What’s going on in Plasma Workspaces 2?


While moving its codebase to Qt5, the KDE Development Platform is undergoing a number of changes that lead to a more modular codebase (called KDE Framework 5) on top of a hardware-accelerated graphics stack. In this post, you’ll learn a bit about the status of Frameworks 5 and porting especially Plasma — that will be known as Plasma Workspaces 2, paying credit to its more convergent architecture.

Let’s start with something visual, before we get to the nitty-gritty:


Video showing a basic port of a Plasma Desktop Containment to Plasma 2

Frameworks 5

A whole bunch of libraries can now be built, installed and packaged separately. Those include (in tier1) Solid, Threadweaver, kdecore, karchive, kwindowsystem, and more, and in tier2 kauth and kconfig. Plasma has already moved into its own repository, and can of course also be built separately.

Kevin has been plugging away at removing problematic interdependencies between those libs, and recently could ditch (i.e. move to kde4support) a few classes that make it easier to just use Qt machinery (QApplication & friends) to bring up “KDE applications”. KAction has gone, KAboutData, so KDE Applications are now less “special” in the Qt world — a good thing for portability.
Splitting and untangling kdeui from kdelibs proves to be a bit more work- intensive than initially hoped. Fracture lines are becoming visible. The problem here is that this task is holding up the parallelization of development, so this has a high priority right now.

We’re also using a continuous integration system now to keep us on our toes with respect to “buildability” (which can be a bit daunting with so heavily shifting ground in kdelibs, this will calm down at some point though).


Video showing a Plasma 2 OpenGL shader demo widget

Plasma & KWin

Good progress, especially in the last month, in three areas:

API reviews: we’ve been doing weekly sessions for libplasma2 API reviews, where we’re going through the entire API and think about improvements for the Plasma 2, post-graphicsview world. As a result, libplasma2 has shrunk to about 1/3 in (compiled) size in its current state. We don’t expect it to grow much, since, in the scenegraph world, it plays another role than previously (although developers used to QML won’t really notice). (Join in the Hangout, if you like, we usually start on Monday morning around 10.00 UTC, just pop up in the #plasma channel and ask Marco to invite you). Our mutual status updates and Cool New Development is recorded and made available on Youtube for interested people, Last Monday’s session can be found here, but today we skipped it — you get this more detailed blog post in return. :)

Imports: Basically our QML runtime, it consists of Plasma Components, extras, bindings for things like dialog, framesvg and dataengines, drag and drop, krunner models, and a bunch of other stuff. I’m working on this right now, and have about 95% of the imports originating from kde-runtime working in Plasma2. We’ll be able to offer almost the same API to Plasma2 QML users, as in Plasma1, so porting of your QML code will be very easy.

Shell: In Plasma2, instead of having specific plasma-desktop, plasma-netbook, plasma-device shells, we will use one “generic” shell that loads containments (which then load applets), wallpaper, toolbox, etc. The shell can dynamically replace these components (change wallpaper, for example).

A few things are new here: in Plasma2, plasmoids provide their config ui via QML files, that are part of the package. That solves the problem that we could not really influence the behaviour of the configuration UIs from QML in Plasma1. It will also allow to transparantly switch between instant apply and “OK/Apply/Cancel” buttons, depending on what fits the usecase. Marco is on this.

Martin has been pushing the removal of the direct X dependency further through porting to XCB. He’s also recently started on a Qt5 port. One problem with KWin is that Martin needs a bunch of changes to have QtQuick and KWin run in the same process, that means making sure that KWin and Plasma (or QtQuick2 really) properly share and interact in the same OpenGL context. There’s a chicken-and-egg situation for kwin, since it needs to load for example window decorations and task switchers (both from QML) to be useful, but it can’t right now. The X11-based windecos won’t make it into Plasma2, so we’d rather avoid porting them just for the time being. Martin is on that though, and he earns our gratitude for going through this painful period in the porting procedure.