An FDBG event can (currently) belong to one of the two following major classes:

constraint event

A constraint is woken.

labeling event

Three events belong to this class, namely:

These events are intercepted by the FDBG core. When any of them occurs, the appropriate visualizer (see FDBG Visualizers) gets called with a representation of the event (a Prolog term) as extra arguments.

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