fix: don't hang waiting for faulty apps to reply (closes #182)

src/api-wrappers/AXUIElement.swift

@@ -53,21 +53,27 @@ extension AXUIElement {
     }
 
     func subscribeWithRetry(_ axObserver: AXObserver, _ notification: String, _ pointer: UnsafeMutableRawPointer?, _ callback: (() -> Void)? = nil, _ runningApplication: NSRunningApplication? = nil, _ wid: CGWindowID? = nil, _ attemptsCount: Int = 0) {
-        if let runningApplication = runningApplication, Applications.appsInSubscriptionRetryLoop.first(where: { $0 == String(runningApplication.processIdentifier) + String(notification) }) == nil { return }
-        if let wid = wid, Windows.windowsInSubscriptionRetryLoop.first(where: { $0 == String(wid) + String(notification) }) == nil { return }
-        let result = AXObserverAddNotification(axObserver, self, notification as CFString, pointer)
-        if result == .success || result == .notificationAlreadyRegistered {
-            callback?()
-            stopRetries(runningApplication, wid, notification)
-            return
-        } else if result == .notificationUnsupported || result == .notImplemented {
-            stopRetries(runningApplication, wid, notification)
-            return
+        DispatchQueue.global(qos: .userInteractive).async {
+            DispatchQueue.main.async {
+                if let runningApplication = runningApplication, Applications.appsInSubscriptionRetryLoop.first(where: { $0 == String(runningApplication.processIdentifier) + String(notification) }) == nil { return }
+                if let wid = wid, Windows.windowsInSubscriptionRetryLoop.first(where: { $0 == String(wid) + String(notification) }) == nil { return }
+            }
+            let result = AXObserverAddNotification(axObserver, self, notification as CFString, pointer)
+            if result == .success || result == .notificationAlreadyRegistered {
+                DispatchQueue.main.async { [weak self] in
+                    callback?()
+                    self?.stopRetries(runningApplication, wid, notification)
+                }
+            } else if result == .notificationUnsupported || result == .notImplemented {
+                DispatchQueue.main.async { [weak self] in
+                    self?.stopRetries(runningApplication, wid, notification)
+                }
+            } else {
+                DispatchQueue.global(qos: .userInteractive).asyncAfter(deadline: .now() + .milliseconds(10), execute: { [weak self] in
+                    self?.subscribeWithRetry(axObserver, notification, pointer, callback, runningApplication, wid, attemptsCount + 1)
+                })
+            }
         }
-        DispatchQueue.main.asyncAfter(deadline: .now() + .milliseconds(10), execute: { [weak self] in
-            guard let self = self else { return }
-            self.subscribeWithRetry(axObserver, notification, pointer, callback, runningApplication, wid, attemptsCount + 1)
-        })
     }
 
     func stopRetries(_ runningApplication: NSRunningApplication?, _ wid: CGWindowID?, _ notification: String) {

src/logic/Applications.swift

@@ -15,8 +15,8 @@ class Applications {
 
     static func initialDiscovery() {
         addInitialRunningApplications()
-        observeRunningApplications()
         addInitialRunningApplicationsWindows()
+        observeRunningApplications()
     }
 
     static func addInitialRunningApplications() {
@@ -28,23 +28,18 @@ class Applications {
     }
 
     static func addInitialRunningApplicationsWindows() {
-        // on initial launch, we use private APIs to bring windows from other spaces into the current space, observe them, then remove them from the current space
         let spaces = Spaces.otherSpaces()
         if spaces.count == 0 {
-            Windows.sortByLevel()
-            return
-        }
-        let windows = Spaces.windowsInSpaces(spaces).filter { window in
-            return Windows.list.first(where: { $0.cgWindowId == window }) == nil
-        }
-        if windows.count > 0 {
-            CGSAddWindowsToSpaces(cgsMainConnectionId, windows as NSArray, [Spaces.currentSpaceId])
             Applications.observeNewWindows()
-            Windows.sortByLevel()
-            CGSRemoveWindowsFromSpaces(cgsMainConnectionId, windows as NSArray, [Spaces.currentSpaceId])
-            return
+        } else {
+            let windows = Spaces.windowsInSpaces(spaces)
+            if windows.count > 0 {
+                // on initial launch, we use private APIs to bring windows from other spaces into the current space, observe them, then remove them from the current space
+                CGSAddWindowsToSpaces(cgsMainConnectionId, windows as NSArray, [Spaces.currentSpaceId])
+                Applications.observeNewWindows()
+                CGSRemoveWindowsFromSpaces(cgsMainConnectionId, windows as NSArray, [Spaces.currentSpaceId])
+            }
         }
-        Windows.sortByLevel()
     }
 
     static func addRunningApplications(_ runningApps: [NSRunningApplication]) {
@@ -71,7 +66,15 @@ class Applications {
     }
 
     private static func filterApplications(_ apps: [NSRunningApplication]) -> [NSRunningApplication] {
-        return apps.filter { $0.activationPolicy != .prohibited || $0.bundleIdentifier == "io.github.hluk.CopyQ" }
+        return apps.filter {
+            ($0.activationPolicy != .prohibited ||
+                    // Bug in CopyQ; see https://github.com/hluk/CopyQ/issues/1330
+                    $0.bundleIdentifier == "io.github.hluk.CopyQ" ||
+                    // Bug in Octave.app; see https://github.com/octave-app/octave-app/issues/193#issuecomment-603648857
+                    $0.localizedName == "octave-gui") &&
+                    // bug in Octave.app; see https://github.com/octave-app/octave-app/issues/193
+                    $0.bundleIdentifier != "org.octave-app.Octave"
+        }
     }
 }
 

src/logic/DispatchQueues.swift

@@ -1,5 +1,6 @@
 import Foundation
 
+// OS events should be observed on background threads
 class DispatchQueues {
     static let focusActions = DispatchQueue(label: "focusActions", qos: .userInteractive)
     static let keyboardEvents = DispatchQueue(label: "keyboardEvents", qos: .userInteractive)

src/logic/Spaces.swift

@@ -8,6 +8,7 @@ class Spaces {
 
     static func observeSpaceChanges() {
         NSWorkspace.shared.notificationCenter.addObserver(forName: NSWorkspace.activeSpaceDidChangeNotification, object: nil, queue: nil, using: { _ in
+            debugPrint("OS event", "activeSpaceDidChangeNotification")
             updateCurrentSpace()
             Applications.observeNewWindows()
             let app = App.shared as! App

src/ui/App.swift

@@ -42,7 +42,8 @@ class App: NSApplication, NSApplicationDelegate {
         Keyboard.listenToGlobalEvents(self)
         preferencesWindow = PreferencesWindow()
         UpdatesTab.observeUserDefaults()
-//        Windows.refreshAllThumbnails()
+        // TODO: undeterministic; events in the queue may still be processing; good enough for now
+        DispatchQueue.main.async { Windows.sortByLevel() }
     }
 
     // keyboard shortcuts are broken without a menu. We generated the default menu from XCode and load it