WsEventRouting — Specs

Summary

WsEventRouting is the pure decision layer for incoming WindowServer notifications: it decodes a raw notification id into a known Notification, maps each to the model Action it implies, and exposes one fact the dispatcher needs (whether the payload carries a Space id). It holds no state and does no IPC — WindowServerEvents turns these decisions into model mutations. Same pure-decision-kernel pattern as SelectionResolver; it superseded the AX event-routing layer that mapped AX notifications to these same actions before WindowServer became the source of window state.

Reverse-engineered id map (the evidence)

Established live on macOS 26 by registering SLSRegisterConnectionNotifyProc across a wide id range and driving each change: 806 moved, 807 resized, 811 created, 804 destroyed, 815/816 ordered-in/out, 808 the focused/front window changed (confirmed cross-app and intra-app), 1325/1326 added/removed-from-Space, 1329 current-Space, 1401 active-Space. Notes that shape the actions:

• Minimize is not its own event — minimizing emits 816 (ordered-out), same as hiding; the action is refreshVisibility, after which WsWindowState reads the minimized bit.
• Space notifications (1325/1326) carry (spaceId, wid) in the payload — membership is free, no query.
• Created (811) ⇒ acquireAndDiscriminate — the wid may be untracked; we must obtain its AX element and run WindowDiscriminator before showing it.

Test scenarios

Mirrors WsEventRoutingTests.swift 1:1.

A. Notification decoding

• testKnownIdsDecode — each confirmed id decodes to its Notification case.
• testUnknownIdsAreNil — heartbeat/other ids (1502, 1503, 1322, 0, 999) decode to nil.

B. Action mapping

• testActionForEachNotification — created→acquireAndDiscriminate, destroyed→remove, moved/resized→updateGeometry, focused→bumpFocusOrder, orderedIn/orderedOut→refreshVisibility, added/removed-Space→updateSpaceMembership, current/active-Space→spaceTransition.

C. Payload

• testOnlySpaceMembershipNotificationsCarrySpaceId — added/removed-from-Space carry a Space id; all others do not.