Re: Bug#42184: org-fontify-whole-*-line in emacs 27

[Kévin Le Gouguec]

Kyle Meyer <kyle@kyleam.com> writes:

>> +(defmacro org--extended-face (attributes)
>> +  "Make face that extends beyond end of line.
>> +
>> +Up to Emacs 26, all faces extended beyond end of line; getting
>> +the same behaviour starting with Emacs 27 requires :extend t."
>> +  `(nconc ,attributes (when (>= emacs-major-version 27) '(:extend t))))
>
> Two minor thoughts, neither really important:
>
>   * Style nit-pick: s/when/and/, as the return value is of interest.

OK; I didn't know 'when' had a "for side-effect only" connotation, I was
using it as a shorthand for (if COND FORM nil).

> ... the main thing I wonder is whether this kludge is necessary at all.
> AFAICT unconditionally including :extend in the face spec doesn't seem
> to bother earlier Emacs versions.

Huh.  Based on the discussion for bug#37774[1][2][3][4], I had assumed
this kind of kludge would be necessary, but both Emacs 25.3 and 26.3
seem to evaluate and byte-compile the following snippet with no errors:

#+begin_src elisp
(defface foobar '((t (:extend t)))
  "Test extend in 26.3"
  :group 'org-faces)

(custom-set-faces
 '(foobar ((t (:extend nil))) t))
#+end_src

Obviously I'm all for removing this shim if it's not needed.  From some
light testing it looks like removing it breaks the customization widget,
though?

I'll post a revised patch as soon as someone can confirm or refute my
observations.

[1] https://debbugs.gnu.org/cgi/bugreport.cgi?bug=37774#41
[2] https://debbugs.gnu.org/cgi/bugreport.cgi?bug=37774#53
[3] https://debbugs.gnu.org/cgi/bugreport.cgi?bug=37774#71
[4] https://debbugs.gnu.org/cgi/bugreport.cgi?bug=37774#80

>                                    Even if there is a reason to avoid
> :extend on older versions, it's perhaps an overkill to add a
> compatibility macro for just one spot.

Right, that macro dates from an earlier patch, where I unconditionally
set :extend t on a bunch of faces[5].  I agree that it's overkill for
just org-block.

[5] https://debbugs.gnu.org/cgi/bugreport.cgi?bug=42184#17

> If org--extended-face stays, org-face.el should be adjusted to load
> org-compat.el.  (`make single' flags this.)

(Ugh, I actually got that right in earlier patches.)


Thanks for the review.  As I said, I'll post an updated patch as soon as
someone confirms or refutes my impression that :extend messes with the
Customize widget for Emacs <27.