Wayland Socket Binding

Bind a child process to a Wayland socket by setting WAYLAND_DISPLAY in its environment.

Overview

When spawning a Wayland client (e.g. a GTK4 app, a panel, a wallpaper daemon), the client needs to know which Wayland display to connect to. This is done via the WAYLAND_DISPLAY environment variable.

ProcessConfig::socket(Some(socket)) tells ProcessManager to extract the socket name (the last path component, e.g. wayland-0) from the Socket and set it as WAYLAND_DISPLAY in the child’s environment.

Example

#![allow(unused)]
fn main() {
use process_manager::{ProcessConfig, ProcessManager, StdioConfig};
use process_manager_socket::{SocketBuilder, SocketManager};

// Create and register a socket
let socket = SocketBuilder::build(&None)?;
let socket_manager = SocketManager::new();
socket_manager.register("default", socket)?;
let socket = socket_manager.get("default").unwrap().clone();

// Spawn a process bound to the socket
let manager = ProcessManager::new();
let config = ProcessConfig::builder()
    .command("gtk4-app".to_string())
    .socket(Some(socket))
    .stdout(StdioConfig::Null)
    .stderr(StdioConfig::Null)
    .build();

let id = manager.start("wayland-client", &config)?;
}

Multi-Output Example

In a multi-output compositor, each output may have its own socket. Clients spawned for a specific output should be bound to that output’s socket:

#![allow(unused)]
fn main() {
use process_manager_socket::{SocketBuilder, SocketManager};
use process_manager::{ProcessConfig, ProcessManager, StdioConfig};

let socket_manager = SocketManager::new();

// Register sockets for each output
socket_manager.register("eDP-1", SocketBuilder::build(&Some("wayland-0".to_string()))?)?;
socket_manager.register("HDMI-1", SocketBuilder::build(&Some("wayland-1".to_string()))?)?;

let manager = ProcessManager::new();

// Spawn a panel on eDP-1
let edp_socket = socket_manager.get("eDP-1").unwrap().clone();
let panel_config = ProcessConfig::builder()
    .command("smearor-swipe-launcher".to_string())
    .socket(Some(edp_socket))
    .stdout(StdioConfig::Null)
    .stderr(StdioConfig::Null)
    .build();
manager.start("panel-eDP-1", &panel_config)?;

// Spawn a wallpaper on HDMI-1
let hdmi_socket = socket_manager.get("HDMI-1").unwrap().clone();
let wallpaper_config = ProcessConfig::builder()
    .command("swaybg".to_string())
    .args(vec!["--image".to_string(), "/path/to/wallpaper.jpg".to_string()])
    .socket(Some(hdmi_socket))
    .stdout(StdioConfig::Null)
    .stderr(StdioConfig::Null)
    .build();
manager.start("wallpaper-HDMI-1", &wallpaper_config)?;
}

How It Works

When config.socket is Some(socket):

1. ProcessManager::start() extracts the socket name from the Socket path (e.g. wayland-0 from /run/user/1000/wayland-0)
2. The socket name is inserted into the child’s environment as WAYLAND_DISPLAY=wayland-0
3. The child process connects to the Wayland display using this environment variable

If config.socket is None, WAYLAND_DISPLAY is not set - the child inherits the parent’s WAYLAND_DISPLAY if present.