- wxPosition& operator +=(const wxPosition& pos) const;
- wxPosition& operator -=(const wxPosition& pos) const;
- wxPosition& operator +=(const wxSize& size) const;
- wxPosition& operator -=(const wxSize& size) const;
+ wxPosition& operator +=(const wxPosition& pos);
+ wxPosition& operator -=(const wxPosition& pos);
+ wxPosition& operator +=(const wxSize& size);
+ wxPosition& operator -=(const wxSize& size);