A visualizer is a Prolog predicate reacting to FDBG events (see FDBG Events). It is called directly by the FDBG core when any FDBG event occurs. It is called visualizer, because usually it should present the events to the user, but in general it can do any kind of processing, like checking invariants, etc.
For all major event classes, a different visualizer type is used. The
set of visualizers you would like to use for a session is specified in
the option list of fdbg_on/1 (see FDBG Options), when
FDBG is switched on.
A specific visualizer can have several arguments, some are supplied by the FDBG core, the rest (if any) should be specified when FDBG is switched on. Note that the obligatory arguments will be appended to the end of the user defined argument list.
The set of built-in visualizers installed by default (see FDBG Options) is the following:
fdbg_show
fdbg_label_show
For details on built-in visualizers, see FDBG Built-In Visualizers.