From e89c7872d8c287fb3affd9c815a1423b366c2bb9 Mon Sep 17 00:00:00 2001
From: Andras Simonyi <andras.simonyi@gmail.com>
Date: Wed, 19 Jun 2024 08:26:19 +0200
Subject: [PATCH] oc-csl: New custom option
 `org-cite-csl-bibtex-titles-to-sentence-case'

* lisp/oc-csl.el (org-cite-csl-bibtex-titles-to-sentence-case): New
variable.
(org-cite-csl--processor): Create the itemgetter using the new option.
* etc/ORG-NEWS (New option
~org-cite-csl-bibtex-titles-to-sentence-case~): Announce the change.
---
 etc/ORG-NEWS   | 11 +++++++++++
 lisp/oc-csl.el | 21 ++++++++++++++++++++-
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/etc/ORG-NEWS b/etc/ORG-NEWS
index b81dabb15..78a60382d 100644
--- a/etc/ORG-NEWS
+++ b/etc/ORG-NEWS
@@ -61,6 +61,17 @@ The default value used to be pulled from =dvipng= process type from
 =latexmk= (when available), or running =latex= multiple times, so that
 all the references are resolved in the generated png.
 
+*** New option ~org-cite-csl-bibtex-titles-to-sentence-case~
+
+When this option is non-nil then title fields in bibtex bibliography
+entries are converted to sentence-case before being formatted
+according to a CSL style, except for entries with a =langid= field
+specifying a non-English language.  When nil, this conversion is
+limited to entries having a =langid= field specifying a variant of
+English.  The default value is ~t~ as the CSL standard assumes that
+English titles are specified in sentence-case but the bibtex
+bibliography format requires them to be written in title-case.
+
 ** New functions and changes in function arguments
 
 # This also includes changes in function behavior from Elisp perspective.
diff --git a/lisp/oc-csl.el b/lisp/oc-csl.el
index b8691bf6f..338f72e9d 100644
--- a/lisp/oc-csl.el
+++ b/lisp/oc-csl.el
@@ -321,6 +321,24 @@ in the bibliography measured in characters."
   :type 'string
   :package-version '(Org . "9.7"))
 
+(defcustom org-cite-csl-bibtex-titles-to-sentence-case t
+  "Convert bibtex title fields to sentence-case by default.
+
+When non-nil, title fields in bibtex bibliography entries are
+converted to sentence-case before being formatted according to a
+CSL style, except for entries with a `langid' field specifying a
+non-English language.  When nil, title conversion is limited to
+entries having a `langid' field specifying a variant of English.
+
+Conversion of titles to sentence-case by default is in most cases
+useful because the CSL standard assumes that English titles are
+specified in sentence-case but the bibtex bibliography format
+requires them to be written in title-case."
+  :group 'org-cite
+  :package-version '(Org . "9.8")
+  :type 'boolean
+  :safe #'booleanp)
+
 
 ;;; Internal variables
 (defconst org-cite-csl--etc-dir
@@ -579,7 +597,8 @@ property in INFO."
              (processor
               (citeproc-create
                (org-cite-csl--style-file info)
-               (citeproc-hash-itemgetter-from-any bibliography)
+               (citeproc-hash-itemgetter-from-any
+                bibliography (not org-cite-csl-bibtex-titles-to-sentence-case))
                (org-cite-csl--locale-getter)
                locale)))
         (plist-put info :cite-citeproc-processor processor)
-- 
2.34.1