Make column width calculations in wxDataViewCtrl and wxHeaderCtrl consistent.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@70338 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/headerctrl.h

@@ -374,6 +374,13 @@ public:
      */
     bool ShowCustomizeDialog();
 
+    /**
+        Returns width needed for given column's title.
+
+        @since 2.9.4
+     */
+    int GetColumnTitleWidth(const wxHeaderColumn& col);
+
 protected:
     /**
         Method to be implemented by the derived classes to return the