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

["Kévin Le Gouguec" <kevin.legouguec@gmail.com>]

Since 27.1-rc1 is out, I'd like to bump this; it'd be a shame if 27.1
shipped with this bug, which seems to be getting some attention (I just
spotted a Reddit thread[1] about it, in addition to the original report
on Debbugs).

[1]: https://old.reddit.com/r/emacs/comments/i26n46/why_does_my_orgmode_look_different_to_leuven/


Kévin Le Gouguec <kevin.legouguec@gmail.com> writes:

> Could Org maintainers weigh in on bug#42184?
>
> To recap my understanding of the issue:
>
> - org-fontify-whole-heading-line controls whether
>   org-set-font-lock-defaults includes the final newline in the headline
>   regexp (resp. org-fontify-whole-block-delimiter-line with begin/end
>   block regexps).
>
> - This assumes that fontifying the final newline is enough to fontify
>   everything beyond this newline.
>
> - This assumption is no longer valid with Emacs 27, where this extension
>   is opt-in, using the :extend face attribute.
>
> With Eli's help, I proposed a patch for org-mode against the emacs-27
> branch that does something similar to what is done for the org-hide
> face: when setting up the major mode, depending on those user options,
> the :extend attribute is (re)set for the relevant faces (using a
> compatibility function defined in org-compat).
>
> I've reattached the patch for convenience.  Does it look sound?
>
> From 07d123c548051eb7f6bbac5c7f5a4e4b8411f976 Mon Sep 17 00:00:00 2001
> From: =?UTF-8?q?K=C3=A9vin=20Le=20Gouguec?= <kevin.legouguec@gmail.com>
> Date: Thu, 9 Jul 2020 16:02:49 +0200
> Subject: [PATCH] Fix org-fontify-whole-*-line by setting face extension
>  (bug#42184)
>
> * lisp/org/org-compat.el (org--set-faces-extend): New function to set
> face extension, for Emacs versions where this attribute exists.
> * lisp/org/org.el (org-mode): Call it to set the extend attribute of
> relevant faces to the correct value.
> ---
>  lisp/org/org-compat.el | 4 ++++
>  lisp/org/org.el        | 6 +++++-
>  2 files changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/lisp/org/org-compat.el b/lisp/org/org-compat.el
> index c1aaf17ca2..fcc325e475 100644
> --- a/lisp/org/org-compat.el
> +++ b/lisp/org/org-compat.el
> @@ -101,6 +101,10 @@ org-table1-hline-regexp
>    (defun org-time-convert-to-list (time)
>      (seconds-to-time (float-time time))))
>  
> +(defun org--set-faces-extend (faces extend-p)
> +  (when (fboundp 'set-face-extend)
> +    (mapc (lambda (f) (set-face-extend f extend-p)) faces)))
> +
>  \f
>  ;;; Emacs < 26.1 compatibility
>  
> diff --git a/lisp/org/org.el b/lisp/org/org.el
> index 568f5b9b87..fb31336ea4 100644
> --- a/lisp/org/org.el
> +++ b/lisp/org/org.el
> @@ -4944,7 +4944,11 @@ org-mode
>    ;; Try to set `org-hide' face correctly.
>    (let ((foreground (org-find-invisible-foreground)))
>      (when foreground
> -      (set-face-foreground 'org-hide foreground))))
> +      (set-face-foreground 'org-hide foreground)))
> +  ;; Set face extension as requested.
> +  (org--set-faces-extend '(org-block-begin-line org-block-end-line)
> +                         org-fontify-whole-block-delimiter-line)
> +  (org--set-faces-extend org-level-faces org-fontify-whole-heading-line))
>  
>  ;; Update `customize-package-emacs-version-alist'
>  (add-to-list 'customize-package-emacs-version-alist