NAME
        ActivateGadget -- Activate a (string or custom) gadget.

    SYNOPSIS
        Success = ActivateGadget( gadget, window, request )
        D0                        A0      A1      A2

        bool activategadget( struct gadget *, struct window *,
                struct requester * );

    FUNCTION
        Activates a string or custom gadget.  If successful, this means
        that the user does not need to click in the gadget before typing.

        The window parameter must point to the window which contains the gadget.
        If the gadget is actually in a requester, the window must contain
        the requester, and a pointer to the requester must also be
        passed. The requester parameter must only be valid if the gadget
        has the GTYP_REQGADGET flag set, a requirement for all requester
        gadgets.

        The success of this function depends on a rather complex set
        of conditions.  The intent is that the user is never interrupted from
        what interactions he may have underway.

        The current set of conditions includes:
        -   The window must be active.  If you are opening a new window
            and want an active gadget in it, it is not sufficient to
            assume that the WFLG_ACTIVATE flag has taken effect by the time
            openwindow() returns, even if you insert a delay of some
            finite amount of time.  Use the IDCMP_ACTIVEWINDOW intuimessage
            to tell when your window really becomes active.  Many
            programs use an event loop that calls ActivateGadget()
            whenever they receive the IDCMP_ACTIVEWINDOW message, and also
            the IDCMP_MOUSEBUTTONS messages, and so on, to keep the
            gadget active until it is used (or the user selects some
            other "Cancel" gadget).

        -   No other gadgets may be in use.  This includes system gadgets,
            such as those for window sizing, dragging, etc.
        -   If the gadget is in a requester, that requester must
            be active. (Use IDCMP_REQSET and IDCMP_REQCLEAR).
        -   The right mouse button cannot be held down (e.g. menus)

        NOTE: Don't try to activate a gadget which is disabled or
        not attached to a window or requester.

    INPUTS
        gadget = pointer to the gadget that you want activated.
        window = pointer to a window structure containing the gadget.
        requester = pointer to a requester (may by null if this isn't
           a requester gadget (i.e. GTYP_REQGADGET is not set)).

    RESULT
        If the conditions above are met, and the gadget is in fact a string
        gadget, then this function will return TRUE, else FALSE.

    BUGS
        At present, this function will not return FALSE if a custom
        gadget declines to be activated.

    SEE ALSO