Crossing the platform divide

Trolltech has announced the official release of Qt 4.4, a much-anticipated update to their popular, cross-platform software development framework. Qt is distributed under a dual-licensing model that enables open-source as well as proprietary commercial development, and it is widely used on the Linux platform, where it provides the underlying widget toolkit used by the KDE desktop environment. It is also used in a variety of commercial applications such as Skype, Google Earth, and Adobe Photoshop Elements.

Some of the most significant features added in Qt 4.4 include a multimedia abstraction layer, an HTML rendering widget based on WebKit, a new concurrency framework, and support for rendering widgets on the toolkit's drawing canvas. This is also the first Qt release to include support for Windows CE and Windows Mobile.

We gave you an early glimpse of Qt 4.4 last year when we tested a prerelease. Now that development is complete and the functionality has been finalized, we can take a closer look. To that end, we conducted extensive testing to see how the new features perform. We also discussed the release with Trolltech CTO Benoit Schillings, who shared some insights about Qt 4.4 and gave us some hints about what we might see in future versions.

Bridging the gap between desktop and mobile development

Qt is supported on all major desktop operating systems, including Linux, Mac OS X, and Windows. It uses native APIs to render widgets, which means that most Qt applications are visually consistent with the underlying operating system. Trolltech also offers a Linux-based mobile operating system stack called Qtopia that is used on a wide range of devices, including the Sony Mylo and some Motorola mobile phone handsets. Qt 4.4 extends the toolkit's portability by bringing full support to Windows CE. Developers can now use Qt to write a single application code base that can be ported trivially to any of the supported operating systems.

Qt has a lot to offer on Windows CE and is well suited for creating graphically rich touchscreen user interfaces. Developers say that it offers good performance and strong support for the native look and feel of the platform. Trolltech's tools support tight integration with Visual Studio, which means that it will be easy for existing Windows CE developers to adopt the framework.

An impressive demo video created by Trolltech shows a series of Qt demo applications running on a Windows Mobile touchscreen device and then on FIC's Linux-based Neo1973. The applications show off some of the most sophisticated graphical capabilities offered by Qt and also demonstrate the toolkit's robust touch-screen support.

An intriguing benefit of Qt support for Windows CE is that it will expand the ecosystem of open source software available for the operating system by enabling developers to port over existing KDE and Qt applications. I know I'd love to be able to run Qtopia applications like FBReader on my Windows Mobile device. Trolltech developers have already experimentally ported some relatively complex KDE 4 applications and gotten them to work on Windows Mobile. For instance, Thomas Hartmann wrote a blog entry last month demonstrating a port of the KDE 4 program Marble, a mapping application with sophisticated drawing. It works seamlessly across several Windows devices.

The high level of portability offered by Qt attracted mobile giant Nokia, which is in the process of acquiring Trolltech. The deal is still pending while it faces regulatory scrutiny in Europe. In an announcement issued earlier this year, Nokia said that it intends to leverage Qt to provide a cross-platform development layer that will work across a broad spectrum of mobile and desktop platforms. Nokia has already announced plans to bring Qt to its S60 and Maemo mobile operating systems.