CB_GETDROPPEDSTATE
wParam = 0; /* not used, must be zero */
lParam = 0L; /* not used, must be zero */
An application sends a CB_GETDROPPEDSTATE message to determine whether the list box of a combo box is visible (dropped down).
This message has no parameters.
The return value is nonzero if the list box is visible; otherwise, it is zero.
This example determines whether the list box of a combo box is visible:
BOOL fDropped;
fDropped = (BOOL) SendDlgItemMessage(hdlg, ID_MYCOMBOBOX,
CB_GETDROPPEDSTATE, 0, 0L);