Adds stickyRow/Column-Header options

If set to `true` the header always stays at the top. Even if the user bounces.

Framework/Sources/SpreadsheetView+Layout.swift

@@ -35,6 +35,17 @@ extension SpreadsheetView {
         layoutRowHeader()
         layoutColumnHeader()
 
+        if self.stickyRowHeader {
+            self.rowHeaderView.frame.origin.y = min(self.rootView.contentOffset.y, 0)
+            self.rowHeaderView.contentOffset.x = self.tableView.contentOffset.x
+            self.cornerView.frame.origin.y = min(self.rootView.contentOffset.y, 0)
+        }
+        if self.stickyColumnHeader {
+            self.columnHeaderView.frame.origin.x = min(self.rootView.contentOffset.x, 0)
+            self.columnHeaderView.contentOffset.y = self.tableView.contentOffset.y
+            self.cornerView.frame.origin.x = min(self.rootView.contentOffset.x, 0)
+        }
+
         if needsReload {
             adjustScrollViewFrames()
 

Framework/Sources/SpreadsheetView.swift

@@ -219,6 +219,20 @@ public class SpreadsheetView: UIView {
             tableView.alwaysBounceHorizontal = newValue
         }
     }
+
+    /// A Boolean value that determines wheather the row header always sticks to the top.
+    /// - Note: `bounces` has to be `true` and there has to be at least one `frozenRow`.
+    /// The default value is `false`.
+    ///
+    /// - SeeAlso: `stickyColumnHeader`
+    public var stickyRowHeader: Bool = false
+
+    /// A Boolean value that determines wheather the column header always sticks to the top.
+    /// - Note: `bounces` has to be `true` and there has to be at least one `frozenColumn`.
+    /// The default value is `false`.
+    ///
+    /// - SeeAlso: `stickyRowHeader`
+    public var stickyColumnHeader: Bool = false
 
     /// A Boolean value that determines whether paging is enabled for the scroll view.
     /// - Note: If the value of this property is `true`, the scroll view stops on multiples of the scroll view’s bounds when the user scrolls.