Whether the text-based or window-based debugger is used is controlled
using the predicates guitracer/0
Entering debug mode is controlled using the normal predicates for this: trace/0
In addition, PceEmacs prolog mode provides the command
Prolog/Break at (
Control-c b) to insert a
break-point at a specific location in the source code.
The graphical tracer is particulary useful for debugging threads. The
tracer must be loaded from the
main thread before it can be
used from a background thread.