Allow user control on what starts and ends a paragraph for bidi

* src/buffer.h (struct buffer): New members
bidi_paragraph_separate_re_ and bidi_paragraph_start_re_.
* src/buffer.c (bset_bidi_paragraph_start_re)
(bset_bidi_paragraph_separate_re): New setters/
(Fbuffer_swap_text): Swap the values of bidi-paragraph-start-re and
bidi-paragraph-separate-re.
(init_buffer_once): Init the values of bidi-paragraph-start-re and
bidi-paragraph-separate-re.
(syms_of_buffer) <bidi-paragraph-start-re, bidi-paragraph-separate-re>:
New per-buffer variables.
* src/bidi.c (bidi_at_paragraph_end, bidi_find_paragraph_start):
Support bidi-paragraph-start-re and bidi-paragraph-separate-re.
(bidi_move_to_visually_next): Handle correctly the case when the
separator matches an empty string.  (Bug#27526)

* doc/emacs/mule.texi (Bidirectional Editing):
* doc/lispref/display.texi (Bidirectional Display): Document
bidi-paragraph-start-re and bidi-paragraph-separate-re.

* etc/NEWS: Mention bidi-paragraph-start-re and
bidi-paragraph-separate-re.

1 files changed, 6 insertions, 0 deletions

diff --git a/src/buffer.h b/src/buffer.h
index be270fe4823..46ca6aa7384 100644
--- a/src/buffer.h
+++ b/src/buffer.h
@@ -611,6 +611,12 @@ struct buffer
      direction dynamically for each paragraph.  */
   Lisp_Object bidi_paragraph_direction_;
 
+  /* If non-nil, a regular expression for bidi paragraph separator.  */
+  Lisp_Object bidi_paragraph_separate_re_;
+
+  /* If non-nil, a regular expression for bidi paragraph start.  */
+  Lisp_Object bidi_paragraph_start_re_;
+
   /* Non-nil means do selective display;
      see doc string in syms_of_buffer (buffer.c) for details.  */
   Lisp_Object selective_display_;