Set SSO Presentation Sheets modal

Riot/Modules/Reauthentication/ReauthFallBackViewController.swift

@@ -39,6 +39,12 @@ final class ReauthFallBackViewController: AuthFallBackViewController, Themable {
         self.setupNavigationBar()
         self.registerThemeServiceDidChangeThemeNotification()
         self.update(theme: self.theme)
+
+        // Tchap: block dismissal of this Reauthentication sheet by dragging down.
+        // The user must use the close button.
+        if #available(iOS 13.0, *) {
+            self.isModalInPresentation = true
+        }
     }
 
     // MARK: - Public

Riot/Modules/Settings/DeactivateAccount/DeactivateAccountViewController.m

@@ -351,9 +351,19 @@ - (void)presentFallbackForURL:(NSURL *)url
 {
     MXLogDebug(@"[DeactivateAccountViewController] Show fallback for url: %@", url)
     SFSafariViewController *safariViewController = [[SFSafariViewController alloc] initWithURL:url];
-    safariViewController.modalPresentationStyle = UIModalPresentationFormSheet;
+    // Tchap: set modalPresentationStyle to 'currentContext' to enable safariViewController to be presented modaly.
+//    safariViewController.modalPresentationStyle = UIModalPresentationFormSheet;
+    safariViewController.modalPresentationStyle = UIModalPresentationCurrentContext;
+
     safariViewController.delegate = self;
 
+    // Tchap: block dismissal of this SFSafariViewController sheet by dragging down.
+    // Else, the underlying activity indicator is not removed.
+    // The user must use the close button.
+    if (@available(iOS 13.0, *)) {
+        safariViewController.modalInPresentation = true;
+    }
+
     [self presentViewController:safariViewController animated:YES completion:nil];
 }