Vertico and completion-preview mode

[Doodler8888]

There is a new addition in emacs 30 called 'completion-preview mode', which allows to see completion suggestions as some sort of an echo. And it renders incorrectly using vertico completion:

There is no such problem using a minibuffer with a non-interactive completion nor ivy:

To reproduce, evaluate '(add-hook 'minibuffer-mode-hook #'completion-preview-mode)'

GNU Emacs 30.0.60 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.43, cairo version 1.18.0) of 2024-08-20

[minad]

Hi! Using these two modes together in the minibuffer is not recommended, and as it seems, is also not supported right now. There is almost no advantage of enabling completion-preview-mode inside the minibuffer. It only adds overhead and leads to interfering key bindings. Also the second example you are showing is misleading. While Vertico prioritizes config.org, completion-preview-mode suggests colors as completion. My recommendation is to only enable completion-preview-mode in non-completing-read minibuffers.

[Doodler8888]

Yeah, i enabled it this way for the eval, shell-command and evil-mode cmd line minibuffers. And i didn't know it's quite easy to enable the mode more selectively when it comes to them.

(defun my-conditional-completion-preview ()
  "Enable completion-preview-mode selectively."
  (if (or (eq this-command 'eval-expression)
          (eq this-command 'shell-command)
          (eq this-command 'evil-ex))
      (completion-preview-mode 1)
    (completion-preview-mode -1)))

(add-hook 'minibuffer-setup-hook #'my-conditional-completion-preview)