wayland-server 0.20.3

Bindings to the standard C implementation of the wayland protocol, server side.
Documentation

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 tighly 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 a struct implementing the Implementation<Resource<I>, I::Request> trait, where I is the interface of the considered object:

// Example implementation for the wl_surface interface
use wayland_server::Resource;
use wayland_server::protocol::wl_surface;
use wayland_server::commons::Implementation;

struct MyImpl {
   // ...
}

impl Implementation<Resource<wl_surface::WlSurface>, wl_surface::Request> for MyImpl {
    fn receive(&mut self, msg: wl_surface::Request, resource: Resource<wl_surface::WlSurface>) {
        // process the message...
    }
}
# fn main() {}

The trait is also automatically implemented for FnMut(I::Request, Resource<I>) closures, so you can use them for simplicity if a full struct would be too cumbersome.

The Resource<I> passed to your implementation is garanteed 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).

The crate also provides an event loop structure. An EventLoop is automatically created at the same time as the Display, and it will handle the connections of your wayland clients. See the EventLoop API documentation for explanations of its use.

It is also possible to both create other event loops and insert other kind of sources of events to the event loops. These functions are typically useful to integrate, as a wayland compositor, with other parts of the system (typically listening on file destrictor describing input devices). Adding sources to an event loop is done via the LoopToken type, that is retrieved by the token() method of EventLoop. See their documentations for more details.