perf: don't compute diffs of running-apps; directly get new/old

src/api-wrappers/HelperExtensions.swift

@@ -315,7 +315,7 @@ extension DispatchTimeInterval {
 }
 
 extension NSRunningApplication {
-    var id: String { "pid:\(String(describing: processIdentifier)) app:\(bundleIdentifier ?? bundleURL?.absoluteString ?? executableURL?.absoluteString ?? localizedName ?? "nil")"  }
+    func debugId() -> String { "pid:\(String(describing: processIdentifier)) app:\(bundleIdentifier ?? bundleURL?.absoluteString ?? executableURL?.absoluteString ?? localizedName ?? "nil")"  }
 }
 
 // 250ms is similar to human delay in processing changes on screen

src/logic/events/RunningApplicationsEvents.swift

@@ -2,26 +2,22 @@ import Cocoa
 
 class RunningApplicationsEvents {
     private static var appsObserver: NSKeyValueObservation!
-    private static var previousValueOfRunningApps: Set<NSRunningApplication>!
 
     static func observe() {
-        previousValueOfRunningApps = Set(NSWorkspace.shared.runningApplications)
         // we can't observe NSWorkspace.didLaunchApplicationNotification or NSWorkspace.didTerminateApplicationNotification
         // these only trigger for some apps, mostly GUI app. We need to track all processes as any could spawn a window
-        appsObserver = NSWorkspace.shared.observe(\.runningApplications, options: [.old, .new], changeHandler: { (_, _) in handleEvent() })
+        appsObserver = NSWorkspace.shared.observe(\.runningApplications, options: [.old, .new], changeHandler: { (_, change) in handleEvent(change) })
     }
 
-    private static func handleEvent() {
-        let workspaceApps = Set(NSWorkspace.shared.runningApplications)
-        let added = workspaceApps.subtracting(previousValueOfRunningApps)
-        let removed = previousValueOfRunningApps.subtracting(workspaceApps)
-        Logger.info("added:", added.map { $0.id }, "removed:", removed.map { $0.id })
-        if !added.isEmpty {
-            Applications.addRunningApplications(Array(added))
+    private static func handleEvent(_ change: NSKeyValueObservedChange<[NSRunningApplication]>) {
+        let added = change.newValue
+        let removed = change.oldValue
+        Logger.debug("added:", added?.map { $0.debugId() }, "removed:", removed?.map { $0.debugId() })
+        if let added {
+            Applications.addRunningApplications(added)
         }
-        if !removed.isEmpty {
-            Applications.removeRunningApplications(Array(removed))
+        if let removed {
+            Applications.removeRunningApplications(removed)
         }
-        previousValueOfRunningApps = workspaceApps
     }
 }