sluggish processing of autocommands

[Dave McCooey]

Hello,

I recently added the following autocommands to my _vimrc file:

:hi ExtraWhiteSpace ctermbg=58  " Orange4 = #5f5f00

autocmd BufWinEnter,InsertLeave * syntax match ExtraWhiteSpace / \+\ze\t\|\t\zs \+\|^ \+\|\s\+$/ containedin=ALL

autocmd InsertEnter * syntax match ExtraWhiteSpace / \+\ze\t\|\t\zs \+\|^ \+\|\s\+\%#\@<!$/ containedin=ALL

With these autocommands in place, I noticed the response time

from vim begins to gradually degrade over time:  The delay between

typing the '.' command and the screen update becomes quite

noticeable (longer than 1 second) even if the command being

repeated with '.' is simple, like inserting a single space character.

It appears that each switch into and out of insert mode (which is what

happens in a '.' command, and which is what the above autocommands

would likely affect) adds a small delay to the next '.' command that is

typed, so that after 30 or so '.' commands, the delay becomes noticeable.

I haven't looked at the source code, but my guess is that each '.' causes

vim to add an element to some list, and this ever-increasing list needs

to be traversed for each subsequent '.' command.

I found that switching to a different file and back (":e file" followed by ":e#")

solves the problem by apparently allowing vim to refresh its internal

data structures, but the problem will eventually return as more '.'

commands are typed.

Without the above buffer-switching remedy, the delay will eventually

reach about 2 to 2.5 seconds (on a 3.4 GHz Core i5), at which point,

vim will automatically "refresh itself" by disabling all syntax highlighting,

and this removes the delay problem.  My guess is that the code has

a sort of fail-safe patch that kicks in when a list gets too long.

I tested each of the above two autocommands by itself, and each

one causes the problem by itself.

Best regards,

Dave McCooey

[ben.k...@gmail.com]

That’s because your autocommand adds a new syntax match every time you enter insert mode. That probably increases syntax highlighting times and makes everything else sluggish. Don’t do that for the same reason we use autogroups. Just add the new match once per buffer (say, autocmd Syntax *). 

[Jürgen Krämer]

[Quoting re-ordered]

Hi Dave,

or you might want to try if

:hi ExtraWhiteSpace ctermbg=58 " Orange4 = #5f5f00

:autocmd BufWinEnter,InsertLeave * match ExtraWhiteSpace / \+\ze\t\|\t\zs \+\|^ \+\|\s\+$/
:autocmd InsertEnter * syntax ExtraWhiteSpace / \+\ze\t\|\t\zs \+\|^ \+\|\s\+\%#\@<!$/

works better.

Regards,
Jürgen

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:wq

[Dave McCooey]

Hi Jürgen,

I had come up with a solution using self-modifying autocommands:

augroup g1

au!

augroup g2

au!

augroup end

function ShowExtraSpace()

au! g1

sy match ExtraSpace / \+\ze\t\|\t\zs \+\|^ \+\|\s\+$/ containedin=ALL

endfunction

au g1 BufWinEnter,InsertLeave * call ShowExtraSpace()

function ShowExtraSpaceInsert()

au! g2

sy match ExtraSpace / \+\ze\t\|\t\zs \+\|^ \+\|\s\+\%#\@<!$/ containedin=ALL

endfunction

au g2 InsertEnter * call ShowExtraSpaceInsert()

The "au!" command in each augroup definition is intended to prevent

the accumulation of duplicate autocommands whenever _vimrc is sourced.

The "au! <group>" command in each function is intended to prevent the

accumulation whenever the event associated with that autocommand occurs.

This solution works, but your suggestion (after changing "syntax" to "match"

in the second autocmd) also works and is simpler.

Thank you!

It is a mystery to me, though, how this simpler solution avoids the accumulation

of autocommands.  Maybe an autocommand that uses "syntax match" needs to

be kept around on a list, while an autocommand that uses "match" alone doesn't?

The "containedin=ALL" may be significant too.

Best regards,

Dave

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