gobject_gdb.py is a GDB script that helps when debugging GObject code—regardless of language. It contains frame decorators for prettifying the signal emission chain, if you break into it.
GLib also has a glib_gdb.py which adds a gforeach command that can be used to pretty print the contents of a GList*, GSList*, or GHashTable* references.
The existence of these extensions is documented in the GLib reference, but I’ve realised I missed the section’s title, so I’ve just fixed it.