From 337014731e89f7f28873b8f5d9a917901e810c95 Mon Sep 17 00:00:00 2001
From: Juan Manuel Macias <maciaschain@posteo.net>
Date: Sat, 8 May 2021 09:03:10 +0200
Subject: [PATCH] Add LaTeX attributes for verse blocks

---
 doc/org-manual.org | 48 ++++++++++++++++++++++++++++++++++++++++++++++
 lisp/ox-latex.el   | 20 +++++++++++++++----
 2 files changed, 64 insertions(+), 4 deletions(-)

diff --git a/doc/org-manual.org b/doc/org-manual.org
index ab12fa70a..c752ce46d 100644
--- a/doc/org-manual.org
+++ b/doc/org-manual.org
@@ -13861,6 +13861,54 @@ The LaTeX export back-end converts horizontal rules by the specified
 -----
 #+end_example
 
+*** Verse blocks in LaTeX export
+:PROPERTIES:
+:DESCRIPTION: Attributes specific to special blocks.
+:END:
+
+#+cindex: verse blocks, in @LaTeX{} export
+#+cindex: @samp{ATTR_LATEX}, keyword
+
+The LaTeX export back-end accepts four attributes for verse blocks:
+=:lines=, =:center=, =:versewidth= and =:latexcode=. The three first
+require the external LaTeX package =verse.sty=, wich is an extension
+of the standard LaTeX environment. The purpose of these attributes is
+explained below.
+
+- =:lines= :: To add marginal verse numbering. Its value is an
+  integer, the sequence in which the verses should be numbered.
+- =:center= :: With value =t= all the verses on the page are optically
+  centered (a typographic convention for poetry), taking as a
+  reference the longest verse, which must be indicated by the
+  attribute =:versewidth=.
+- =:versewidth= :: Its value is a literal text string with the longest
+  verse.
+- =:latexcode= :: It accepts any arbitrary LaTeX code that can be
+  included within a LaTeX =verse= environment.
+
+A complete example with Shakespeare's first sonnet:
+
+#+begin_src org
+,#+ATTR_LaTeX: :center t :latexcode \color{red} :lines 5
+,#+ATTR_LaTeX: :versewidth Feed’st thy light’st flame with self-substantial fuel,
+,#+begin_verse
+From fairest creatures we desire increase,
+That thereby beauty’s rose might never die,
+But as the riper should by time decrease,
+His tender heir mught bear his memeory:
+But thou, contracted to thine own bright eyes,
+Feed’st thy light’st flame with self-substantial fuel,
+Making a famine where abundance lies,
+Thyself thy foe, to thy sweet self too cruel.
+Thou that art now the world’s fresh ornament
+And only herald to the gaudy spring,
+Within thine own bud buriest thy content
+And, tender churl, makest waste in niggarding.
+Pity the world, or else this glutton be,
+To eat the world’s due, by the grave and thee.
+,#+end_verse
+#+end_src
+
 ** Markdown Export
 :PROPERTIES:
 :DESCRIPTION: Exporting to Markdown.
diff --git a/lisp/ox-latex.el b/lisp/ox-latex.el
index c3fc83b1b..0376dffd1 100644
--- a/lisp/ox-latex.el
+++ b/lisp/ox-latex.el
@@ -3513,6 +3513,17 @@ channel."
   "Transcode a VERSE-BLOCK element from Org to LaTeX.
 CONTENTS is verse block contents.  INFO is a plist holding
 contextual information."
+  (let*
+      ((lin (org-export-read-attribute :attr_latex verse-block :lines))
+       (latcode (org-export-read-attribute :attr_latex verse-block :latexcode))
+       (cent (org-export-read-attribute :attr_latex verse-block :center))
+       (attr (concat
+	      (if cent "[\\versewidth]" "")
+	      (if lin (format "\n\\poemlines{%s}" lin) "")
+	      (if latcode (format "\n%s" latcode) "")))
+       (versewidth (org-export-read-attribute :attr_latex verse-block :versewidth))
+       (vwidth (if versewidth (format "\\settowidth{\\versewidth}{%s}\n" versewidth) ""))
+       (linreset (if lin "\n\\poemlines{0}" "")))
   (concat
    (org-latex--wrap-label
     verse-block
@@ -3520,19 +3531,20 @@ contextual information."
     ;; character and change each white space at beginning of a line
     ;; into a space of 1 em.  Also change each blank line with
     ;; a vertical space of 1 em.
-    (format "\\begin{verse}\n%s\\end{verse}"
+    (format "%s\\begin{verse}%s\n%s\\end{verse}%s"
+	      vwidth
+	      attr
 	    (replace-regexp-in-string
 	     "^[ \t]+" (lambda (m) (format "\\hspace*{%dem}" (length m)))
 	     (replace-regexp-in-string
 	      "^[ \t]*\\\\\\\\$" "\\vspace*{1em}"
 	      (replace-regexp-in-string
 	       "\\([ \t]*\\\\\\\\\\)?[ \t]*\n" "\\\\\n"
-	       contents nil t) nil t) nil t))
+	       contents nil t) nil t) nil t) linreset)
     info)
    ;; Insert footnote definitions, if any, after the environment, so
    ;; the special formatting above is not applied to them.
-   (org-latex--delayed-footnotes-definitions verse-block info)))
-
+   (org-latex--delayed-footnotes-definitions verse-block info))))
 
 
 ;;; End-user functions
-- 
2.26.0