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PATCH: multibyte FAQ

This adds notes on multibyte input to the FAQ.

Your attention is also drawn to the list of systems where multibyte mode
works in INSTALL.  This is all the information I currently have, and
much of it is actually guesswork.

RCS file: /cvsroot/zsh/zsh/INSTALL,v
retrieving revision 1.21
diff -u -r1.21 INSTALL
--- INSTALL	24 Nov 2005 11:46:47 -0000	1.21
+++ INSTALL	14 Dec 2005 18:24:42 -0000
@@ -272,7 +272,16 @@
 --disable-multibyte.  Reports of systems where multibyte support was not
 enabled by default but --enable-multibyte resulted in a usable shell would
 be appreciated.  The developers are not aware of any need to use
---disable-multibyte and this should be reported as a bug.
+--disable-multibyte and this should be reported as a bug.  Currently
+multibyte mode is believed to work automatically on:
+  - All(?) current GNU/Linux distributions
+  - All(?) current BSD variants
+  - OS X 10.4.3
+and to work when configured with --enable-multibyte on:
+  - Solaris 8 and later
 The main shell is not yet aware of multibyte characters, so for example the
 length of a scalar parameter will return the number of bytes, not
@@ -281,6 +290,8 @@
 work correctly with characters in multibyte character sets beyond the ASCII
+See chapter 5 in the FAQ for some notes on multibyte input.
 Memory Routines
Index: Etc/FAQ.yo
RCS file: /cvsroot/zsh/zsh/Etc/FAQ.yo,v
retrieving revision 1.28
diff -u -r1.28 FAQ.yo
--- Etc/FAQ.yo	6 Dec 2005 10:50:37 -0000	1.28
+++ Etc/FAQ.yo	14 Dec 2005 18:24:48 -0000
@@ -43,11 +43,11 @@
-myreport(Z-Shell Frequently-Asked Questions)(Peter Stephenson)(2005/07/18)
+myreport(Z-Shell Frequently-Asked Questions)(Peter Stephenson)(2005/12/14)
 COMMENT(-- the following are for Usenet and must appear first)\
 mydit(Archive-Name:) unix-faq/shell/zsh
-mydit(Last-Modified:) 2005/07/18
+mydit(Last-Modified:) 2005/12/14
 mydit(Submitted-By:) email(pws@xxxxxxxxxxxxxxxxxxxxxxxx (Peter Stephenson))
 mydit(Posting-Frequency:) Monthly
 mydit(Copyright:) (C) P.W. Stephenson, 1995--2005 (see end of document)
@@ -126,11 +126,18 @@
 4.5. How do I get started with programmable completion?
 4.6. Suppose I want to complete all files during a special completion?
-Chapter 5:  The future of zsh
-5.1. What bugs are currently known and unfixed? (Plus recent important changes)
-5.2. Where do I report bugs, get more info / who's working on zsh?
-5.3. What's on the wish-list?
-5.4. Did zsh have problems in the year 2000?
+Chapter 5:  Multibyte input
+5.1. What is multibyte input?
+5.2. How does zsh handle multibyte input?
+5.3. How do I ensure multibyte input works on my system?
+5.4. How can I input characters that aren't on my keyboard?
+Chapter 6:  The future of zsh
+6.1. What bugs are currently known and unfixed? (Plus recent important changes)
+6.2. Where do I report bugs, get more info / who's working on zsh?
+6.3. What's on the wish-list?
+6.4. Did zsh have problems in the year 2000?
@@ -1945,6 +1952,175 @@
   such as expansion or approximate completion.
+chapter(Multibyte input)
+sect(What is multibyte input?)
+  For a long time computers had a simple idea of a character: each octet
+  (8-bit byte) of text contained one character.  This meant an application
+  could only use 256 characters at once.  The first 128 characters (0 to
+  127) on Unix and similar systems usually corresponded to the ASCII
+  character set, as they still do.  So all other possibilities had to be
+  crammed into the remaining 128.  This was done by picking the appropriate
+  character set for the use you were making.  For example, ISO 8859
+  specified a set of extensions to ASCII for various alphabets.
+  This was fine for simple extensions and certain short enough relatives of
+  the Latin alphabet (with no more than a few dozen alphabetic characters),
+  but useless for complex alphabets.  Also, having a different character
+  set for each language is inconvenient: you have to start a new terminal
+  to run the shell with each character set.  So the character set had to be
+  extended.  To cut a long story short, the world has mostly standardised
+  on a character set called Unicode, related to the international standard
+  ISO 10646.  The intention is that this will contain every single
+  character used in all the languages of the world.
+  This has far too many characters to fit into a single octet.  What's
+  more, UNIX utilities such as zsh are so used to dealing with ASCII that
+  removing it would cause no end of trouble.  So what happens is this: the
+  128 ASCII characters are kept exactly the same (and they're the same as
+  the first 128 characters of Unicode), but the remaining 128 characters
+  are used to build up any other Unicode character by combining multiple
+  octets together.  The shell doesn't need to interpret these directly; it
+  just needs to ask the system library how many octets form the next
+  character, and if there's a valid character there at all.  (It can also
+  ask the system what width the character takes up on the screen, so that
+  characters no longer need to be exacxtly one position wide.)
+  The way this is done is called UTF-8.  Multibyte encodings of other
+  character sets exist (you might encounter them for Asian character sets);
+  zsh will be able to use any such encoding as long as it contains ASCII as
+  a single-octet subset and the system can provide information about other
+  characters.  However, in the case of Unicode, UTF-8 is the only one you
+  are likely to enounter.
+  (In case you're confused: Unicode is the characters set, while UTF-8 is
+  an encoding of it.  You might hear about other encodings, such as UCS-2
+  and UCS-4 which are basically the character's index in the character set
+  as a two-octet or four-octet integer.  You might see files encoded this
+  way, for example on Windows, but the shell can't deal directly with text
+  in those formats.)
+sect(How does zsh handle multibyte input?)
+  Until version 4.3, zsh didn't handle multibyte input properly at all.
+  Each octet in a multibyte character would look to the shell like a
+  separate character.  If your terminal handled the character set,
+  characters might appear correct on screen, but trying to edit them would
+  cause all sorts of odd effects.  (It was possible to edit in zsh using
+  single-byte extensions of ASCII such as the ISO 8859 family, however.)
+  From version 4.3, multibyte input is handled in the line editor if zsh
+  has been compiled with the appropriate definitions.  This will happen
+  automatically if the compiler defines __STDC_ISO_10646__, which is true
+  for many recent GNU-based systems.  On other systems you must configure
+  zsh with the argument --enable-multibyte to configure.  (The reason for
+  this is that the presence of __STDC_ISO_10646__ ensures all the required
+  library support is present, short-circuiting a large number of
+  configuration tests.)  Explicit use of --enable-multibyte should work on
+  many other recent UNIX systems; if it works on yours, and that's not
+  mentioned in the shell documentation, please report this to
+  zsh-workers@xxxxxxxxxx, and if it doesn't but you can work out why not
+  we'd also be interested in hearing.
+  You can test if multibyte handling is compiled into your version of the
+  shell by running:
+  verb(
+    (bindkey -m)
+  )
+  which should output a warning:
+  verb(
+    bindkey: warning: `bindkey -m' disables multibyte support
+  )
+  If it doesn't, you don't have multibyte support in your shell.  The
+  parentheses are there to run the command in a subshell, which protects
+  your interactive shell from the effects being warned about.
+  Multibyte strings are not yet handled anywhere else in the shell.  This
+  means, for example, patterns treat multibyte characters as a set of single
+  octets and the ${#var} syntax counts octets, not characters.  There will
+  probably be new syntax to ensure that zsh can work both in its traditional
+  way as well as when interpreting multibyte characters.
+sect(How do I ensure multibyte input works on my system?)
+  Once you have a version of zsh with multibyte support, you need to
+  ensure the envivronment is correct.  We'll assume you're using UTF-8.
+  Many modern systems may come set up correctly already.  Try one of
+  the editing widgets described in the next section to see.
+  There are basically three components.
+  itemize(
+   it() The locale.  This describes a whole series of features specific
+      to countries or regions of which the character set is one.  Usually
+      it is controlled by the environment variable tt(LANG) (there are
+      others but this is the one to start with).  You need to find a
+      locale whose name contains mytt(UTF-8).  This will be a variant on
+      your usual locale, which typically indicates the language and
+      country; for example, mine is mytt(en_GB.UTF-8).  Luckily, zsh can
+      complete locale names, so if you have the new completion system
+      loaded you can type mytt(export LANG=) and attempt to complete a
+      suitable locale.  It's the locale that tells the shell to expect the
+      right form of multibyte input.  (However, there's no guarantee that
+      the shell is actually going to get this input: for example, if you
+      edit file names that have been created using a different character
+      set it won't work properly.)
+   it() The terminal emulator.  Those that are supplied with a recent
+      desktop environment, such as gnome-terminal, are likely to have
+      extensive support for localization and may work correctly as soon
+      as they know the locale.
+   it() The font.  If you selected this from a menu in your terminal
+      emulator, there's a good chance it already selected the right
+      character set to go with it.  If you hand-picked an old fashioned
+      X font with a lot of dashes, you need to make sure it ends with
+      the right character encoding, mytt(iso-10646-1) (and not, for
+      example, mytt(iso-8859-1)).  Not all characters will be available
+      in any font, and some fonts may have a more restricted range of
+      Unicode characters than others.
+  )
+sect(How can I input characters that aren't on my keyboard?)
+  Two functions are provided with zsh that help you input characters.
+  As with all editing widgets implemented by functions, you need to
+  mark the function for autoload, create the widget, and, if you are
+  going to use it frequently, bind it to a key sequence.  The
+  following binds tt(insert-composed-char) to F5 on my keyboard:
+  verb(
+    autoload -Uz insert-composed-char
+    zle -N insert-composed-char
+    bindkey '\e[15~' insert-composed-char
+  )
+  The two widgets are described in the tt(zshcontrib(1)) manual
+  page, but here is a brief summary:
+  tt(insert-composed-char) is followed by two characters that
+  are a mnemonic for a multibyte character.  For example mytt(a:)
+  is a with an umlaut; mytt(cH) is the symbol for hearts on a playing
+  card.  Various accented characters, European and related alphabets,
+  and punctuation and mathematical symbols are available.  The
+  mnemonics are mostly those given by RFC 1345, see
+  url(http://www.faqs.org/rfcs/rfc1345.html)\
+  tt(insert-unicode-char) is used to input a Unicode character by
+  its hexadecimal number.  This is the number given in the Unicode
+  character charts, see for example \
+  You need to execute the function, then type the hexadecimal number
+  (you can omit any leading zeroes), then execute the function again.
+  Both functions can be used without multibyte mode, provided the locale is
+  correct and the character selected exists in the current character set;
+  however, using UTF-8 massively extends the number of valid characters
+  that can be produced.
 chapter(The future of zsh)
 sect(What bugs are currently known and unfixed? (Plus recent \

Peter Stephenson <pws@xxxxxxx>                  Software Engineer
CSR PLC, Churchill House, Cambridge Business Park, Cowley Road
Cambridge, CB4 0WZ, UK                          Tel: +44 (0)1223 692070

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