skylighting

A Haskell syntax highlighting library with tokenizers derived from KDE XML syntax highlighting descriptions.

A command-line highlighter, skylighting, is also provided.

Motivation

This library is the successor to highlighting-kate, which had some problems that were difficult to resolve given its architecture.

In highlighting-kate, the XML syntax descriptions were converted into individual parsec parsers, which were then compiled. This made it difficult to handle IncludeRules properly without circular imports. There was also no way to load a syntax description dynamically.

Skylighting, by contrast, parses the XML syntax descriptions into Haskell data structures, which are then interpreted by a "tokenize" function. IncludeRules can now be handled properly, and users can add new syntax descriptions dynamically. It is also now possible to convert .theme files directly into styles.

Skylighting is also faster than highlighting-kate, by a factor of 3 in some cases.

Installing

To install the latest release from Hackage, do

stack install skylighting

or

cabal install skylighting

If you want the command-line tool, set the executable flag using --flag "skylighting:executable" in stack or -fexecutable in cabal.

The release tarballs include generated files not present in this repository. Building from this repository is a two-step process. In the first step we build a program, skylighting-extract, which reads XML syntax highlighting definitions from the xml directory and writes Haskell source files. In the second we actually build the library.

Using stack:

make bootstrap
make

Using cabal:

cabal install -fbootstrap --disable-optimizations
cabal run skylighting-extract -- xml/*.xml
cabal install -f-bootstrap --disable-optimizations

Command-line tool

A command-line executable, skylighting, is installed if the executable cabal flag is set in building.

For help, skylighting --help.

Adding new syntaxes

To compile with additional syntaxes, simply add the syntax definition (XML) file to the xml directory and repeat the bootstrap build described above.

Note that both the library and the executable can dynamically load syntax definitions, so you may not need to compile them in.

License

Skylighting is licensed under the GPL, because some of the xml syntax descriptions from which its tokenizers are generated are GPL-licensed.

References

Kate syntax highlighting documentation: https://docs.kde.org/stable5/en/applications/katepart/highlight.html

Kate highlighting definitions: https://github.com/KDE/syntax-highlighting/tree/master/data/syntax