Modified undo behavior

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Tip 1054 Printable Monobook Previous Next

created 2005 · complexity intermediate · author Nigeria · version 6.0

This page is dodgy. The contents may not be useful for Vim 7. If you think this tip is useful, please edit it to make the problem and its solution more understandable, and remove the {{Dodgy}} tag.

The main tip is overly complex and probably has unforseen side effects. See the comments or the duplicate tip for a better solution.

I was getting frustrated with the default undo behavior in Vim because sometimes one of my "changes" would be very long (many lines), and I would want to undo one line at a time. So I came up with the idea to change the behavior with the following code that can be inserted into your vimrc:

function! EnterStuff()
  let theLine = getline(line("."))
  let pos = col("'^")
  execute "normal mqu\<C-r>`q"
  if(pos > len(theLine))
    startinsert!
  else
    if(pos > 1)
      normal l
    endif
    startinsert
  endif
endfunction

function! ChangeUndoMode(theNum)
  if(a:theNum == 1)
    inoremap <C-w> <C-w>^O^[
    inoremap <CR> <Esc>:call EnterStuff()<CR><CR>
  elseif(a:theNum == 2)
    inoremap <C-w> <C-w>^O^[
    inoremap <BS> <BS>^O^[
    inoremap <DEL> <DEL>^O^[
    inoremap <CR> <Esc>:call EnterStuff()<CR><CR>
  else
    iunmap <C-w>
    iunmap <BS>
    iunmap <DEL>
    iunmap <CR>
  endif
endfunction
call ChangeUndoMode(1)
nmap \sun :call ChangeUndoMode(1)<CR>
nmap \gun :call ChangeUndoMode(2)<CR>
nmap \bun :call ChangeUndoMode(3)<CR>

Be sure to write "^O^[" as two characters: ctrl-o and ESC.

So the above code works fairly well. <C-w>, <BS>, <DEL>, <CR> all add to the undo list. The <CR> one took me a long time to figure out. The way it is done in the above code is the only way I know that doesn't mess up indentation. ^O^[ automatically screws up indentation.

Comments[]

You can use <c-g>u to break the undo chain:

inoremap <BS> <c-g>u<BS>
inoremap <CR> <c-g>u<CR>
inoremap <del> <c-g>u<del>
inoremap <c-w> <c-g>u<c-w>

should have the same effects.

One more thing you can do is hit <End> while typing a sentence to end the undo sequence. The only reason <C-g>u is needed in the above example is because it doesn't screw up auto-indentation. Normally though, hitting <End> is a great way to end the undo sequence.

My <End> does not break the undo chain. I had to explicitly imap it to do so:

inoremap <End> <C-g>u<End>

The <C-G>u trick seems not to be mentioned in gvim 6.1 docs and does not work either with this version.

Be careful: "<C-g>u<Space>" breaks abbreviations induced by a <Space>

Very odd. Try

:imap <Space> <Space><C-g>u

to make abbrevs work. Do not try

:imap <Space> <C-g>u<Space>

Vim will hang after using Space (use <C-c> to stop).

Modified undo behavior

Comments[]

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