@cindex IPA
@cindex Japanese
@cindex Korean
+@cindex Cyrillic
@cindex Russian
- If you compile XEmacs with mule option, it supports a wide variety of
+ If you compile XEmacs with Mule option, it supports a wide variety of
world scripts, including Latin script, as well as Arabic script,
Simplified Chinese script (for mainland of China), Traditional Chinese
script (for Taiwan and Hong-Kong), Greek script, Hebrew script, IPA
* Language Environments:: Setting things up for the language you use.
* Input Methods:: Entering text characters not on your keyboard.
* Select Input Method:: Specifying your choice of input methods.
+* Mule and Fonts:: Additional font-related issues
* Coding Systems:: Character set conversion when you read and
write files, and so on.
* Recognize Coding:: How XEmacs figures out which conversion to use.
@end menu
@node Mule Intro, Language Environments, Mule, Mule
-@section Introduction to world scripts
-
- The users of these scripts have established many more-or-less standard
-coding systems for storing files.
-@c XEmacs internally uses a single multibyte character encoding, so that it
-@c can intermix characters from all these scripts in a single buffer or
-@c string. This encoding represents each non-ASCII character as a sequence
-@c of bytes in the range 0200 through 0377.
+@section What is Mule?
+
+Mule is the MUltiLingual Extension to XEmacs. It provides facilities
+not only for handling text written in many different languages, but in
+fact multilingual texts containing several languages in the same buffer.
+This goes beyond the simple facilities offered by Unicode for
+representation of multilingual text. Mule also supports input methods,
+composing display using fonts in various different encodings, changing
+character syntax and other editing facilities to correspond to local
+language usage, and more.
+
+The most obvious problem is that of the different character coding
+systems used by different languages. ASCII supplies all the characters
+needed for most computer programming languages and US English (it lacks
+the currency symbol for British English), but other Western European
+languages (French, Spanish, German) require more than 96 code positions
+for accented characters. In fact, even with 8 bits to represent 96 more
+character (including accented characters and symbols such as currency
+symbols), some languages' alphabets remain incomplete (Croatian,
+Polish). (The 64 "missing characters" are reserved for control
+characters.) Furthermore, many European languages have their own
+alphabets, which must conflict with the accented characters since the
+ASCII characters are needed for computer interaction (error and log
+messages are typically in ASCII).
+
+For economy of space, historical practice has been for each language to
+establish its own encoding for the characters it needs. This allows
+most European languages to represented with one octet (byte) per
+character. However, many Asian languages have thousands of characters
+and require two or more octets per character. For multilingual
+purposes, the ISO 2022 standard establishes escape codes that allow
+switching encodings in midstream. (It's also ISO 2022 that establishes
+the standard that code points 0-31 and 128-159 are control codes.)
+
+However, this is error-prone and complex for internal processing. For
+this reason XEmacs uses an internal coding system which can encode all
+of the world's scripts. Unfortunately, for historical reasons, this
+code is not Unicode, although we are moving in that direction.
+
XEmacs translates between the internal character encoding and various
other coding systems when reading and writing files, when exchanging
data with subprocesses, and (in some cases) in the @kbd{C-q} command
-(see below).
+(see below). The internal encoding is never visible to the user in a
+production XEmacs, but unfortunately the process cannot be completely
+transparent to the user. This is because the same ranges of octets may
+represent 1-octet ISO-8859-1 (which is satisfactory for most Western
+European use prior to the introduction of the Euro currency), 1-octet
+ISO-8859-15 (which substitutes the Euro for the rarely used "generic
+currency" symbol), 1-octet ISO-8859-5 (Cyrillic), or multioctet EUC-JP
+(Japanese). There's no way to tell without being able to read!
+
+A number of heuristics are incorporated in Mule for automatic
+recognition, there are facilities for the user to set defaults, and
+where necessary (rarely, we hope) to set coding systems directly.
@kindex C-h h
@findex view-hello-file
@cindex language environments
All supported character sets are supported in XEmacs buffers if it is
-compile with mule; there is no need to select a particular language in
+compiled with Mule; there is no need to select a particular language in
order to display its characters in an XEmacs buffer. However, it is
important to select a @dfn{language environment} in order to set various
defaults. The language environment really represents a choice of
the XEmacs session. The supported language environments include:
@quotation
-Chinese-BIG5, Chinese-CNS, Chinese-GB, Cyrillic-ISO, English, Ethiopic,
-Greek, Japanese, Korean, Latin-1, Latin-2, Latin-3, Latin-4, Latin-5.
+ASCII, Chinese-BIG5, Chinese-GB, Croatian, Cyrillic-ALT, Cyrillic-ISO,
+Cyrillic-KOI8, Cyrillic-Win, Czech, English, Ethiopic, French, German,
+Greek, Hebrew, IPA, Japanese, Korean, Latin-1, Latin-2, Latin-3, Latin-4,
+Latin-5, Norwegian, Polish, Romanian, Slovenian, Thai-XTIS, Vietnamese.
@end quotation
Some operating systems let you specify the language you are using by
characters to type next is displayed in the echo area (but not when you
are in the minibuffer).
-@node Select Input Method, Coding Systems, Input Methods, Mule
+@node Select Input Method, Mule and Fonts, Input Methods, Mule
@section Selecting an Input Method
@table @kbd
list-input-methods}. The list gives information about each input
method, including the string that stands for it in the mode line.
-@node Coding Systems, Recognize Coding, Select Input Method, Mule
+@node Mule and Fonts, Coding Systems, Select Input Method, Mule
+@section Mule and Fonts
+@cindex fonts
+@cindex font registry
+@cindex font encoding
+@cindex CCL programs
+
+(This section is X11-specific.)
+
+Text in XEmacs buffers is displayed using various faces. In addition to
+specifying properties of a face, such as font and color, there are some
+additional properties of Mule charsets that are used in text.
+
+There is currently two properties of a charset that could be adjusted by
+user: font registry and so called @dfn{ccl-program}.
+
+Font registry is a regular expression matching the font registry field
+for this character set. For example, both the @code{ascii} and
+@w{@code{latin-iso8859-1}} charsets use the registry @code{"ISO8859-1"}.
+This field is used to choose an appropriate font when the user gives a
+general font specification such as @w{@samp{-*-courier-medium-r-*-140-*}},
+i.e. a 14-point upright medium-weight Courier font.
+
+You can set font registry for a charset using
+@samp{set-charset-registry} function in one of your startup files. This
+function takes two arguments: character set (as a symbol) and font
+registry (as a string).
+
+E.@w{ }g., for Cyrillic texts Mule uses @w{@code{cyrillic-iso8859-5}}
+charset with @samp{"ISO8859-5"} as a default registry, and we want to
+use @samp{"koi8-r"} instead, because fonts in that encoding are
+installed on our system. Use:
+
+@example
+(set-charset-registry 'cyrillic-iso8859-5 "koi8-r")
+@end example
+
+(Please note that you probably also want to set font registry for
+@samp{ascii} charset so that mixed English/Cyrillic texts be displayed
+using the same font.)
+
+"CCL-programs" are a little special-purpose scripts defined within
+XEmacs or in some package. Those scripts allow XEmacs to use fonts that
+are in different encoding from the encoding that is used by Mule for
+text in buffer. Returning to the above example, we need to somehow tell
+XEmacs that we have different encodings of fonts and text and so it
+needs to convert characters between those encodings when displaying.
+That's what @samp{set-charset-ccl-program} function is used for. There
+are quite a few various CCL programs defined within XEmacs, and there is
+no comprehensive list of them, so you currently have to consult sources.
+@c FIXME: there must be a list of CCL programs
+
+We know that there is a CCL program called @samp{ccl-encode-koi8-r-font}
+that is used exactly for needed purpose: to convert characters between
+@samp{ISO8859-5} encoding and @samp{koi8-r}. Use:
+
+@example
+(set-charset-ccl-program 'cyrillic-iso8859-5 'ccl-encode-koi8-r-font)
+@end example
+
+There are several more uses for CCL programs, not related to fonts, but
+those uses are not described here.
+
+
+@node Coding Systems, Recognize Coding, Mule and Fonts, Mule
@section Coding Systems
@cindex coding systems
@item M-x list-coding-systems
Display a list of all the supported coding systems.
+
+@item C-u M-x list-coding-systems
+Display comprehensive list of specific details of all supported coding
+systems.
@end table
-@kindex C-h C
+@kindex C-x @key{RET} C
@findex describe-coding-system
- The command @kbd{C-h C} (@code{describe-coding-system}) displays
+ The command @kbd{C-x RET C} (@code{describe-coding-system}) displays
information about particular coding systems. You can specify a coding
system name as argument; alternatively, with an empty argument, it
describes the coding systems currently selected for various purposes,
@node Recognize Coding, Specify Coding, Coding Systems, Mule
@section Recognizing Coding Systems
+@c #### This section is out of date. The following set-*-coding-system
+@c functions are known:
+
+@c set-buffer-file-coding-system
+@c set-buffer-file-coding-system-for-read
+@c set-buffer-process-coding-system
+@c set-console-tty-coding-system
+@c set-console-tty-input-coding-system
+@c set-console-tty-output-coding-system
+@c set-default-buffer-file-coding-system
+@c set-default-coding-systems
+@c set-default-file-coding-system
+@c set-file-coding-system
+@c set-file-coding-system-for-read
+@c set-keyboard-coding-system
+@c set-pathname-coding-system
+@c set-process-coding-system
+@c set-process-input-coding-system
+@c set-process-output-coding-system
+@c set-terminal-coding-system
+
+@c Some are marked as broken. Agenda: (1) Update this section using
+@c docstrings. Note that they may be inaccurate. (2) Correct the
+@c documentation here, updating docstrings at the same time.
+
+@c Document this.
+
+@c set-language-environment-coding-systems
+
+@c What are these?
+
+@c dontusethis-set-value-file-name-coding-system-handler
+@c dontusethis-set-value-keyboard-coding-system-handler
+@c dontusethis-set-value-terminal-coding-system-handler
+
Most of the time, XEmacs can recognize which coding system to use for
any given file--once you have specified your preferences.
command.
@item C-x @key{RET} k @var{coding} @key{RET}
-Use coding system @var{coding} for keyboard input.
+Use coding system @var{coding} for keyboard input. (This feature is
+non-functional and is temporarily disabled.)
@item C-x @key{RET} t @var{coding} @key{RET}
Use coding system @var{coding} for terminal output.
printing characters. Coding systems typically translate sequences of
non-graphic characters.
+(This feature is non-functional and is temporarily disabled.)
+
@kindex C-x RET p
@findex set-buffer-process-coding-system
The command @kbd{C-x @key{RET} p} (@code{set-buffer-process-coding-system})
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