Server-side Wayland connector
Overview
This crate provides the interfaces and machinery to safely create servers
for the wayland protocol. It is a rust wrapper around the libwayland-server.so
C library.
The wayland protocol revolves around the creation of various objects and the exchange
of messages associated to these objects. Whenever a client connects, a Display object
is automatically created in their object space, which they use as a root to create new
objects and bootstrap their state.
Protocol and messages handling model
The protocol being bi-directional, you can send and receive messages. Sending messages is
done via methods of Resource<_> objects, receiving and handling them is done by providing
implementations.
Resources
The protocol and message model is very similar to the one of wayland-client, with the
main difference being that the handles to objects are represented by the Resource<I>
type.
These resources are used to send messages to the clients (they are called "events" in the
wayland context). This is done by the Resource::<I>::send(..) method.
There is not a 1 to 1 mapping between Resource<I> instances and protocol objects. Rather,
you can think of Resource<I> as an Rc-like handle to a wayland object. Multiple instances
of it can exist referring to the same protocol object.
Similarly, the lifetimes of the protocol objects and the Resource<I> are not tightly tied.
As protocol objects are created and destroyed by protocol messages, it can happen that an object
gets destroyed while one or more Resource<I> still refers to it. In such case, these resources
will be disabled and their alive() method will start to return false. Events that are
subsequently sent to them are ignored.
Implementations
To receive and process messages from the clients to you (in wayland context they are
called "requests"), you need to provide an Implementation for each wayland object
created in the protocol session. Whenever a new protocol object is created, you will
receive a NewResource<I> object. Providing an implementation via its implement() method
will turn it into a regular Resource<I> object.
All objects must be implemented, even if it is an implementation doing nothing.
Failure to do so (by dropping the NewResource<I> for example) can cause future fatal
protocol errors if the client tries to send a request to this object.
An implementation is just an FnMut(I::Request, Resource<I>) where I is the interface
of the considered object.
The Resource<I> passed to your implementation is guaranteed to be alive (as it just received
a request), unless the exact message received is a destructor (which is indicated in the API
documentations).
Event loops and general structure
The core of your server is the Display object. It represent the ability of your program to
process wayland messages. Once this object is created, you can configure it to listen on one
or more sockets for incoming client connections (see the Display docs for details).
To properly function, this wayland implementation also needs an event loop structure,
which is here provided by the calloop crate. It is a public dependency and is reexported
as wayland_server::calloop.