A Haskell syntax highlighting library with tokenizers derived from KDE XML syntax highlighting descriptions.
A command-line highlighter program,
skylighting, is also provided.
This project is divided up into two packages:
skylighting-core: this provides KDE XML parsing, data types, and output formatters. This includes the core functionality of the skylighting project licensed under the BSD3 license, along with the KDE XML files, some of which are licensed under the LGPL or GPL. This package does not provide any built-in parsers corresponding to the XML descriptions, however. For that, use
skylighting: this exposes the
skylighting-coreAPI but also provides bundled Haskell parser modules derived from the XML descriptions in the
corepackage. This package is entirely licensed under the GPL.
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
directly into styles.
Skylighting is also faster than highlighting-kate, by a factor of 3 in some cases.
To install the latest release from Hackage, do
stack install skylighting
cabal install skylighting
If you want the command-line tool, set the
--flag "skylighting:executable" in stack or
-fexecutable in cabal.
The release tarball for the
skylighting package includes generated
files not present in this repository. Building from this repository is
a two-step process. In the first step we build the
package, which provides 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
# First, build skylighting-extract cabal build -fexecutable skylighting-core # This will print the path of the built executable. # Replace $EXE with this path in the following steps # Now, generate the syntax files cd ../skylighting $EXE ../skylighting-core/xml cabal install -fexecutable
stack build --flag skylighting-core:executable skylighting-core cd skylighting stack exec skylighting-extract -- ../skylighting-core/xml cd .. stack install --flag skylighting:executable
A command-line executable,
skylighting, is installed if
executable cabal flag is set in building.
Adding new syntaxes
To compile with additional syntaxes, simply add the syntax definition
(XML) file to the
xml directory of the
skylighting-core package 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. If you
prefer this approach, you can use the
directly which provides the XML files without the generated code
produced by the bootstrap process described above.
If the syntax definition you are adding is not already in the KDE repository, please submit it upstream so it can be included there. You can do that here, providing the file (or changes) and a test: https://invent.kde.org/frameworks/syntax-highlighting/-/merge_requests. Here is a sample merge request: https://invent.kde.org/frameworks/syntax-highlighting/-/merge_requests/20/diffs. If creating a proper merge request is too much work, at least submit an issue to https://invent.kde.org/frameworks/syntax-highlighting/-/issues alerting the KDE developers of the availability of a new or changed syntax definition; they can then decide whether to integrate it.
We normally pull changes in syntax definitions from upstream before each release.
skylighting package is licensed under the GPL because some of the
XML syntax descriptions from which its tokenizers are generated are
GPL-licensed. However, the
skylighting-core package, which provides
the core types and functions of this project is licensed under the BSD3
license and bundles the GPL-licensed XML files separately.
The KDE project now recommends that new syntax highlighting files be MIT licensed.
Kate syntax highlighting documentation: https://docs.kde.org/stable5/en/kate/katepart/highlight.html
Kate highlighting definitions: KDE repository