detecting insert-normal mode

Question

I notice that when in insert, pressing <C-o> will take me to normal mode, but once I finish pressing a sequence of keys, I get taken back to insert mode. I find this very useful, but I want a way of programatically detecting this, so I can reflect the difference in my statusline. The help page for mode() only mentions normal mode, whereas I can see with set showmode, vim displays -- (insert) -- instead of -- INSERT -- so clearly it differentiates between the two to some extent.

Note; I have set noshowmode set because I want to have just my statusline display the mode. I am looking for a way to do this without using showmode.

Answer 1

The help page for mode() only mentions normal mode

That's not true. The help page (:h mode()) is quite complete. You have to supply an optional argument for the mode() function.

let s:mode = mode(1)
if s:mode[0] ==# 'n'
    if s:mode[1] ==# 'i'
        " normal using i_CTRL-O
    elseif s:mode[1] ==# 'o'
        " normal Operator-pending
    else
        " just normal
    endif
endif

If :h mode() page does not mention niI, niR etc. then this version of Vim does not support this feature and should be updated first.