The FMEVENT_INITMENU message is sent to an extension dynamic-link library (DLL) when the user selects the menu for the extension from File Manager's menu bar. The extension can use this notification to initialize menu items in the menu.
lParam
Specifies the menu handle in the high-order word. The low-order word specifies the delta value for the menu item.
This message does not return a value.
An extension 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 as the top-level menu.