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Event handlers

When an event takes place (e.g. selecting a menu entry, clicking an action button, ...) the AppBasic manager calls a special procedure known as an event handler. If an application wishes to specify how the event is to be handled (responded to) the definition of an appropriate event-handler should be placed in the !RunImage directory. The three fundamental types of event are Toolbox events, Wimp events and the initial event. They each have associated sets of event-handlers.

menu/gifBASIC files containing ‘skeleton’ definitions of event-handlers can be automatically placed in !RunImage by selecting leaf entries from the Event handlers submenu of the application processing menu. Programming consists essentially of ‘filling in’ the details of these skeleton definitions. Other procedures can be called whose definitions should then also be placed in !RunImage.

The application processing menu is popped up by dragging the application onto AppBasic's iconbar icon or double-clicking the application while holding down the Ctrl key.