skylighting
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
.
skylighting
: this exposes the skylighting-core
API but also
provides bundled Haskell parser modules derived from the XML
descriptions in the core
package. This package is entirely licensed
under the GPL.
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 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 skylighting-core
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 skylighting
package.
Using cabal:
# 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/*.xml
cabal install -fexecutable
Using stack:
stack build --flag skylighting-core:executable skylighting-core
cd skylighting
stack exec skylighting-extract -- ../skylighting-core/xml/*.xml
cd ..
stack install --flag skylighting:executable
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 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 skylighting-core
package
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.
License
The 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.
References
Kate syntax highlighting documentation:
https://docs.kde.org/stable5/en/kate/katepart/highlight.html
Kate highlighting definitions: KDE repository