Kate's highlighting capabilities are amazing. If you want you can highlight really complex syntax, without having to hardcode rules in C++. As an example, we'll take a look at how Lua comments can be realized:
- --[=[ starts a multiline comment (the '=' chars are optional)
- ]=] ends the multiline comment
- the number of '=' chars in ]=] must match the number of --[=[
That means: When the highlighting processor matches the end of a multiline comment, it has to know how many '=' chars started the comment. Thanks to the concept of
dynamic rules and contexts Kate is able to do that. The highlighting file looks like this. First comes the header
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE language SYSTEM "language.dtd" >
<language name="Test" version="1.0" kateversion="2.4" section="Markup" extensions="" mimetype="">
<highlighting>
Then the body with the contexts. We start in the first context called
"Normal Text". When the regular expression
--[(=*)[ matches it switches to the context Comment.
<contexts>
<context attribute="Normal Text" lineEndContext="#stay" name="Normal">
<RegExpr attribute="Comment" context="Comment" String="--\[(=*)\[" dynamic="true"/>
</context>
The part
(=*) is now available as %1 in the rule below:
<context name="Comment" attribute="Comment" lineEndContext="#stay" dynamic="true" >
<RegExpr attribute="Comment" context="#pop" String="\]%1\]" dynamic="true" />
</context>
</contexts>
The last part is the footer:
<itemDatas>
<itemData name="Normal Text" defStyleNum="dsNormal" />
<itemData name="Comment" defStyleNum="dsComment" />
</itemDatas>
</highlighting>
</language>
If you want to know more about Kate's highlighting,
have a look at the documentation :) There are also
lots of bug reports, so if you want to contribute you can fix them!
PS: As I don't know much about Lua, comments might work differently. That does not really matter, as the example still shows what you can do :)
The code is not in svn yet (here is the code for now). I still had issues with correct resizing and believe there was also a bug in the plasma lib when I developed it which seems to be fixed now. I didn't have time for more testing, but finally this has to go in for KDE 4.2 :)
