Show invisibles

TextMate has an option to ‘Show invisibles’, which lets you see tab and end-of-line characters. When this is enabled, tab characters appear as a small triangle (▸), and end of lines appear as a ‘not sign’ (¬). This is helpful for distinguishing between tabs and spaces, and for revealing trailing spaces at the end of a line.

In Vim, we can display invisible characters by enabling :set list. You can hide these characters again by running :set nolist, or you can toggle between showing and hiding them by running :set list!. If you want to be able to do this quickly, you might like to map the toggling command to something more convenient. Try putting the following in your .vimrc:

nmap <leader>l :set list!<CR>

Now you can toggle between showing and hiding invisible characters with \l (backslash-L). [Note that if you have set your mapleader to a value other than backslash, you will have to use that instead].

Customize symbols

By default, the tab character is represented literally as ^I, and end-of-lines are represented by a dollar sign.

We can customise the symbols used to represent invisible characters by changing the listchars setting. If you want to use the same symbols as TextMate does, put the following into your .vimrc:

set listchars=tab:▸\ ,eol:¬

If you like, you can customise other invisible characters besides tabs and end-of-lines. For more information, get help on listchars:

:help listchars

Colortheme symbols

Depending on the colorscheme you are using, you may want to change the colors of tab and end-of-lines symbols. I prefer to make them close in color to the background, so that they are only just visible, and not too distracting. The syntax keyword for an end-of-line is “NonText”, and for tab characters it is “SpecialKey”. I have added these lines to my prefered colorscheme file:

"Invisible character colors 
highlight NonText guifg=#4a4a59
highlight SpecialKey guifg=#4a4a59

Aside on inserting literal characters

You shouldn’t have any problems if you copy and paste the listchars setting from the shownotes into your .vimrc file. But just in case, here is a method for inserting any Unicode character directly in Vim.

In insert mode, press ctrl-V, then type u followed by the numeric code for the symbol you want to insert. e.g.:

ctrl-v u00ac inserts '¬' (the not sign)
ctrl-v u25b8 inserts '▸' (the triangle symbol)

You can also insert a tab character in insert mode by typing:

ctrl-v ctrl-i

As you can see, the default ^I symbol that Vim uses to represent a tab character is the same as the literal key sequence that we can use to insert this character. So if you’ve ever wondered why :set list showed tab characters by default as ‘ctrl-I’, now you know: that’s how Vim represents tab characters internally.