[newlib-cygwin] describe new locale modifier @cjkwide for user guide

[Corinna Vinschen]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=e4c65b2e918107287845ab345bc0607bde0323f7

commit e4c65b2e918107287845ab345bc0607bde0323f7
Author: Thomas Wolff <towo@towo.net>
Date:   Thu Mar 8 00:29:25 2018 +0100

    describe new locale modifier @cjkwide for user guide

Diff:
---
 winsup/doc/setup-locale.xml | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/winsup/doc/setup-locale.xml b/winsup/doc/setup-locale.xml
index 29502a2..4872ae2 100644
--- a/winsup/doc/setup-locale.xml
+++ b/winsup/doc/setup-locale.xml
@@ -166,6 +166,19 @@ can be used to force wcwidth/wcswidth to return 1 for the ambiguous width
 characters.
 </para></listitem>
 
+<listitem><para>
+For the same class of "CJK Ambiguous Width" characters, it may be
+desirable to handle them as double-width even when a non-CJK language
+setting is selected.  This supports e.g. certain graphic symbols used
+by "Powerline" and provided by "Powerline fonts".  Some terminals have
+options to enforce this width handling (xterm -cjk_width,
+mintty -o Charwidth=ambig-wide, putty configuration) but that alone
+makes character rendering and locale information inconsistent for those
+characters.  The locale modifier "@cjkwide" supports consistent locale
+response with this option; it forces wcwidth/wcswidth to return 2 for the
+ambiguous width characters.
+</para></listitem>
+
 </itemizedlist>
 
 </sect2>