[Video] Visibility detection view (#4741)

Co-authored-by: Samuel Newman <10959775+mozzius@users.noreply.github.com>

modules/expo-bluesky-swiss-army/ios/Visibility/VisiblityView.swift

@@ -0,0 +1,69 @@
+import ExpoModulesCore
+
+class VisibilityView: ExpoView {
+  var enabled = false {
+    didSet {
+      if enabled {
+        VisibilityViewManager.shared.removeView(self)
+      }
+    }
+  }
+
+  private let onChangeStatus = EventDispatcher()
+  private var isCurrentlyActiveView = false
+
+  required init(appContext: AppContext? = nil) {
+    super.init(appContext: appContext)
+  }
+
+  public override func willMove(toWindow newWindow: UIWindow?) {
+    super.willMove(toWindow: newWindow)
+
+    if !self.enabled {
+      return
+    }
+
+    if newWindow == nil {
+      VisibilityViewManager.shared.removeView(self)
+    } else {
+      VisibilityViewManager.shared.addView(self)
+    }
+  }
+
+  func setIsCurrentlyActive(isActive: Bool) {
+    if isCurrentlyActiveView == isActive {
+      return
+    }
+    self.isCurrentlyActiveView = isActive
+    self.onChangeStatus([
+      "isActive": isActive
+    ])
+  }
+}
+
+// 🚨 DANGER 🚨
+// These functions need to be called from the main thread. Xcode will warn you if you call one of them
+// off the main thread, so pay attention!
+extension UIView {
+  func getPositionOnScreen() -> CGRect? {
+    if let window = self.window {
+      return self.convert(self.bounds, to: window)
+    }
+    return nil
+  }
+
+  func isViewableEnough() -> Bool {
+    guard let window = self.window else {
+      return false
+    }
+
+    let viewFrameOnScreen = self.convert(self.bounds, to: window)
+    let screenBounds = window.bounds
+    let intersection = viewFrameOnScreen.intersection(screenBounds)
+
+    let viewHeight = viewFrameOnScreen.height
+    let intersectionHeight = intersection.height
+
+    return intersectionHeight >= 0.5 * viewHeight
+  }
+}