An application sends a CB_GETDROPPEDSTATE message to determine whether the list box of a combo box is dropped down.
CB_GETDROPPEDSTATE
wParam = 0; // not used; must be zero
lParam = 0; // not used; must be zero
This message has no parameters.
If the list box is visible, the return value is TRUE; otherwise, it is FALSE.
Windows NT: Requires version 3.1 or later.
Windows: Requires Windows 95 or later.
Windows CE: Requires version 1.0 or later.
Header: Declared in winuser.h.
Combo Boxes Overview, Combo Box Messages, CB_SHOWDROPDOWN