Can't extend visual selection if (vim) windows show different buffers

[ggandor]

Can't extend visual selection if (vim) windows show different buffers

[ggandor]

This is the one: d1084c0. It's about :DoMatchParen then. I will look into the source of matchparen again (help is still appreciated though).

[TheBlob42]

I think I found the issue for what is happening.
See this line from the visual mode documentation (:h Visual):

If you use <Esc>, click the left mouse button or use any command that does a jump to another buffer
while in Visual mode, the highlighting stops and no text is affected.

When checking the source for the DoMatchParen command we can see that windo is used to activate the highlighting in all visible windows:

func s:DoMatchParen()
  runtime plugin/matchparen.vim
  let w = winnr()
  silent windo doau CursorMoved <-- this line here
  exe "noau ". w . "wincmd w"
endfunc

windo will navigate to every window of the current tabpage and execute the given command there (see :h windo). As soon as one of those windows is visiting another buffer than the current one the highlighting stops as stated in the visual mode documentation. That is the reason it works for splits showing the same buffer.

We could have a simple workaround to prevent this like the following:

(fn force-matchparen-highlight []
  ; NOTE: :DoMatchParen overwrites the current dot-repeat setting,
  ;       that should be (re)set after this call!
  (let [mode (vim.fn.mode)] ; save current mode
    (when (= (vim.fn.exists ":DoMatchParen") 2)
      (vim.cmd :DoMatchParen)
      (when (or (= mode "v") (= mode "V") (= mode "CTRL-V")) ; if last mode was "visual"
        (vim.cmd "normal gv")))))                            ; restore selection

[ggandor]

Yep, I can reproduce, unfortunately. This is a pretty serious bug, and at the moment I have absolutely no idea what could cause this, and when will I have the time to hunt it down. (Thanks for raising this btw!)

[ggandor]

Okay, the good news is that this bug is not present in the older commits, so it's binary-searchable at least. I'm kinda relieved :)

[ggandor]

Wow, you're invaluable :) I think this might also be the reason why it breaks dot-repeat (the selection is gone).

On the other hand, have you actually tried the workaround? I tried reselecting with gv, but that did not work for me. The visual selection is not updated at that point, apparently, it restores the previous state. (Though I don't really understand why.)

But again, we can do something simpler: let's not use :DoMatchParen at all, but trigger the refresh manually then, with doautocmd CursorMoved, for our window only. This is a very clean solution.

[TheBlob42]

No problem, I am always happy to help 🙂

For me it did work with gv, but never the less I like the solution using doautocmd CursorMoved way better. No need to "restart" matchparen for all open windows.