KDE 4 Preview

KDE 4, first announced two years ago, is the next step for the popular UNIX desktop environment. With the shift to a new major version of the toolkit used to build KDE, developers are able to break free of requirements for compatibility and make radical changes to the codebase.

The default desktop infrastructure, well remembered as operating on similar lines since KDE 2, is being completely redesigned. The new desktop shell, Plasma, promises to re-invent the desktop paradigm. Headed by Aaron Siego, Plasma's team of developers has been working on a complete replacement for the previous infrastructure of the KDE panel and desktop, and the results are breathtaking.

Plasma incorporates most of what is seen on screen at first login. It is a flexible, fully scalable and rotatable desktop shell with the ability to embed mini-applications and media as applets or widgets known as plasmoids. The concept of applets is not a new one to desktop design, but Plasma brings a few innovations to the table.

Figure 1. Plasma, Showing Some of the Included Plasmoids

Plasma divorces the data engine from the presentation, allowing developers to write a data engine once and then present this in an arbitrary number of ways in an applet. For example, once an engine to extract system performance state has been written, multiple plasmoids can present this information in different ways. A desktop plasmoid might have a large, detail-rich display, but the same data displayed on the panel might recognise its spatial constraints and display a simpler view.

Native Plasma applets can be implemented as containments, which are simply applets that can contain another applet. The panel is a containment, as is the desktop itself, and an applet contained within the panel can be dragged to the desktop or another panel, and vice versa, reforming and reflowing itself to fit its physical constraints.

This flexibility opens up, among other possibilities, the ability for scalable displays to enable a content-rich desktop on a PC or a display that's more suited to low-screen resolutions on an embedded device. KDE 4.1 plans to support OS X dashboard widgets, hinging on new features in a release of WebKit scheduled for early 2008.

Oxygen is the name chosen for the cohesive look and feel for the new KDE desktop. As well as creating beauty, the Oxygen team of artists is working with user interface guidelines to ensure that identification of elements is a priority. The result is a clean break from the previous KDE style, obviously inspired in part by already-existing artwork, but bringing it together with something fresh that is distinctly Oxygen's own. Oxygen also incorporates the system sound package, combining with the rest of the artwork to create something that is uniquely KDE.

Figure 2. The Oxygen Icon Set

With a team of three core icon designers, Oxygen relies on a set of strict style guidelines and an official colour palette to ensure a consistent result. The colours chosen are rich without being overpowering, and the icon design is modern and appealing.

An advantage of the new Oxygen icon theme is that it will be the first truly open KDE icon theme. The previous default for the long-running KDE 3 series, Crystal, never had its sources made available. The Oxygen team has been working exclusively in SVG, ensuring the set remains open.

The Oxygen style and window decoration is a large-scale departure from the Plastik style that became default in the late 3.x series. The muted pale gray and blue colours have made way for a brilliant off-white for both window decoration and controls. Green, orange and blue highlights are used sparingly with pleasing effect. The result looks extremely clean and modern, although such a large departure no doubt will draw some criticism. A wide range of colour schemes are available to suit almost every taste.

Figure 3. Oxygen uses bold highlights with low-contrast widgets to achieve a clean and modern look.

One minor concern about the new style is how much screen real estate it seems to use. We looked at KDE 4 on a Lenovo ThinkPad at 1400x1050 pixels, which seemed adequate for the task but by no means overgenerous. People still using 1024x768 or lower resolutions may struggle with the defaults.

A new wallpaper set has been collated, with the Oxygen artists acting as judges to select community submissions. The team chose 15 wallpapers, and the results are breathtaking. This kind of community involvement is unquestionably one of the strengths of the open-source development model.

Figure 4. A Small Selection of the KDE 4 Default Wallpapers

Unfortunately, we were unable to preview the Oxygen sound theme properly—at the time of this writing, KDE 4 had not yet been released, and something about our sound card was causing the KDE sound system, Phonon, to crash.