Refactor PasswordSetupUI, PassportUI, GalleryUI and related modules

submodules/ScreenCaptureDetection/Sources/ScreenCaptureDetection.swift

@@ -0,0 +1,77 @@
+import Foundation
+import SwiftSignalKit
+import UIKit
+
+public enum ScreenCaptureEvent {
+    case still
+    case video
+}
+
+private final class ScreenRecordingObserver: NSObject {
+    let f: (Bool) -> Void
+    
+    init(_ f: @escaping (Bool) -> Void) {
+        self.f = f
+        
+        super.init()
+        
+        UIScreen.main.addObserver(self, forKeyPath: "captured", options: [.new], context: nil)
+    }
+    
+    func clear() {
+        UIScreen.main.removeObserver(self, forKeyPath: "captured")
+    }
+    
+    override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
+        if keyPath == "captured" {
+            if let value = change?[.newKey] as? Bool {
+                self.f(value)
+            }
+        }
+    }
+}
+
+private func screenRecordingActive() -> Signal<Bool, NoError> {
+    return Signal { subscriber in
+        if #available(iOSApplicationExtension 11.0, iOS 11.0, *) {
+            subscriber.putNext(UIScreen.main.isCaptured)
+            let observer = ScreenRecordingObserver({ value in
+                subscriber.putNext(value)
+            })
+            return ActionDisposable {
+                Queue.mainQueue().async {
+                    observer.clear()
+                }
+            }
+        } else {
+            subscriber.putNext(false)
+            return EmptyDisposable
+        }
+    } |> runOn(Queue.mainQueue())
+}
+
+public func screenCaptureEvents() -> Signal<ScreenCaptureEvent, NoError> {
+    return Signal { subscriber in
+        let observer = NotificationCenter.default.addObserver(forName: UIApplication.userDidTakeScreenshotNotification, object: nil, queue: .main, using: { _ in
+            subscriber.putNext(.still)
+        })
+        
+        var previous = false
+        let screenRecordingDisposable = screenRecordingActive().start(next: { value in
+            if value != previous {
+                previous = value
+                if value {
+                    subscriber.putNext(.video)
+                }
+            }
+        })
+        
+        return ActionDisposable {
+            Queue.mainQueue().async {
+                NotificationCenter.default.removeObserver(observer)
+                screenRecordingDisposable.dispose()
+            }
+        }
+    }
+    |> runOn(Queue.mainQueue())
+}