Outputs and Surface Management

The output and surface management is defined in src/outputs.rs. It handles multi-monitor support and layer surface creation.

The Outputs Struct

#![allow(unused)]
fn main() {
pub struct Outputs {
    entries: Vec<(OutputKey, Option<ShellInfo>, Option<OutputId>)>,
    toast: Option<OverlaySurface>,      // Notification toast surface (if shown)
    osd: Option<OverlaySurface>,        // OSD surface (if shown)
    // ...
    visibility: BarVisibility,          // Shown or Hidden (toggled via SIGUSR1/IPC)
}
}

Each entry in entries represents a known monitor:

Field	Type	Description
Key	`OutputKey`	Monitor `name` (e.g., `"eDP-1"`, or `"Fallback"`) and `description` (name + make + model, used for matching configured targets)
ShellInfo	`Option<ShellInfo>`	Layer surfaces for this output (if active)
OutputId	`Option<OutputId>`	Wayland output ID (if discovered)

ShellInfo

#![allow(unused)]
fn main() {
pub struct ShellInfo {
    pub id: SurfaceId,           // Main surface ID
    pub position: Position,      // Top or Bottom
    pub layer: config::Layer,    // Wayland layer
    pub layout: BarLayout,       // Surface mode + resolved outer margin
    pub menu: Menu,              // Menu surface state
    pub scale_factor: f64,
    pub output_logical_height: Option<u32>, // For computing toast input regions
}
}

Surface Creation

Each output gets a bar layer surface created via create_output_layers():

#![allow(unused)]
fn main() {
fn create_output_layers<Message: 'static>(
    layout: BarLayout,
    output_id: Option<OutputId>,
    position: Position,
    layer: config::Layer,
    scale_factor: f64,
    visibility: BarVisibility,
) -> (SurfaceId, Task<Message>) {
    // Main layer: "ashell-main-layer"
    //   - Anchored to top or bottom edge + left + right
    //   - Exclusive zone = bar height + margin (0 when hidden)
    //   - Keyboard interactivity: None
}
}

The geometry (anchor, size, exclusive zone, margin, input region) comes from Outputs::bar_geometry(). Menu surfaces are not created up front: a fullscreen "ashell-menu-layer" surface is created when a menu opens and destroyed when it closes (see Menu System). The notification toast and OSD are separate overlay surfaces, created on demand by show_toast_layer() / show_osd_layer().

HasOutput Enum

Used in App::view() to determine what to render for a given surface ID:

#![allow(unused)]
fn main() {
pub enum HasOutput<'a> {
    Main,                       // Render the bar
    Menu(Option<&'a OpenMenu>), // Render the menu (if open)
    Toast,                      // Render notification toasts
    Osd,                        // Render the OSD
}
}

Sync on Config Change

When the config changes, Outputs::sync() reconciles the current surfaces with the new configuration:

Creates surfaces for newly targeted outputs
Destroys surfaces for outputs no longer targeted
Recreates surfaces whose layer changed
Updates position, layout, and scale factor for existing surfaces

Adding and Removing Outputs

When Wayland reports output events:

Output added: If the output matches the config filter (All/Active/Targets), create surfaces for it.
Output removed: Destroy the associated surfaces.
Fallback: At startup a "Fallback" bar surface (not bound to an output) is used until real outputs are detected; the first added output replaces it. If removing an output leaves no bar surfaces, a new fallback surface is created.

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