Event Polling (Magic xpa 4.x)
This topic discusses when the runtime engine handles events.
A handler that corresponds to an event is not necessarily immediately invoked when the event is triggered. The point when a handler is invoked depends on the event type and the way it is triggered.
In some cases handlers are executed immediately when the event for which they are defined is triggered.
Synchronous Raise Event Operation
A handler whose event is triggered by a synchronous Raise Event operation is invoked immediately when the Raise Event operation is executed.
Error Event
A handler defined to handle an Error event is immediately invoked when the event is triggered.
Other events enter an event queue when they are triggered. The engine polls the events in this queue at pre-set times. The handlers are invoked when events are polled out of the event queue.
Asynchronous Raise Event Operations
An event triggered by an asynchronous Raise Event operation is entered into the event queue to be handled later.
System, Internal, Timer, and User Events
All events, other than Error events, are entered into the event queue when they are triggered.
Expression Events
Expression events are also entered into the event queue when they are triggered. However, they are not immediately triggered when the expression evaluates to a True value. The expression evaluates each time period when the keyboard was idle. The Keyboard idle time is an environment setting defined in the Environment dialog box. The expression is evaluated when the Keyboard idle time interval passes, and if it evaluates to a True value, the event is triggered and enters the event queue.
In this section, you can find information about:
Polling the Events from the Queue
