Compositor Service and Abstraction Layer

The compositor service (src/services/compositor/) abstracts over multiple Wayland compositors, with dedicated backends for Hyprland, Niri, and MangoWC and a generic Wayland fallback for other compositors.

Architecture

services/compositor/
├── mod.rs       # Service trait impl, backend detection, broadcast system
├── types.rs     # CompositorState, CompositorEvent, CompositorCommand, CompositorChoice
├── hyprland.rs  # Hyprland IPC integration
├── niri.rs      # Niri IPC integration
├── mangowc.rs   # MangoWC integration (via the `mmsg` IPC CLI)
└── generic.rs   # Generic Wayland fallback (ext-workspace / wlr-foreign-toplevel)

Backend Detection

The compositor is detected automatically, falling back to the generic backend when no dedicated one matches:

#![allow(unused)]
fn main() {
fn detect_backend() -> Option<CompositorChoice> {
    if hyprland::is_available() {         // Checks HYPRLAND_INSTANCE_SIGNATURE
        Some(CompositorChoice::Hyprland)
    } else if niri::is_available() {      // Checks NIRI_SOCKET / NIRI_SOCKET_PATH
        Some(CompositorChoice::Niri)
    } else if mangowc::is_available() {   // Probes `mmsg get version`
        Some(CompositorChoice::Mango)
    } else if generic::is_available() {   // Checks WAYLAND_DISPLAY
        Some(CompositorChoice::Generic)
    } else {
        None
    }
}
}

The detected backend is stored in a global OnceLock and never changes during the process lifetime.

Broadcast Pattern

Unlike other services that use direct channels, the compositor service uses a broadcast pattern via tokio::sync::broadcast:

#![allow(unused)]
fn main() {
static BROADCASTER: OnceCell<broadcast::Sender<ServiceEvent<CompositorService>>> =
    OnceCell::const_new();
}

This allows multiple subscribers (e.g., Workspaces, WindowTitle, KeyboardLayout modules) to receive the same compositor events without duplication.

Flow

Compositor IPC Socket
    │
    ▼ (single listener thread)
broadcaster_event_loop()
    │
    ▼ broadcast::Sender::send()
    ├── Subscriber 1 (Workspaces module)
    ├── Subscriber 2 (WindowTitle module)
    ├── Subscriber 3 (KeyboardLayout module)
    └── Subscriber 4 (KeyboardSubmap module)

Each call to CompositorService::subscribe() creates a new broadcast::Receiver, getting all events from that point forward.

CompositorState

The unified state across all backends:

#![allow(unused)]
fn main() {
pub struct CompositorState {
    pub workspaces: Vec<CompositorWorkspace>,
    pub monitors: Vec<CompositorMonitor>,
    pub active_workspace_ids: Vec<i32>,
    pub active_window: Option<ActiveWindow>,
    pub keyboard_layout: String,
    pub submap: Option<String>,
}
}

CompositorEvent

#![allow(unused)]
fn main() {
pub enum CompositorEvent {
    ActionPerformed,                        // Command completed successfully
    StateChanged(Box<CompositorState>),    // Full state update
}
}

CompositorCommand

Commands that can be sent to the compositor:

#![allow(unused)]
fn main() {
pub enum CompositorCommand {
    FocusWorkspace(i32),
    FocusNamedWorkspace(String),
    FocusSpecialWorkspace(String),
    FocusMonitor(i128),
    ToggleSpecialWorkspace(String),
    ScrollWorkspace(i32),           // +1 or -1
    CustomDispatch(String, String), // For "vdesk"
    NextLayout,
}
}

Backend Implementations

Hyprland (hyprland.rs)

Uses the hyprland crate for IPC communication:

• Connects to Hyprland’s Unix domain socket
• Listens for events (workspace changes, window focus, layout changes)
• Sends commands via the dispatcher

Niri (niri.rs)

Uses the niri-ipc crate:

• Connects to Niri’s IPC socket (path from NIRI_SOCKET env var)
• Listens for events and translates them to the common CompositorEvent format
• Sends commands via the IPC protocol

MangoWC (mangowc.rs)

Drives MangoWC through its mmsg IPC CLI:

• Watches mmsg watch all-monitors for change events and rebuilds the full state from each one
• Maps MangoWC tags onto workspaces; since several tags can be active at once, it reports them all via CompositorState::active_workspace_ids
• Sends commands by shelling out to mmsg dispatch

Generic Wayland (generic.rs)

Fallback for compositors without a dedicated backend, using standard Wayland protocols on a single connection:

• wl_output for monitors, ext-workspace-v1 for workspaces, and wlr-foreign-toplevel-management for the active window
• Rebuilds the full CompositorState on every change
• Only FocusWorkspace is supported as a command; others return an error