When a selected IME needs information about the font used by the composition window, the IMR_COMPOSITIONFONT message is sent to the application through the WM_IME_REQUEST message.
lParam= (LPARAM) lpLOGFONT;
Returns a nonzero value if the application filled in the LOGFONT structure specified by lParam. Otherwise, returns zero.
This notification may be sent by the IME to a window that cleared the ISC_SHOWUICOMPOSITIONWINDOW flag in the WM_SETCONTEXT message handler.
Input Method Editor Overview, Input Method Editor Messages, WM_IME_REQUEST