+WindowHandles gs_windowHandles;
+
+#ifdef wxHAS_MSW_BACKGROUND_ERASE_HOOK
+
+// temporary override for WM_ERASEBKGND processing: we don't store this in
+// wxWindow itself as we don't need it during most of the time so don't
+// increase the size of all window objects unnecessarily
+WX_DECLARE_HASH_MAP(wxWindow *, wxWindow *,
+ wxPointerHash, wxPointerEqual,
+ EraseBgHooks);
+
+EraseBgHooks gs_eraseBgHooks;
+
+#endif // wxHAS_MSW_BACKGROUND_ERASE_HOOK
+
+} // anonymous namespace