5 The MLWorks Motif Interface Library

5.9 Events

Events are implemented similarly to callbacks. To add an event handler to a widget, use the function Xm.Event.addHandler. This corresponds to the C function XtAddEventHandler. The event mask is specified by a list of constructors of the Xm.Event.make type. The handler function itself takes an argument of the abstract type Xm.Event.event_data, which can be converted to concrete data using the Xm.Event.convertEvent function.

The Xm.Event.event datatype defines the concrete data resulting from converting the abstract type. Particular classes of events are defined by the expose_event, motion_event, button_event, and key_event types.

The values of the button and state fields of the event datatypes are not automatically converted to ML values, because they aren't always needed. When these values are needed, they must be explicitly converted using the convertState and convertButton functions.

MLWorks Reference Manual (version 1.0) - 3 DEC 1996

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