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import Foundation
/// Retains the handler for the lifetime of the registration.
///
/// The raw pointer returned by ``Notifier/register(_:handler:)``
/// is a retained reference to this box; it is released when
/// the registration is cancelled.
private final class NotifyBox {
let handler: @Sendable () -> Void
init(_ handler: @escaping @Sendable () -> Void) { self.handler = handler }
}
/// Delivers refresh triggers via Darwin notifications.
///
/// Wraps CoreFoundation notifications — the macOS-native,
/// signal-like way to trigger behaviour from the shell with
/// no client binary, using `notifyutil`:
///
/// ```
/// notifyutil -p <prefix><name>
/// ```
///
/// Each category of events uses a different ``prefix``
/// to avoid collisions. For example, block refresh
/// notifications use ``touchPrefix``:
///
/// ```
/// notifyutil -p house.panini.phbar.touch.<name>
/// ```
///
/// > Note: `notify.h` isn't part of Swift's Darwin module,
/// > so we go through `CFNotificationCenter`, which talks
/// > to the same subsystem.
/// >
/// > The callback fires on an arbitrary thread; handlers
/// > must hop to the main actor themselves (see ``AppDelegate``).
enum Notifier {
/// Prefix for block refresh notifications.
///
/// Use `notifyutil -p house.panini.phbar.touch.<name>` to trigger
/// a block update from the shell.
static let touchPrefix = "house.panini.phbar.touch."
/// Register `handler` to fire whenever the notification is posted.
///
/// - Parameters:
/// - name: The notification name suffix.
/// - prefix: The full notification name will be `prefix + name`.
/// Defaults to ``touchPrefix``.
/// - handler: Closure to invoke when the notification fires.
///
/// The returned token is a retained pointer used to keep the handler
/// alive and to cancel the registration later. The handler runs on an
/// arbitrary thread, so hop to the main actor inside it if you touch
/// UI or published state.
@discardableResult
static func register(
_ name: String,
prefix: String = Notifier.touchPrefix,
handler: @escaping @Sendable () -> Void
) -> UnsafeMutableRawPointer {
let fullName = prefix + name
let ctx = Unmanaged.passRetained(NotifyBox(handler)).toOpaque()
CFNotificationCenterAddObserver(
CFNotificationCenterGetDarwinNotifyCenter(),
ctx,
{ _, observer, _, _, _ in
guard let observer else { return }
let box = Unmanaged<NotifyBox>.fromOpaque(observer).takeUnretainedValue()
box.handler()
},
fullName as CFString,
nil,
.deliverImmediately
)
return ctx
}
/// Remove and release a registration.
///
/// Pass the token returned by ``Notifier/register(_:handler:)``.
/// Optional: process exit clears all pending registrations anyway.
static func cancel(_ token: UnsafeMutableRawPointer) {
let center = CFNotificationCenterGetDarwinNotifyCenter()
CFNotificationCenterRemoveEveryObserver(center, token)
Unmanaged<NotifyBox>.fromOpaque(token).release()
}
}
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