vim-go's syntactic highlighting makes vim super slow when dealing with long lines

[louis-paul]

I needed to run a quick test on a snipped of text, which I pasted directly into my code (+/- 800 chars), between quotes. Immediately, the whole editor became unresponsive, taking seconds to make simple moves with hjkl.

Disabling vim-go or syntactic highlighting makes the problem go away instantly.

[fatih]

Probably due to large regex rules defined here: https://github.com/fatih/vim-go/blob/master/syntax/go.vim

You can try to use the old regex engine:

set re=1

Btw there are lots of settings for each syntax group that you can disable, does it help if you disable some of them?

https://github.com/fatih/vim-go/blob/master/doc/vim-go.txt#L425

If yes maybe it's due one of those syntax groups that causes which we can try to solve

[louis-paul]

I've played a bit with settings and it seems that go_highlight_functions produces the major hog of performances. When disabling it and disabling/enabling syntactic highlighting, vim goes a lot faster (but still feels irresponsive).

With more testing, disabling go_highlight_structs at the same time makes the editor responsive again.

[fatih]

Those were added later additionally to the other syntax groups. What I can do is, disable them by default and let the users enable it.

[louis-paul]

Isn't there a way to optimize those, even if that means disabling them on long lines? They are very useful for syntax highlighting, and the very long line problem is a bit an edge-case since most developers will limit their code to 80 characters per line.

[fatih]

You are right. My idea was just an improvement over the current situation, which would make other people experience better for the sake of loosing a nice syntax for functions/structs .. etc. I'm going to change the default, but will not close this issue until we fixed that issue completely :)

[mgutz]

It's not vim-go. Had same issues accidentally opening concatenated files. Try this in your .vimrc

" disable current line hilite
set nocursorline

" color to col 128
set synmaxcol=128

[fatih]

I agree with @mgutz. I also have this in my vimrc:

set nocursorcolumn
syntax sync minlines=256
set re=1

[louis-paul]

Following @mgutz advice effectively solves the problem. Any idea why disabling the syntax groups speeds up vim like that?

Thanks for your help to you two!

[fatih]

Coloring is expensive, and Vim is really bad at rendering colors (I have to use MacVim, it's slow under Terminal). I think that's why it's slow.

[louis-paul]

For the record, I only had 4 functions colored by the syntax groups. Also, it's really the set synmaxcol=128 that boosts everything, enabling current line highlighting does not seems to affect performance.

Thanks again, and keep up the good work at Koding @fatih!

[fatih]

@Artemis2 thank you too for the good feedback on the issue. Happy that I could help you! :)

[ghost]

I've played a bit with settings and it seems that go_highlight_functions produces the major hog of performances. When disabling it and disabling/enabling syntactic highlighting, vim goes a lot faster (but still feels irresponsive).

With more testing, disabling go_highlight_structs at the same time makes the editor responsive again.

Function and function calls both slow down completion. For me function call and fields highlighting slowed down.

" Highlight Function Calls
let g:go_highlight_functions      = 1
let g:go_highlight_function_calls = 1

" Highlight struct fields 
let g:go_highlight_fields = 1