2

Here is an attempt to write a function which will remove trashy characters (^F, ^S, ^Z, zero-width space, etc) on save, and keep cursor position.

colorscheme desert
set guifont=Consolas:h10
set encoding=utf-8
setglobal fileencoding=utf-8
set noexpandtab
set list
set listchars=tab:→\ ,space:·

set nobackup
set noswapfile
set noundofile

function! RemoveTrash()
  let l:save = winsaveview()
  keeppatterns %s/[^[:print:]\t]//g
  call winrestview(l:save)
endfun

augroup Test
  autocmd!
  autocmd BufWritePre * :call RemoveTrash()
augroup END

The overall idea about function was taken from Martin Tournoij's answer about removing whitespace: https://vi.stackexchange.com/a/456, and regex was taken lincz's answer: https://stackoverflow.com/a/16135425.

Here is the test file:

>---foo##bar##baz
>---foo##bar##baz
>---foo##bar##baz

To post it here I replaced tab characters with >--- and control characters (^F, ^S) with ##.

However, when I save the file, the cursor position isn't really saved - it slightly moves to the right side accordingly number of control characters before it. Here are two examples:

  • If you have cursor on letter a in bar - it will be moved to r.
  • If you have cursor on letter b in baz - it will be moved to z (because there are two control characters before it).

And here are screenshots for the first example:

enter image description here

How to fix it?

DJMcMayhem posted an answer at February the 5th, but it seems it doesn't properly work for tab-indented lines. That's why I started a bounty. I tried to fix it by changing getcurpos()[2] to getcurpos()[4], but my "knowledge" of Vimscript is too low.

  • 1
    The cursor position is correctly saved, just the text moved to the left, as you deleted characters. – Ralf Feb 5 at 18:35
1
+150

Like Ralf said, your function is correctly saving the cursor position. The issue is when characters to the left of your cursor get deleted.

Here's what I came up with:

function! RemoveTrash()
  let l:initialCol = getcurpos()[2]
  let l:line = getline('.')[0:initialCol-1]

  let l:numRemoved = len(l:line) - len(substitute(l:line, '[^[:print:]\t]', "", "g"))

  let l:save = winsaveview()
  keeppatterns %s/[^[:print:]\t]//ge
  call winrestview(l:save)

  if l:numRemoved != 0
    call cursor(line('.'), (l:initialCol-l:numRemoved))
  endif
endfun

It keeps track of the old cursor position, and then calculates how many characters before that column will be deleted, and compensates.


Edit: switched exec normal | to cursor(), since that function compensates for tabs whereas | does not.

Edit 2: Added the /e flag to the substitute command so that it will not throw an error if there are no unprintables to remove.

  • It works, thanks. (I just want to wait 15-20 minutes before marked as "answered"). As I understand, you intentionally use two different types of quote signs (single and double)? – john c. j. Feb 5 at 18:58
  • @johncj Yes. I generally default to double quotes because I like them more, but I had some issues when I tried using them with substitute. I don't remember exactly, but I know that vim treats backslashes differently in single vs double quotes – DJMcMayhem Feb 5 at 19:02
  • Just in case, Google suggest to use single quoted strings: google.github.io/styleguide/… – john c. j. Feb 5 at 20:07
  • Also, echo l:numberOfCharsRemoved oftenly shows "0" for some reason (though removing itself works correctly). – john c. j. Feb 5 at 20:33
  • Oh yes, that echo shouldn't be there, I just forgot to remove it. If it's 0, that just means there won't be any unprintables on the current line, so nothing to worry about. – DJMcMayhem Feb 5 at 20:49

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