Implement copying of a buffer portion while preserving visual order.

 See http://lists.gnu.org/archive/html/emacs-devel/2014-11/msg02203.html
 and http://lists.gnu.org/archive/html/emacs-devel/2014-12/msg00063.html
 for the rationale.

 lisp/simple.el (bidi-directional-controls-chars)
 (bidi-directional-non-controls-chars): New variables.
 (squeeze-bidi-context-1, squeeze-bidi-context)
 (line-substring-with-bidi-context)
 (buffer-substring-with-bidi-context): New functions.

 doc/lispref/display.texi (Bidirectional Display): Document
 'buffer-substring-with-bidi-context'.
 doc/lispref/text.texi (Buffer Contents): Mention
 'buffer-substring-with-bidi-context' with a cross-reference.

 etc/NEWS: Mention 'buffer-substring-with-bidi-context'.

2 files changed, 11 insertions, 0 deletions

diff --git a/etc/ChangeLog b/etc/ChangeLog
index 4f672dfce5e..84a1c483b47 100644
--- a/etc/ChangeLog
+++ b/etc/ChangeLog
@@ -1,3 +1,7 @@
+2014-12-04  Eli Zaretskii  <eliz@gnu.org>
+
+        * NEWS: Mention 'buffer-substring-with-bidi-context'.
+
 2014-12-02  Eli Zaretskii  <eliz@gnu.org>
 
         * NEWS: Mention 'bidi-find-overridden-directionality'.
diff --git a/etc/NEWS b/etc/NEWS
index f3890a51aad..ae92fa957b9 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -105,6 +105,13 @@ overridden by directional override control characters.  Lisp programs
 can use this to detect potential phishing of URLs and other links that
 exploits bidirectional display reordering.
 
++++
+** The new function `buffer-substring-with-bidi-context' allows to
+copy a portion of a buffer into a different location while preserving
+the visual appearance both of the copied text and the text at
+destination, even when the copied text includes mixed bidirectional
+text and directional control characters.
+
 *** The ls-lisp package uses `string-collate-lessp' to sort file names.
 If you want the old, locale-independent sorting, customize the new
 option `ls-lisp-use-string-collate' to a nil value.