Change/Set color to a string in statusline

Question

I'll preface by saying that I am using Airline, plytophogy/vim-virtualenv plugin and gruvbox as the Airline theme.

I am trying to change the color of some string in the status line to, say, orange. In my case that is the "@my_env" string that states my current working environment:

Currently, the line in my .vimrc that is responsible for this text is:

let g:airline_section_c='%t @%{virtualenv#statusline()}'

Based on this question, I tried to change my .vimrc line to

let g:airline_section_c='%t %#orange#@%{virtualenv#statusline()}'

which seems to have highlighted the statusline from "@my_env" onwards:

It seems that using %#any_color# or even %##by itself produces the same effect.

So my question is: Is there a way to set a color for a string in the statusline?

Answer 1

It looks like there are actually several questions to be answered here.

1. Is there a way to set a color for a string in the statusline?

Yes there is. As the help for the statusline states, you can inject highlighting groups into the statusline by either using %#<NAME># to start using the highlighting group <NAME> or use %1*, to start using highlighting group User1. Use the numbers 1-9 to select the corresponding highlighting group User1-User9. Restore the highlighting group by using %*. Restoring in this case means, to use again the StatusLine (or StatusLineNC for non-active windows) highlighting group. (This part is important, I'll come back to this in a bit.)

However, this only works, if the actual highlighting group does exists. So you have to define the group like this:

:hi MyRedHighlightingGroup ctermfg=red ctermbg=black guifg=red guibg=black

Simply throwing magical color names into the statusline like your orange won't make it work. I guess you must have defined the orange highlighting group somewhere.

2. How to use airline and customize the different sections

In contrast to what was assumed in the comments, there is no magic going on here. But let me explain.

As you have already noticed, it is pretty easy to customize the airline sections, by simply putting the definitions into the global variable g:airline_section_X. (Use a window local variable to have this applied only to a particular window):

let g:airline_section_c='%t %#orange#@%{virtualenv#statusline()}'

So this will display the Filename, and start highlighting in orange (provided the highlighting group does actually exists) the output of the function virtualenv#statusline() until the next section.

Now airline makes heavy use of customized highlighting groups, as you can tell, if you look at the output of :hi because you'll notice many, many airline groups that all start with airline_xxx. Basically each section has its own highlighting group, plus groups that will be injected before the next section starts (the airline_x_to_airline_y groups), so that the powerline symbols look nice and show a fancy transition between each section.

So if you want to reset the highlighting group to the one that was previously used, you must not used %*, as this will switch the highlighting group to be used to StatusLine (or StatusLineNC for non-active windows), since this highlighting group is not used at all for an airline managed statusline. Instead, you probably want to reset to the actual used highlighting group (which for the mentioned section c is airline_c):

let g:airline_section_c='%t %#orange#@%{virtualenv#statusline()}%#airline_c#'

As this will correctly switch back to the highlighting group used in section c. Note, that when the window becomes inactive, airline will automatically try to use the corresponding highlighting group orange_inactive, so that needs to be defined as well.

Also note, that section c for airline is actually a bit different here for inactive windows. Because in order to distinguish inactive sections containing different buffers, airline will automatically append the buffer number to the c, else it could not use different inactive highlighting groups. So this might be an additional complexity for section c. Might be easier to use one of the other pre-defined sections.

3. Some tips on debugging airline

In any case, you can always examine the result of the defined statusline using

echo airline#statusline(<winnr>)

where <winnr> is the window number. A bit simpler even is to use :echo eval(&statusline[2:]), to see the resulting statusline option for the current window. In a similar way, you can always see the result of the tabline using :echo eval(&tabline[2:]).

(On a related note: this also means, that if the statusline wraps, or some characters are not correctly aligned, that this almost always means it is either a font incompatibility or a Vim bug or a problem between different used unicode libraries between Vim and the terminal. Airline cannot influence it, since in the end it is merely setting the statusline option).