fix: avoid macos bug where many permission dialogs pop (closes #5106)

src/logic/events/WindowCaptureEvents.swift

@@ -56,11 +56,12 @@ class WindowCaptureScreenshots {
     }
 
     private static func oneTimeCapture(_ scWindow: SCWindow, _ source: RefreshCausedBy) {
+        guard !App.app.isTerminating else { return }
         let config = SCStreamConfiguration.forWindow(scWindow, false)
         let filter = SCContentFilter(desktopIndependentWindow: scWindow)
-        SCScreenshotManager.captureSampleBuffer(contentFilter: filter, configuration: config) { sampleBuffer, error in
-            guard let sampleBuffer, error == nil else { Logger.error { "\(sampleBuffer == nil) \(error)" }; return }
+        ActiveWindowCaptures.increment()
         SCScreenshotManager.captureImage(contentFilter: filter, configuration: config) { cgImage, error in
+            ActiveWindowCaptures.decrement()
             guard let cgImage, error == nil else { Logger.error { "\(cgImage == nil) \(error)" }; return }
             guard source != .refreshOnlyThumbnailsAfterShowUi || App.app.appIsBeingUsed else { return }
             DispatchQueue.main.async {
@@ -89,9 +90,12 @@ class WindowCaptureScreenshotsPrivateApi {
     }
 
     private static func oneTimeCapture(_ wid: CGWindowID) -> CGImage? {
+        guard !App.app.isTerminating else { return nil }
         // we use CGSHWCaptureWindowList because it can screenshot minimized windows, which CGWindowListCreateImage can't
         var windowId_ = wid
+        ActiveWindowCaptures.increment()
         let list = CGSHWCaptureWindowList(CGS_CONNECTION, &windowId_, 1, [.ignoreGlobalClipShape, .bestResolution, .fullSize]).takeRetainedValue() as! [CGImage]
+        ActiveWindowCaptures.decrement()
         return list.first
     }
 }
@@ -282,3 +286,27 @@ extension CMSampleBuffer {
         return device.makeTexture(descriptor: desc, iosurface: surface, plane: 0)
     }
 }
+
+class ActiveWindowCaptures {
+    private static var count: Int = 0
+    private static let semaphore = DispatchSemaphore(value: 1)
+
+    static func increment() {
+        semaphore.wait()
+        count += 1
+        semaphore.signal()
+    }
+
+    static func decrement() {
+        semaphore.wait()
+        count -= 1
+        semaphore.signal()
+    }
+
+    static func value() -> Int {
+        semaphore.wait()
+        let current = count
+        semaphore.signal()
+        return current
+    }
+}

src/main.swift

@@ -5,9 +5,9 @@ if let command = CliClient.detectCommand() {
     CliClient.sendCommandAndProcessResponse(command)
 }
 
-// - if the app is quit/force-quit from Activity Monitor, it will receive SIGTERM and applicationWillTerminate won't be called
-// - if the app crashes in swift code (e.g. unexpected nil object), SIGTRAP is sent
-// we intercept these signals, and do an emergency exit
+// - SIGTERM: if the app is quit/force-quit from Activity Monitor, it will receive SIGTERM and applicationWillTerminate won't be called
+// - SIGTRAP: if the app crashes in swift code (e.g. unexpected nil object), SIGTRAP is sent
+// - SIGKILL: if we stop the app using SIGKILL (e.g. stopping from IntelliJ, or from the terminal), there is no chance to intercept it
 [SIGTERM, SIGTRAP].forEach {
     signal($0) { s in
         emergencyExit("Exiting after receiving signal", s)
@@ -34,5 +34,18 @@ fileprivate func emergencyExit(_ logs: Any?...) {
     setNativeCommandTabEnabled(true)
     print(logs)
     printStackTrace()
+    makeSureAllCapturesAreFinished()
     exit(0)
 }
+
+func makeSureAllCapturesAreFinished() {
+    App.app.isTerminating = true
+    let timeout = 5.0
+    let startTime = DispatchTime.now()
+    var elapsedTime = 0.0
+    while ActiveWindowCaptures.value() > 0 && elapsedTime <= timeout {
+        Logger.warning { "There are \(ActiveWindowCaptures.value()) screenshots in progress. We need to wait for them to avoid a bug where macOS shows permission dialogs to the user for no reason." }
+        Thread.sleep(forTimeInterval: 0.1)
+        elapsedTime = Double(DispatchTime.now().uptimeNanoseconds - startTime.uptimeNanoseconds) / 1_000_000_000
+    }
+}

src/ui/App.swift

@@ -17,6 +17,7 @@ class App: AppCenterApplication {
     static let website = "https://alt-tab-macos.netlify.app"
     static let appIcon = CGImage.named("app.icns")
     static var app: App!
+    var isTerminating = false
     var thumbnailsPanel: ThumbnailsPanel!
     var previewPanel: PreviewPanel!
     var preferencesWindow: PreferencesWindow!
@@ -331,6 +332,12 @@ extension App: NSApplicationDelegate {
         // symbolic hotkeys state persist after the app is quit; we restore this shortcut before quitting
         setNativeCommandTabEnabled(true)
     }
+
+    func applicationShouldTerminate(_ sender: NSApplication) -> NSApplication.TerminateReply {
+        Logger.info { "" }
+        makeSureAllCapturesAreFinished()
+        return .terminateNow
+    }
 }
 
 enum RefreshCausedBy {