I did it using a function. I tested it, but maybe in some particular case you will have to fix some bugs. Try adding this to your vimrc:
set et
function! Inserttab()
let insert = ""
let line = getline('.')
let pos = getpos('.')[2]
let before = ""
let after = line
if pos != 1
let before = line[ 0: pos - 1]
let after = line[pos : strlen(line) ]
endif
if pos != 1 && substitute(before, "[ \t]", "", "g") != ""
let insert = "\t"
else
let insert = " "
endif
let line = before . insert . after
call setline('.', line)
call cursor(line('.'), strlen(before . insert))
endfunction
inoremap <tab> <esc>:call Inserttab()<CR>a
Basicaly it does remap your key in visual mode to the function Inserttab(). Also note that if you change ts for something other than 4 it will still output 4 spaces instead of two because the value is hard coded.
Also im not very familiar with vim scripts, but I think all the variables used will be global which is a bad thing.
I forgot to mention that to "see" white spaces you can use set list
. You disable this with set nolist
. Also in normal mode you can use ga
to see information about the character your cursor is on.
Edit
I realise that you may want to insert tab at the beginin of the line. My script insert space at the begining and tab anywhere else.
If you really want a tab every time you hit tab key you could simply use this:
set et
function! Inserttab()
let insert = ""
let line = getline('.')
let pos = getpos('.')[2]
let before = ""
let after = line
if pos != 1
let before = line[ 0: pos - 1]
let after = line[pos : strlen(line) ]
endif
let insert = "\t"
let line = before . insert . after
call setline('.', line)
call cursor(line('.'), strlen(before . insert))
endfunction
inoremap <tab> <esc>:call Inserttab()<CR>a
But I dont see the point, with this version you will never be able to indent manually from insert mode.