Plasma Next: What’s changing?

In the past week, we hit something that really feels like a milestone in Plasma development. Plasma 2 has become somewhat usable, at least if your pain level is high enough. It occurred to me after I realized after a few hours of using it that the workspace shell running on my laptop was not actually the current stable release of Plasma, but the development version. Great thing, I thought, went ahead and fixed a sizing bug in the systemtray widget, then changed the default layout to include Kickoff, Taskmanager and Systemtray in the panel, as these elements are the most important ones to have in the panel — exposure even to just our development team surely won’t hurt. This experience also marks a point where we have to take a step back and look at our general direction. Sure, we could do a “minimal port” and just make everything build and work on top of Qt5.

One of the technologies we’ve been using more and more in the Plasma workspaces is QtQuick, a declarative language that allows you to very easily write stunning UIs, without the need to use C++ for these parts. Our experience is that it makes developing, improving and maintaining applications a lot easier, and generally leads to much nicer user interfaces. QtQuick, being a very young technology in Qt4, has matured since then, and received a major technology update in Qt5. It moved from a traditional painter-based mechanism to a scenegraph model, and much closer onto the graphics hardware. That means that we usually get much better performance out of it, and that it allows a whole bunch of neat tricks on top of that. In Qt 5.2 (which is the Qt release we’re basing our work on), it received another big upgrade. The scenegraph renderer has been replaced, with huge performance gain as the result. (Read Gunnar’s article about it, it’s really impressive!) QtQuick also received a new QML engine, which brings major improvements to its internal data handling, but also to important topics such as maintainability. The new v4 engine uses Qt types internally, so a lot less marshalling is needed between runtime objects, and some architectural barriers have also been removed. Lars has written an excellent article about the new QML engine.

So on a technological level, we have decided to not do this. We want a more modular software stack underneath, so we decided to rework the KDE Development Platform into something that is more useful in its pieces. The result of that (the process isn’t finished yet, but rapture lines are becoming very visible) is KDE Frameworks 5, a modular set of Qt-based libraries with well-defined dependencies which separately are all very useful to 3rd party developers, and combined give you all the functionality to build highly integrated complex applications on top. Plasma next builds on Frameworks 5. In the past 1.5 years, we have spent a lot of time on reworking the build system and removing interdependencies between various “sublibraries” that made up kdelibs. This has progressed really well, we are in fact able to build and use many of our libraries standalone already. We’re currently restructuring the last libraries to accommodate a split, and will then “physically” split the libs into separate repositories. In order to not make the effort to build a KDE application or workspace explode, we have developed tooling that can build sets of modules for you. You get to choose the granularity we work with. In order to make it easier for third parties to find and use our libraries, we have set up Inqlude.org, which has information about these (and other) libraries. This is very much work in progress, but it does already give a good picture of what’s to come.

For the user, we want to keep this whole process as smooth as possible. Porting applications to Frameworks 5 is rather easy, as regarding kdelibs, it mostly involves changes to the build system, some mild Qt5 porting, and only a few API changes. It is nowhere nearly as disruptive as the move from KDE3 to KDE4 (yes, our software was still called KDE${N} back then!).
In Plasma, it’s a little more complicated, as much more changed under the hood (a completely new way to get graphics onto the screen, deprecation of larger parts of our API, more device-independence reflected in our architecture). Our goal for the first release is to not introduce functional regressions however. We want to keep the basic usecases of a Desktop fully working, preferably noticeably improved. In the past years, we have already moved a lot of the individual components (such as the task manager, widgets for battery, network management, etc.) that make up our workspace to QML, this pays off now as those things are rather easy to port, and give a very mature impression right off the bat. We do realize that we have some cleaning up to do, and now is a good time to do this. We want to introduce a greater degree of consistency across the workspace experience. Technically, this can be achieved by more and smarter sharing of code, so common UI patterns become more, well, common. Plasma’s design language will be more pronounced, and at the same time, easier to change to your liking. More on that in another article, however.

As it currently looks like, we will release a first technology preview of both, Frameworks 5 libraries and Plasma Next in December. This won’t be a complete thing by any means, but a way to check on and gauge progress. At the same time, you’ll get to have a good look at Plasma Next, which, while building on the new technology stack, will resemble our current offering quite a bit still. It is much more a technology preview, than a user experience preview. So don’t judge too early, rather, get your hacking shoes on and join the fun. :)