Extending Kate with Python

So there I am, a confirmed Kate user, and now I need to find my way around a codebase of over 100,000 files using GNU ID utils. The rather crude answer for Kate 3 was to write a wrapper around the lid(1) utility and the DCOP scripting interface of Kate, all driven from the built-in Konsole. The result was clunky but somewhat usable. But Kate 3? In 2010? Because the version of KDE on our primary development environment is the venerable KDE 3.3!

Eventually though, I decide the time had come for something a little nicer, and the answer seemed to lie in Kate 4 and scripting, except that the Javascript API didn’t seem to offer a way to get to the ID database. That had me stumped for a while until I came across Pâté, which allowed Kate 4 to be extended in Python. Sadly, it was unmaintained and there things stalled until, inexorably, I got to the point where the itch needed scratching.

That most basic driver of Open Source usually comes with strings attached, like the need to find a way to work in a new codebase, and with a new team of hackers. Plus, in the this case, the minor issue of being pretty much a Python newbie. Luckily it turns out that Kate has one of the most responsive teams I’ve encountered, the Pâté code seemed reasonably tractable, and the Python C API solidly documented. What could possibly go wrong? :-) Not that much, because we now have:

  • A Kate plugin based on Pâté
  • A Python debugger console Pâté plugin
  • And oh yes, an ID file integration Pâté plugin

The Kate plugin has a configuration page that allows individual Python plugins to be enabled or disabled, and if need be, system installed plugins to be overridden. Like the original Pâté, Python plugins can hook into Kate’s menus and shortcuts. Unlike the original, this version:

  • Allows Python plugins to supply Kate configuration pages just like native Kate plugins
  • Uses Python pickling to save configuration data, so arbitrary Python objects can be part of a plugin’s configuration
  • Provides for reloading Python plugins, which is really handy when writing new plugins
  • Supported threaded Python
  • Provides direct access to the documentation for Python plugins (though if anybody can figure out how to be information for variables, as well as classes and function, that would be wonderful!)
  • The sample Console and ID plugins try to show a selection of techniques

But help is always welcome to do better (How *should* i18n be done? What might Python 3 involve? What about some decent developer docs?). Any takers or clues much appreciated!

GSoC 2012: Vi Input Mode

Like last summer I am mentoring a student working on Kate’s Vi mode this summer. This year’s student is Vegard Øye from Oslo, Norway. I’ll let him introduce himself:

My name is Vegard Øye. I am a computer science student at the University of Oslo, Norway. I also have a bachelor’s degree in electrical engineering from Sør-Trøndelag University College in Trondheim, where I programmed for integrated circuits. It was a lot of fun, so I decided to embark on a grade with an even larger emphasis on programming.

My goal is to make modal editing more widespread outside of Vim. There is a Zen-like benefit to using a tool that does just what you tell it to – slicing and dicing text with surgical precision. My focus is not on adding new features to Kate (although I have implemented a few), but on sharpening existing functionality. In particular, I want to improve the integration between Kate’s vi mode and its extension system, as well as sort out various bugs pertaining to the vi mode.

Vegard has already done some really great work, and his changes should be trickling in to Kate’s git repository the next weeks. You can follow his work at http://quickgit.kde.org/index.php?p=clones%2Fkate%2Fvegardoye%2Fvegard_gsoc_2012.git.

Why KDE, and Kate

I’ve been using and contributing to KDE on-and-off for a while, but our friends over in Gnome land were already busy by the time I got into the game. So why did I conceptually commit to KDE, and thence Kate? Consistency.

I grew up on VAX/VMS where it was possible – and even easy – to mix Ada code with C and Pascal, mix in a CLI that used the standard parser, generate error messages that looked and *were* like every other message in the system. Everything felt integrated.

And the editors? Ah yes, the editors. VAX EDT was where I started, and I *loved* the fact that I used the same editor whether I was writing a VAXmail, posting a VAXnote, or editing a file. So it was a bit of a dilemma when I encountered VAX Emacs, with all its seductive extensibility. I ended up using Emacs for serious editing, and EDT for everything else…that was hateful. Eventually, TPU and its precocious offspring LSE restored the status ante, and my sanity.

Scroll forward a few years, past Windows NT 3.5 and Visual Studio where I got hooked on GUIs, and we get to Qt and KDE libs. Even though there were several KDE text editors in those early days, it was a reasonable bet we’d rationalise, and I’m delighted to say we did (even when Kmail’s default isn’t KWrite – at least the look’n'feel was the same). I even went round making every Find and Replace dialog throughout KDE the same.

So we get to Kate. Right out of the box, even in its Kate 3 incarnation, I loved Kate. Standalone was good, in KDevelop it was even better. I didn’t miss the relative lack of extensibility because well, it did pretty much everything I wanted. And then I changed job…