As many other components of the Plasma Workspaces, Plasma Desktop’s default Containment is being ported to QML. A technology preview of the containment is being demoed and can be tested by a wider audience now. While the port is mainly replicating the current desktop containment in QML, its interaction scheme to position and manipulate widgets on the desktop has been improved.
First of all, a note: The code presented in this article is not part of the upcoming Plasma Desktop 4.10. It can easily be installed on top of it, it might see inclusion in the summer 2013 release, however
In our Roadmap, you learn that KDE is currently porting many aspects of its workspaces to QML, with the goal to create a more modern user experience on top of state-of-the-art technologies such as Qt5, OpenGL scenegraph and Wayland. The move to QML is a gradual process, made possible by the componentized architecture of Plasma. Widgets and other components that make up the workspace are replaced with QML ports one by one. The premise is to not introduce regressions by shipping each component “when it’s ready”. Ultimately, we need a complete set of QML components to run the whole desktop (and at some point also apps) directly on top of the graphics hardware, leading to higher graphics performance and more available resources on the CPU.
One of the important pieces is the Desktop containment. This is the component in Plasma that is responsible for managing and laying out widgets on the desktop and creating the toolbox (which makes some “workspace actions” available to the user. In general, a “Containment” is an area on the screen (a panel, the desktop background, the dashboard, …), and it takes care of managing widgets, their position and sizing within. It also offers access to action specific to widgets, or the containment or workspace.
The currently shipped (also in 4.10) default Desktop containment is written in C++, using QGraphicsWidgets and offers free placing of widgets on the desktop, with a bit of edge and overlap detection and repositioning poured in.
User interaction improvements
Most of the new containment is exactly the same as in the current default — this is done by design, we do not want to introduce radical changes to the workspace (and the users’ workflows), but rather improve gradually and in an iterative process. There are two areas (which in fact are closely related) where we did change a few things: positioning/sizing and visual cleanliness. These are expressed in two changes: integration of applet handle and positioning aids.
In order to reduce visual clutter, we integrated the applet handle into the applet’s background frame. Previously, it would be its own frame, and shift out as separate element from under the widget. Merging handle and background frame reduces the number of distinct elements on the screen and allows less intrusive transitions when the widget handle becomes visible.
The second important change is that we now provide helpers when the user moves and resizes a widget. When moving, we show a halo at the position the applet will snap to when dragged. This makes widget placement more predictable and allows the user to get it right in one go. We also align the widgets to an invisible grid, so applets automatically end up being aligned pixel-perfectly with each other, which leads to a more ergonomic workflow, cleaner appearance of the workspace, and again to less visual clutter.
Platform improvements: Bindings and Toolbox
An important aspect of the work on the QML containment, was to improve the bindings which load declarative code (QML) into Plasma shells, these improvements are included in Plasma 4.10, due to be released in early february. This includes the necessary platform features to allow running fully-featured QML containments, something which we have done in Plasma Active for a while, but within a more confined context.
As a result of this work, Plasma can now also load toolboxes written in QML. The Plasma Toolbox is the little widget with the Plasma icon you can see on top of many containments, and which gives access to actions such as add widgets, settings, shortcuts, etc.. The toolbox used with the containment shown is a 1:1 port of its counterpart in the current default (C++) toolbox. The name of the toolbox package is currently hard-coded in the bindings (it loads it from the org.kde.toolbox package and silently falls back to the C++ implementation if that isn’t found — a 4.10 feature), but it also opens up this part of the workspace to QtQuick goodness. The toolbox is basically a translucent layer on top of the desktop, so much freedom is given to other implementations).
A template and a bridge
The code is not only there to replace the current containment, it also serves as a template for new developments. With the new containment bindings in place, it is now very easy to create your own containment, modify someone else’s and publish them to share them. The containment shown is just one example for what we can do with the QML integration features in Plasma. As Plasmoid packages are architecture independent, this of course works across devices and different workspaces.
The work that is upcoming in Plasma Desktop is further bridging the gap between Plasma’s interfaces for different devices and formfactors. Some of its code has been introduced in Plasma Active, and is now available in a more generic fashion also for Plasma Desktop (and Netbook). This brings us closer to one of our goals, having only one shell that dynamically loads a suitable interface (Containment, Widgets) for a given formfactor, use case, output device, etc.
Give it a spin
If you’re interested and would like to try it (we appreciate feedback, it’s especially valuable in this phase!), there are two ways to get this containment. The minimal requirement for it is Plasma 4.10-beta1.
If you’re using git, you will find the code in the branch called “plasma/sebas/desktop-qml”, just check it out and build it, install it, run kbuildsycoca4, and you’re done.
If you are using the packages, you can easily install the following two Plasmoid packages to your system:
If your system is using a version prior to KDE SC 4.10-beta1, the packages will install, but not work.
The following commands install the necessary Plasma packages into your
home KDE install directory.
# create the package directory and go there mkdir -p `kde4-config --prefix`/share/apps/plasma/packages/org.kde.toolbox cd `kde4-config --prefix`/share/apps/plasma/packages/org.kde.toolbox # unpack the plasmoid package unzip ~/path/to/toolbox-git28012013.plasmoid # check if it's installed correctly, # this should list metadata.desktop and contents/ ls -la `kde4-config --prefix`/share/apps/plasma/packages/org.kde.toolbox
[Edit: changes –localprefix to –prefix, as we’ve found a bug in –localprefix code.]
Then install the desktop containment package (If you’re updating the containment at a later stage, use plasmapkg -u.):
plasmapkg -i desktop-git28012013.plasmoid
You can now choose the new containment from Layout dropdown in the Desktop Settings, pick “Default Desktop (QML)” there.
I would like to thank Blue Systems for supporting my work on the above topics.