An application sends the IMC_SETCANDIDATEPOS message to an IME window to set the position of the candidate window. This message is intended for applications that display composition characters on their own but use the IME window to display candidates.
msg = (UINT) WM_IME_CONTROL;
wParam = (WPARAM) IMC_SETCANDIDATEPOS;
lParam = (LPARAM) &CandForm;
Return zero if successful, nonzero otherwise.