= HIGHLIGHT MANUAL
André Simon
v4.15, Dec 2024
:lang: en
:toc: left
:toc-title: Contents
:toclevels: 4
:sectnums:
:sectnumlevels: 2
:sectanchors:
// Misc Settings:
:experimental: true
:icons: font
:linkattrs: true

// =====================================
// Custom Attributes for Reference Links
// =====================================
// Highlight Docs (asciidoc):
:README_DE: pass:q[link:README_DE.adoc[`README_DE`]]
:README_LANGLIST: pass:q[link:README_LANGLIST.adoc[`README_LANGLIST`]]
:README_PLUGINS: pass:q[link:README_PLUGINS.adoc[`README_PLUGINS`]]
:README_REGEX: pass:q[link:README_REGEX.adoc[`README_REGEX`]]
:README_TESTCASES: pass:q[link:README_TESTCASES.adoc[`README_TESTCASES`]]
:README_LSP_CLIENT: pass:q[link:README_LSP_CLIENT.adoc[`README_LSP_CLIENT`]]
// Highlight Docs (unconverted):
:INSTALL: pass:q[link:INSTALL[`INSTALL`]]
// Source files:
:cpp_qt_lua: pass:q[link:plugins/cpp_qt.lua[`cpp_qt.lua`^]]
:lsp_conf: pass:q[link:lsp.conf[`lsp.conf`^]]
:filetypes_conf: pass:q[link:filetypes.conf[`filetypes.conf`^]]
:fileopenfilter_conf: pass:q[link:gui_files/ext/fileopenfilter.conf[`gui_files/ext/fileopenfilter.conf`^]]
:makefile: pass:q[link:makefile[`makefile`^]]
// Folders:
:langDefs: pass:q[link:langDefs/[`langDefs/`^]]
:themes: pass:q[link:themes/[`themes/`^]]
:themes_base16: pass:q[link:themes/base16/[`themes/base16/`^]]
// Extras Folder:
:extras: pass:q[link:extras/[`extras/`]]
:extras_swig: pass:q[link:extras/swig/[`extras/swig/`]]
:README_SWIG: pass:q[link:extras/swig/README_SWIG[`README_SWIG`]]
:extras_pandoc: pass:q[link:extras/pandoc/[`extras/pandoc/`]]
:README_pandoc: pass:q[link:extras/pandoc/README.html[`README.html`]]
:extras_tcl: pass:q[link:extras/tcl/[`extras/tcl/`]]
:README_TCL: pass:q[link:extras/tcl/README_TCL[`README_TCL`]]
// External Links:
:andre-simon_de: pass:[http://www.andre-simon.de[www.andre-simon.de^]]


OSI Certified Open Source Software

Deutsche Anleitung: {README_DE}


== OVERVIEW

Highlight converts sourcecode to HTML, XHTML, RTF, ODT, LaTeX, TeX, SVG,
BBCode, Pango markup and terminal escape sequences with coloured syntax
highlighting. Syntax definitions and colour themes are customizable.


=== INTENDED PURPOSE

Highlight was created to provide a versatile yet user-friendly syntax
highlighter for multiple output formats. Instead of hardcoding syntax and
colouring information, all necessary data is saved in configuration scripts.
These Lua scripts can be edited and enhanced with plug-ins.


=== FEATURE LIST

* highlighting of keywords, types, strings, numbers, escape sequences,
  comments, operators and preprocessor directives
* coloured output in HTML, XHTML 1.1, RTF, TeX, LaTeX, SVG, BBCode, Pango
  Markup and terminal escape sequences
* supports referenced stylesheet files for HTML, LaTeX, TeX or SVG output
* configuration files are Lua scripts
* supports plug-in scripts to tweak language definitions and themes
* syntax elements are defined as regular expressions or plain string lists
* customizable keyword groups
* recognition of nested languages within a file
* reformatting and indentation of C, C++, C# and Java source code
* wrapping of long lines
* configurable output of line numbers


=== SUPPORTED PROGRAMMING AND MARKUP LANGUAGES


Please see {README_LANGLIST} for the current set of supported languages.
To get a list and associated file extensions you may also run:

..............................
highlight --list-scripts=langs
..............................


== USAGE AND OPTIONS

=== QUICK INTRODUCTION

The following examples show how to produce a highlighted C++ file, using
`main.cpp` as input file:


Generate HTML::
+
.................................................
highlight -i main.cpp -o main.cpp.html
highlight < main.cpp > main.cpp.html --syntax cpp
highlight < source.tmp > main.cpp.html --syntax-by-name main.cpp
.................................................
+
You will find the HTML file and `highlight.css` in the working directory.
If you use IO redirection (2nd example), you must define the programming
language with `--syntax` or `--syntax-by-name`.


Generate HTML with embedded CSS definitions and line numbers::
+
.....................................................................
highlight -i main.cpp -o main.cpp.html --include-style --line-numbers
.....................................................................


Generate HTML with inline CSS definitions::
+
...................................................
highlight -i main.cpp -o main.cpp.html --inline-css
...................................................


Generate LaTeX using "`horstmann`" source formatting style and "`neon`" colour theme::
+
................................................................................
highlight -O latex -i main.cpp -o main.cpp.tex --reformat horstmann --style neon
................................................................................
+
The following output formats may be defined with `--out-format`:
+
[horizontal]
`html`      ::: HTML5 (default)
`xhtml`     ::: XHTML 1.1
`tex`       ::: Plain TeX
`latex`     ::: LaTeX
`rtf`       ::: RTF
`odt`       ::: OpenDocument Text (Flat XML)
`svg`       ::: SVG
`bbcode`    ::: BBCode
`pango`     ::: Pango markup
`ansi`      ::: Terminal 16 color escape codes
`xterm256`  ::: Terminal 256 color escape codes
`truecolor` ::: Terminal 16m color escape codes


Customize font settings::
+
..........................................................................
highlight --syntax ada --font-size 12 --font "'Courier New',monospace"
highlight --syntax ada --out-format=latex --font-size tiny --font sffamily
..........................................................................


Define an output directory::
+
.......................................
highlight -d some/target/dir/ *.cpp *.h
.......................................



See `highlight --help` or `man highlight` for more details.


=== CLI OPTIONS

The command line version of highlight offers the following options:

................................................................................
USAGE: highlight [OPTIONS]... [FILES]...

General options:

 -B, --batch-recursive=<wc>     convert all matching files, searches subdirs
                                  (Example: -B '*.cpp')
 -D, --data-dir=<directory>     set path to data directory
     --config-file=<file>       set path to a lang or theme file
 -d, --outdir=<directory>       name of output directory
 -h, --help[=topic]             print this help or a topic description
                                  <topic> = [syntax, theme, plugin, config, test, lsp]
 -i, --input=<file>             name of single input file
 -o, --output=<file>            name of single output file
 -P, --progress                 print progress bar in batch mode
 -q, --quiet                    suppress progress info in batch mode
 -S, --syntax=<type|path>       specify type of source code or syntax file path
     --syntax-by-name=<name>    specify type of source code by given name
                                  will not read a file of this name, useful for stdin
     --syntax-supported         test if the given syntax can be loaded
 -v, --verbose                  print debug info; repeat to show more information
     --force[=syntax]           generate output if input syntax is unknown
     --list-scripts=<type>      list installed scripts
                                  <type> = [langs, themes, plugins]
     --list-cat=<categories>    filter the scripts by the given categories
                                  (example: --list-cat='source;script')
     --max-size=<size>          set maximum input file size
                                  (examples: 512M, 1G; default: 256M)
     --plug-in=<script>         execute Lua plug-in script; repeat option to
                                  execute multiple plug-ins
     --plug-in-param=<value>    set plug-in input parameter
     --print-config             print path configuration
     --print-style              print stylesheet only (see --style-outfile)
     --skip=<list>              ignore listed unknown file types
                                  (Example: --skip='bak;c~;h~')
     --stdout                   output to stdout (batch mode, --print-style)
     --validate-input           test if input is text, remove Unicode BOM
     --service-mode             run in service mode, not stopping until signaled
     --version                  print version and copyright information


Output formatting options:

 -O, --out-format=<format>      output file in given format
                                  <format>=[html, xhtml, latex, tex, odt, rtf,
                                  ansi, xterm256, truecolor, bbcode, pango, svg]
 -c, --style-outfile=<file>     name of style file or print to stdout, if
                                  'stdout' is given as file argument
 -e, --style-infile=<file>      to be included in style-outfile (deprecated)
                                  use a plug-in file instead
 -f, --fragment                 omit document header and footer
 -F, --reformat=<style>         reformats and indents output in given style
                                  <style> = [allman, gnu, google, horstmann,
                                  java, kr, linux, lisp, mozilla, otbs, pico,
                                  vtk, ratliff, stroustrup, webkit, whitesmith]
 -I, --include-style            include style definition in output file
     --indent-guides            draw guides in leading whitespace (implies -t 4)
 -J, --line-length=<num>        line length before wrapping (see -V, -W)
 -j, --line-number-length=<num> line number width incl. left padding (default: 5)
     --line-range=<start-end>   output only lines from number <start> to <end>
     --skip-leading-cols=<num>  output the first <num> columns of each line
                                  unhighlighted (example: hg or svn annotate)
 -k, --font=<font>              set font (specific to output format)
 -K, --font-size=<num?>         set font size (specific to output format)
 -l, --line-numbers             print line numbers in output file
 -m, --line-number-start=<cnt>  start line numbering with cnt (assumes -l)
 -s, --style=<style|path>       set colour style (theme) or theme file path
 -t, --replace-tabs=<num>       replace tabs by <num> spaces
 -T, --doc-title=<title>        document title
 -u, --encoding=<enc>           set output encoding which matches input file
                                  encoding; omit encoding info if set to NONE
 -V, --wrap-simple              wrap lines after 80 (default) characters w/o
                                  indenting function parameters and statements
 -W, --wrap                     wrap lines after 80 (default) characters
     --wrap-no-numbers          omit line numbers of wrapped lines
                                  (assumes -l)
 -z, --zeroes                   pad line numbers with 0's
     --isolate                  output each syntax token separately (verbose output)
     --keep-injections          output plug-in injections in spite of -f
     --kw-case=<case>           change case of case insensitive keywords
                                  <case> =  [upper, lower, capitalize]
     --no-trailing-nl[=mode]    omit trailing newline. If mode is empty-file, omit
                                  only for empty input
     --no-version-info          omit version info comment


(X)HTML output options:

 -a, --anchors                  attach anchor to line numbers
 -y, --anchor-prefix=<str>      set anchor name prefix
 -N, --anchor-filename          use input file name as anchor prefix
 -C, --print-index              print index with hyperlinks to output files
 -n, --ordered-list             print lines as ordered list items
     --class-name=<name>        set CSS class name prefix;
                                  omit class name if set to NONE
     --inline-css               output CSS within each tag (verbose output)
     --enclose-pre              enclose fragmented output with pre tag
                                  (assumes -f)


LaTeX output options:

 -b, --babel                    disable Babel package shorthands
 -r, --replace-quotes           replace double quotes by \dq{}
     --beamer                   adapt output for the Beamer package
     --pretty-symbols           improve appearance of brackets and other symbols


RTF output options:

     --page-color               include page color attributes
 -x, --page-size=<ps>           set page size
                                  <ps> = [a3, a4, a5, b4, b5, b6, letter]
     --char-styles              include character stylesheets


SVG output options:

     --height                   set image height (units allowed)
     --width                    set image width (see --height)


Terminal escape output options (xterm256 or truecolor):

     --canvas[=width]           set background colour padding (default: 80)


Language Server options:

     --ls-profile=<server>      read LSP configuration from lsp.conf
     --ls-delay=<ms>            set server initialization delay
     --ls-exec=<bin>            set server executable name
     --ls-option=<option>       set server CLI option (can be repeated)
     --ls-hover                 execute hover requests (HTML output only)
     --ls-semantic              retrieve semantic token types (requires LSP 3.16)
     --ls-syntax=<lang>         set syntax which is understood by the server
     --ls-syntax-error          retrieve syntax error information
                                  (assumes --ls-hover or --ls-semantic)
     --ls-workspace=<dir>       set workspace directory to init. the server
     --ls-legacy                do not require a server capabilities response
................................................................................

=== GUI OPTIONS

The GUI provides a selection of the CLI's capabilities and features a live
preview of the output file's appearance. Refer to the project website for
accompanying screenshots and screencasts.
Invoke highlight-gui with the `--portable` option to save its settings in the
binary's current directory (instead of using the registry).


=== INPUT AND OUTPUT

If the `--input` and `--output` options are not defined, Highlight will
automatically use stdin and stdout for file processing.
Reading from stdin can also be triggered by the `-` option.

If no input file is defined by `--input` or provided at prompt, highlight cannot
determine the language type through the file extension (excluding some scripting
languages that can be derived from the shebang on the first input line).
In this scenario, you must specify the language for highlight with `--syntax` or
`--syntax-by-name` (this usually should be the file suffix of the source file or
its name, respectively).
Example: If you want to convert a Python file, highlight needs to load the
`py.lang` definition. The correct argument of `--syntax` would be `py`.

................................................................................
highlight test.py
highlight < test.py --syntax py       # --syntax option necessary
cat test.py | highlight --syntax py
................................................................................

If multiple suffixes exist (like `C`, `cc`, `cpp` and `h` for C++ files),
they are mapped to a language definition in {filetypes_conf}.

Highlight enters the batch processing mode if multiple input files are given
or if `--batch-recursive` is set.
In batch mode, highlight will save the generated files using the original
filename, appending the extension of the chosen output type.
If files in the input directories happen to share the same name, the output
files will be prefixed with their source path name.
The `--out-dir` option is recommended in batch mode. Use `--quiet` to improve
performance (recommended for usage in shell scripts).

==== HTML, TeX, LaTeX and SVG output

The HTML, TeX, LaTeX and SVG output formats allow to reference a stylesheet
file which contains the formatting information.

In HTML and SVG output, this file contains CSS definitions and is saved as
`highlight.css`. In LaTeX and TeX, it contains macro definitions, and is saved
as 'highlight.sty'.

Name and path of the stylesheet may be modified with `--style-outfile`.
If the `--outdir` option is given, all generated output, including stylesheets,
are stored in this directory.

Use `--include-style` to embed the style information in the output documents
without referencing a stylesheet.

Referenced stylesheets have the advantage to share all formatting information
in a single file, which affects all referencing documents.

With `--style-infile` you define a file to be included in the final formatting
information of the document. This way you enhance or redefine the default
highlight style definitions without editing generated code.
Note: Using a plug-in script is the preferred way to enhance styling.

==== Terminal output:

ANSI terminal output is limited to the 16 colours of the terminal palette, so
themes are ignored with `--out-format=ansi` unless their elements define an
`AnsiIndex` attribute. Elements without one keep the hard coded default sequence,
and theme font attributes are not applied in this format.
Use `--out-format=xterm256` to enable output in 256 colours. The 256 colour mode
is supported by recent releases of xterm, rxvt and Putty (amongst others).
Recently published terminal emulators also support 16m colors, this mode is
enabled with `--out-format=truecolor`.

.....................................................
highlight --out-format=ansi <inputfile> | less -R
highlight --out-format=xterm256 <inputfile> | less -R
.....................................................

==== Text processing:

If the language definition is specified as `txt`, no highlighting takes place.

.......................................................
highlight -S txt --out-format=latex README > README.tex
.......................................................


==== Service Mode:

Since version 4.6 highlight can be invoked as a long running process to process
files using stdin and stdout. This might result in better performance, e.g.,
when used in a file viewer application.

Service mode (`--service-mode`) is designed to allow several inputs to be
parsed on demand from an external application without restarting highlight
each time. Service mode runs continuously until a kill signal is sent, EOF is
read from STDIN, or the "exit" command is sent instead of a mode line specified
below. Service mode expects each input to be separated by a EOF character on a
line by itself (if EOF was set to '\0' then "\n\0\n"). Before each file
(including the first file) a new mode line must be sent with any mode changes
to occur (even if no changes are desired a new line must be sent).

Mode options are changed with key value pairs like `option=value` separated by
a semicolon (no trailing semicolon for last item needed). Any options not
changed will retain their previous value.

The following options are supported:

[horizontal]
`syntax=file.ext` ::: to change the syntax to the extension from the filename,
or syntax=<syntax_suffix> to set the syntax to use directly (e.g., csharp).

`tag=##` ::: if provided and not empty will be printed by itself on a new line
to stdout after a file has been processed.

`eof=##` ::: A single character (0x00-0xFE) that stdin will contain to separate
one file from the next. Recommend 0x00 if you can send it, otherwise 0x01-0x07
are generally easy for most clients to send, e.g., 0x07 ('\a') for bell. It is
nearly impossible to send several characters above 128 in Windows through most
terminal emulators.

Note the EOF char must occur on its own new line; it cannot be found mid-line.
There is no need for a new line between the previous EOF and the next mode
options line. You also cannot send the EOF char to a new line as it is used as a
delimiter already as described.

Finally any file contents can be sent however the file cannot contain the EOF
char. The requirement for the EOF char to be on a line by itself could be
altered.
Also adds disable echo (`--disable-echo`) for win32 builds to disable console
echo back for STDIN. This can be controlled fairly easily in linux with stty if
desired by the user, but windows does not have something similar. If we want to
expand disable-echo to other platforms that have stty doing

...........................................................
tcgetattr(fileno(stdin), &term);
term.c_lflag &= ~ECHO;
tcsetattr(fileno(stdin), 0, &term);
...........................................................

See extras/highlight-service.py for an interactive Python script.


=== ADVANCED OPTIONS

==== Prevent parsing of binary input files

If highlight might process untrusted input, you can disable parsing of binary
files using `--validate-input`. This flag causes highlight to match the input file
header with a list of magic numbers. If a binary file type is detected, highlight
quits with an error message. This switch also removes an UTF-8 BOM in the output.

==== Test new configuration scripts

The option `--config-file` helps to test new config files. The argument file must be
a lang or theme.

...........................................................
highlight --config-file xxx.lang --config-file yyy.theme -I
...........................................................

==== Debug language definitions

Use `--verbose` to display Lua and syntax data. Apply twice to print more information.

==== Remove an UTF8 BOM:

Use `--validate-input` to get rid of UTF8 byte order marks.

==== Force output to stdout

Use `--stdout` to write output files in batch mode to stdout.

==== Portable GUI (Windows build)

Invoke highlight-gui.exe with the `--portable` switch to save its configuration
in text files instead of the registry.


=== ENVIRONMENT VARIABLES

The command line version recognizes these variables:

* `HIGHLIGHT_DATADIR`: sets the path to highlight's configuration scripts
* `HIGHLIGHT_OPTIONS`: may contain command line options, but no input file paths.

=== SYNTAX TESTING

Since version 2.45, highlight supports special notations within comments to
test its syntax recognition.
See {README_TESTCASES} for details.

=== LSP CLIENT

Since version 4.0, highlight supports LSP to enhance its output.
See {README_LSP_CLIENT} for details.

== CONFIGURATION

=== FILE FORMAT

Configuration files are Lua scripts.

For more details about the Lua syntax, please refer to:

* http://www.lua.org/manual/5.1/manual.html

These constructs are sufficient to edit the scripts:

Variable assignment::
`name = value` +
(variables have no type, only values have)

Strings::
`string1="string literal with escape: \n"` +
`string2=[[raw string without escape sequence]]`
+
If raw string content starts with `[` or ends with `]`, pad the parenthesis
with space to avoid a syntax error. Highlight will strip the string.
+
If the string is a regular expression containing a set with a character class
like [[:space:]], use string delimiters with a "`filler`": +
`[=[ regex string ]=]`

Comments::
`-- line comment` +
`--[[ block comment ]]`

Arrays::
`array = { first=1, second="2", 3, { 4,5 } }`


=== LANGUAGE DEFINITIONS

A language definition describes syntax elements of a programming language which
will be highlighted by different colours and font types.
Save the new file in {langDefs}, using the following name convention:

..........................................
<usual extension of sourcecode files>.lang
..........................................

Examples:

[horizontal]
PHP::  -> `php.lang`
Java:: -> `java.lang`

If multiple suffixes exist, list them in {filetypes_conf}.


==== Syntax elements

................................................................................
Keywords = { { Id, List|Regex, Group?, Priority?, Constraints? } }

  Id:          Integer, keyword group id (can be reused for several groups).
               Default themes support 4 and base16 themes 6 groups.
  List:        List, list of keywords
  Regex:       String, regular expression
  Group:       Integer, capturing group id of regular expression, defines part of
               regex which should be returned as keyword (optional; if not set,
               the match with the highest group number is returned (counts from
               left to right))
  Priority:    Integer, if not zero no more regexes will be evaluated if this
               regex matches
  Constraints: table consisting of:
               Line: Integer, limit match to line number,
               Filename: String, limit match to input file name

Regular expressions are evaluated in their order within Keywords. If a regex
does not appear to match, there might be a conflicting expression listed before.


Comments = { {Block, Nested?, Delimiter={Open, Close?} }

  Block:     Boolean, true if comment is a block comment
  Nested:    Boolean, true if block comments can be nested (optional)
  Delimiter: List, contains open delimiter regex (line comment) or open and close
             delimiter regexes (block comment)


Strings = { Delimiter|DelimiterPairs={Open, Close, Raw?}, Escape?, Interpolation?,
            RawPrefix?, AssertEqualLength? }

  Delimiter:         String, regular expression which describes string delimiters
  DelimiterPairs:    List, includes open and close delimiter expressions if not
                     equal, includes optional Raw flag as boolean which marks
                     delimiter pair to contain a raw string
  Escape:            String, regex of escape sequences (optional)
  Interpolation:     String, regex of interpolation sequences (optional)
  RawPrefix:         String, defines raw string indicator (optional)
  AssertEqualLength: Boolean, set true if delimiters must have the same length


PreProcessor = { Prefix, Continuation? }

  Prefix:        String, regular expression which describes open delimiter
  Continuation:  String, contains line continuation character (optional).


NestedSections = {Lang, Delimiter= {} }

  Lang:      String, name of nested language
  Delimiter: List, contains open and close delimiters of the code section


KeywordFormatHints={ { Id, Bold?, Italic?, Underline? } }
  Id:         Integer, keyword group id whose attributes should be changed
  Bold:       Boolean, font weight property
  Italic:     Boolean, font style property
  Underline:  Boolean, font decoration property

These hints may have no effect if multiple syntax types are highlighted in batch
mode without --include-style.

Description:       String, Defines syntax description

Categories:        Table, List of categories (config, source, script, etc)

Digits:            String, Regular expression which defines digits (optional)

Identifiers:       String, Regular expression which defines identifiers
                   (optional)

Operators:         String, Regular expression which defines operators

EnableIndentation: Boolean, set true if syntax may be reformatted and indented

IgnoreCase:        Boolean, set true if keyword case should be ignored

EncodingHint:      String, default input file encoding

................................................................................


==== Global variables

The following variables are available within a language definition:

[horizontal]
`HL_LANG_DIR`:: path of language definition directory (use with Lua dofile function)
`Identifiers`:: Default regex for identifiers
`Digits`::      Default regex for numbers

The following integer variables represent the internal highlighting states:

* `HL_STANDARD`
* `HL_STRING`
* `HL_NUMBER`
* `HL_LINE_COMMENT`
* `HL_BLOCK_COMMENT`
* `HL_ESC_SEQ`
* `HL_PREPROC`
* `HL_PREPROC_STRING`
* `HL_OPERATOR`
* `HL_INTERPOLATION`
* `HL_LINENUMBER`
* `HL_KEYWORD`
* `HL_STRING_END`
* `HL_LINE_COMMENT_END`
* `HL_BLOCK_COMMENT_END`
* `HL_ESC_SEQ_END`
* `HL_PREPROC_END`
* `HL_OPERATOR_END`
* `HL_INTERPOLATION_END`
* `HL_KEYWORD_END`
* `HL_EMBEDDED_CODE_BEGIN`
* `HL_EMBEDDED_CODE_END`
* `HL_IDENTIFIER_BEGIN`
* `HL_IDENTIFIER_END`
* `HL_UNKNOWN`
* `HL_REJECT`

==== The function `OnStateChange`

This function is a hook which is called if an internal state changes (e.g. from
`HL_STANDARD` to `HL_KEYWORD` if a keyword is found). It can be used to alter
the new state or to manipulate syntax elements like keyword lists.

[[OnStateChange]]
................................................................................
OnStateChange(oldState, newState, token, kwGroupID, lineno, column)

  Hook Event: Highlighting parser state change
  Parameters: oldState:  old state
              newState:  intended new state
              token:     the current token which triggered the new state
              kwGroupID: if newState is HL_KEYWORD, the parameter
                         contains the keyword group ID
              lineno:    line number (since 3.50)
              column:    line column (since 3.50)
  Returns:    Correct state to continue OR HL_REJECT
................................................................................

Return `HL_REJECT` if the recognized token and state should be discarded; the
first character of token will be outputted and highlighted as `oldState`.

See {README_PLUGINS} for more available functions.


.Example

[source,lua]
--------------------------------------------------------------------------------
Description="C and C++"

Categories = {"source"}

Keywords={
  {  Id=1,
   List={"goto", "break", "return", "continue", "asm", "case", "default",
         -- [..]
        }
  },
  -- [..]
}

Strings = {
  Delimiter=[["|']],
  RawPrefix="R",
}

Comments = {
   { Block=true,
     Nested=false,
     Delimiter = { [[\/\*]], [[\*\/]] }  },
   { Block=false,
     Delimiter = { [[//]] } }
}

IgnoreCase=false

PreProcessor = {
  Prefix=[[#]],
  Continuation="\\",
}

Operators=[[\(|\)|\[|\]|\{|\}|\,|\;|\.|\:|\&|\<|\>|\!|\=|\/|\*|\%|\+|\-|\~]]

EnableIndentation=true

-- resolve issue with C++14 number separator syntax
function OnStateChange(oldState, newState, token)

   if token=="'" and oldState==HL_NUMBER and newState==HL_STRING then
      return HL_NUMBER
   end

   return newState
end
--------------------------------------------------------------------------------


=== REGULAR EXPRESSIONS

Please see {README_REGEX} for the supported regex constructs.


=== THEME DEFINITIONS

Colour themes contain the formatting information of the syntax elements which
are described in language definitions.

The files have to be stored as `.theme` in {themes}.
Apply a theme with the `--style` option. Prepend `base16/` to the name in order
to use one of the included Base16 themes (located in {themes_base16}).


==== Format attributes

................................................................................
Attributes = {Colour, Bold?, Italic?, Underline?, AnsiIndex?, Custom? }
................................................................................

[horizontal]
Colour::    String, defines colour in HTML hex notation (`#rrggbb`)
Bold::      Boolean, true if font should be bold (optional)
Italic::    Boolean, true if font should be italic (optional)
Underline:: Boolean, true if font should be underlined (optional)
AnsiIndex:: Number, terminal palette index 0-15, applied with
            `--out-format=ansi` only (optional)
Custom::    Array, contains `Format` and `Style` for custom styles

==== Theme elements

................................................................................
Description:   = String, Defines theme description

Categories     = Table, List of categories (dark, light, etc)

Default        = Attributes (Colour of unspecified text)

Canvas         = Attributes (Background colour)

Number         = Attributes (numbers)

Escape         = Attributes (escape sequences)

String         = Attributes (strings)

Interpolation  = Attributes (interpolation sequences)

PreProcessor   = Attributes (preprocessor directives)

StringPreProc  = Attributes (strings within preprocessor directives)

BlockComment   = Attributes (block comments)

LineComment    = Attributes (line comments)

LineNum        = Attributes (line numbers)

Operator       = Attributes (operators)

Hover          = Attributes (LSP Hover elements)

Error          = Attributes (LSP syntax errors)

ErrorMessage   = Attributes (LSP error descriptions)

Keywords= {
  Attributes1,
  Attributes2,
  Attributes3,
  Attributes4,
  Attributes5,
  Attributes6,
}

AttributesN: Formatting of keyword group N.

SemanticAttributesN: An array consisting of:
                     `Type`: Token Identifier of the LS protocol (V 3.16)
                     `Style`: formatting of the token
................................................................................

.Example
[source,lua]
--------------------------------------------------------------------------------
Description = "vim autumn"

Categories = {"light", "vim"}

Default	= { Colour="#404040" }
Canvas	= { Colour="#fff4e8" }
Number	= { Colour="#00884c" }
Escape	= { Colour="#8040f0" }
String	= { Colour="#00884c" }
BlockComment	= { Colour="#ff5050" }
StringPreProc = String
LineComment   = BlockComment
Operator      = { Colour="#513d2b" }
LineNum      = { Colour="#555555" }
PreProcessor      = {  Colour="#660000" }
Interpolation  = { Colour="#CA6DE1" }

Keywords = {
  { Colour="#80a030" },
  { Colour="#b06c58" },
  { Colour="#30a188" },
  { Colour="#990000" },
  { Colour="#9a85ff" },
  { Colour="#85adff" },
}

-- new LSP based elements:

SemanticTokenTypes = {
  { Type = 'type', Style = Keywords[2] },
  { Type = 'class', Style =  Keywords[1] },
  { Type = 'struct', Style =  Keywords[4] },
  { Type = 'interface', Style = Keywords[1] },
  { Type = 'parameter', Style = Keywords[6] },
  { Type = 'variable', Style = Keywords[5] },
  { Type = 'enumMember', Style = Keywords[5] },
  { Type = 'function', Style = Keywords[4] },
  { Type = 'method', Style = Keywords[4] },
  { Type = 'keyword', Style =  Keywords[1]},
  { Type = 'number', Style = Number },
  { Type = 'regexp', Style = String },
  { Type = 'operator', Style = Operator },
}

--ErrorMessage = {
--  Custom = {
--    { Format = "html", Style = "color: blue; border:solid 1px blue; margin-left: 3em" }
--  }
--}
--------------------------------------------------------------------------------

=== KEYWORD GROUPS

You may define custom keyword groups and corresponding highlighting styles.
This is useful if you want to highlight functions of a third party library,
macros, constants etc.

You define a new group in two steps:

1. Define a new group in your language definition or plug-in:
+
[source,lua]
--------------------------------------------------------------------------------
table.insert(Keywords, {
  {Id=5, List = {"ERROR", "DEBUG", "WARN"} }
})
--------------------------------------------------------------------------------

2. Add a corresponding highlighting style in your colour theme or plug-in:
+
[source,lua]
--------------------------------------------------------------------------------
if #Keywords==4 then
    table.insert(Keywords, {Colour= "#ff0000", Bold=true})
end
--------------------------------------------------------------------------------

It is recommended to define keyword groups in user-defined plugin scripts to
avoid editing of original highlight files.
See the {cpp_qt_lua} sample plug-in script and {README_PLUGINS} for details.


=== PLUG-INS

The `--plug-in` option reads the path of a Lua script which overrides or
enhances the settings of theme and language definition files. Plug-ins make
it possible to apply custom settings without the need to edit installed
configuration files.
You can apply multiple plugins by using the `--plug-in` option more than once.
See {README_PLUGINS} for a detailed description and examples of packaged plugins.



=== FILE MAPPING

The script {filetypes_conf} assigns file extensions and shebang descriptions to
language definitions.
A configuration is mandatory only if multiple file extensions are linked to
one syntax or if a extension is ambiguous. Otherwise the syntax definition whose
name corresponds to the input file extension will be applied.

Format:

................................................................................
FileMapping={
  {  Lang, Filenames|Extensions|Shebang },
}

Lang:       String, name of language definition
Filenames:  list of strings, contains filenames referring to "Lang"
Extensions: list of strings, contains file extensions referring to "Lang"
Shebang:    String, Regular expression which matches the first line of the input
            file

Behaviour upon ambiguous file extensions:
- CLI: the first association listed here will be used
- GUI: a syntax selection prompt will be shown
................................................................................

Edit the file {fileopenfilter_conf} to add new syntax types to
the GUI's file open filter.


=== CONFIG FILE SEARCH

Configuration scripts are searched in the following directories:

1. `~/.highlight/`
2. user defined directory set with `--data-dir`
3. value of the environment variable `HIGHLIGHT_DATADIR`
4. `/usr/share/highlight/`
5. `/etc/highlight/` (default location of `filetypes.conf` and `lsp.conf`)
6. current working directory (fallback)

These subdirectories are expected to contain the corresponding scripts:

* langDefs: `*.lang`
* themes: `*.theme`
* plugins: `*.lua`

A custom `filetypes.conf` may be placed directly in `~/.highlight/`.
This search order enables you to enhance the installed scripts without the need
to copy preinstalled files somewhere else.

Use `--print-config` to determine your settings::
+
........................
highlight --print-config
........................


== EMBEDDING HIGHLIGHT

=== SAMPLE SCRIPTS

See the {extras} subdirectory in the highlight package for some scripts in PHP,
Perl and Python  which invoke highlight and retrieve its output as string.
These scripts may be used as reference to develop plug-ins for other apps.

=== PANDOC

PP macros file and tutorial are located in {extras_pandoc}.
See {README_pandoc} for usage instruction and example files as reference.

=== SWIG

A SWIG interface file is located in {extras_swig}.
See {README_SWIG} for installation instructions and the example scripts in Perl,
PHP and Python as programming reference.

=== TCL

A TCL extension is located in {extras_tcl}.
See {README_TCL} for installation instructions.


== BUILDING AND INSTALLING

=== PRECOMPILED PACKAGES

The file {INSTALL} describes the installation from source and includes links to
precompiled packages.


=== BUILDING DEPENDENCIES

Highlight is known to compile with gcc and clang.

It depends on Boost headers and Lua 5.x/LuaJit developer packages.

The optional GUI depends on Qt5 developer packages.

Please see the {makefile} for further options.


== DEVELOPER CONTACT

Andre Simon

a.simon@mailbox.org

{andre-simon_de}

Git project with repository, bug tracker:

* https://gitlab.com/saalen/highlight/

// EOF //
