Quote Originally Posted by Schmidt View Post
DefWindowProcW is just "a more direct SendMessageW-replacement" (which bypasses the current WinProc-Handler) -
and as already reported, the Unicode-Caption is "landed" just fine per WM_SETTEXT in the hWnd in question
(since it can be successfully retrieved in Unicode-Format per WM_GETTEXT as well).

As Krool was mentioning, it is the WM_NCPaint-message which is finally responsible for the rendering
of that now successfully placed W-String-Caption.
Probably could have worded my response so people didn't have to review the thread I linked to, but the gist is rather simple: If themed, DefWindowProcW can be used else DefWindowProcA typically applies for VB forms. And DefWindowProcA doesn't do unicode.