Vim_opfuncsteady.md

Vim will move the cursor to the beginning of an object after invoking operator upon it. From an interactive editing perspective this may be considered annoying however it is the consistent choice as operators can be destructive. As such restoring the cursor to its prior position after invoking an operator on an object may not make sense.

There are many ways possible to alter this behaviour to your preference with mappings and/or scripting. But with custom operator mappings this can be particularly ugly.

A common method is to drop a mark or save a view in the mapping. However the mapping must end with g@ so Vim will wait for the operator, meaning the mapping itself can't move the cursor movement back to its original location. As such the movement would have to be placed inside the function that operatorfunc has been set to. I consider this quite ugly as functions should not have to have such a priori knowledge about the mappings that are calling them. Note that dropping a mark or saving a view inside the operatorfunc function is not an option as the cursor has already been moved by the time this is invoked.

A neat solution to this is to save a view whenever operatorfunc is set with an autocmd. Then whenever the cursor is moved check if operatorfunc is set, if so restore the view, dispose of the temporary variable containing said view, and unset operatorfunc with autocmd's disabled as to avoid a loop.

To avoid having an autocmd always fire when the cursor is moved we can instantiate it only when operatorfunc is set. Now that this instantiation occurs whenever operatorfunc is set we can make two further refinements. Firstly we can stop checking if operatorfunc is set and secondly the autocmd that restores the view can be one shot.

function! OpfuncSteady() abort
  let w:opfuncview = winsaveview()
  autocmd OpfuncSteady CursorMoved,TextYankPost *
    \ call winrestview(w:opfuncview)
    \ | unlet w:opfuncview
    \ | noautocmd set operatorfunc=
    \ | autocmd! OpfuncSteady CursorMoved,TextYankPost *
endfunction

augroup OpfuncSteady
  autocmd!
  autocmd OptionSet operatorfunc call OpfuncSteady()
augroup END

One could even create re-implementations of Vim's built in operators to leverage this technique, though I'll leave that as an exercise for the reader.

Hi @George-B. I'm interested in testing whether this approach works with the repeat . operator. Could you share a small example showing how to use your implementation? For example, I would like to create a mapping for gq that formats the lines covered by the motion and leaves the cursor in the same place.

Hi Martin,

I've been meaning to factor this out into a proper plugin for some time but just haven't got around to it. This doesn't work with . as-is and it's not something I've looked into, though I'm sure it could be done with the help of something like repeat.vim.

For example, I would like to create a mapping for gq that formats the lines covered by the motion and leaves the cursor in the same place.

I've not implemented in my own config as this is potentially what I describe as "destructive" in the post above. That is after the operation is performed the line and column the cursor was initially on may no longer reside within the object that was operated upon. For example if you are near the end of a paragraph and gqip ends up reducing the number of lines a paragraph takes up you'd be restoring you cursor to a position no longer inside that paragraph. This is precisely why Vim's default behavior, whilst not the most elegant at first glance, makes sense.

That said assuming you're not relying on an external 'formatprg' Vim's gw has you covered. It does not suffer from what I have just described as it is more sophisticated in that it truly "puts the cursor back at the same position in the text" as described in the help.

The same could be implemented for this but that probably outgrows the scope of a gist and would be something for a proper plugin.

Cheers,
George

Ohh wow! I did not know that qw was something. It also works with the repeat operator. Thank you very much!!