Called when the source is finalized. At this point, the source
will have been destroyed, had its callback cleared, and have been removed
from its #GMainContext, but it will still have its final reference count,
so methods can be called on it from within this function.
Called when the source is finalized. At this point, the source will have been destroyed, had its callback cleared, and have been removed from its #GMainContext, but it will still have its final reference count, so methods can be called on it from within this function.