Re: [patch] ox-latex.el: fix blank lines behavior in verse block

["Juan Manuel Macías" <maciaschain@posteo.net>]

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Ihor Radchenko writes:

> Thanks!
>
>> * (org-latex-verse-block): now the treatment of blank lines is
>> consistent with the syntax of the LaTeX `verse' environment, and the
>> one provided by the `verse' package. If the `:literal' attribute is
>> used, all blank lines are preserved and exported as
>
> Please use double space between sentences and start sentences with
> capital letter.
>
>> +- =:literal= :: With value t, all blank lines are preserved and
>> +  exported as =\vspace*{\baselineskip}=, including the blank lines
>> +  before or after contents.  Note that without the =:literal=
>> +  attribute, one or more blank lines between stanzas are exported as a
>> +  single blank line, and any blank lines before or after the content
>> +  are removed, which is more consistent with the syntax of the LaTeX
>> +  `verse' environment, and the one provided by the `verse' package.
>> +  If the =verse= package is loaded, the vertical spacing between all
>> +  stanzas can be controlled by the global length =\stanzaskip= (see
>> +  https://www.ctan.org/pkg/verse).
>
> s/`verse'/=verse=/
>   
> And you need to update `test-ox-latex/verse' test - it is currently failing.

Sorry for the typos... Here goes the corrected patch again, with the
updated test.

-- 
Juan Manuel Macías

https://juanmanuelmacias.com

https://lunotipia.juanmanuelmacias.com

https://gnutas.juanmanuelmacias.com

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From bd956aa947e080ef10aa851f339414dc1cda1baf Mon Sep 17 00:00:00 2001
From: Juan Manuel Macias <maciaschain@posteo.net>
Date: Mon, 14 Aug 2023 21:48:58 +0200
Subject: [PATCH] lisp/ox-latex.el: Add the `:literal' attribute to verse
 block.

* (org-latex-verse-block): Now the treatment of blank lines is
consistent with the syntax of the LaTeX `verse' environment, and the
one provided by the `verse' package.  If the `:literal' attribute is
used, all blank lines are preserved and exported as
`\vspace*{\baselineskip}', including the blank lines before or after
contents.  The rx code has been suggested by Ihor Radchenko, to
improve readability.

* doc/org-manual.org (Verse blocks in LaTeX export): The new feature
is documented.

* testing/lisp/test-ox-latex.el (test-ox-latex/verse): Updated.
---
 doc/org-manual.org            | 18 ++++++++++++++----
 lisp/ox-latex.el              | 36 ++++++++++++++++++++++++++---------
 testing/lisp/test-ox-latex.el |  8 ++++----
 3 files changed, 45 insertions(+), 17 deletions(-)

diff --git a/doc/org-manual.org b/doc/org-manual.org
index e59efc417..ce0521dee 100644
--- a/doc/org-manual.org
+++ b/doc/org-manual.org
@@ -14425,10 +14425,10 @@ The LaTeX export backend converts horizontal rules by the specified
 #+cindex: verse blocks, in @LaTeX{} export
 #+cindex: @samp{ATTR_LATEX}, keyword
 
-The LaTeX export backend accepts four attributes for verse blocks:
-=:lines=, =:center=, =:versewidth= and =:latexcode=.  The three first
-require the external LaTeX package =verse.sty=, which is an extension
-of the standard LaTeX environment.
+The LaTeX export backend accepts five attributes for verse blocks:
+=:lines=, =:center=, =:versewidth=, =:latexcode= and =:literal=.  The
+three first require the external LaTeX package =verse.sty=, which is
+an extension of the standard LaTeX environment.
 
 - =:lines= :: To add marginal verse numbering.  Its value is an
   integer, the sequence in which the verses should be numbered.
@@ -14440,6 +14440,16 @@ of the standard LaTeX environment.
   verse.
 - =:latexcode= :: It accepts any arbitrary LaTeX code that can be
   included within a LaTeX =verse= environment.
+- =:literal= :: With value t, all blank lines are preserved and
+  exported as =\vspace*{\baselineskip}=, including the blank lines
+  before or after contents.  Note that without the =:literal=
+  attribute, one or more blank lines between stanzas are exported as a
+  single blank line, and any blank lines before or after the content
+  are removed, which is more consistent with the syntax of the LaTeX
+  `verse' environment, and the one provided by the =verse= package.
+  If the =verse= package is loaded, the vertical spacing between all
+  stanzas can be controlled by the global length =\stanzaskip= (see
+  https://www.ctan.org/pkg/verse).
 
 A complete example with Shakespeare's first sonnet:
 
diff --git a/lisp/ox-latex.el b/lisp/ox-latex.el
index 31cad1dc4..d11e3befa 100644
--- a/lisp/ox-latex.el
+++ b/lisp/ox-latex.el
@@ -4116,10 +4116,11 @@ 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))
+         (lit (org-export-read-attribute :attr_latex verse-block :literal))
          (attr (concat
-	        (if cent "[\\versewidth]" "")
-	        (if lin (format "\n\\poemlines{%s}" lin) "")
-	        (if latcode (format "\n%s" latcode) "")))
+		(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}" "")))
@@ -4128,20 +4129,37 @@ contextual information."
       verse-block
       ;; In a verse environment, add a line break to each newline
       ;; 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.
+      ;; into a normal space, calculated with `\fontdimen2\font'.  One
+      ;; or more blank lines between lines are exported as a single
+      ;; blank line.  If the `:lines' attribute is used, the last
+      ;; verse of each stanza ends with the string `\\!', according to
+      ;; the syntax of the `verse' package. The separation between
+      ;; stanzas can be controlled with the length `\stanzaskip', of
+      ;; the aforementioned package.  If the `:literal' attribute is
+      ;; used, all blank lines are preserved and exported as
+      ;; `\vspace*{\baselineskip}', including the blank lines before
+      ;; or after CONTENTS.
       (format "%s\\begin{verse}%s\n%s\\end{verse}%s"
 	      vwidth
 	      attr
 	      (replace-regexp-in-string
-	       "^[ \t]+" (lambda (m) (format "\\hspace*{%dem}" (length m)))
+	       "^[ \t]+" (lambda (m) (format "\\hspace*{%d\\fontdimen2\\font}" (length m)))
 	       (replace-regexp-in-string
-                (concat "^[ \t]*" (regexp-quote org-latex-line-break-safe) "$")
-	        "\\vspace*{1em}"
+                (if (not lit)
+		    (rx-to-string
+                     `(seq (group ,org-latex-line-break-safe "\n")
+		           (1+ (group line-start (0+ space) ,org-latex-line-break-safe "\n"))))
+		  (concat "^[ \t]*" (regexp-quote org-latex-line-break-safe) "$"))
+	        (if (not lit)
+		    (if lin "\\\\!\n\n" "\n\n")
+		  "\\vspace*{\\baselineskip}")
 	        (replace-regexp-in-string
 	         "\\([ \t]*\\\\\\\\\\)?[ \t]*\n"
                  (concat org-latex-line-break-safe "\n")
-	         contents nil t)
+	         (if (not lit)
+		     (concat (org-trim contents t) "\n")
+		   contents)
+                 nil t)
                 nil t)
                nil t)
               linreset)
diff --git a/testing/lisp/test-ox-latex.el b/testing/lisp/test-ox-latex.el
index adb3a60ea..79ef8793b 100644
--- a/testing/lisp/test-ox-latex.el
+++ b/testing/lisp/test-ox-latex.el
@@ -61,11 +61,11 @@ lorem ipsum dolor
      (search-forward
       "\\begin{verse}
 lorem ipsum dolor\\\\[0pt]
+lorem ipsum dolor
+
 lorem ipsum dolor\\\\[0pt]
-\\vspace*{1em}
-lorem ipsum dolor\\\\[0pt]
-lorem ipsum dolor\\\\[0pt]
-\\vspace*{1em}
+lorem ipsum dolor
+
 lorem ipsum dolor\\\\[0pt]
 lorem ipsum dolor\\\\[0pt]
 \\end{verse}"))))
-- 
2.41.0