Creates a source that triggers if cancellable is cancelled and
calls its callback of type GCancellableSourceFunc. This is
primarily useful for attaching to another (non-cancellable) source
with g_source_add_child_source() to add cancellability to it.
For convenience, you can call this with a NULL GCancellable,
in which case the source will never trigger.
Since 2.28
Creates a source that triggers if cancellable is cancelled and calls its callback of type GCancellableSourceFunc. This is primarily useful for attaching to another (non-cancellable) source with g_source_add_child_source() to add cancellability to it. For convenience, you can call this with a NULL GCancellable, in which case the source will never trigger. Since 2.28