Thanks for working on this David, I like the idea.

David Edmondson <dme@dme.org> writes:

> @@ -2491,6 +2498,16 @@ rcirc-markup-urls
>             (end (match-end 0))
>             (url (match-string-no-properties 0))
>             (link-text (buffer-substring-no-properties start end)))
> +      ;; Truncate the visible part of URLs if required and necessary.
> +      (when (and rcirc-url-max-length
> +		 (> (- end start) rcirc-url-max-length))
> +	(let* ((ellipsis "...")
> +               (new-end (- (+ start rcirc-url-max-length)
> +                           (length ellipsis))))
> +	  (delete-region new-end end)
> +	  (goto-char new-end)
> +	  (insert ellipsis)
> +	  (setq end (point))))
>        ;; Add a button for the URL.  Note that we use `make-text-button',
>        ;; rather than `make-button', as text-buttons are much faster in
>        ;; large buffers.

Couldn't we reuse url-truncate-url-for-viewing, which tries to be smart
about where it places the ellipsis, for this?  I think the existing code
can also be cleaned up a little: