WPF - Add ExperimentalExtensions.UsePopupMouseTransform to allow for custom implementation

Issue #2820

Author: amaitland

CefSharp.Wpf/Experimental/ExperimentalExtensions.cs

@@ -2,11 +2,34 @@
 
 namespace CefSharp.Wpf.Experimental
 {
+    /// <summary>
+    /// Experimental Extensions
+    /// </summary>
     public static class ExperimentalExtensions
     {
+        /// <summary>
+        /// Html dropdown goes off screen when near bottom of page by default
+        /// Calling this method to use the <see cref="MousePositionTransform"/> implementation
+        /// to reopsition Popups and mouse.
+        ///
+        /// Issue https://github.com/cefsharp/CefSharp/issues/2820
+        /// </summary>
+        /// <param name="chromiumWebBrowser">browser</param>
         public static void UsePopupMouseTransform(this ChromiumWebBrowser chromiumWebBrowser)
         {
             chromiumWebBrowser.MousePositionTransform = new MousePositionTransform();
         }
+
+        /// <summary>
+        /// Use a custom <see cref="IMousePositionTransform"/> implemntation
+        /// </summary>
+        /// <param name="chromiumWebBrowser">browser</param>
+        /// <param name="mousePositionTransform">custom implementation of <see cref="IMousePositionTransform"/>
+        /// or defaults to <see cref="NoOpMousePositionTransform"/> if null.
+        /// </param>
+        public static void UsePopupMouseTransform(this ChromiumWebBrowser chromiumWebBrowser, IMousePositionTransform mousePositionTransform)
+        {
+            chromiumWebBrowser.MousePositionTransform = mousePositionTransform ?? new NoOpMousePositionTransform();
+        }
     }
 }