Language/Library Selection

There are two immediately obvious choices of cross platform language for graphical user interface development: C++ and Java. C++ is a fast, object-oriented language which has been in wide use for many years, and ported to a large range of platforms. Its downsides include the sometimes messy implementation of an object oriented system based upon the older, non-object oriented C language. Java is much newer, a bytecode interpreted language that runs inside a virtual machine referred to as the JVM. It has a cleaner object system than C++. It was designed to be cross-platform from the ground up, and offers a GUI toolkit that looks consistent across many platforms. Running inside a virtual machine often impacts the performance of Java based applications, especially on older hardware.

The existence of cross-platform C++ GUI toolkits such as QT,QT is available from http://www.trolltech.no/. FOX,The FOX toolkit is available from http://www.fox-toolkit.org/. FLTK,The Fast Light Toolkit (FLTK) is available from http://www.fltk.org/. and wxWindows,wxWindows is available from http://www.wxwindows.org/. give rise to a number of advantages over Java:

1. Speed
2. Lower memory consumption
3. Can be compiled statically for easy installation
4. Cross-platform native look and feel is achievable

The choice of GUI toolkit for use with C++ was made by elimination:

• QT only offers free software licensing for the X11 platform, failing point number 3 of the design criteria.
• FOX lacks native support for MacOS (an X server is required), failing point 1 of the design criteria.
• FLTK only supports Unix and Microsoft Windows platforms, again failing point 1 of the design criteria.
• wxWindows is left, without suffering from any of the problems above.

Having settled in on a programming language and GUI toolkit, we can now worry about choosing a companion library for parsing and creating XML messages. A C XML library known to be portable across all our target platforms (and more) is Libxml2.The XML C parser and toolkit of Gnome, libxml: http://www.xmlsoft.org/, http://www.gnome.org/.