PATCH: Allow class attribute for headline in HTML export

[Jens Lechtenboerger <lechten@wi.uni-muenster.de>]

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Dear all,

the attached patch allows to add a class attribute to headline
elements in HTML export.  Is that acceptable for inclusion?

Best wishes
Jens

P.S. The change is tiny, but I assigned copyright to the FSF in
2015.


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From e8f16b04903bc32c4ea006727c82dbcb40b591a8 Mon Sep 17 00:00:00 2001
From: Jens Lechtenboerger <jens.lechtenboerger@fsfe.org>
Date: Sun, 2 Dec 2018 19:05:55 +0100
Subject: [PATCH] ox-html.el: New property HTML_HEADLINE_CLASS for class of
 headline

* lisp/ox-html.el (org-html-headline): Add new property
HTML_HEADLINE_CLASS to assign class attribute to headline.

* doc/org-manual.org: Document new property HTML_HEADLINE_CLASS.
---
 doc/org-manual.org | 6 +++++-
 lisp/ox-html.el    | 5 ++++-
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/doc/org-manual.org b/doc/org-manual.org
index 458e59a4a..9d14c4cdc 100644
--- a/doc/org-manual.org
+++ b/doc/org-manual.org
@@ -12780,7 +12780,11 @@ external file.
 In order to add styles to a sub-tree, use the =HTML_CONTAINER_CLASS=
 property to assign a class to the tree.  In order to specify CSS
 styles for a particular headline, you can use the ID specified in
-a =CUSTOM_ID= property.
+a =CUSTOM_ID= property or =HTML_HEADLINE_CLASS= as described next.
+
+#+cindex: @samp{HTML_HEADLINE_CLASS}, property
+In order to assign a class to a headline, use the =HTML_HEADLINE_CLASS=
+property.
 
 Never change the ~org-html-style-default~ constant.  Instead use other
 simpler ways of customizing as described above.
diff --git a/lisp/ox-html.el b/lisp/ox-html.el
index 6a81be126..d9d976753 100644
--- a/lisp/ox-html.el
+++ b/lisp/ox-html.el
@@ -2608,6 +2608,7 @@ holding contextual information."
 		  (format "</%s>\n" html-type))))
 	;; Standard headline.  Export it as a section.
         (let ((extra-class (org-element-property :HTML_CONTAINER_CLASS headline))
+	      (headline-class (org-element-property :HTML_HEADLINE_CLASS headline))
               (first-content (car (org-element-contents headline))))
           (format "<%s id=\"%s\" class=\"%s\">%s%s</%s>\n"
                   (org-html--container headline info)
@@ -2616,9 +2617,11 @@ holding contextual information."
                   (concat (format "outline-%d" level)
                           (and extra-class " ")
                           extra-class)
-                  (format "\n<h%d id=\"%s\">%s</h%d>\n"
+                  (format "\n<h%d id=\"%s\"%s>%s</h%d>\n"
                           level
                           id
+			  (when headline-class
+			    (format " class=\"%s\"" headline-class))
                           (concat
                            (and numberedp
                                 (format
-- 
2.17.1