma Style Gallery.

Command-line interface

A command-line interface to Chroma is included.

Binaries are available to install from the releases page.

The CLI can be used as a preprocessor to colorise output of less(1), see documentation for the LESSOPEN environment variable.

The --fail flag can be used to suppress output and return with exit status 1 to facilitate falling back to some other preprocessor in case chroma does not resolve a specific lexer to use for the given file. For example:

export LESSOPEN='| p() { chroma --fail "$1" || cat "$1"; }; p "%s"'

Replace cat with your favourite fallback preprocessor.

When invoked as .lessfilter, the --fail flag is automatically turned on under the hood for easy integration with lesspipe shipping with Debian and derivatives; for that setup the chroma executable can be just symlinked to ~/.lessfilter.

What's missing compared to Pygments?

  • Quite a few lexers, for various reasons (pull-requests welcome):
    • Pygments lexers for complex languages often include custom code to handle certain aspects, such as Raku's ability to nest code inside regular expressions. These require time and effort to convert.
    • I mostly only converted languages I had heard of, to reduce the porting cost.
  • Some more esoteric features of Pygments are omitted for simplicity.
  • Though the Chroma API supports content detection, very few languages support them. I have plans to implement a statistical analyser at some point, but not enough time.



Package chroma takes source code and other structured text and converts it into syntax highlighted HTML, ANSI- coloured text, etc.

Chroma is based heavily on Pygments, and includes translators for Pygments lexers and styles.

For more information, go here:



View Source
const (
	Whitespace = TextWhitespace

	Date = LiteralDate

	String          = LiteralString
	StringAffix     = LiteralStringAffix
	StringBacktick  = LiteralStringBacktick
	StringChar      = LiteralStringChar
	StringDelimiter = LiteralStringDelimiter
	StringDoc       = LiteralStringDoc
	StringDouble    = LiteralStringDouble
	StringEscape    = LiteralStringEscape
	StringHeredoc   = LiteralStringHeredoc
	StringInterpol  = LiteralStringInterpol
	StringOther     = LiteralStringOther
	StringRegex     = LiteralStringRegex
	StringSingle    = LiteralStringSingle
	StringSymbol    = LiteralStringSymbol

	Number            = LiteralNumber
	NumberBin         = LiteralNumberBin
	NumberFloat       = LiteralNumberFloat
	NumberHex         = LiteralNumberHex
	NumberInteger     = LiteralNumberInteger
	NumberIntegerLong = LiteralNumberIntegerLong
	NumberOct         = LiteralNumberOct



View Source
var ANSI2RGB = map[string]string{
	"#ansiblack":     "000000",
	"#ansidarkred":   "7f0000",
	"#ansidarkgreen": "007f00",
	"#ansibrown":     "7f7fe0",
	"#ansidarkblue":  "00007f",
	"#ansipurple":    "7f007f",
	"#ansiteal":      "007f7f",
	"#ansilightgray": "e5e5e5",

	"#ansidarkgray":  "555555",
	"#ansired":       "ff0000",
	"#ansigreen":     "00ff00",
	"#ansiyellow":    "ffff00",
	"#ansiblue":      "0000ff",
	"#ansifuchsia":   "ff00ff",
	"#ansiturquoise": "00ffff",
	"#ansiwhite":     "ffffff",

	"#black":     "000000",
	"#darkred":   "7f0000",
	"#darkgreen": "007f00",
	"#brown":     "7f7fe0",
	"#darkblue":  "00007f",
	"#purple":    "7f007f",
	"#teal":      "007f7f",
	"#lightgray": "e5e5e5",

	"#darkgray":  "555555",
	"#red":       "ff0000",
	"#green":     "00ff00",
	"#yellow":    "ffff00",
	"#blue":      "0000ff",
	"#fuchsia":   "ff00ff",
	"#turquoise": "00ffff",
	"#white":     "ffffff",

ANSI2RGB maps ANSI colour names, as supported by Chroma, to hex RGB values.

View Source
var (
	StandardTypes = map[TokenType]string{
		Background:       "bg",
		PreWrapper:       "chroma",
		Line:             "line",
		LineNumbers:      "ln",
		LineNumbersTable: "lnt",
		LineHighlight:    "hl",
		LineTable:        "lntable",
		LineTableTD:      "lntd",
		CodeLine:         "cl",
		Text:             "",
		Whitespace:       "w",
		Error:            "err",
		Other:            "x",

		Keyword:            "k",
		KeywordConstant:    "kc",
		KeywordDeclaration: "kd",
		KeywordNamespace:   "kn",
		KeywordPseudo:      "kp",
		KeywordReserved:    "kr",
		KeywordType:        "kt",

		Name:                 "n",
		NameAttribute:        "na",
		NameBuiltin:          "nb",
		NameBuiltinPseudo:    "bp",
		NameClass:            "nc",
		NameConstant:         "no",
		NameDecorator:        "nd",
		NameEntity:           "ni",
		NameException:        "ne",
		NameFunction:         "nf",
		NameFunctionMagic:    "fm",
		NameProperty:         "py",
		NameLabel:            "nl",
		NameNamespace:        "nn",
		NameOther:            "nx",
		NameTag:              "nt",
		NameVariable:         "nv",
		NameVariableClass:    "vc",
		NameVariableGlobal:   "vg",
		NameVariableInstance: "vi",
		NameVariableMagic:    "vm",

		Literal:     "l",
		LiteralDate: "ld",

		String:          "s",
		StringAffix:     "sa",
		StringBacktick:  "sb",
		StringChar:      "sc",
		StringDelimiter: "dl",
		StringDoc:       "sd",
		StringDouble:    "s2",
		StringEscape:    "se",
		StringHeredoc:   "sh",
		StringInterpol:  "si",
		StringOther:     "sx",
		StringRegex:     "sr",
		StringSingle:    "s1",
		StringSymbol:    "ss",

		Number:            "m",
		NumberBin:         "mb",
		NumberFloat:       "mf",
		NumberHex:         "mh",
		NumberInteger:     "mi",
		NumberIntegerLong: "il",
		NumberOct:         "mo",

		Operator:     "o",
		OperatorWord: "ow",

		Punctuation: "p",

		Comment:            "c",
		CommentHashbang:    "ch",
		CommentMultiline:   "cm",
		CommentPreproc:     "cp",
		CommentPreprocFile: "cpf",
		CommentSingle:      "c1",
		CommentSpecial:     "cs",

		Generic:           "g",
		GenericDeleted:    "gd",
		GenericEmph:       "ge",
		GenericError:      "gr",
		GenericHeading:    "gh",
		GenericInserted:   "gi",
		GenericOutput:     "go",
		GenericPrompt:     "gp",
		GenericStrong:     "gs",
		GenericSubheading: "gu",
		GenericTraceback:  "gt",
		GenericUnderline:  "gl",


func SplitTokensIntoLines added in v0.6.1

func SplitTokensIntoLines(tokens []Token) (out [][]Token)

SplitTokensIntoLines splits tokens containing newlines in two.

func Stringify added in v0.5.0

func Stringify(tokens ...Token) string

Stringify returns the raw string for a set of tokens.

func Words

func Words(prefix, suffix string, words ...string) string

Words creates a regex that matches any of the given literal words.


type Analyser

type Analyser interface {
	AnalyseText(text string) float32

Analyser determines how appropriate this lexer is for the given text.

type Colour

type Colour int32

Colour represents an RGB colour.

func MustParseColour

func MustParseColour(colour string) Colour

MustParseColour is like ParseColour except it panics if the colour is invalid.

Will panic if colour is in an invalid format.

func NewColour

func NewColour(r, g, b uint8) Colour

NewColour creates a Colour directly from RGB values.

func ParseColour

func ParseColour(colour string) Colour

ParseColour in the forms #rgb, #rrggbb, #ansi<colour>, or #<colour>. Will return an "unset" colour if invalid.

func (Colour) Blue

func (c Colour) Blue() uint8

Blue component of colour.

func (Colour) Brighten

func (c Colour) Brighten(factor float64) Colour

Brighten returns a copy of this colour with its brightness adjusted.

If factor is negative, the colour is darkened.

Uses approach described here (

func (Colour) BrightenOrDarken added in v0.6.3

func (c Colour) BrightenOrDarken(factor float64) Colour

BrightenOrDarken brightens a colour if it is < 0.5 brighteness or darkens if > 0.5 brightness.

func (Colour) Brightness

func (c Colour) Brightness() float64

Brightness of the colour (roughly) in the range 0.0 to 1.0

func (Colour) Distance

func (c Colour) Distance(e2 Colour) float64

Distance between this colour and another.

This uses the approach described here ( This is not as accurate as LAB, et. al. but is *vastly* simpler and sufficient for our needs.

func (Colour) GoString

func (c Colour) GoString() string

func (Colour) Green

func (c Colour) Green() uint8

Green component of colour.

func (Colour) IsSet

func (c Colour) IsSet() bool

IsSet returns true if the colour is set.

func (Colour) Red

func (c Colour) Red() uint8

Red component of colour.

func (Colour) String

func (c Colour) String() string

type Colours

type Colours []Colour

Colours is an orderable set of colours.

func (Colours) Len

func (c Colours) Len() int

func (Colours) Less

func (c Colours) Less(i, j int) bool

func (Colours) Swap

func (c Colours) Swap(i, j int)

type CompiledRule

type CompiledRule struct {
	Regexp *regexp2.Regexp
	// contains filtered or unexported fields

A CompiledRule is a Rule with a pre-compiled regex.

Note that regular expressions are lazily compiled on first use of the lexer.

type CompiledRules

type CompiledRules map[string][]*CompiledRule

CompiledRules is a map of rule name to sequence of compiled rules in that rule.

type Config

type Config struct {
	// Name of the lexer.
	Name string

	// Shortcuts for the lexer
	Aliases []string

	// File name globs
	Filenames []string

	// Secondary file name globs
	AliasFilenames []string

	// MIME types
	MimeTypes []string

	// Regex matching is case-insensitive.
	CaseInsensitive bool

	// Regex matches all characters.
	DotAll bool

	// Regex does not match across lines ($ matches EOL).
	// Defaults to multiline.
	NotMultiline bool

	// Make sure that the input ends with a newline. This
	// is required for some lexers that consume input linewise.
	EnsureNL bool

	// Priority of lexer.
	// If this is 0 it will be treated as a default of 1.
	Priority float32

Config for a lexer.

type Emitter

type Emitter interface {
	// Emit tokens for the given regex groups.
	Emit(groups []string, state *LexerState) Iterator

An Emitter takes group matches and returns tokens.

func ByGroupNames added in v0.9.2

func ByGroupNames(emitters map[string]Emitter) Emitter

ByGroupNames emits a token for each named matching group in the rule's regex.

func ByGroups

func ByGroups(emitters ...Emitter) Emitter

ByGroups emits a token for each matching group in the rule's regex.

func Using

func Using(lexer Lexer) Emitter

Using returns an Emitter that uses a given Lexer for parsing and emitting.

func UsingByGroup added in v0.5.0

func UsingByGroup(sublexerGetFunc func(string) Lexer, sublexerNameGroup, codeGroup int, emitters ...Emitter) Emitter

UsingByGroup emits tokens for the matched groups in the regex using a "sublexer". Used when lexing code blocks where the name of a sublexer is contained within the block, for example on a Markdown text block or SQL language block.

The sublexer will be retrieved using sublexerGetFunc (typically internal.Get), using the captured value from the matched sublexerNameGroup.

If sublexerGetFunc returns a non-nil lexer for the captured sublexerNameGroup, then tokens for the matched codeGroup will be emitted using the retrieved lexer. Otherwise, if the sublexer is nil, then tokens will be emitted from the passed emitter.


var Markdown = internal.Register(MustNewLexer(
		Name:      "markdown",
		Aliases:   []string{"md", "mkd"},
		Filenames: []string{"*.md", "*.mkd", "*.markdown"},
		MimeTypes: []string{"text/x-markdown"},
		"root": {
					2, 4,
					String, String, String, Text, String,

See the lexers/m/markdown.go for the complete example.

Note: panic's if the number emitters does not equal the number of matched groups in the regex.

func UsingSelf

func UsingSelf(stateName string) Emitter

UsingSelf is like Using, but uses the current Lexer.

type EmitterFunc

type EmitterFunc func(groups []string, state *LexerState) Iterator

EmitterFunc is a function that is an Emitter.

func (EmitterFunc) Emit

func (e EmitterFunc) Emit(groups []string, state *LexerState) Iterator

Emit tokens for groups.

type Formatter

type Formatter interface {
	// Format returns a formatting function for tokens.
	// If the iterator panics, the Formatter should recover.
	Format(w io.Writer, style *Style, iterator Iterator) error

A Formatter for Chroma lexers.

func RecoveringFormatter

func RecoveringFormatter(formatter Formatter) Formatter

RecoveringFormatter wraps a formatter with panic recovery.

type FormatterFunc

type FormatterFunc func(w io.Writer, style *Style, iterator Iterator) error

A FormatterFunc is a Formatter implemented as a function.

Guards against iterator panics.

func (FormatterFunc) Format

func (f FormatterFunc) Format(w io.Writer, s *Style, it Iterator) (err error)

type Iterator

type Iterator func() Token

An Iterator across tokens.

EOF will be returned at the end of the Token stream.

If an error occurs within an Iterator, it may propagate this in a panic. Formatters should recover.

func Concaterator

func Concaterator(iterators ...Iterator) Iterator

Concaterator concatenates tokens from a series of iterators.

func Literator

func Literator(tokens ...Token) Iterator

Literator converts a sequence of literal Tokens into an Iterator.

func (Iterator) Tokens

func (i Iterator) Tokens() []Token

Tokens consumes all tokens from the iterator and returns them as a slice.

type Lexer

type Lexer interface {
	// Config describing the features of the Lexer.
	Config() *Config
	// Tokenise returns an Iterator over tokens in text.
	Tokenise(options *TokeniseOptions, text string) (Iterator, error)

A Lexer for tokenising source code.

func Coalesce

func Coalesce(lexer Lexer) Lexer

Coalesce is a Lexer interceptor that collapses runs of common types into a single token.

func DelegatingLexer added in v0.5.0

func DelegatingLexer(root Lexer, language Lexer) Lexer

DelegatingLexer combines two lexers to handle the common case of a language embedded inside another, such as PHP inside HTML or PHP inside plain text.

It takes two lexer as arguments: a root lexer and a language lexer. First everything is scanned using the language lexer, which must return "Other" for unrecognised tokens. Then all "Other" tokens are lexed using the root lexer. Finally, these two sets of tokens are merged.

The lexers from the template lexer package use this base lexer.

func RemappingLexer added in v0.2.0

func RemappingLexer(lexer Lexer, mapper func(Token) []Token) Lexer

RemappingLexer remaps a token to a set of, potentially empty, tokens.

func TypeRemappingLexer added in v0.2.0

func TypeRemappingLexer(lexer Lexer, mapping TypeMapping) Lexer

TypeRemappingLexer remaps types of tokens coming from a parent Lexer.

eg. Map "defvaralias" tokens of type NameVariable to NameFunction:

mapping := TypeMapping{
	{NameVariable, NameFunction, []string{"defvaralias"},
lexer = TypeRemappingLexer(lexer, mapping)

type LexerMutator

type LexerMutator interface {
	// Rules are the lexer rules, state is the state key for the rule the mutator is associated with.
	MutateLexer(rules CompiledRules, state string, rule int) error

A LexerMutator is an additional interface that a Mutator can implement to modify the lexer when it is compiled.

type LexerState

type LexerState struct {
	Lexer *RegexLexer
	Text  []rune
	Pos   int
	Rules CompiledRules
	Stack []string
	State string
	Rule  int
	// Group matches.
	Groups []string
	// Named Group matches.
	NamedGroups map[string]string
	// Custum context for mutators.
	MutatorContext map[interface{}]interface{}
	// contains filtered or unexported fields

LexerState contains the state for a single lex.

func (*LexerState) Get

func (l *LexerState) Get(key interface{}) interface{}

Get mutator context.

func (*LexerState) Iterator

func (l *LexerState) Iterator() Token

Iterator returns the next Token from the lexer.

func (*LexerState) Set

func (l *LexerState) Set(key interface{}, value interface{})

Set mutator context.

type Lexers

type Lexers []Lexer

Lexers is a slice of lexers sortable by name.

func (Lexers) Len

func (l Lexers) Len() int

func (Lexers) Less

func (l Lexers) Less(i, j int) bool

func (Lexers) Swap

func (l Lexers) Swap(i, j int)

type Mutator

type Mutator interface {
	// Mutate the lexer state machine as it is processing.
	Mutate(state *LexerState) error

A Mutator modifies the behaviour of the lexer.

func Combined

func Combined(states ...string) Mutator

Combined creates a new anonymous state from the given states, and pushes that state.

type MutatorFunc

type MutatorFunc func(state *LexerState) error

A MutatorFunc is a Mutator that mutates the lexer state machine as it is processing.

func Mutators

func Mutators(modifiers ...Mutator) MutatorFunc

Mutators applies a set of Mutators in order.

func Pop

func Pop(n int) MutatorFunc

Pop state from the stack when rule matches.

func Push

func Push(states ...string) MutatorFunc

Push states onto the stack.

func (MutatorFunc) Mutate

func (m MutatorFunc) Mutate(state *LexerState) error

type PrioritisedLexers added in v0.2.0

type PrioritisedLexers []Lexer

PrioritisedLexers is a slice of lexers sortable by priority.

func (PrioritisedLexers) Len added in v0.2.0

func (l PrioritisedLexers) Len() int

func (PrioritisedLexers) Less added in v0.2.0

func (l PrioritisedLexers) Less(i, j int) bool

func (PrioritisedLexers) Swap added in v0.2.0

func (l PrioritisedLexers) Swap(i, j int)

type RegexLexer

type RegexLexer struct {
	// contains filtered or unexported fields

RegexLexer is the default lexer implementation used in Chroma.

func MustNewLazyLexer added in v0.9.0

func MustNewLazyLexer(config *Config, rulesFunc func() Rules) *RegexLexer

MustNewLazyLexer creates a new Lexer with deferred rules generation or panics.

func MustNewLexer deprecated

func MustNewLexer(config *Config, rules Rules) *RegexLexer

MustNewLexer creates a new Lexer or panics.

Deprecated: Use MustNewLazyLexer instead.

func NewLazyLexer added in v0.9.0

func NewLazyLexer(config *Config, rulesFunc func() Rules) (*RegexLexer, error)

NewLazyLexer creates a new regex-based Lexer with deferred rules generation.

func NewLexer deprecated

func NewLexer(config *Config, rules Rules) (*RegexLexer, error)

NewLexer creates a new regex-based Lexer.

"rules" is a state machine transitition map. Each key is a state. Values are sets of rules that match input, optionally modify lexer state, and output tokens.

Deprecated: Use NewLazyLexer instead.

func (*RegexLexer) AnalyseText

func (r *RegexLexer) AnalyseText(text string) float32

func (*RegexLexer) Config

func (r *RegexLexer) Config() *Config

func (*RegexLexer) SetAnalyser

func (r *RegexLexer) SetAnalyser(analyser func(text string) float32) *RegexLexer

SetAnalyser sets the analyser function used to perform content inspection.

func (*RegexLexer) Tokenise

func (r *RegexLexer) Tokenise(options *TokeniseOptions, text string) (Iterator, error)

func (*RegexLexer) Trace

func (r *RegexLexer) Trace(trace bool) *RegexLexer

Trace enables debug tracing.

type Rule

type Rule struct {
	Pattern string
	Type    Emitter
	Mutator Mutator

A Rule is the fundamental matching unit of the Regex lexer state machine.

func Default

func Default(mutators ...Mutator) Rule

Default returns a Rule that applies a set of Mutators.

func Include

func Include(state string) Rule

Include the given state.

type Rules

type Rules map[string][]Rule

Rules maps from state to a sequence of Rules.

func (Rules) Clone added in v0.3.0

func (r Rules) Clone() Rules

Clone returns a clone of the Rules.

func (Rules) Merge added in v0.8.0

func (r Rules) Merge(rules Rules) Rules

Merge creates a clone of "r" then merges "rules" into the clone.

func (Rules) Rename added in v0.8.0

func (r Rules) Rename(oldRule, newRule string) Rules

Rename clones rules then a rule.

type Style

type Style struct {
	Name string
	// contains filtered or unexported fields

A Style definition.

See for details. Semantics are intended to be identical.

func MustNewStyle

func MustNewStyle(name string, entries StyleEntries) *Style

MustNewStyle creates a new style or panics.

func NewStyle

func NewStyle(name string, entries StyleEntries) (*Style, error)

NewStyle creates a new style definition.

func (*Style) Builder

func (s *Style) Builder() *StyleBuilder

Builder creates a mutable builder from this Style.

The builder can then be safely modified. This is a cheap operation.

func (*Style) Get

func (s *Style) Get(ttype TokenType) StyleEntry

Get a style entry. Will try sub-category or category if an exact match is not found, and finally return the Background.

func (*Style) Has

func (s *Style) Has(ttype TokenType) bool

Has checks if an exact style entry match exists for a token type.

This is distinct from Get() which will merge parent tokens.

func (*Style) Types

func (s *Style) Types() []TokenType

Types that are styled.

type StyleBuilder

type StyleBuilder struct {
	// contains filtered or unexported fields

A StyleBuilder is a mutable structure for building styles.

Once built, a Style is immutable.

func NewStyleBuilder

func NewStyleBuilder(name string) *StyleBuilder

func (*StyleBuilder) Add

func (s *StyleBuilder) Add(ttype TokenType, entry string) *StyleBuilder

Add an entry to the Style map.

See for details.

func (*StyleBuilder) AddAll

func (s *StyleBuilder) AddAll(entries StyleEntries) *StyleBuilder

func (*StyleBuilder) AddEntry

func (s *StyleBuilder) AddEntry(ttype TokenType, entry StyleEntry) *StyleBuilder

func (*StyleBuilder) Build

func (s *StyleBuilder) Build() (*Style, error)

func (*StyleBuilder) Get

func (s *StyleBuilder) Get(ttype TokenType) StyleEntry

type StyleEntries

type StyleEntries map[TokenType]string

StyleEntries mapping TokenType to colour definition.

type StyleEntry

type StyleEntry struct {
	// Hex colours.
	Colour     Colour
	Background Colour
	Border     Colour

	Bold      Trilean
	Italic    Trilean
	Underline Trilean
	NoInherit bool

A StyleEntry in the Style map.

func ParseStyleEntry

func ParseStyleEntry(entry string) (StyleEntry, error)

ParseStyleEntry parses a Pygments style entry.

func (StyleEntry) Inherit

func (s StyleEntry) Inherit(ancestors ...StyleEntry) StyleEntry

Inherit styles from ancestors.

Ancestors should be provided from oldest to newest.

func (StyleEntry) IsZero

func (s StyleEntry) IsZero() bool

func (StyleEntry) String

func (s StyleEntry) String() string

func (StyleEntry) Sub

func (s StyleEntry) Sub(e StyleEntry) StyleEntry

Sub subtracts e from s where elements match.

type Token

type Token struct {
	Type  TokenType `json:"type"`
	Value string    `json:"value"`

Token output to formatter.

var EOF Token

EOF is returned by lexers at the end of input.

func Tokenise

func Tokenise(lexer Lexer, options *TokeniseOptions, text string) ([]Token, error)

Tokenise text using lexer, returning tokens as a slice.

func (*Token) Clone

func (t *Token) Clone() Token

Clone returns a clone of the Token.

func (*Token) GoString

func (t *Token) GoString() string

func (*Token) String

func (t *Token) String() string

type TokenType

type TokenType int

TokenType is the type of token to highlight.

It is also an Emitter, emitting a single token of itself

const (
	// Default background style.
	Background TokenType = -1 - iota
	// PreWrapper style.
	// Line style.
	// Line numbers in output.
	// Line numbers in output when in table.
	// Line higlight style.
	// Line numbers table wrapper style.
	// Line numbers table TD wrapper style.
	// Code line wrapper style.
	// Input that could not be tokenised.
	// Other is used by the Delegate lexer to indicate which tokens should be handled by the delegate.
	// No highlighting.
	// Used as an EOF marker / nil token
	EOFType TokenType = 0

Meta token types.

const (
	Keyword TokenType = 1000 + iota


const (
	Name TokenType = 2000 + iota


const (
	Literal TokenType = 3000 + iota


const (
	LiteralString TokenType = 3100 + iota


const (
	LiteralNumber TokenType = 3200 + iota


const (
	Operator TokenType = 4000 + iota


const (
	Comment TokenType = 6000 + iota


const (
	CommentPreproc TokenType = 6100 + iota

Preprocessor "comments".

const (
	Generic TokenType = 7000 + iota

Generic tokens.

const (
	Text TokenType = 8000 + iota


const (
	Punctuation TokenType = 5000 + iota


func (TokenType) Category

func (t TokenType) Category() TokenType

func (TokenType) Emit

func (t TokenType) Emit(groups []string, _ *LexerState) Iterator

func (TokenType) InCategory

func (t TokenType) InCategory(other TokenType) bool

func (TokenType) InSubCategory

func (t TokenType) InSubCategory(other TokenType) bool

func (TokenType) MarshalJSON added in v0.2.1

func (t TokenType) MarshalJSON() ([]byte, error)

func (TokenType) Parent added in v0.1.1

func (t TokenType) Parent() TokenType

func (TokenType) String

func (i TokenType) String() string

func (TokenType) SubCategory

func (t TokenType) SubCategory() TokenType

func (*TokenType) UnmarshalJSON added in v0.2.1

func (t *TokenType) UnmarshalJSON(data []byte) error

type TokeniseOptions

type TokeniseOptions struct {
	// State to start tokenisation in. Defaults to "root".
	State string
	// Nested tokenisation.
	Nested bool

	// If true, all EOLs are converted into LF
	// by replacing CRLF and CR
	EnsureLF bool

TokeniseOptions contains options for tokenisers.

type Trilean

type Trilean uint8

Trilean value for StyleEntry value inheritance.

const (
	Pass Trilean = iota

Trilean states.

func (Trilean) Prefix

func (t Trilean) Prefix(s string) string

Prefix returns s with "no" as a prefix if Trilean is no.

func (Trilean) String

func (t Trilean) String() string

type TypeMapping added in v0.2.0

type TypeMapping []struct {
	From, To TokenType
	Words    []string

TypeMapping defines type maps for the TypeRemappingLexer.


Path Synopsis
chroma Module
chromad Module
Package svg contains an SVG formatter.
Package svg contains an SVG formatter.
Package lexers contains the registry of all lexers.
Package lexers contains the registry of all lexers.
Package circular exists to break circular dependencies between lexers.
Package circular exists to break circular dependencies between lexers.
Package internal contains common API functions and structures shared between lexer packages.
Package internal contains common API functions and structures shared between lexer packages.
Package quick provides simple, no-configuration source code highlighting.
Package quick provides simple, no-configuration source code highlighting.

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