Scarriffle
dccf8671b2
git-subtree-dir: CalendarrKit git-subtree-mainline:8bc32faa7fgit-subtree-split:9ea1a8705d
63 lines
2.6 KiB
Swift
63 lines
2.6 KiB
Swift
import Foundation
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/// Cross-process "the snapshot changed" broadcast.
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///
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/// Two sandboxed apps cannot see each other's `NotificationCenter`, and neither
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/// can poll the container cheaply. Darwin notifications are the one signal that
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/// crosses the process boundary without an extra entitlement, a running
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/// connection, or a shared framework.
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///
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/// The payload is always empty — Darwin notifications carry no data. The signal
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/// means only "read again". If it is ever missed, a consumer that also reloads
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/// on window activation degrades to a slightly stale view rather than a wrong one.
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public enum SnapshotChangeNotifier {
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public static let name = "com.scarriffleservices.calendarr.snapshot-changed"
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/// Announce that the snapshot was rewritten. Called by `SnapshotStore`.
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public static func post() {
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CFNotificationCenterPostNotification(
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CFNotificationCenterGetDarwinNotifyCenter(),
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CFNotificationName(name as CFString),
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nil, nil, true)
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}
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/// Start listening. The handler runs on an arbitrary thread, so hop to
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/// whatever actor your UI needs before touching state.
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///
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/// Returns a token you must keep alive; deinit removes the observer.
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public static func observe(_ handler: @escaping @Sendable () -> Void) -> ObservationToken {
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ObservationToken(handler: handler)
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}
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public final class ObservationToken: @unchecked Sendable {
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private let handler: @Sendable () -> Void
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fileprivate init(handler: @escaping @Sendable () -> Void) {
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self.handler = handler
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// Darwin notifications hand back no context pointer we can rely on
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// across process boundaries, so route through an unretained pointer
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// to this token and look it up in the callback.
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let observer = Unmanaged.passUnretained(self).toOpaque()
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CFNotificationCenterAddObserver(
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CFNotificationCenterGetDarwinNotifyCenter(),
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observer,
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{ _, observer, _, _, _ in
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guard let observer else { return }
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Unmanaged<ObservationToken>.fromOpaque(observer)
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.takeUnretainedValue().handler()
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},
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SnapshotChangeNotifier.name as CFString,
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nil,
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.deliverImmediately)
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}
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deinit {
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CFNotificationCenterRemoveObserver(
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CFNotificationCenterGetDarwinNotifyCenter(),
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Unmanaged.passUnretained(self).toOpaque(),
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CFNotificationName(SnapshotChangeNotifier.name as CFString),
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nil)
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}
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}
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}
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