The first question for the budding gadget developer is then which gadget
technology to choose. In an ideal world, there would only be a single standardised package format and only a single standardised API. This would allow gadgets to be used on any platform and the question of choosing a format would not even arise. Alas, we don't live in an ideal world and therefore different platforms and markets have produced different gadget formats. For example, there are Windows desktop gadgets, Linux desktop gadgets, Google gadgets, and gadgets designed to be integrated into web portals. We will look at the different types of gadgets and their use in brief.
Formerly known as Windows sidebar, Windows gadgets are based on the widget engine for Microsoft gadgets, which runs on the Windows platform only. A minimal gadget contains an XML configuration file (gadget.xml) and an HTML file (main.html). Other web files can be added. These are zipped for distribution and the resulting file is renamed to *.gadget. Windows gadgets have access to a special API divided into three parts. 1. Gadget objects provide gadget state and event handling. 2. System objects provide access to files, network and OS functions. 3. Presentation objects provide visual functionality, namely background, image, and text handling. Many Windows desktop gadgets can also be run (with slight modifications) inside a Windows Live homepage. The latter don't have access to the system API and cannot modify the page's DOM object tree.
There is a variety of widget engines available for Linux and the market seems to be highly fragmented. For the already mentioned Google gadgets, Linux users can download the open source Google-Gadgets-For-Linux software that allows Google gadgets to be run without Google Desktop. In addition, there are the following widget engines, among others, for which a limited choice of existing widgets is available:
Gdesklet – is a Gnome program for running gadgets on a Linux desktop. Despite its name, it can be also be used with other Desktop managers other than Gnome, like KDE or Xfce. Desklets are applets programmed in the Python language.