The FMEVENT_INITMENU message is sent to an extension DLL when the user selects the menu for the extension from the File Manager menu bar. The extension can use this notification to initialize menu items in the menu.
FMEVENT_INITMENU hmenu = (HMENU) lParam; /* handle of File Manager menu */
An extension DLL should return zero if it processes this message.
An extension DLL receives this message only when the user selects the top-level menu. If the extension contains submenus, it must initialize them at the same time it initializes the top-level menu.