Qt Cross-platform C++ GUI Application Framework Technical Overview v. 1.3 © 2000 Trolltech AS 1. Contents 1. Contents...................................................................................................................................................... 2 2. Introduction ................................................................................................................................................ 3 3. Architecture ................................................................................................................................................ 4 3.1. Cross-Platform Development .............................................................................................................. 4 3.2. API Layering ....................................................................................................................................... 5 3.3. Look and Feel ...................................................................................................................................... 6 3.4. Performance......................................................................................................................................... 7 3.5. Maintenance......................................................................................................................................... 7 3.6. API design ........................................................................................................................................... 7 3.7. Efficiency............................................................................................................................................. 8 3.8. Component Programming.................................................................................................................... 8 4. Internationalization................................................................................................................................... 10 4.1. Unicode.............................................................................................................................................. 10 4.2. Localization ....................................................................................................................................... 10 5. Graphical User Interfaces (GUI)............................................................................................................... 12 5.1. Basic Concepts .................................................................................................................................. 12 5.2. User Interface Composition............................................................................................................... 12 5.3. Layout Management .......................................................................................................................... 12 5.4. Customizing Widgets......................................................................................................................... 14 6. Visual Development ................................................................................................................................. 16 7. Graphics.................................................................................................................................................... 18 7.1. Device Independent Graphics............................................................................................................ 18 7.2. Special Paint Devices ........................................................................................................................ 18 7.3. The 2D Graphics API ........................................................................................................................ 18 7.4. Image Handling ................................................................................................................................. 19 7.5. Canvas ............................................................................................................................................... 20 7.6. 3D Graphics....................................................................................................................................... 20 8. Tool Classes.............................................................................................................................................. 22 8.1. Operating System Services ................................................................................................................ 22 8.2. Text Classes....................................................................................................................................... 23 8.3. Collection Classes.............................................................................................................................. 23 8.4. Network Classes ................................................................................................................................ 24 8.5. Threading........................................................................................................................................... 24 9. Appendix 1: Widget Set............................................................................................................................ 25 10. Ready-made Dialogs............................................................................................................................... 27 11. Appendix 2: Complete API Class List.................................................................................................... 28 Qt is a trademark of Trolltech AS. All other company and product names are trademarks or registered trademarks of their respective owners. Qt – A technical Overview Page 2 of 29 2. Introduction For many years software producers have been faced with the problem of how to target a market with such diverse operating and window systems. And there is no reason to think this situation is about to change. It is now clear that the early nineties’ rumors of the impending death of Unix were exaggerated. The current boom of Linux and its positioning as a competitor on the desktop ensure that the software market will continue to have many different platforms in the foreseeable future. A major challenge in targeting multiple platforms has been the cost of developing and maintaining an application for several different platforms. Because of the inherent differences among these platforms, the porting of an application to a new platform can involve costly redesign and reimplementation. Qt is a software development application framework that solves the most critical challenges of cross-platform application development and maintenance. The following presentation explains the principles software developers can use with Qt to create single-code applications for end-users on different platforms. Qt is produced by Trolltech. Qt has been marketed since 1995 and is now being used by such leading companies as HP, IBM, Intel, Siemens, Ericsson and Xerox. Qt widely used on Linux; in fact, it is the basis of the popular KDE desktop environment included in virtually every Linux distribution. Details of all the functionality Qt provides are outside the scope of this document. For further technical information we refer you to: • The Qt Reference Documentation. Latest version is available on-line at doc.trolltech.com. • Programming with Qt, by Matthias Kalle Dalheimer. O’Reilly, 1999. This book is available in several languages: English, Norwegian, French, Japanese, Korean, Portuguese and German. • Teach Yourself Qt Programming in 24 Hours, by Daniel Solin, SAMS, 2000 • KDE- und Qt-Programmierung, by Burkhard Lehner, Addison-Wesley Longman Verlag, 2000. Currently available only in German. An updated list of all available documentation is available on-line at www.trolltech.com/developer/literature. Qt is a continuously evolving toolkit. The following summarizes the main features of the current version of Qt, which is version 2.2. Further information about Qt is available at the Trolltech web site: www.trolltech.com Qt – A technical Overview Page 3 of 29 3. Architecture Qt is a cross-platform C++ application framework. It is implemented as a class library and provides a rich API (Application Programmer’s Interface) for application developers. Qt offers a wide spectrum of useful functionality but focuses mainly on the GUI (Graphical User Interface). Thus, for application developers Qt replaces Motif, MFC, and/or other GUI toolkits. 3.1. Cross-Platform Development Qt is cross-platform: the Qt class library is implemented for several different operating and window systems., and the API is identical for all platforms. This means that an application written with Qt on one platform can be made to run on another simply by recompiling it on the new platform and linking it with the Qt library for that platform. In fact, the Qt library is binary compatible on all supported Windows variants. Thus, with Qt, software producers can develop and maintain an application for multiple platforms by developing and maintaining a single application source code base. Qt is currently implemented for three main groups of operating systems: • Unix - including Linux, HP-UX, Sun Solaris, Digital Unix, SGI Irix, IBM AIX, SCO Unix, and several BSD variants. The Qt library is implemented using the X11 libraries and the X Window system. • Windows - including Windows 95, 98, NT and 2000. The Qt library is implemented using the Windows GDI API