From ab5fc7c8215e1066449da4eb0e027f8250cc9f49 Mon Sep 17 00:00:00 2001
From: Marcin Borkowski <mbork@mbork.pl>
Date: Wed, 27 Apr 2016 08:59:15 +0200
Subject: [PATCH] Add the function `fill-polish-nobreak-p'

* lisp/textmodes/fill.el (fill-polish-nobreak-p): Prevent
line-breaking after a single-letter word even if this word is not
preceded by a space.  Fixes bug #20871.
---
 doc/emacs/text.texi    |  7 +++++--
 etc/NEWS               |  5 +++++
 lisp/textmodes/fill.el | 12 ++++++++++++
 3 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/doc/emacs/text.texi b/doc/emacs/text.texi
index d1e451175ed..4dcbaec03ec 100644
--- a/doc/emacs/text.texi
+++ b/doc/emacs/text.texi
@@ -616,8 +616,11 @@ line.  If a function returns a non-@code{nil} value, Emacs will not
 break the line there.  Functions you can use there include:
 @code{fill-single-word-nobreak-p} (don't break after the first word of
 a sentence or before the last); @code{fill-single-char-nobreak-p}
-(don't break after a one-letter word); and @code{fill-french-nobreak-p}
-(don't break after @samp{(} or before @samp{)}, @samp{:} or @samp{?}).
+(don't break after a one-letter word preceded by a whitespace
+character); @code{fill-french-nobreak-p} (don't break after @samp{(}
+or before @samp{)}, @samp{:} or @samp{?}); and
+@code{fill-polish-nobreak-p} (don't break after a one letter word,
+even if preceded by a non-whitespace character).
 
 @node Fill Prefix
 @subsection The Fill Prefix
diff --git a/etc/NEWS b/etc/NEWS
index 85d12733670..6bf124cfce1 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -468,6 +468,11 @@ current buffer with the contents of the accessible portion of a
 different buffer while keeping point, mark, markers, and text
 properties as intact as possible.
 
++++
+** New function 'fill-polish-nobreak-p', to be used in 'fill-nobreak-predicate'.
+It blocks line breaking after a one-letter word, also in the case when
+this word is preceded by a non-space, but non-alphanumeric character.
+
 
 * Changes in Specialized Modes and Packages in Emacs 26.1
 
diff --git a/lisp/textmodes/fill.el b/lisp/textmodes/fill.el
index ee523ed5f5c..b640adb7a7b 100644
--- a/lisp/textmodes/fill.el
+++ b/lisp/textmodes/fill.el
@@ -338,6 +338,18 @@ places."
 	      (and (memq (preceding-char) '(?\t ?\s))
 		   (eq (char-syntax (following-char)) ?w)))))))
 
+(defun fill-polish-nobreak-p ()
+  "Return nil if Polish style allows breaking the line at point.
+This function may be used in the `fill-nobreak-predicate' hook.
+It is almost the same as `fill-single-char-nobreak-p', with the
+exception that it does not require the one-letter word to be
+preceded by a space.  This blocks line-breaking in cases like
+\"(a jednak)\"."
+  (save-excursion
+    (skip-chars-backward " \t")
+    (backward-char 2)
+    (looking-at "[^[:alpha:]]\\cl")))
+
 (defun fill-single-char-nobreak-p ()
   "Return non-nil if a one-letter word is before point.
 This function is suitable for adding to the hook `fill-nobreak-predicate',
-- 
2.39.5