Returns TRUE when the wildmenu is active and FALSE otherwise. See 'wildmenu' and 'wildmode'. This can be used in mappings to handle the 'wildcharm' option gracefully. (Makes only sense with mapmode-c mappings).

For example to make <c-j> work like <down> in wildmode, use:

:cnoremap <expr> <C-j> wildmenumode() ? "\<Down>\<Tab>" : "\<c-j>"

(Note, this needs the 'wildcharm' option set appropriately).