The K Desktop Environment (KDE) is built on the QT GUI toolkit. QT is more than a set of widgets: it has evolved over the last few years into a high quality cross platform application development environment with a rich set of tools and utility libraries. “The Book of Qt 4: The Art of Building Qt Applications”, written by Daniel Molkentin and published by No Starch Press, thoroughly describes in exquisite detail the main widgets, algorithms and utility libraries (as well as tools such as the QT designer) needed during the application creation cycle.