http://bugs.winehq.org/show_bug.cgi?id=16466
--- Comment #16 from Mikolaj Zalewski mikolaj.zalewski@gmail.com 2009-01-12 15:37:49 --- I ment dlls/comctl32/tests/treeview.c.
If you are not sure, then you should check it before submitting the patch. It seems there are no text callback tests, but it should be easy to add one. You should add some handling of TVN_GETDISPINFO to MyWndProc to return e.g. "abc". Add an item with LPSTR_CALLBACK and do a TVN_GETITEM to check if it works. Then add another item with a text e.g. "xyz" and do a TVN_SETITEM with TVIF_TEXT and NULL. Use TVN_GETITEM on this second item to check what it returns.
Of course, you should run this test on Windows to make sure the results are correct and then modify Wine so that it also passes it. Your test should be failing before your modifications and passing after them.