How Events Are Handled (Magic xpa 4.x)

As mentioned earlier, only the main program’s events can be revealed for the use of host applications. The revealed events then become part of the host application in the same way that a revealed program becomes a part of the application. Component events are handled in the Runtime task tree in the same way as regular events are handled.

As an example of the way an event is handled, let's take a look at the figure above. Here, a component program raises an event, which is handled along the task tree. In other words, a handler for this event will first be searched in Program C, then in the main program of the component, then in Program A, which called Program C, and finally in the host main program. When there is a handler in each program, as in the current example, the handler will be handled accordingly along the task tree. If the handler propagate property is set to No in any of the programs, that handler will be the last handler for that event in the task tree.

If Program A were to raise the event, a handler would only be searched in the host application, in other words in Program A and in the host main program.

More information about the way events are handled may be found in the MSE Concept Paper on Event-Driven Architecture.