int dal_but_set_lfp (idm, fnc)

Sets a button-listener callback function.

Input Parameters Significance
DtvLong idm button area Id
BUT_FNC_LAY_LNR fnc pointer to button-listener function

Output Parameters Significance
none -

Return Code Significance
0 all OK
1 old button-listener function was overwritten
-1 no button area Id passed

With the help of the button-listener callback function you can react on changes to the local button area structure. The button-listener function is automatically invoked by all functions that change button areas, such as dal_but_cre_sel.

The button-listener function must correspond to the specification void fnc(idb, typ, fnc_nam, par). The parameters are:

If the same listener function is used for all objects (menus, button areas, masks), the enumeration type DTV_LAY_LNR_TYP can be used to determine from which object the listener function was called.