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Replacing the lightline.vim plugin with a custom statusline/tabline

DATE: 2018-01-11

AUTHOR: John L. Godlee

Yesterday I decided, in an effort to remove plugin dependencies in my .vimrc and to learn a bit more about how VIM works, to get rid of lightline.vim[1] and replace it with a statusline and tabline of my own design.

1: https://github.com/itchyny/lightline.vim

Statusline basics

I'v never had any problems with lightline in the year or so that I've been using it. I've never used VIM without lightline in fact. Lightline provides lots of useful information as standard, such as the file name, the cursor position in the file, the file type, and importantly, it changes colour depending on what mode you are in, insert, visual, normal, etc..

Lightline

Lightline insert mode

But, just having lightline do everything for me isn't particularly exciting. So first thing was to see what the default statusline looks like:

Default status line

Very boring, all you can see is the file name.

Ideally, I want some useful information about my document in the statusline, namely in order from most to least wanted:

• What mode I am in
• The file name
• The git branch the file is on
• Whether the file has been modified since the last save
• The file type, e.g. markdown, java, html
• How far through the document I am, as a percentage
• How far through the document I am, as line number
• The column number

All of these, except the git branch, can be easily added to the statusline with code found in the help file for the statusline, (:help statusline)

To add an item to the statusline, in your .vimrc add a line that starts:

set statusline=

Then add one of the 'printf' style codes in the help file. e.g. for the file name, otherwise known as the tail of the filepath (%t):

set statusline=%t

After reloading your .vimrc (:source .vimrc) you will see nothing has changed. Yay!

To test it's actually worked, try adding some other codes:

set statusline=%t%m%y%p%l%c

which produces this:

Status line with content

which is very ugly, and not particularly easy to read, either in the vimrc or in the statusline itself. First, let's rectify this in the .vimrc. I like to separate out my statusline code so that each item or group of items is on its own line. The syntax used below is similar to that used to design a prompt in the bash shell:

set statusline=%t	" file name
set statusline+=%m	" modified?
set statusline+=%y	" file type
set statusline+=%p	" percentage through file
set statusline+=%l	" line number
set statusline+=%c	" column number

Source your .vimrc to see that nothing has changed in the statusline, but the .vimrc is much easier to read.

Now we can break up the information in the statusline a bit, using spaces and special characters.

First, I want a space between certain items, which I can add by adding set statusline+=\ lines to my statusline code. Note the actual space after the \. You can also add normal characters to the statusline. For instance, to break up the line and column number you could add a : by adding set statusline+=::

set statusline=%t	" file name
set statusline+=\ 	" space
set statusline+=%m	" modified?
set statusline+=\ 	" space
set statusline+=%y	" file type
set statusline+=\ 	" space
set statusline+=%p	" percentage through file
set statusline+=\ 	" space
set statusline+=%l	" line number
set statusline+=:	" colon separator
set statusline+=%c	" column number

Status line with spacing between content

Now. I don't really want the information about my position in the file on the left side, I'd rather have it on the right side. I can switch to the right side of the statusline by adding set statusline+=%= before the lines you want to appear on the right side:

set statusline=%t	" file name
set statusline+=\ 	" space
set statusline+=%m	" modified?
set statusline+=\ 	" space
set statusline+=%y	" file type
set statusline+=\ 	" space

set statusline+=%=      " switch to right side

set statusline+=%p	" percentage through file
set statusline+=\ 	" space
set statusline+=%l	" line number
set statusline+=:	" colon separator
set statusline+=%c	" column number

Status line split left and right

So that's the basics of a statusline covered I think. Now onto making our own functions

Custom items and functions in statusline

I didn't come up with the ideas presented here myself, I adapted them from online sources. Three things on my list of desired features in the statusline don't appear as standard codes in the help file, those things are displaying the mode I am in, changing the colour based on the mode, and the git branch.

Display the mode

First let's do the mode, which is fairly easy, because VIM already has a global variable called currentmode, so I just need to give the default outputs some aliases that are easier to read:

let g:currentmode={
    \ 'n'  : 'Normal',
    \ 'no' : 'N·Operator Pending',
    \ 'v'  : 'Visual',
    \ 'V'  : 'V·Line',
    \ '^V' : 'V·Block',
    \ 's'  : 'Select',
    \ 'S'  : 'S·Line',
    \ '^S' : 'S·Block',
    \ 'i'  : 'Insert',
    \ 'R'  : 'R',
    \ 'Rv' : 'V·Replace',
    \ 'c'  : 'Command',
    \ 'cv' : 'Vim Ex',
    \ 'ce' : 'Ex',
    \ 'r'  : 'Prompt',
    \ 'rm' : 'More',
    \ 'r?' : 'Confirm',
    \ '!'  : 'Shell',
    \ 't'  : 'Terminal'
    \}

then call the variable in the statusline code:

set statusline=%{g:currentmode[mode()]}	" mode
set statusline+=\ 	" space
set statusline+=%t	" file name
set statusline+=\ 	" space
set statusline+=%m	" modified?
set statusline+=\ 	" space
set statusline+=%y	" file type
set statusline+=\ 	" space

set statusline+=%=      " switch to right side

set statusline+=%p	" percentage through file
set statusline+=\ 	" space
set statusline+=%l	" line number
set statusline+=:	" colon separator
set statusline+=%c	" column number

Git branch

The git branch is a bit harder, requiring vim script and running some shell commands in the .vimrc. Here is my code to define a function to show the git branch in the statusline:

function CurrentGitBranch()
    let gitoutput = system('git status -b '.shellescape(expand('%')).' | head -1 | grep -oE "[^ ]+$" | tr -d "[:cntrl:]"')
    if gitoutput =~ "invalid"
        let b:gitstatus = ''
    else
        let b:gitstatus = gitoutput
    endif
endfunc

autocmd BufEnter,BufWritePost * call CurrentGitBranch()

Let's go through this line by line.

• function CurrentGitBranch() defines a function called CurrentGitBranch().
• let gitoutput = system('git status -b '.shellescape(expand('%')).' | head -1 | grep -oE "[^ ]+$" | tr -d "[:cntrl:]"') defines a variable called gitoutput. * It uses the system() command to run git status -b using the open file .shellescape(expand('&')) as the file to runthe command on. * | head -1 | grep -oE "[^ ]+$" | tr -d "[:cntrl:]" is a series of pipes which returns the first line of git status then greps the final word, then removes the ^@ control sequence, which would otherwise appear in the statusline.
• if gitoutput =~ "invalid" is the start of an if statement which defines b:gitstatus as either an empty string if no file is open (which would normally return a line containing the word invalid, or defines it as the contents of gitoutput.
• autocmd BufEnter,BufWritePost * call CurrentGitBranch() runs the function.

To add b:gitstatus to the statusline, follow the same rules as for the current mode function we did earlier.

set statusline=%{g:currentmode[mode()]}	" mode
set statusline+=\ 	" space
set statusline+=%t	" file name
set statusline+=\ 	" space	
set statusline+=%{b:gitstatus}		" git branch
set statusline+=%m	" modified?
set statusline+=\ 	" space
set statusline+=%y	" file type
set statusline+=\ 	" space

set statusline+=%=      " switch to right side

set statusline+=%p	" percentage through file
set statusline+=\ 	" space
set statusline+=%l	" line number
set statusline+=:	" colon separator
set statusline+=%c	" column number

Status line with git repository

Conditional colour changing

For the colour changing status bar you can use another function:

function! ChangeStatuslineColor()
  if (mode() ==# 'i')
    exe 'hi User1 ctermfg=black ctermbg=white'
  else
    exe 'hi User1 ctermfg=white ctermbg=black'
  endif
  return ''
endfunction

This defines the User1 colour palette, with foreground (text) and background colours, reversing the colours depending on the current mode. To add it to the statusline:

set statusline=%{ChangeStatuslineColor()}	" Load function
set statusline+=%1*	" Change colour palette to `User1`
set statusline+=%{g:currentmode[mode()]}	" Display the mode
set statusline+=%0*	" Return to default colour palette
set statusline+=\ 	" space
set statusline+=%t	" file name
set statusline+=\ 	" space	
set statusline+=%{b:gitstatus}		" git branch
set statusline+=%m	" modified?
set statusline+=\ 	" space
set statusline+=%y	" file type
set statusline+=\ 	" space

set statusline+=%=      " switch to right side

set statusline+=%p	" percentage through file
set statusline+=\ 	" space
set statusline+=%l	" line number
set statusline+=:	" colon separator
set statusline+=%c	" column number

Status line with colour

Obviously you can change the colours to whatever you desire, using ANSI colour codes to extend the colour range, and if you have an X terminal, just change cterm to xterm and you can then use Xterm colour codes. You could also add extra elseif statements to add other modes. Lightline for example turns orange when in visual mode.

My actual statusline

While the above has all the basic functionality, it's very ugly. For my real statusline I tweaked things a little bit more:

" statusline always showing, even when NERDTree is hidden
set laststatus=2

" Map of modes and their codes for statusline
let g:currentmode={
    \ 'n'  : 'Normal',
    \ 'no' : 'N·Operator Pending',
    \ 'v'  : 'Visual',
    \ 'V'  : 'V·Line',
    \ '^V' : 'V·Block',
    \ 's'  : 'Select',
    \ 'S'  : 'S·Line',
    \ '^S' : 'S·Block',
    \ 'i'  : 'Insert',
    \ 'R'  : 'R',
    \ 'Rv' : 'V·Replace',
    \ 'c'  : 'Command',
    \ 'cv' : 'Vim Ex',
    \ 'ce' : 'Ex',
    \ 'r'  : 'Prompt',
    \ 'rm' : 'More',
    \ 'r?' : 'Confirm',
    \ '!'  : 'Shell',
    \ 't'  : 'Terminal'
    \}

" Change statusline colour based on mode 
function! ChangeStatuslineColor()
  if (mode() ==# 'i')
    exe 'hi StatusLine ctermbg=black ctermfg=032'
  elseif (mode() =~# '\v(v|V)')
    exe 'hi StatusLine ctermbg=black ctermfg=172'
  else    
    exe 'hi Statusline ctermbg=white ctermfg=black'
  endif
  return ''
endfunction

" Get git branch in statusline
function CurrentGitBranch()
    let gitoutput = system('git status -b '.shellescape(expand('%')).' | head -1 | grep -oE "[^ ]+$" | tr -d "[:cntrl:]"') 
    if gitoutput =~ "invalid"
        let b:gitstatus = ''
    else
        let b:gitstatus = gitoutput 
    endif
endfunc

autocmd BufEnter,BufWritePost * call CurrentGitBranch()

" Statusline
" left side
set statusline=%{ChangeStatuslineColor()}	" Change colour
set statusline+=\ %-8.{toupper(g:currentmode[mode()])} 	" Current mode
set statusline+=\ \|\  	" Vert-line and space   
set statusline+=%t	" File name
set statusline+=\ \|\  	" Vert-line and space   
set statusline+=%{b:gitstatus}		" git branch
set statusline+=%=	" Switch to right side

" right side
set statusline+=%m%r " Modified and read only flags
set statusline+=\ 		"Space
set statusline+=%y	" File type
set statusline+=\ \|\ 	" Space, Vert-line and space
set statusline+=%3.p%%	" Percentage through file - min size 3
set statusline+=\ \|\ 	" Vert-line and Space
set statusline+=%8.(%4.l:%-3.c%)	" Line and column number in group
set statusline+=\ 		" Space

My status line

My status line - insert mode

The tabline

Less important, but still something that lightline used to do which now I do myself is the tabline. With lightline the tabline looks like this:

Lightline tab line

Setting the tabline manually isn't as easy as the statusline. Technically you can set the tabline using the same code as the statusline (e.g. set tabline=%t), but this will result in the following, regardless of how many tabs are actually open:

Default tab line

I don't entirely understand how the tabline works at the moment, so I borrowed this tabline function from this website[2]:

2: http://dhruvasagar.com/2014/04/06/vim-custom-tabline

function! MyTabLine()
  let s = ''
  for i in range(tabpagenr('


))
    let tabnr = i + 1 " range() starts at 0
    let winnr = tabpagewinnr(tabnr)
    let buflist = tabpagebuflist(tabnr)
    let bufnr = buflist[winnr - 1]
    let bufname = fnamemodify(bufname(bufnr), ':t')

    let s .= '%' . tabnr . 'T'
    let s .= (tabnr == tabpagenr() ? '%#TabLineSel#' : '%#TabLine#')
    let s .= ' ' . tabnr

    let n = tabpagewinnr(tabnr,'


)
    if n > 1 | let s .= ':' . n | endif

    let s .= empty(bufname) ? ' [No Name] ' : ' ' . bufname . ' '

    let bufmodified = getbufvar(bufnr, "&mod")
    if bufmodified | let s .= '+ ' | endif
  endfor
  let s .= '%#TabLineFill#'
  return s
endfunction

Then to run it:

set tabline=%!MyTabLine()

My tabline