The open source KDE desktop environment for Unix was built with Qt, a C++ class library for writing GUI applications that run on Unix, Linux, Windows 95/98, Windows 2000, and Windows NT platforms. Qt emulates the look and feel of Motif, but is easier to use. The learning curve for Qt can be steep. This text is designed to act as a reference for beginners. It shows how to program in Qt, guiding the user through the steps of writing a simple paint application. Exercises with fully worked out answers help to deepen understanding of the topics. The book presents all of the GUI elements in Qt, along with advice about when and how to use them. For seasoned Qt programmers, there's also lots of information on topics including advanced 2D transformations, drag-and-drop, writing custom image file filters, networking with the new Qt Network Extension, XML processing, and Unicode handling.