Re: Box cursor at EoL

[Stefan Monnier]

> (defun change-cursor-at-end-of-line ()
>   "Change shape of cursor to value of `cursor-type-at-eol' at end of line.
>
> When the cursor is moved away from end of line, its shape returns
> to its default value. This gives a cue about trailing whitespace
> that is even less in your face than `whitespace-newline-mode'.
>
> Add this to `post-command-hook' to enable the feature."
>   (while-no-input
>     (if (eolp)
>         (setq cursor-type cursor-type-at-eol)
>       (setq cursor-type (default-value 'cursor-type))
>       )))

I suspect the `while-no-input` makes no difference here.
And the next three lines can be simplified to:

    (setq cursor-type
          (if (eolp) cursor-type-at-eol (default-value 'cursor-type)))

> ;; Oddly this doesn't seem to always work with Emacs 27.1. Never
> ;; noticed any problem with 26.3.
> (add-hook 'post-command-hook 'change-cursor-at-end-of-line)

Nowadays you could also use the `pre-redisplay-function` hook which
could have some advantages, but in any case the limit of the above
approach is that it can't correctly account for all the cases where the
buffer is displayed in several windows, with some windows' cursor at
EOL and others not :-(


        Stefan