document GetWheelAxis

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@57078 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/event.h

@@ -1683,6 +1683,14 @@ public:
     */
     int GetWheelRotation() const;
 
+    /**
+        Gets the axis the wheel operation concerns; @c 0 is the Y axis as on
+        most mouse wheels, @c 1 is the X axis.
+
+        Note that only some models of mouse have horizontal wheel axis.
+    */
+    int GetWheelAxis() const;
+
     /**
         Returns X coordinate of the physical mouse event position.
     */