Support signals in introspection XML

[semafor]

Looking at the code, and based on experiments, it does not look like dbusmock currently supports mocking pre-existing signals. It supports EmitSignals, but though I lack the appropriate terminology, it seems there are emitted signals and pre-existing signals?

E.g. using qt, connecting to a signal known to exist on an interface, I get:

QObject::connect: No such signal com::canonical::SystemImage::DownloadStarted() in …systemimage.cpp:99

[martinpitt]

The D-Bus specification just has "signals"; they all get emitted somewhere (that's the point of them), and otherwise behave pretty much like a method call without a return call/value.

What could happen there is that signals don't appear in the interface introspection XML, as they don't get declared? And whatever code you use may rely on that?