Added multiple selection feature to wxPropertyGrid (enabled by setting wxPG_EX_MULTIPLE_SELECTION style)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@61681 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/propgrid/manager.h

@@ -388,6 +388,12 @@ public:
     */
     bool IsPageModified( size_t index ) const;
 
+    /**
+        Returns true if property is selected. Since selection is page
+        based, this function checks every page in the manager.
+    */
+    virtual bool IsPropertySelected( wxPGPropArg id ) const;
+
     /**
         Removes a page.