// a callback function used for sorting tree items, it should return -1 if the
// first item precedes the second, +1 if the second precedes the first or 0 if
// they're equivalent
-class WXDLLIMPEXP_CORE wxTreeItemData;
+class WXDLLIMPEXP_FWD_CORE wxTreeItemData;
typedef int (*wxTreeItemCmpFunc)(wxTreeItemData *item1, wxTreeItemData *item2);
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