Show alert when user tries to activate local video without camera permissions.

// FREEBIE

Signal/src/call/CallService.swift

@@ -779,6 +779,37 @@ protocol CallServiceObserver: class {
     func setHasLocalVideo(hasLocalVideo: Bool) {
         assertOnSignalingQueue()
 
+        let authStatus = AVCaptureDevice.authorizationStatus(forMediaType:AVMediaTypeVideo)
+        switch authStatus {
+        case .notDetermined:
+            Logger.debug("\(TAG) authStatus: AVAuthorizationStatusNotDetermined")
+            break
+        case .restricted:
+            Logger.debug("\(TAG) authStatus: AVAuthorizationStatusRestricted")
+            break
+        case .denied:
+            Logger.debug("\(TAG) authStatus: AVAuthorizationStatusDenied")
+            break
+        case .authorized:
+            Logger.debug("\(TAG) authStatus: AVAuthorizationStatusAuthorized")
+            break
+        }
+
+        // TODO: We could also check this whenever the app returns from the background,
+        //       since the user could disable this priviledge at all times.
+        if authStatus != .authorized {
+            DispatchQueue.main.async {
+                let title = NSLocalizedString("CAMERA_PERMISSION_MISSING_TITLE", comment: "Alert title when camera is not authorized")
+                let message = NSLocalizedString("CAMERA_PERMISSION_MISSING_BODY", comment: "Alert body when camera is not authorized")
+                let okButton = NSLocalizedString("OK", comment:"")
+
+                let alert = UIAlertView(title:title, message:message, delegate:nil, cancelButtonTitle:okButton)
+                alert.show()
+            }
+
+            return
+        }
+
         guard let peerConnectionClient = self.peerConnectionClient else {
             handleFailedCall(error: .assertionError(description:"\(TAG) peerConnectionClient unexpectedly nil in \(#function)"))
             return

Signal/translations/en.lproj/Localizable.strings

@@ -68,7 +68,7 @@
 "ATTACHMENT_QUEUED" = "New attachment queued for retrieval.";
 
 /* No comment provided by engineer. */
-"AUDIO_PERMISSION_MESSAGE" = "Signal requires access to your microphone to work properly. You can restore the permission in the Settings app >> Privacy >> Microphone >> Signal";
+"AUDIO_PERMISSION_MESSAGE" = "Signal requires access to your microphone to work properly. You can grant this permission in the Settings app >> Privacy >> Microphone >> Signal";
 
 /* Accessibilty label for placing call button */
 "CALL_LABEL" = "Call";
@@ -76,6 +76,12 @@
 /* notification action */
 "CALLBACK_BUTTON_TITLE" = "Call back";
 
+/* Alert body when camera is not authorized */
+"CAMERA_PERMISSION_MISSING_BODY" = "Signal requires access to your camera for video calls. You can grant this permission in the Settings app >> Privacy >> Camera >> Signal";
+
+/* Alert title when camera is not authorized */
+"CAMERA_PERMISSION_MISSING_TITLE" = "Error";
+
 /* Activity Sheet label */
 "COMPARE_SAFETY_NUMBER_ACTION" = "Compare with Clipboard";