An application sends the IMC_SETCOMPOSITIONFONT message to an IME window to specify the logical font to use for displaying intermediate characters in the composition window.
msg = (UINT) WM_IME_CONTROL;
wParam = (WPARAM) IMC_SETCOMPOSITIONFONT;
lParam = (LPARAM) &LogFont;
Returns zero if successful, nonzero otherwise.
When processing this message, the IME window changes the current selected font in the input context.