Struct HostState 

pub struct HostState {
    pub pending_window_creations: VecDeque<PendingWindowCreation>,
    pub browser_panes: HashMap<String, BrowserPaneEntry>,
    pub browsers: HashMap<String, BrowserHandle>,
    pub active_drag: Option<DragSession>,
    pub pool: PoolState,
    pub quit_state: QuitState,
    pub top_level_creation: TopLevelCreationState,
    pub window_opacities: HashMap<String, f32>,
    pub lifecycle: HostLifecyclePhase,
    pub event_version: u64,
}

State owned by the host reducer.

Held inside AppState.host_state: parking_lot::Mutex<HostState>. Locked briefly by host_dispatch; never held across CEF callbacks or SendMessage (snapshot-and-drop discipline — see spec §6).

Fields

pending_window_creations: VecDeque<PendingWindowCreation>

FIFO queue of pre-create handoffs. Pushed by callers (pane/creation.rs, commands/window.rs::open_new_window, commands/drag.rs::tear_off, commands/window_pool.rs::spawn_pool_window) before post_create_window. Popped by client.rs::on_after_created when CEF reports a new browser. Peeked at the back by wrr/win_event.rs::handle_event to label OS-level WM_CREATE events with the upcoming label.

Invariants:

• At most one entry per (in-flight) browser create.
• on_after_created always pops the head it expects to find.
• The “main” window is special-cased in on_after_created and never has a corresponding entry here.

browser_panes: HashMap<String, BrowserPaneEntry>

H.1 — pane lifecycle map. Replaces the deleted pane::lifecycle::PaneStateMachine. Keyed by block_id. Authoritative; BrowserPaneManager (browser_panes.rs) is now a zero-sized handle that delegates all mutations through host_dispatch.

browsers: HashMap<String, BrowserHandle>

H.2 — browser handle registry. Replaces the deleted AppState.browsers: Mutex<HashMap<String, Browser>>. Keyed by label (e.g., window-..., browser-pane-..., window-pool-...). Authoritative; read via AppState::get_browser, list_browsers, etc.

active_drag: Option<DragSession>

H.3 — active drag session (singleton). Replaces the deleted AppState.active_drag: Mutex<Option<DragSession>>.

pool: PoolState

H.4 — pool state (queue + unpromoted + in-flight semaphore + just_promoted_labels bridge from PR #708). Replaces the deleted window_pool / unpromoted_pool_labels fields on AppState.

quit_state: QuitState

H.5 — quit lifecycle. Replaces the deleted AppState.is_quitting: AtomicBool.

top_level_creation: TopLevelCreationState

H.6 — top-level window creation runner state (queue, in-flight, history). Event-driven; no watchdog. Currently DORMANT — the reducer arms (EnqueueTopLevelWindow, TopLevelCallbackFired, etc.) exist but no production code dispatches to them. The ui_tasks::post_create_window direct-call path is still authoritative. Wire-up is a low-priority structural improvement; see master spec §4.3 and discussion #707.

window_opacities: HashMap<String, f32>

Per-window opacity state. Keyed by label, value is clamped [0.0, 1.0]. Absent means fully opaque (1.0). Mutated by SetWindowOpacity; read by get_window_opacity and the restore path in app-init. Win32 side-effect (SetLayeredWindowAttributes) is applied by the IPC handler AFTER dispatch, not inside the reducer. See SPEC_PER_WINDOW_OPACITY_2026-05-14.md §7.1.

lifecycle: HostLifecyclePhase

Lifecycle phase. Running is the operating state; the others gate command acceptance.

event_version: u64

Monotonic event-version counter (per host-process run). Same invariant as launcher / srv reducers.

Implementations

impl HostState

fn bump_version(&mut self) -> u64

Allocate the next event version. Called inside reducer arms when emitting an event.

Trait Implementations

impl Default for HostState

fn default() -> Self

Returns the “default value” for a type.