KDE 4 is the current series of releases of the K Desktop Environment. The first version (4.0.0) of this series was released on 11 January 2008.

The new series includes updates to several of KDE's core components, notably a port to Qt 4. It contains a new multimedia API, called Phonon, a device integration framework called Solid and a new style guide and default icon set called Oxygen. It also includes the new desktop and panel user interface tool, called Plasma, which supports desktop widgets, replacing SuperKaramba and similar to Apple's Dashboard widgets. The port to Qt 4 will facilitate support for non-X11-based platforms, including Microsoft Windows and Mac OS X. One of the overall goals of KDE 4 is to be more easily portable to different operating systems.

Major releases (4.x) are scheduled for every six months, while minor bugfix releases (4.x.x) are released monthly.

Major updates

This is a short overview of major changes in KDE 4. Not all of these changes are available in the first (4.0) release.

General

The port to the Qt 4 series is expected to enable KDE 4 to use less memory and be noticeably faster than KDE 3. The KDE libraries themselves have also been completed more efficient. Qt 4 is available under the GPL for Mac OS X and Windows, which will allow KDE 4 to run on those platforms. The ports to both platforms are in an early state but expected to be suitable for regular use by the release of KDE 4.1. Both ports are trying to use as little divergent code as possible to make the applications function almost identically on all platforms. During Google's Summer of Code 2007 an icon cache was created to speed up application start up times for use in KDE 4. Improvements were varied - Kfind, an application which used several hundred icons, started up in almost a quarter of the time it took previously. Other applications and a full KDE session started up a little over a second faster.

Many applications in the Extragear module have received numerous improvements with the new features of KDE 4 and Qt 4. But since they follow their own release schedule, they may not be available at the time of the first KDE 4 release. Popular applications like Amarok, K3b, digiKam, Gwenview and KOffice (though not part of the extragear module) are being ported.

Visual

The most noticeable changes for users are the new icons, theme and sounds provided by the Oxygen Project. These represent a break from previous KDE icons and graphics, which had a cartoonish look. Instead Oxygen icons will opt for a more photo realistic style. The Oxygen Project builds on the freedesktop.org Icon Naming Specification and Icon Theme Specification, allowing consistency across applications. The Oxygen team will be using community help for better visuals in KDE 4, with both alternate icon sets and the winners of a wallpaper contest held by the Oxygen project being included in KDE 4. There will also be a new set of human interface guidelines for a more standardized layout.

Plasma is a rewrite of several core KDE applications, like the desktop drawing and most notably the widget engine. Plasma will allow for a more customizable desktop and more versatile widgets.

KWin, the KDE Window Manager from KDE 3, now provides its own compositing effects, similar to Compiz. Compositing is disabled by default in 4.0.

Development

Phonon is the name of the new multimedia API in KDE 4. Phonon is a different approach to multimedia backends than in previous versions of KDE, as Phonon only functions as a wrapper. Abstracting the various multimedia frameworks available for unix-like operating systems into runtime switchable backends that can be accessed through a single API. This was done to give a stable API for KDE 4 and to prevent it from depending on a single multimedia framework. Applications that use the Phonon API can be switched between multimedia frameworks seamlessly by simply changing the backend used in system settings. Trolltech adopted Phonon for multimedia use in Qt 4.4 and are developing backends for Gstreamer, Windows and OS X in the KDE SVN repository under the LGPL.

Solid is the hardware API in KDE 4. It functions similarly to Phonon as it doesn't manage hardware on its own but makes existing solutions accessible through a single API. The present solution uses HAL, NetworkManager and BlueZ (the official Linux bluetooth stack), but any and all parts can be replaced without breaking the application, making applications using Solid extremely flexible and portable.

ThreadWeaver is a programming library to help applications take advantage of multicore processors and is included with kdelibs.

Kross is the new scripting framework for KDE 4. Kross itself is not a scripting language, but makes it easier for developers to add support for other scripting languages. Once an application adds support for Kross, any language Kross supports can be used by developers. New scripting languages can be added by creating a plugin for Kross, which benefits all applications using it.

Decibel is a Telepathy based communication framework, which is expected to be fully used by Kopete by KDE 4.2 and will allow for easy embedding of chat inside applications.

Strigi is the default search tool for KDE 4, chosen for its speed and few dependencies. In concert with other software like Soprano, an RDF storage framework, and the NEPOMUK specification, Strigi will provide the beginnings of a semantic desktop in KDE 4. Users can tag files with extra information through Dolphin, which Strigi can index for more accurate searches.

KDE 4 uses CMake for its build system. Since previous versions of KDE were only on Unix systems, autotools were used, but a new build system was needed for builds on operating systems like Windows and Mac OS X. CMake also dramatically simplified the build process. The autotools build system had become so complicated by KDE 3 that few developers understood it, requiring hours of work for simple changes. In early 2007 CMake was shown to compile the KDE 4 version of KDElibs 40 % faster than the autotools compiled KDE 3 version.

DXS, previously known as GHNS (Get Hot New Stuff) is a web service that lets applications download and install data from the Internet in one click. It was used in the KDE 3 series but has been extended for use throughout KDE 4. One example was Kstars, that can use Astromical data that is free for personal use but you can't redistribute it. DXS allows for that data to be easily downloaded and installed from within the application instead of manually downloading it.

Akonadi is a new PIM framework for KDE 4 that will be included in later releases. Akonadi is a unification of previously separate KDE PIM components. In the past each application would have its own method for storing information and handling data. Akonadi itself functions as a server that provides data and search functions to PIM applications. It is also able to update the status of contacts. So if one application changes information about a contact, all other applications are instantly informed of the change.

KDE 4.0

The majority of development went into implementing most of the new technologies and frameworks of KDE 4. Plasma and the Oxygen style were two of the biggest user-facing changes.

Dolphin replaces Konqueror as the default file manager in KDE 4.0. This was done to address complaints of Konqueror being too complicated for a simple file manager. However Dolphin and Konqueror will share as much code as possible, and Dolphin can be embedded in Konqueror to allow Konqueror to still be used as a file manager.

Okular replaces several document viewers used in KDE 3, like KPDF, KGhostView and KDVI. Okular makes use of software libraries and can be extended to view almost any kind of document. Like Konqueror and KPDF in KDE 3, Okular can be embedded in other applications.

Alpha releases

On May 11, 2007, KDE 4.0 Alpha 1 was released marking the end of the addition of large features to the KDE base libraries and shifting the focus onto integrating the new technologies into applications and the basic desktop. Alpha 1 included new frameworks to build applications with, providing improved hardware and multimedia integration through Solid and Phonon. There are also new applications that centre on a smooth user experience (such as Dolphin and Okular) and a new visual appearance through Oxygen icons.

On 2007-07-04, Alpha 2 was released. The release focused on integrating the Plasma desktop, improving functionality and stabilizing KDE.

Beta releases

On 2007-08-02, Beta 1 was released. Major features included a pixmap cache – speeding up icon loading, KDE PIM improvements, improved KWin effects and configuration, better interaction between Konqueror and Dolphin and Metalink support added to KGet for improved downloads.

On 2007-09-06, Beta 2 was released with improved BSD and Solaris support. The release included the addition of the Blitz graphic library – allowing for developers to use high performance graphical tricks like icon animation – and an overhaul of KRDC (K Remote Desktop Client) for Google's Summer of Code. Plasma was also integrated with Amarok to give Amarok's central context view. In addition, several improvements made during the Summer of Code (color mixing, music notation, Flake architecture) were included in the release of the third alpha for KOffice 2.

On 2007-10-16 Beta 3 was released. The beta 3 release is focused on stabilizing and finishing the design of libraries for the release of the KDE Development Platform. The major improvements include improvements to Plasma with many new features and the addition of the applet browser. The KDE PIM software set will not be completely ready for the 4.0 release, but many applications have been ported with improvements. The new Akonadi PIM service is planned to be finished by the 4.1 release. The Educational software received many improvements in Marble, Parley (formerly known as KVoctrain) with bugfixes in others. A program called Step, an interactive physics simulator, was started and finished as part of the Google Summer of Code. Kopete will receive a straight port to be ready by 4.0 and there were also general Konqueror and KHTML improvements.

On 2007-10-30 Beta 4 was released. A list of release blockers was compiled, listing issues that need to be resolved before KDE will start with the release candidate cycle for the desktop. The goals were to centre on stabilization and fixing the release blockers. At the same time, the first release candidate of the KDE 4.0 Development Platform was released. The development platform contains all the base libraries to develop KDE applications, including “high-level widget libraries, a network abstraction layer and various libraries for multimedia integration, hardware integration and transparent access to resources on the network.”

Release candidates and stable releases

On November 20, 2007 Release Candidate (RC) 1 was released. This release was called a "Release Candidate" despite Plasma requiring further work and not being ready for release. On 2007-12-11 RC2 was released. The codebase was declared feature-complete. Some work was still required to fix bugs, finish off artwork and smoothen out the user experience.

KDE 4.0 was released on January 11, 2008. Despite being a stable release, it is intended for early adopters. Users wanting a stable, "feature complete" desktop may wish to continue using KDE 3.5 for now. There will be maintenance releases every month, which will fix bugs and may also add some minor features.

KDE 4.1

Planning and development have already commenced for the 4.1 release, which is expected to be available in July. KDE 4.1 should include the Decibel VoIP and real-time communication framework, GStreamer, QuickTime 7, and DirectShow 9 Phonon backends and ports to Windows, Mac OS X, and OpenSolaris. Plasma improvements include Plasma packages, an add-on creator, support for QT widgets and WebKit integration - allowing Apple Dashboard widgets to be displayed. Kopete will also receive extra work.

New applications include:

Dragon Player multimedia player (formally Codeine)

Lokalize computer-aided translation system (formerly Kaider)

KDevelop and KDevplatform modules

KDE-PIM module, with some Akonadi functionality

Release schedule