widget engine(转)

　　In computer software, a widget engine is a software service available to users for running and displaying desktop widgets on the desktop. Desktop widgets are physically inspired applets that give access to information and frequently used functions such as clocks, calendars, news aggregators, etc.
　　The term widget engine is not to be confused with that of a widget toolkit. Toolkits are destined to GUI programmers, who combine several widgets to form a single application. A widget in a toolkit provide a single, low level interaction, and is prepared to communicate with other widgets in the toolkit. On the other hand, widget engines are intended for end users and each desktop widget is a stand-alone, task-oriented application which can be composed of several related interactions on its own.
　　The desktop widget model is attractive because of ease of development. Most of these widgets can be created with a few images and about 10 to several hundred lines of XML/JavaScript/VBScript source code. A single host software system, such as a web browser, runs all the loaded widgets. This allows several desktop widgets to be built sharing resources and code.
　　Contents
　　* 1 Desktop widgets
　　* 2 Mobile widgets
　　* 3 Information flow of Desktop Widgets
　　* 4 See also
　　* 5 Notes and references
　　* 6 External links
　　Desktop widgets
　　Examples of desktop widgets, shown here in DesktopX
　　Examples of desktop widgets, shown here in DesktopX
　　The Wikipedia Widget, in Dashboard running under Mac OS X v10.4
　　The Wikipedia Widget, in Dashboard running under Mac OS X v10.4
　　Early developer version of Plasma Desktop with Plasmoids
　　Early developer version of Plasma Desktop with Plasmoids
　　Widgets are downloadable interactive virtual tools that provide services such as showing the user the latest news, the current weather, the time, a calendar, a dictionary, a map program, a calculator, desktop notes, photo viewers, or even a language translator, among other things.
　　Examples of widget engines include:
　　* Dashboard widgets of Apple Macintosh
　　* Microsoft gadgets in Windows Vista and in the Windows Live system
　　* Plasmoids are widgets in Plasma the workspace for the KDE desktop environment.
　　* gDesklets of Linux systems.
　　* Panels or gadgets in Google Desktop
　　* Yahoo! Widgets
　　* Klips in Klipfolio
　　* Mobile widgets, WidSets
　　Originally, desk accessories were developed to provide a small degree of multitasking, but when real multitasking OSes became available, these were replaced by normal applications.
　　Early examples of widgets were desk accessories on Mac OS (these, however, cannot access the internet). The Active Desktop system, developed by Microsoft, was the first system to enable desktop objects with internet access.[verification needed] Widgets resemble the tiny freeware apps that were developed by enthusiasts during the 80s.
　　On 9 November 2006, the Web Application Formats Working Group in W3C released the first public working draft of Widgets 1.0.[1] Widget is on its way to standardization.
　　Mobile widgets
　　Most mobile widgets are like desktop widgets, but for a mobile phone. Mobile widgets can maximize screen space use and may be especially useful in placing live data-rich applications on the device home-screen/"phone-top". Several J2ME-based mobile widget engines exist including WidSets, WidX, Webwag and BluePulse. However the lack of standards-based APIs for Java to control the mobile device home-screen make it harder for these engines to expose widgets on the phone-top.
　　Several AJAX-based widget platforms are also available for mobile devices including Access' NetFront, Openwave's MIDAS and Opera's Opera Platform.
　　Information flow of Desktop Widgets
　　A desktop widget is a small footprint application, which resides on the user’s desktop using a small desktop space and computer resources, such as the HDD and RAM. Its purpose is to provide relevant information to the user in a non-intrusive manner and using few resources. Basically, desktop widgets enable the user view on demand, capsuled information from predetermined data sources. Ideally, a desktop widget must present personalized content, based on the user’s preferences. It is supposed to beam the most important information that a user requires on a day to day basis. Most of the desktop widgets are available as free downloads from the vendors’ Web sites.