Callback for top card if trait collection changes (#18)

Author: nighthawk

Sources/TGCardViewController/TGCardViewController.swift

@@ -470,6 +470,8 @@ open class TGCardViewController: UIViewController {
     // to landscape mode, the card will be in the extended state, which requires
     // the card's contents to be scrollable. Hence, we reenable the scolling.
     updateCardScrolling(allow: true, view: topCardView)
+    
+    topCard?.traitCollectionDidChange(previousTraitCollection)
   }
 
   private func updateCardScrolling(allow: Bool, view: TGCardView?) {

Sources/TGCardViewController/cards/TGCard.swift

@@ -270,6 +270,14 @@ open class TGCard: UIResponder, TGPreferrableView {
     viewIsVisible = false
   }
 
+  /// Called when the card is the top card and the trait collection of the TGCardViewController change
+  ///
+  /// Get the current/new trait collection by calling `controller?.traitCollection`.
+  ///
+  /// - Parameter previousTraitCollection: Previous trait collection, if any
+  open func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
+  }
+  
   /// Called when the card moved, potentially to a new position
   ///
   /// - Parameters: