Add wxDataViewCtrl::GenericGetHeader() accessor

And show how to use it to increase the header size in the sample.

include/wx/dataview.h

@@ -30,6 +30,7 @@
 
 class WXDLLIMPEXP_FWD_CORE wxImageList;
 class WXDLLIMPEXP_FWD_CORE wxItemAttr;
+class WXDLLIMPEXP_FWD_CORE wxHeaderCtrl;
 
 #if !(defined(__WXGTK20__) || defined(__WXOSX__) ) || defined(__WXUNIVERSAL__)
 // #if !(defined(__WXOSX__)) || defined(__WXUNIVERSAL__)

include/wx/generic/dataview.h

@@ -263,6 +263,11 @@ public:
     wxColour GetAlternateRowColour() const { return m_alternateRowColour; }
     void SetAlternateRowColour(const wxColour& colour);
 
+    // The returned pointer is null if the control has wxDV_NO_HEADER style.
+    //
+    // This method is only available in the generic versions.
+    wxHeaderCtrl* GenericGetHeader() const;
+
 protected:
     void EnsureVisibleRowCol( int row, int column );