The interface struct has the type,version and methods of the
interface.
Make spa interfaces extend from spa_interface and make a
separate structure for the methods.
Pass a generic void* as the first argument of methods, like
we don in PipeWire.
Bundle the methods + implementation in a versioned inteface
and use that to invoke methods. This way we can do version
checks on the methods.
Make resource and proxy interfaces that we can can call. We
can then make the core interfaces independent on proxy/resource and
hide them in the lower layers.
Add add_listener method to methods of core interfaces, just
like SPA.
Don't use special callback in node to receive the results. Instead,
use a generic result callback to receive the result. This makes things
a bit more symetric and generic again because then you can choose how
to match the result to the request and you have a generic way to handle
both the sync and async case. We can then also remove the wait method.
This also makes the remote interface and spa interface to objects very
similar.
Make a helper object to receive and dispatch results. Use this in the
helper for enum_params.
Make device use the same result callbacks.
Add return values to events and method callbacks. This makes it
possible to pass any error or async return value.
Add sync/done/error in both directions so that both proxy and resource
and perform/reply sync and produce errors.
Return a SPA_ASYNC from remote method calls (and events), keep the
sequence number in the connection.
With the core sync/done we can remove the client-node done method and
it's internal sequence number along with the seq number in method calls.
We can also use the method/event async return value to perform a sync
with as the unique sequence number for this method.
Add sync method and done/error event to proxy and resource.
Make some more varargs error functions
Make pw_resource_error always just send the error to the resource id.
Make sure we send errors to the right destination.
Add proxy error event and emit it when the core finds an error for
the given proxy id.
The client error is supposed to be sent to all resources of a client
for the given global.
