An application sends a CB_GETEXTENDEDUI message to determine whether a combo box has the default user interface or the extended user interface.
CB_GETEXTENDEDUI
wParam = 0; // not used; must be zero
lParam = 0; // not used; must be zero
This message has no parameters.
If the combo box has the extended user interface, the return value is TRUE; otherwise, it is FALSE.
By default, the f4 key opens or closes the list and the down arrow changes the current selection. In a combo box with the extended user interface, the f4 key is disabled and pressing the down arrow key opens the drop-down list.
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_SETEXTENDEDUI