The world of open source cross-platform programming got a little bigger this week with the release of Qt 4, a popular application framework.

The latest release has gone a step further into cross platform with the release of an open source version of its toolkit for Windows, which includes integration with Microsoft's Visual Studio .NET.

Qt (pronounced "cute") is developed by Norway-based Trolltech and is perhaps best known as the framework behind the open source KDE (define)graphical environment. Qt is a C++ application development framework that provides a common API (define)across multiple platforms, which allows developers to write applications once and deploy on multiple platforms, including Windows, Linux/UNIX and Mac OS X.

GNOME, KDE's competing open source graphical environment, is based on Qt's competing framework, GTK+ which recently released version 2.7.

Though GTK and Qt frameworks sometimes compete for the same open source developers, Trolltech's president, Eirik Chambe-Eng, said the comparisons don't really stack up.

"Concerning GTK, we believe it is good for Linux that there is one C-based toolkit (GTK) and one C++ based toolkit (Qt), both available under Open Source licenses," Chambe-Eng told internetnews.com. "That way, developers can choose which one fits their needs best."

Like its predecessor, Qt 4.0 is dual-licensed under both a commercial license for closed proprietary development and the GNU GPL (define)open source development projects. Unlike its predecessor though, Qt 4.0 also offers an open source version for Windows, which is intended to help open source developers target Windows users.

Commercial Windows developers will also benefit from Qt 4.0 thanks, to a new integration with Microsoft's Visual Studio .NET.

Trolltech claims that the revamped Qt 4 also provides improvements in memory consumption and speed. Multi-threading support has also been extended, which helps developers take advantage of multi-core processors.

The graphics subsystem has also been improved with support for off-screen rendering, interchangeable underlying paint engines, alpha-blending, gradients, anti-aliasing and painter paths.

Qt 4.0 is currently available in a number of different editions, including Desktop, Desktop Light editions, which target Qt's traditional GUI developer audience.

Trolltech has also developed a console edition of Qt, which is geared for not GUI server software and business logic software development.

"In Qt 4 we have created a special server edition with a focus on server side development, basically opening a new market for us and making the advantages of Qt's superior API available to a new group of developers," Chambe-Eng said. "In the future Qt will expand into other markets as well."