An application sends the IMC_GETCOMPOSITIONWINDOW message to an IME window to get the position of the composition window. Because the IME may adjust the position of a composition window, an application uses this message to get the actual position to decide whether to reposition the window.
msg = (UINT) WM_IME_CONTROL;
wParam = (WPARAM) IMC_GETCOMPOSITIONWINDOW;
lParam = (LPARAM) &CompForm;
Returns zero if successful, nonzero otherwise.
The returned position is in window coordinates relative to the window having the current input focus.