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

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

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

• DtvLong idb: Mask Id
• DTV_LAY_LNR_TYP typ: Enumeration type, for masks DTV_LAY_MAS
• char *fnc_nam: Name of the calling mask-changing function

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.