Set line numbers only while in normal mode

Question

I don't have much use for line numbers while in insert mode so I would like to turn them off. However they are great for normal mode.

Constantly using set nu! is tiresome. Is there a way to tie set nu! to exiting and entering normal mode?

Any solutions using the above or any other method?

Answer 1

You can do this with autocommands.

au InsertEnter * set nonumber
au InsertLeave * set number

Not much explanation is needed. This does exactly what you asked for. It ties "entering and exiting insert mode" to "turning line numbers on and off".

Answer 2

Here's an alternative solution which will only hide the numbers, but won't actually change the margin on the left so you text doesn't jump around so much when entering/leaving insert mode:

set number

augroup number
    autocmd!
    autocmd InsertEnter * highlight LineNr ctermfg=white guifg=white
    autocmd InsertLeave * highlight LineNr ctermfg=130 guifg=Brown
augroup end

When entering insert mode this will set the text colour to the background colour. In my case this is white, but this may be different in your case. When we leave insert mode it resets it to the default for my colour scheme.

You can find out the default for your colour scheme with:

:highlight LineNr
LineNr         xxx term=underline ctermfg=130 guifg=Brown