Engineering

PermissionCoordinator: probing macOS without freezing the UI

Yome TeamApr 6, 20264 min read

The 个人设置 screen used to stutter every second. Root cause: PermissionCoordinator was running 13 synchronous LaunchServices / EventKit / Accessibility probes on the main actor at 1 Hz. Diagnosis was easy; the fix is the part worth writing down.

Three changes, one fix

First, every probe became a nonisolated static helper — probeCalendar, probeReminder, probeAccessibility, probeAutomationItem, probeAutomationStatus. Second, refresh() now dispatches the entire batch onto Task.detached(.utility) and only hops back to MainActor to publish the diff. Third, polling backed off from 1 s to 5 s, with an isRefreshing coalescing flag so concurrent calls collapse.

PermissionCoordinator.swift⟡swift

func refresh() {
  guard !isRefreshing else { return }
  isRefreshing = true
  Task.detached(priority: .utility) { [weak self] in
    let snap = Self.probeAll()
    await MainActor.run {
      self?.publishIfChanged(snap)
      self?.isRefreshing = false
    }
  }
}

MainActor + sync IO never mix

Even one synchronous LaunchServices probe on the main thread stalls SwiftUI long enough to drop a frame. The general pattern: any system probe goes off-main; only the diff publish hops back.

Result

个人设置 reopen latency dropped from ~180 ms to instant; CPU at idle dropped to baseline. No change to public API — pure internal refactor.

1	func refresh() {
2	guard !isRefreshing else { return }
3	isRefreshing = true
4	Task.detached(priority: .utility) { [weak self] in
5	let snap = Self.probeAll()
6	await MainActor.run {
7	self?.publishIfChanged(snap)
8	self?.isRefreshing = false
9	}
10	}
11	}