Post an error if the client attempts to create input panel surface for surface...
Post an error if the client attempts to create input panel surface for surface that already has role
If a client attempts to create an input panel surface for a wl_surface that already has a role assigned, we must post a protocol error or else the behavior of the input panel surface will be undefined.
Posting an error of 0 is not really correct, but on the other hand the spec has no any error enums.