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diff --git a/doc/emacs/mule.texi b/doc/emacs/mule.texi new file mode 100644 index 0000000000..c71c820dc2 --- /dev/null +++ b/doc/emacs/mule.texi @@ -0,0 +1,1535 @@ +@c This is part of the Emacs manual. +@c Copyright (C) 1997, 1999, 2000, 2001, 2002, 2003, 2004, +@c 2005, 2006, 2007 Free Software Foundation, Inc. +@c See file emacs.texi for copying conditions. +@node International, Major Modes, Frames, Top +@chapter International Character Set Support +@cindex MULE +@cindex international scripts +@cindex multibyte characters +@cindex encoding of characters + +@cindex Celtic +@cindex Chinese +@cindex Cyrillic +@cindex Czech +@cindex Devanagari +@cindex Hindi +@cindex Marathi +@cindex Ethiopic +@cindex German +@cindex Greek +@cindex Hebrew +@cindex IPA +@cindex Japanese +@cindex Korean +@cindex Lao +@cindex Latin +@cindex Polish +@cindex Romanian +@cindex Slovak +@cindex Slovenian +@cindex Thai +@cindex Tibetan +@cindex Turkish +@cindex Vietnamese +@cindex Dutch +@cindex Spanish + Emacs supports a wide variety of international character sets, +including European and Vietnamese variants of the Latin alphabet, as +well as Cyrillic, Devanagari (for Hindi and Marathi), Ethiopic, Greek, +Han (for Chinese and Japanese), Hangul (for Korean), Hebrew, IPA, +Kannada, Lao, Malayalam, Tamil, Thai, Tibetan, and Vietnamese scripts. +Emacs also supports various encodings of these characters used by +other internationalized software, such as word processors and mailers. + + Emacs allows editing text with international characters by supporting +all the related activities: + +@itemize @bullet +@item +You can visit files with non-@acronym{ASCII} characters, save non-@acronym{ASCII} text, and +pass non-@acronym{ASCII} text between Emacs and programs it invokes (such as +compilers, spell-checkers, and mailers). Setting your language +environment (@pxref{Language Environments}) takes care of setting up the +coding systems and other options for a specific language or culture. +Alternatively, you can specify how Emacs should encode or decode text +for each command; see @ref{Text Coding}. + +@item +You can display non-@acronym{ASCII} characters encoded by the various +scripts. This works by using appropriate fonts on graphics displays +(@pxref{Defining Fontsets}), and by sending special codes to text-only +displays (@pxref{Terminal Coding}). If some characters are displayed +incorrectly, refer to @ref{Undisplayable Characters}, which describes +possible problems and explains how to solve them. + +@item +You can insert non-@acronym{ASCII} characters or search for them. To do that, +you can specify an input method (@pxref{Select Input Method}) suitable +for your language, or use the default input method set up when you set +your language environment. If +your keyboard can produce non-@acronym{ASCII} characters, you can select an +appropriate keyboard coding system (@pxref{Terminal Coding}), and Emacs +will accept those characters. Latin-1 characters can also be input by +using the @kbd{C-x 8} prefix, see @ref{Unibyte Mode}. + +On X Window systems, your locale should be set to an appropriate value +to make sure Emacs interprets keyboard input correctly; see +@ref{Language Environments, locales}. +@end itemize + + The rest of this chapter describes these issues in detail. + +@menu +* International Chars:: Basic concepts of multibyte characters. +* Enabling Multibyte:: Controlling whether to use multibyte characters. +* 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. +* Multibyte Conversion:: How single-byte characters convert to multibyte. +* Coding Systems:: Character set conversion when you read and + write files, and so on. +* Recognize Coding:: How Emacs figures out which conversion to use. +* Specify Coding:: Specifying a file's coding system explicitly. +* Output Coding:: Choosing coding systems for output. +* Text Coding:: Choosing conversion to use for file text. +* Communication Coding:: Coding systems for interprocess communication. +* File Name Coding:: Coding systems for file @emph{names}. +* Terminal Coding:: Specifying coding systems for converting + terminal input and output. +* Fontsets:: Fontsets are collections of fonts + that cover the whole spectrum of characters. +* Defining Fontsets:: Defining a new fontset. +* Undisplayable Characters:: When characters don't display. +* Unibyte Mode:: You can pick one European character set + to use without multibyte characters. +* Charsets:: How Emacs groups its internal character codes. +@end menu + +@node International Chars +@section Introduction to International Character Sets + + The users of international character sets and scripts have +established many more-or-less standard coding systems for storing +files. Emacs internally uses a single multibyte character encoding, +so that it can intermix characters from all these scripts in a single +buffer or string. This encoding represents each non-@acronym{ASCII} +character as a sequence of bytes in the range 0200 through 0377. +Emacs translates between the multibyte 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 +(@pxref{Multibyte Conversion}). + +@kindex C-h h +@findex view-hello-file +@cindex undisplayable characters +@cindex @samp{?} in display + The command @kbd{C-h h} (@code{view-hello-file}) displays the file +@file{etc/HELLO}, which shows how to say ``hello'' in many languages. +This illustrates various scripts. If some characters can't be +displayed on your terminal, they appear as @samp{?} or as hollow boxes +(@pxref{Undisplayable Characters}). + + Keyboards, even in the countries where these character sets are used, +generally don't have keys for all the characters in them. So Emacs +supports various @dfn{input methods}, typically one for each script or +language, to make it convenient to type them. + +@kindex C-x RET + The prefix key @kbd{C-x @key{RET}} is used for commands that pertain +to multibyte characters, coding systems, and input methods. + +@node Enabling Multibyte +@section Enabling Multibyte Characters + + By default, Emacs starts in multibyte mode, because that allows you to +use all the supported languages and scripts without limitations. + +@cindex turn multibyte support on or off + You can enable or disable multibyte character support, either for +Emacs as a whole, or for a single buffer. When multibyte characters +are disabled in a buffer, we call that @dfn{unibyte mode}. Then each +byte in that buffer represents a character, even codes 0200 through +0377. + + The old features for supporting the European character sets, ISO +Latin-1 and ISO Latin-2, work in unibyte mode as they did in Emacs 19 +and also work for the other ISO 8859 character sets. However, there +is no need to turn off multibyte character support to use ISO Latin; +the Emacs multibyte character set includes all the characters in these +character sets, and Emacs can translate automatically to and from the +ISO codes. + + To edit a particular file in unibyte representation, visit it using +@code{find-file-literally}. @xref{Visiting}. To convert a buffer in +multibyte representation into a single-byte representation of the same +characters, the easiest way is to save the contents in a file, kill the +buffer, and find the file again with @code{find-file-literally}. You +can also use @kbd{C-x @key{RET} c} +(@code{universal-coding-system-argument}) and specify @samp{raw-text} as +the coding system with which to find or save a file. @xref{Text +Coding}. Finding a file as @samp{raw-text} doesn't disable format +conversion, uncompression and auto mode selection as +@code{find-file-literally} does. + +@vindex enable-multibyte-characters +@vindex default-enable-multibyte-characters + To turn off multibyte character support by default, start Emacs with +the @samp{--unibyte} option (@pxref{Initial Options}), or set the +environment variable @env{EMACS_UNIBYTE}. You can also customize +@code{enable-multibyte-characters} or, equivalently, directly set the +variable @code{default-enable-multibyte-characters} to @code{nil} in +your init file to have basically the same effect as @samp{--unibyte}. + +@findex toggle-enable-multibyte-characters + To convert a unibyte session to a multibyte session, set +@code{default-enable-multibyte-characters} to @code{t}. Buffers which +were created in the unibyte session before you turn on multibyte support +will stay unibyte. You can turn on multibyte support in a specific +buffer by invoking the command @code{toggle-enable-multibyte-characters} +in that buffer. + +@cindex Lisp files, and multibyte operation +@cindex multibyte operation, and Lisp files +@cindex unibyte operation, and Lisp files +@cindex init file, and non-@acronym{ASCII} characters +@cindex environment variables, and non-@acronym{ASCII} characters + With @samp{--unibyte}, multibyte strings are not created during +initialization from the values of environment variables, +@file{/etc/passwd} entries etc.@: that contain non-@acronym{ASCII} 8-bit +characters. + + Emacs normally loads Lisp files as multibyte, regardless of whether +you used @samp{--unibyte}. This includes the Emacs initialization file, +@file{.emacs}, and the initialization files of Emacs packages such as +Gnus. However, you can specify unibyte loading for a particular Lisp +file, by putting @w{@samp{-*-unibyte: t;-*-}} in a comment on the first +line (@pxref{File Variables}). Then that file is always loaded as +unibyte text, even if you did not start Emacs with @samp{--unibyte}. +The motivation for these conventions is that it is more reliable to +always load any particular Lisp file in the same way. However, you can +load a Lisp file as unibyte, on any one occasion, by typing @kbd{C-x +@key{RET} c raw-text @key{RET}} immediately before loading it. + + The mode line indicates whether multibyte character support is +enabled in the current buffer. If it is, there are two or more +characters (most often two dashes) near the beginning of the mode +line, before the indication of the visited file's end-of-line +convention (colon, backslash, etc.). When multibyte characters +are not enabled, nothing precedes the colon except a single dash. +@xref{Mode Line}, for more details about this. + +@node Language Environments +@section Language Environments +@cindex language environments + + All supported character sets are supported in Emacs buffers whenever +multibyte characters are enabled; there is no need to select a +particular language in order to display its characters in an Emacs +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 preferred script (more or less) rather than a +choice of language. + + The language environment controls which coding systems to recognize +when reading text (@pxref{Recognize Coding}). This applies to files, +incoming mail, netnews, and any other text you read into Emacs. It may +also specify the default coding system to use when you create a file. +Each language environment also specifies a default input method. + +@findex set-language-environment +@vindex current-language-environment + To select a language environment, you can customize the variable +@code{current-language-environment} or use the command @kbd{M-x +set-language-environment}. It makes no difference which buffer is +current when you use this command, because the effects apply globally to +the Emacs session. The supported language environments include: + +@cindex Euro sign +@cindex UTF-8 +@quotation +ASCII, Belarusian, Brazilian Portuguese, Bulgarian, Chinese-BIG5, +Chinese-CNS, Chinese-EUC-TW, Chinese-GB, Croatian, Cyrillic-ALT, +Cyrillic-ISO, Cyrillic-KOI8, Czech, Devanagari, Dutch, English, +Esperanto, Ethiopic, French, Georgian, German, Greek, Hebrew, IPA, +Italian, Japanese, Kannada, Korean, Lao, Latin-1, Latin-2, Latin-3, +Latin-4, Latin-5, Latin-6, Latin-7, Latin-8 (Celtic), Latin-9 (updated +Latin-1 with the Euro sign), Latvian, Lithuanian, Malayalam, Polish, +Romanian, Russian, Slovak, Slovenian, Spanish, Swedish, Tajik, Tamil, +Thai, Tibetan, Turkish, UTF-8 (for a setup which prefers Unicode +characters and files encoded in UTF-8), Ukrainian, Vietnamese, Welsh, +and Windows-1255 (for a setup which prefers Cyrillic characters and +files encoded in Windows-1255). +@tex +\hbadness=10000\par % just avoid underfull hbox warning +@end tex +@end quotation + +@cindex fonts for various scripts +@cindex Intlfonts package, installation + To display the script(s) used by your language environment on a +graphical display, you need to have a suitable font. If some of the +characters appear as empty boxes, you should install the GNU Intlfonts +package, which includes fonts for most supported scripts.@footnote{If +you run Emacs on X, you need to inform the X server about the location +of the newly installed fonts with the following commands: + +@example + xset fp+ /usr/local/share/emacs/fonts + xset fp rehash +@end example +} +@xref{Fontsets}, for more details about setting up your fonts. + +@findex set-locale-environment +@vindex locale-language-names +@vindex locale-charset-language-names +@cindex locales + Some operating systems let you specify the character-set locale you +are using by setting the locale environment variables @env{LC_ALL}, +@env{LC_CTYPE}, or @env{LANG}.@footnote{If more than one of these is +set, the first one that is nonempty specifies your locale for this +purpose.} During startup, Emacs looks up your character-set locale's +name in the system locale alias table, matches its canonical name +against entries in the value of the variables +@code{locale-charset-language-names} and @code{locale-language-names}, +and selects the corresponding language environment if a match is found. +(The former variable overrides the latter.) It also adjusts the display +table and terminal coding system, the locale coding system, the +preferred coding system as needed for the locale, and---last but not +least---the way Emacs decodes non-@acronym{ASCII} characters sent by your keyboard. + + If you modify the @env{LC_ALL}, @env{LC_CTYPE}, or @env{LANG} +environment variables while running Emacs, you may want to invoke the +@code{set-locale-environment} function afterwards to readjust the +language environment from the new locale. + +@vindex locale-preferred-coding-systems + The @code{set-locale-environment} function normally uses the preferred +coding system established by the language environment to decode system +messages. But if your locale matches an entry in the variable +@code{locale-preferred-coding-systems}, Emacs uses the corresponding +coding system instead. For example, if the locale @samp{ja_JP.PCK} +matches @code{japanese-shift-jis} in +@code{locale-preferred-coding-systems}, Emacs uses that encoding even +though it might normally use @code{japanese-iso-8bit}. + + You can override the language environment chosen at startup with +explicit use of the command @code{set-language-environment}, or with +customization of @code{current-language-environment} in your init +file. + +@kindex C-h L +@findex describe-language-environment + To display information about the effects of a certain language +environment @var{lang-env}, use the command @kbd{C-h L @var{lang-env} +@key{RET}} (@code{describe-language-environment}). This tells you +which languages this language environment is useful for, and lists the +character sets, coding systems, and input methods that go with it. It +also shows some sample text to illustrate scripts used in this +language environment. If you give an empty input for @var{lang-env}, +this command describes the chosen language environment. + +@vindex set-language-environment-hook + You can customize any language environment with the normal hook +@code{set-language-environment-hook}. The command +@code{set-language-environment} runs that hook after setting up the new +language environment. The hook functions can test for a specific +language environment by checking the variable +@code{current-language-environment}. This hook is where you should +put non-default settings for specific language environment, such as +coding systems for keyboard input and terminal output, the default +input method, etc. + +@vindex exit-language-environment-hook + Before it starts to set up the new language environment, +@code{set-language-environment} first runs the hook +@code{exit-language-environment-hook}. This hook is useful for undoing +customizations that were made with @code{set-language-environment-hook}. +For instance, if you set up a special key binding in a specific language +environment using @code{set-language-environment-hook}, you should set +up @code{exit-language-environment-hook} to restore the normal binding +for that key. + +@node Input Methods +@section Input Methods + +@cindex input methods + An @dfn{input method} is a kind of character conversion designed +specifically for interactive input. In Emacs, typically each language +has its own input method; sometimes several languages which use the same +characters can share one input method. A few languages support several +input methods. + + The simplest kind of input method works by mapping @acronym{ASCII} letters +into another alphabet; this allows you to use one other alphabet +instead of @acronym{ASCII}. The Greek and Russian input methods +work this way. + + A more powerful technique is composition: converting sequences of +characters into one letter. Many European input methods use composition +to produce a single non-@acronym{ASCII} letter from a sequence that consists of a +letter followed by accent characters (or vice versa). For example, some +methods convert the sequence @kbd{a'} into a single accented letter. +These input methods have no special commands of their own; all they do +is compose sequences of printing characters. + + The input methods for syllabic scripts typically use mapping followed +by composition. The input methods for Thai and Korean work this way. +First, letters are mapped into symbols for particular sounds or tone +marks; then, sequences of these which make up a whole syllable are +mapped into one syllable sign. + + Chinese and Japanese require more complex methods. In Chinese input +methods, first you enter the phonetic spelling of a Chinese word (in +input method @code{chinese-py}, among others), or a sequence of +portions of the character (input methods @code{chinese-4corner} and +@code{chinese-sw}, and others). One input sequence typically +corresponds to many possible Chinese characters. You select the one +you mean using keys such as @kbd{C-f}, @kbd{C-b}, @kbd{C-n}, +@kbd{C-p}, and digits, which have special meanings in this situation. + + The possible characters are conceptually arranged in several rows, +with each row holding up to 10 alternatives. Normally, Emacs displays +just one row at a time, in the echo area; @code{(@var{i}/@var{j})} +appears at the beginning, to indicate that this is the @var{i}th row +out of a total of @var{j} rows. Type @kbd{C-n} or @kbd{C-p} to +display the next row or the previous row. + + Type @kbd{C-f} and @kbd{C-b} to move forward and backward among +the alternatives in the current row. As you do this, Emacs highlights +the current alternative with a special color; type @code{C-@key{SPC}} +to select the current alternative and use it as input. The +alternatives in the row are also numbered; the number appears before +the alternative. Typing a digit @var{n} selects the @var{n}th +alternative of the current row and uses it as input. + + @key{TAB} in these Chinese input methods displays a buffer showing +all the possible characters at once; then clicking @kbd{Mouse-2} on +one of them selects that alternative. The keys @kbd{C-f}, @kbd{C-b}, +@kbd{C-n}, @kbd{C-p}, and digits continue to work as usual, but they +do the highlighting in the buffer showing the possible characters, +rather than in the echo area. + + In Japanese input methods, first you input a whole word using +phonetic spelling; then, after the word is in the buffer, Emacs +converts it into one or more characters using a large dictionary. One +phonetic spelling corresponds to a number of different Japanese words; +to select one of them, use @kbd{C-n} and @kbd{C-p} to cycle through +the alternatives. + + Sometimes it is useful to cut off input method processing so that the +characters you have just entered will not combine with subsequent +characters. For example, in input method @code{latin-1-postfix}, the +sequence @kbd{e '} combines to form an @samp{e} with an accent. What if +you want to enter them as separate characters? + + One way is to type the accent twice; this is a special feature for +entering the separate letter and accent. For example, @kbd{e ' '} gives +you the two characters @samp{e'}. Another way is to type another letter +after the @kbd{e}---something that won't combine with that---and +immediately delete it. For example, you could type @kbd{e e @key{DEL} +'} to get separate @samp{e} and @samp{'}. + + Another method, more general but not quite as easy to type, is to use +@kbd{C-\ C-\} between two characters to stop them from combining. This +is the command @kbd{C-\} (@code{toggle-input-method}) used twice. +@ifnottex +@xref{Select Input Method}. +@end ifnottex + +@cindex incremental search, input method interference + @kbd{C-\ C-\} is especially useful inside an incremental search, +because it stops waiting for more characters to combine, and starts +searching for what you have already entered. + + To find out how to input the character after point using the current +input method, type @kbd{C-u C-x =}. @xref{Position Info}. + +@vindex input-method-verbose-flag +@vindex input-method-highlight-flag + The variables @code{input-method-highlight-flag} and +@code{input-method-verbose-flag} control how input methods explain +what is happening. If @code{input-method-highlight-flag} is +non-@code{nil}, the partial sequence is highlighted in the buffer (for +most input methods---some disable this feature). If +@code{input-method-verbose-flag} is non-@code{nil}, the list of +possible characters to type next is displayed in the echo area (but +not when you are in the minibuffer). + +@node Select Input Method +@section Selecting an Input Method + +@table @kbd +@item C-\ +Enable or disable use of the selected input method. + +@item C-x @key{RET} C-\ @var{method} @key{RET} +Select a new input method for the current buffer. + +@item C-h I @var{method} @key{RET} +@itemx C-h C-\ @var{method} @key{RET} +@findex describe-input-method +@kindex C-h I +@kindex C-h C-\ +Describe the input method @var{method} (@code{describe-input-method}). +By default, it describes the current input method (if any). This +description should give you the full details of how to use any +particular input method. + +@item M-x list-input-methods +Display a list of all the supported input methods. +@end table + +@findex set-input-method +@vindex current-input-method +@kindex C-x RET C-\ + To choose an input method for the current buffer, use @kbd{C-x +@key{RET} C-\} (@code{set-input-method}). This command reads the +input method name from the minibuffer; the name normally starts with the +language environment that it is meant to be used with. The variable +@code{current-input-method} records which input method is selected. + +@findex toggle-input-method +@kindex C-\ + Input methods use various sequences of @acronym{ASCII} characters to +stand for non-@acronym{ASCII} characters. Sometimes it is useful to +turn off the input method temporarily. To do this, type @kbd{C-\} +(@code{toggle-input-method}). To reenable the input method, type +@kbd{C-\} again. + + If you type @kbd{C-\} and you have not yet selected an input method, +it prompts for you to specify one. This has the same effect as using +@kbd{C-x @key{RET} C-\} to specify an input method. + + When invoked with a numeric argument, as in @kbd{C-u C-\}, +@code{toggle-input-method} always prompts you for an input method, +suggesting the most recently selected one as the default. + +@vindex default-input-method + Selecting a language environment specifies a default input method for +use in various buffers. When you have a default input method, you can +select it in the current buffer by typing @kbd{C-\}. The variable +@code{default-input-method} specifies the default input method +(@code{nil} means there is none). + + In some language environments, which support several different input +methods, you might want to use an input method different from the +default chosen by @code{set-language-environment}. You can instruct +Emacs to select a different default input method for a certain +language environment, if you wish, by using +@code{set-language-environment-hook} (@pxref{Language Environments, +set-language-environment-hook}). For example: + +@lisp +(defun my-chinese-setup () + "Set up my private Chinese environment." + (if (equal current-language-environment "Chinese-GB") + (setq default-input-method "chinese-tonepy"))) +(add-hook 'set-language-environment-hook 'my-chinese-setup) +@end lisp + +@noindent +This sets the default input method to be @code{chinese-tonepy} +whenever you choose a Chinese-GB language environment. + +@findex quail-set-keyboard-layout + Some input methods for alphabetic scripts work by (in effect) +remapping the keyboard to emulate various keyboard layouts commonly used +for those scripts. How to do this remapping properly depends on your +actual keyboard layout. To specify which layout your keyboard has, use +the command @kbd{M-x quail-set-keyboard-layout}. + +@findex quail-show-key + You can use the command @kbd{M-x quail-show-key} to show what key (or +key sequence) to type in order to input the character following point, +using the selected keyboard layout. The command @kbd{C-u C-x =} also +shows that information in addition to the other information about the +character. + +@findex list-input-methods + To see a list of all the supported input methods, type @kbd{M-x +list-input-methods}. The list gives information about each input +method, including the string that stands for it in the mode line. + +@node Multibyte Conversion +@section Unibyte and Multibyte Non-@acronym{ASCII} characters + + When multibyte characters are enabled, character codes 0240 (octal) +through 0377 (octal) are not really legitimate in the buffer. The valid +non-@acronym{ASCII} printing characters have codes that start from 0400. + + If you type a self-inserting character in the range 0240 through +0377, or if you use @kbd{C-q} to insert one, Emacs assumes you +intended to use one of the ISO Latin-@var{n} character sets, and +converts it to the Emacs code representing that Latin-@var{n} +character. You select @emph{which} ISO Latin character set to use +through your choice of language environment +@iftex +(see above). +@end iftex +@ifnottex +(@pxref{Language Environments}). +@end ifnottex +If you do not specify a choice, the default is Latin-1. + + If you insert a character in the range 0200 through 0237, which +forms the @code{eight-bit-control} character set, it is inserted +literally. You should normally avoid doing this since buffers +containing such characters have to be written out in either the +@code{emacs-mule} or @code{raw-text} coding system, which is usually +not what you want. + +@node Coding Systems +@section Coding Systems +@cindex coding systems + + Users of various languages have established many more-or-less standard +coding systems for representing them. Emacs does not use these coding +systems internally; instead, it converts from various coding systems to +its own system when reading data, and converts the internal coding +system to other coding systems when writing data. Conversion is +possible in reading or writing files, in sending or receiving from the +terminal, and in exchanging data with subprocesses. + + Emacs assigns a name to each coding system. Most coding systems are +used for one language, and the name of the coding system starts with the +language name. Some coding systems are used for several languages; +their names usually start with @samp{iso}. There are also special +coding systems @code{no-conversion}, @code{raw-text} and +@code{emacs-mule} which do not convert printing characters at all. + +@cindex international files from DOS/Windows systems + A special class of coding systems, collectively known as +@dfn{codepages}, is designed to support text encoded by MS-Windows and +MS-DOS software. The names of these coding systems are +@code{cp@var{nnnn}}, where @var{nnnn} is a 3- or 4-digit number of the +codepage. You can use these encodings just like any other coding +system; for example, to visit a file encoded in codepage 850, type +@kbd{C-x @key{RET} c cp850 @key{RET} C-x C-f @var{filename} +@key{RET}}@footnote{ +In the MS-DOS port of Emacs, you need to create a @code{cp@var{nnn}} +coding system with @kbd{M-x codepage-setup}, before you can use it. +@iftex +@xref{MS-DOS and MULE,,,emacs-extra,Specialized Emacs Features}. +@end iftex +@ifnottex +@xref{MS-DOS and MULE}. +@end ifnottex +}. + + In addition to converting various representations of non-@acronym{ASCII} +characters, a coding system can perform end-of-line conversion. Emacs +handles three different conventions for how to separate lines in a file: +newline, carriage-return linefeed, and just carriage-return. + +@table @kbd +@item C-h C @var{coding} @key{RET} +Describe coding system @var{coding}. + +@item C-h C @key{RET} +Describe the coding systems currently in use. + +@item M-x list-coding-systems +Display a list of all the supported coding systems. +@end table + +@kindex C-h C +@findex describe-coding-system + The command @kbd{C-h C} (@code{describe-coding-system}) displays +information about particular coding systems, including the end-of-line +conversion specified by those coding systems. You can specify a coding +system name as the argument; alternatively, with an empty argument, it +describes the coding systems currently selected for various purposes, +both in the current buffer and as the defaults, and the priority list +for recognizing coding systems (@pxref{Recognize Coding}). + +@findex list-coding-systems + To display a list of all the supported coding systems, type @kbd{M-x +list-coding-systems}. The list gives information about each coding +system, including the letter that stands for it in the mode line +(@pxref{Mode Line}). + +@cindex end-of-line conversion +@cindex line endings +@cindex MS-DOS end-of-line conversion +@cindex Macintosh end-of-line conversion + Each of the coding systems that appear in this list---except for +@code{no-conversion}, which means no conversion of any kind---specifies +how and whether to convert printing characters, but leaves the choice of +end-of-line conversion to be decided based on the contents of each file. +For example, if the file appears to use the sequence carriage-return +linefeed to separate lines, DOS end-of-line conversion will be used. + + Each of the listed coding systems has three variants which specify +exactly what to do for end-of-line conversion: + +@table @code +@item @dots{}-unix +Don't do any end-of-line conversion; assume the file uses +newline to separate lines. (This is the convention normally used +on Unix and GNU systems.) + +@item @dots{}-dos +Assume the file uses carriage-return linefeed to separate lines, and do +the appropriate conversion. (This is the convention normally used on +Microsoft systems.@footnote{It is also specified for MIME @samp{text/*} +bodies and in other network transport contexts. It is different +from the SGML reference syntax record-start/record-end format which +Emacs doesn't support directly.}) + +@item @dots{}-mac +Assume the file uses carriage-return to separate lines, and do the +appropriate conversion. (This is the convention normally used on the +Macintosh system.) +@end table + + These variant coding systems are omitted from the +@code{list-coding-systems} display for brevity, since they are entirely +predictable. For example, the coding system @code{iso-latin-1} has +variants @code{iso-latin-1-unix}, @code{iso-latin-1-dos} and +@code{iso-latin-1-mac}. + +@cindex @code{undecided}, coding system + The coding systems @code{unix}, @code{dos}, and @code{mac} are +aliases for @code{undecided-unix}, @code{undecided-dos}, and +@code{undecided-mac}, respectively. These coding systems specify only +the end-of-line conversion, and leave the character code conversion to +be deduced from the text itself. + + The coding system @code{raw-text} is good for a file which is mainly +@acronym{ASCII} text, but may contain byte values above 127 which are +not meant to encode non-@acronym{ASCII} characters. With +@code{raw-text}, Emacs copies those byte values unchanged, and sets +@code{enable-multibyte-characters} to @code{nil} in the current buffer +so that they will be interpreted properly. @code{raw-text} handles +end-of-line conversion in the usual way, based on the data +encountered, and has the usual three variants to specify the kind of +end-of-line conversion to use. + + In contrast, the coding system @code{no-conversion} specifies no +character code conversion at all---none for non-@acronym{ASCII} byte values and +none for end of line. This is useful for reading or writing binary +files, tar files, and other files that must be examined verbatim. It, +too, sets @code{enable-multibyte-characters} to @code{nil}. + + The easiest way to edit a file with no conversion of any kind is with +the @kbd{M-x find-file-literally} command. This uses +@code{no-conversion}, and also suppresses other Emacs features that +might convert the file contents before you see them. @xref{Visiting}. + + The coding system @code{emacs-mule} means that the file contains +non-@acronym{ASCII} characters stored with the internal Emacs encoding. It +handles end-of-line conversion based on the data encountered, and has +the usual three variants to specify the kind of end-of-line conversion. + +@findex unify-8859-on-decoding-mode +@anchor{Character Translation} + The @dfn{character translation} feature can modify the effect of +various coding systems, by changing the internal Emacs codes that +decoding produces. For instance, the command +@code{unify-8859-on-decoding-mode} enables a mode that ``unifies'' the +Latin alphabets when decoding text. This works by converting all +non-@acronym{ASCII} Latin-@var{n} characters to either Latin-1 or +Unicode characters. This way it is easier to use various +Latin-@var{n} alphabets together. (In a future Emacs version we hope +to move towards full Unicode support and complete unification of +character sets.) + +@vindex enable-character-translation + If you set the variable @code{enable-character-translation} to +@code{nil}, that disables all character translation (including +@code{unify-8859-on-decoding-mode}). + +@node Recognize Coding +@section Recognizing Coding Systems + + Emacs tries to recognize which coding system to use for a given text +as an integral part of reading that text. (This applies to files +being read, output from subprocesses, text from X selections, etc.) +Emacs can select the right coding system automatically most of the +time---once you have specified your preferences. + + Some coding systems can be recognized or distinguished by which byte +sequences appear in the data. However, there are coding systems that +cannot be distinguished, not even potentially. For example, there is no +way to distinguish between Latin-1 and Latin-2; they use the same byte +values with different meanings. + + Emacs handles this situation by means of a priority list of coding +systems. Whenever Emacs reads a file, if you do not specify the coding +system to use, Emacs checks the data against each coding system, +starting with the first in priority and working down the list, until it +finds a coding system that fits the data. Then it converts the file +contents assuming that they are represented in this coding system. + + The priority list of coding systems depends on the selected language +environment (@pxref{Language Environments}). For example, if you use +French, you probably want Emacs to prefer Latin-1 to Latin-2; if you use +Czech, you probably want Latin-2 to be preferred. This is one of the +reasons to specify a language environment. + +@findex prefer-coding-system + However, you can alter the coding system priority list in detail +with the command @kbd{M-x prefer-coding-system}. This command reads +the name of a coding system from the minibuffer, and adds it to the +front of the priority list, so that it is preferred to all others. If +you use this command several times, each use adds one element to the +front of the priority list. + + If you use a coding system that specifies the end-of-line conversion +type, such as @code{iso-8859-1-dos}, what this means is that Emacs +should attempt to recognize @code{iso-8859-1} with priority, and should +use DOS end-of-line conversion when it does recognize @code{iso-8859-1}. + +@vindex file-coding-system-alist + Sometimes a file name indicates which coding system to use for the +file. The variable @code{file-coding-system-alist} specifies this +correspondence. There is a special function +@code{modify-coding-system-alist} for adding elements to this list. For +example, to read and write all @samp{.txt} files using the coding system +@code{chinese-iso-8bit}, you can execute this Lisp expression: + +@smallexample +(modify-coding-system-alist 'file "\\.txt\\'" 'chinese-iso-8bit) +@end smallexample + +@noindent +The first argument should be @code{file}, the second argument should be +a regular expression that determines which files this applies to, and +the third argument says which coding system to use for these files. + +@vindex inhibit-eol-conversion +@cindex DOS-style end-of-line display + Emacs recognizes which kind of end-of-line conversion to use based on +the contents of the file: if it sees only carriage-returns, or only +carriage-return linefeed sequences, then it chooses the end-of-line +conversion accordingly. You can inhibit the automatic use of +end-of-line conversion by setting the variable @code{inhibit-eol-conversion} +to non-@code{nil}. If you do that, DOS-style files will be displayed +with the @samp{^M} characters visible in the buffer; some people +prefer this to the more subtle @samp{(DOS)} end-of-line type +indication near the left edge of the mode line (@pxref{Mode Line, +eol-mnemonic}). + +@vindex inhibit-iso-escape-detection +@cindex escape sequences in files + By default, the automatic detection of coding system is sensitive to +escape sequences. If Emacs sees a sequence of characters that begin +with an escape character, and the sequence is valid as an ISO-2022 +code, that tells Emacs to use one of the ISO-2022 encodings to decode +the file. + + However, there may be cases that you want to read escape sequences +in a file as is. In such a case, you can set the variable +@code{inhibit-iso-escape-detection} to non-@code{nil}. Then the code +detection ignores any escape sequences, and never uses an ISO-2022 +encoding. The result is that all escape sequences become visible in +the buffer. + + The default value of @code{inhibit-iso-escape-detection} is +@code{nil}. We recommend that you not change it permanently, only for +one specific operation. That's because many Emacs Lisp source files +in the Emacs distribution contain non-@acronym{ASCII} characters encoded in the +coding system @code{iso-2022-7bit}, and they won't be +decoded correctly when you visit those files if you suppress the +escape sequence detection. + +@vindex auto-coding-alist +@vindex auto-coding-regexp-alist +@vindex auto-coding-functions + The variables @code{auto-coding-alist}, +@code{auto-coding-regexp-alist} and @code{auto-coding-functions} are +the strongest way to specify the coding system for certain patterns of +file names, or for files containing certain patterns; these variables +even override @samp{-*-coding:-*-} tags in the file itself. Emacs +uses @code{auto-coding-alist} for tar and archive files, to prevent it +from being confused by a @samp{-*-coding:-*-} tag in a member of the +archive and thinking it applies to the archive file as a whole. +Likewise, Emacs uses @code{auto-coding-regexp-alist} to ensure that +RMAIL files, whose names in general don't match any particular +pattern, are decoded correctly. One of the builtin +@code{auto-coding-functions} detects the encoding for XML files. + +@vindex rmail-decode-mime-charset + When you get new mail in Rmail, each message is translated +automatically from the coding system it is written in, as if it were a +separate file. This uses the priority list of coding systems that you +have specified. If a MIME message specifies a character set, Rmail +obeys that specification, unless @code{rmail-decode-mime-charset} is +@code{nil}. + +@vindex rmail-file-coding-system + For reading and saving Rmail files themselves, Emacs uses the coding +system specified by the variable @code{rmail-file-coding-system}. The +default value is @code{nil}, which means that Rmail files are not +translated (they are read and written in the Emacs internal character +code). + +@node Specify Coding +@section Specifying a File's Coding System + + If Emacs recognizes the encoding of a file incorrectly, you can +reread the file using the correct coding system by typing @kbd{C-x +@key{RET} r @var{coding-system} @key{RET}}. To see what coding system +Emacs actually used to decode the file, look at the coding system +mnemonic letter near the left edge of the mode line (@pxref{Mode +Line}), or type @kbd{C-h C @key{RET}}. + +@vindex coding + You can specify the coding system for a particular file in the file +itself, using the @w{@samp{-*-@dots{}-*-}} construct at the beginning, +or a local variables list at the end (@pxref{File Variables}). You do +this by defining a value for the ``variable'' named @code{coding}. +Emacs does not really have a variable @code{coding}; instead of +setting a variable, this uses the specified coding system for the +file. For example, @samp{-*-mode: C; coding: latin-1;-*-} specifies +use of the Latin-1 coding system, as well as C mode. When you specify +the coding explicitly in the file, that overrides +@code{file-coding-system-alist}. + + If you add the character @samp{!} at the end of the coding system +name in @code{coding}, it disables any character translation +(@pxref{Character Translation}) while decoding the file. This is +useful when you need to make sure that the character codes in the +Emacs buffer will not vary due to changes in user settings; for +instance, for the sake of strings in Emacs Lisp source files. + +@node Output Coding +@section Choosing Coding Systems for Output + +@vindex buffer-file-coding-system + Once Emacs has chosen a coding system for a buffer, it stores that +coding system in @code{buffer-file-coding-system}. That makes it the +default for operations that write from this buffer into a file, such +as @code{save-buffer} and @code{write-region}. You can specify a +different coding system for further file output from the buffer using +@code{set-buffer-file-coding-system} (@pxref{Text Coding}). + + You can insert any character Emacs supports into any Emacs buffer, +but most coding systems can only handle a subset of these characters. +Therefore, you can insert characters that cannot be encoded with the +coding system that will be used to save the buffer. For example, you +could start with an @acronym{ASCII} file and insert a few Latin-1 +characters into it, or you could edit a text file in Polish encoded in +@code{iso-8859-2} and add some Russian words to it. When you save +that buffer, Emacs cannot use the current value of +@code{buffer-file-coding-system}, because the characters you added +cannot be encoded by that coding system. + + When that happens, Emacs tries the most-preferred coding system (set +by @kbd{M-x prefer-coding-system} or @kbd{M-x +set-language-environment}), and if that coding system can safely +encode all of the characters in the buffer, Emacs uses it, and stores +its value in @code{buffer-file-coding-system}. Otherwise, Emacs +displays a list of coding systems suitable for encoding the buffer's +contents, and asks you to choose one of those coding systems. + + If you insert the unsuitable characters in a mail message, Emacs +behaves a bit differently. It additionally checks whether the +most-preferred coding system is recommended for use in MIME messages; +if not, Emacs tells you that the most-preferred coding system is not +recommended and prompts you for another coding system. This is so you +won't inadvertently send a message encoded in a way that your +recipient's mail software will have difficulty decoding. (You can +still use an unsuitable coding system if you type its name in response +to the question.) + +@vindex sendmail-coding-system + When you send a message with Mail mode (@pxref{Sending Mail}), Emacs has +four different ways to determine the coding system to use for encoding +the message text. It tries the buffer's own value of +@code{buffer-file-coding-system}, if that is non-@code{nil}. Otherwise, +it uses the value of @code{sendmail-coding-system}, if that is +non-@code{nil}. The third way is to use the default coding system for +new files, which is controlled by your choice of language environment, +if that is non-@code{nil}. If all of these three values are @code{nil}, +Emacs encodes outgoing mail using the Latin-1 coding system. + +@node Text Coding +@section Specifying a Coding System for File Text + + In cases where Emacs does not automatically choose the right coding +system for a file's contents, you can use these commands to specify +one: + +@table @kbd +@item C-x @key{RET} f @var{coding} @key{RET} +Use coding system @var{coding} for saving or revisiting the visited +file in the current buffer. + +@item C-x @key{RET} c @var{coding} @key{RET} +Specify coding system @var{coding} for the immediately following +command. + +@item C-x @key{RET} r @var{coding} @key{RET} +Revisit the current file using the coding system @var{coding}. + +@item M-x recode-region @key{RET} @var{right} @key{RET} @var{wrong} @key{RET} +Convert a region that was decoded using coding system @var{wrong}, +decoding it using coding system @var{right} instead. +@end table + +@kindex C-x RET f +@findex set-buffer-file-coding-system + The command @kbd{C-x @key{RET} f} +(@code{set-buffer-file-coding-system}) sets the file coding system for +the current buffer---in other words, it says which coding system to +use when saving or reverting the visited file. You specify which +coding system using the minibuffer. If you specify a coding system +that cannot handle all of the characters in the buffer, Emacs warns +you about the troublesome characters when you actually save the +buffer. + +@cindex specify end-of-line conversion + You can also use this command to specify the end-of-line conversion +(@pxref{Coding Systems, end-of-line conversion}) for encoding the +current buffer. For example, @kbd{C-x @key{RET} f dos @key{RET}} will +cause Emacs to save the current buffer's text with DOS-style CRLF line +endings. + +@kindex C-x RET c +@findex universal-coding-system-argument + Another way to specify the coding system for a file is when you visit +the file. First use the command @kbd{C-x @key{RET} c} +(@code{universal-coding-system-argument}); this command uses the +minibuffer to read a coding system name. After you exit the minibuffer, +the specified coding system is used for @emph{the immediately following +command}. + + So if the immediately following command is @kbd{C-x C-f}, for example, +it reads the file using that coding system (and records the coding +system for when you later save the file). Or if the immediately following +command is @kbd{C-x C-w}, it writes the file using that coding system. +When you specify the coding system for saving in this way, instead +of with @kbd{C-x @key{RET} f}, there is no warning if the buffer +contains characters that the coding system cannot handle. + + Other file commands affected by a specified coding system include +@kbd{C-x i} and @kbd{C-x C-v}, as well as the other-window variants +of @kbd{C-x C-f}. @kbd{C-x @key{RET} c} also affects commands that +start subprocesses, including @kbd{M-x shell} (@pxref{Shell}). If the +immediately following command does not use the coding system, then +@kbd{C-x @key{RET} c} ultimately has no effect. + + An easy way to visit a file with no conversion is with the @kbd{M-x +find-file-literally} command. @xref{Visiting}. + +@vindex default-buffer-file-coding-system + The variable @code{default-buffer-file-coding-system} specifies the +choice of coding system to use when you create a new file. It applies +when you find a new file, and when you create a buffer and then save it +in a file. Selecting a language environment typically sets this +variable to a good choice of default coding system for that language +environment. + +@kindex C-x RET r +@findex revert-buffer-with-coding-system + If you visit a file with a wrong coding system, you can correct this +with @kbd{C-x @key{RET} r} (@code{revert-buffer-with-coding-system}). +This visits the current file again, using a coding system you specify. + +@findex recode-region + If a piece of text has already been inserted into a buffer using the +wrong coding system, you can redo the decoding of it using @kbd{M-x +recode-region}. This prompts you for the proper coding system, then +for the wrong coding system that was actually used, and does the +conversion. It first encodes the region using the wrong coding system, +then decodes it again using the proper coding system. + +@node Communication Coding +@section Coding Systems for Interprocess Communication + + This section explains how to specify coding systems for use +in communication with other processes. + +@table @kbd +@item C-x @key{RET} x @var{coding} @key{RET} +Use coding system @var{coding} for transferring selections to and from +other window-based applications. + +@item C-x @key{RET} X @var{coding} @key{RET} +Use coding system @var{coding} for transferring @emph{one} +selection---the next one---to or from another window-based application. + +@item C-x @key{RET} p @var{input-coding} @key{RET} @var{output-coding} @key{RET} +Use coding systems @var{input-coding} and @var{output-coding} for +subprocess input and output in the current buffer. + +@item C-x @key{RET} c @var{coding} @key{RET} +Specify coding system @var{coding} for the immediately following +command. +@end table + +@kindex C-x RET x +@kindex C-x RET X +@findex set-selection-coding-system +@findex set-next-selection-coding-system + The command @kbd{C-x @key{RET} x} (@code{set-selection-coding-system}) +specifies the coding system for sending selected text to other windowing +applications, and for receiving the text of selections made in other +applications. This command applies to all subsequent selections, until +you override it by using the command again. The command @kbd{C-x +@key{RET} X} (@code{set-next-selection-coding-system}) specifies the +coding system for the next selection made in Emacs or read by Emacs. + +@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}) +specifies the coding system for input and output to a subprocess. This +command applies to the current buffer; normally, each subprocess has its +own buffer, and thus you can use this command to specify translation to +and from a particular subprocess by giving the command in the +corresponding buffer. + + You can also use @kbd{C-x @key{RET} c} just before the command that +runs or starts a subprocess, to specify the coding system to use for +communication with that subprocess. + + The default for translation of process input and output depends on the +current language environment. + +@vindex locale-coding-system +@cindex decoding non-@acronym{ASCII} keyboard input on X + The variable @code{locale-coding-system} specifies a coding system +to use when encoding and decoding system strings such as system error +messages and @code{format-time-string} formats and time stamps. That +coding system is also used for decoding non-@acronym{ASCII} keyboard input on X +Window systems. You should choose a coding system that is compatible +with the underlying system's text representation, which is normally +specified by one of the environment variables @env{LC_ALL}, +@env{LC_CTYPE}, and @env{LANG}. (The first one, in the order +specified above, whose value is nonempty is the one that determines +the text representation.) + +@node File Name Coding +@section Coding Systems for File Names + +@table @kbd +@item C-x @key{RET} F @var{coding} @key{RET} +Use coding system @var{coding} for encoding and decoding file +@emph{names}. +@end table + +@vindex file-name-coding-system +@cindex file names with non-@acronym{ASCII} characters + The variable @code{file-name-coding-system} specifies a coding +system to use for encoding file names. It has no effect on reading +and writing the @emph{contents} of files. + +@findex set-file-name-coding-system +@kindex C-x @key{RET} F + If you set the variable to a coding system name (as a Lisp symbol or +a string), Emacs encodes file names using that coding system for all +file operations. This makes it possible to use non-@acronym{ASCII} +characters in file names---or, at least, those non-@acronym{ASCII} +characters which the specified coding system can encode. Use @kbd{C-x +@key{RET} F} (@code{set-file-name-coding-system}) to specify this +interactively. + + If @code{file-name-coding-system} is @code{nil}, Emacs uses a +default coding system determined by the selected language environment. +In the default language environment, any non-@acronym{ASCII} +characters in file names are not encoded specially; they appear in the +file system using the internal Emacs representation. + + @strong{Warning:} if you change @code{file-name-coding-system} (or the +language environment) in the middle of an Emacs session, problems can +result if you have already visited files whose names were encoded using +the earlier coding system and cannot be encoded (or are encoded +differently) under the new coding system. If you try to save one of +these buffers under the visited file name, saving may use the wrong file +name, or it may get an error. If such a problem happens, use @kbd{C-x +C-w} to specify a new file name for that buffer. + +@findex recode-file-name + If a mistake occurs when encoding a file name, use the command +@kbd{M-x recode-file-name} to change the file name's coding +system. This prompts for an existing file name, its old coding +system, and the coding system to which you wish to convert. + +@node Terminal Coding +@section Coding Systems for Terminal I/O + +@table @kbd +@item C-x @key{RET} k @var{coding} @key{RET} +Use coding system @var{coding} for keyboard input. + +@item C-x @key{RET} t @var{coding} @key{RET} +Use coding system @var{coding} for terminal output. +@end table + +@kindex C-x RET t +@findex set-terminal-coding-system + The command @kbd{C-x @key{RET} t} (@code{set-terminal-coding-system}) +specifies the coding system for terminal output. If you specify a +character code for terminal output, all characters output to the +terminal are translated into that coding system. + + This feature is useful for certain character-only terminals built to +support specific languages or character sets---for example, European +terminals that support one of the ISO Latin character sets. You need to +specify the terminal coding system when using multibyte text, so that +Emacs knows which characters the terminal can actually handle. + + By default, output to the terminal is not translated at all, unless +Emacs can deduce the proper coding system from your terminal type or +your locale specification (@pxref{Language Environments}). + +@kindex C-x RET k +@findex set-keyboard-coding-system +@vindex keyboard-coding-system + The command @kbd{C-x @key{RET} k} (@code{set-keyboard-coding-system}) +or the variable @code{keyboard-coding-system} specifies the coding +system for keyboard input. Character-code translation of keyboard +input is useful for terminals with keys that send non-@acronym{ASCII} +graphic characters---for example, some terminals designed for ISO +Latin-1 or subsets of it. + + By default, keyboard input is translated based on your system locale +setting. If your terminal does not really support the encoding +implied by your locale (for example, if you find it inserts a +non-@acronym{ASCII} character if you type @kbd{M-i}), you will need to set +@code{keyboard-coding-system} to @code{nil} to turn off encoding. +You can do this by putting + +@lisp +(set-keyboard-coding-system nil) +@end lisp + +@noindent +in your @file{~/.emacs} file. + + There is a similarity between using a coding system translation for +keyboard input, and using an input method: both define sequences of +keyboard input that translate into single characters. However, input +methods are designed to be convenient for interactive use by humans, and +the sequences that are translated are typically sequences of @acronym{ASCII} +printing characters. Coding systems typically translate sequences of +non-graphic characters. + +@node Fontsets +@section Fontsets +@cindex fontsets + + A font typically defines shapes for a single alphabet or script. +Therefore, displaying the entire range of scripts that Emacs supports +requires a collection of many fonts. In Emacs, such a collection is +called a @dfn{fontset}. A fontset is defined by a list of fonts, each +assigned to handle a range of character codes. + + Each fontset has a name, like a font. However, while fonts are +stored in the system and the available font names are defined by the +system, fontsets are defined within Emacs itself. Once you have +defined a fontset, you can use it within Emacs by specifying its name, +anywhere that you could use a single font. Of course, Emacs fontsets +can use only the fonts that the system supports; if certain characters +appear on the screen as hollow boxes, this means that the fontset in +use for them has no font for those characters.@footnote{The Emacs +installation instructions have information on additional font +support.} + + Emacs creates two fontsets automatically: the @dfn{standard fontset} +and the @dfn{startup fontset}. The standard fontset is most likely to +have fonts for a wide variety of non-@acronym{ASCII} characters; +however, this is not the default for Emacs to use. (By default, Emacs +tries to find a font that has bold and italic variants.) You can +specify use of the standard fontset with the @samp{-fn} option. For +example, + +@example +emacs -fn fontset-standard +@end example + +@noindent +You can also specify a fontset with the @samp{Font} resource (@pxref{X +Resources}). + + A fontset does not necessarily specify a font for every character +code. If a fontset specifies no font for a certain character, or if it +specifies a font that does not exist on your system, then it cannot +display that character properly. It will display that character as an +empty box instead. + +@node Defining Fontsets +@section Defining fontsets + +@vindex standard-fontset-spec +@cindex standard fontset + Emacs creates a standard fontset automatically according to the value +of @code{standard-fontset-spec}. This fontset's name is + +@example +-*-fixed-medium-r-normal-*-16-*-*-*-*-*-fontset-standard +@end example + +@noindent +or just @samp{fontset-standard} for short. + + Bold, italic, and bold-italic variants of the standard fontset are +created automatically. Their names have @samp{bold} instead of +@samp{medium}, or @samp{i} instead of @samp{r}, or both. + +@cindex startup fontset + If you specify a default @acronym{ASCII} font with the @samp{Font} resource or +the @samp{-fn} argument, Emacs generates a fontset from it +automatically. This is the @dfn{startup fontset} and its name is +@code{fontset-startup}. It does this by replacing the @var{foundry}, +@var{family}, @var{add_style}, and @var{average_width} fields of the +font name with @samp{*}, replacing @var{charset_registry} field with +@samp{fontset}, and replacing @var{charset_encoding} field with +@samp{startup}, then using the resulting string to specify a fontset. + + For instance, if you start Emacs this way, + +@example +emacs -fn "*courier-medium-r-normal--14-140-*-iso8859-1" +@end example + +@noindent +Emacs generates the following fontset and uses it for the initial X +window frame: + +@example +-*-*-medium-r-normal-*-14-140-*-*-*-*-fontset-startup +@end example + + With the X resource @samp{Emacs.Font}, you can specify a fontset name +just like an actual font name. But be careful not to specify a fontset +name in a wildcard resource like @samp{Emacs*Font}---that wildcard +specification matches various other resources, such as for menus, and +menus cannot handle fontsets. + + You can specify additional fontsets using X resources named +@samp{Fontset-@var{n}}, where @var{n} is an integer starting from 0. +The resource value should have this form: + +@smallexample +@var{fontpattern}, @r{[}@var{charset}:@var{font}@r{]@dots{}} +@end smallexample + +@noindent +@var{fontpattern} should have the form of a standard X font name, except +for the last two fields. They should have the form +@samp{fontset-@var{alias}}. + + The fontset has two names, one long and one short. The long name is +@var{fontpattern}. The short name is @samp{fontset-@var{alias}}. You +can refer to the fontset by either name. + + The construct @samp{@var{charset}:@var{font}} specifies which font to +use (in this fontset) for one particular character set. Here, +@var{charset} is the name of a character set, and @var{font} is the +font to use for that character set. You can use this construct any +number of times in defining one fontset. + + For the other character sets, Emacs chooses a font based on +@var{fontpattern}. It replaces @samp{fontset-@var{alias}} with values +that describe the character set. For the @acronym{ASCII} character font, +@samp{fontset-@var{alias}} is replaced with @samp{ISO8859-1}. + + In addition, when several consecutive fields are wildcards, Emacs +collapses them into a single wildcard. This is to prevent use of +auto-scaled fonts. Fonts made by scaling larger fonts are not usable +for editing, and scaling a smaller font is not useful because it is +better to use the smaller font in its own size, which is what Emacs +does. + + Thus if @var{fontpattern} is this, + +@example +-*-fixed-medium-r-normal-*-24-*-*-*-*-*-fontset-24 +@end example + +@noindent +the font specification for @acronym{ASCII} characters would be this: + +@example +-*-fixed-medium-r-normal-*-24-*-ISO8859-1 +@end example + +@noindent +and the font specification for Chinese GB2312 characters would be this: + +@example +-*-fixed-medium-r-normal-*-24-*-gb2312*-* +@end example + + You may not have any Chinese font matching the above font +specification. Most X distributions include only Chinese fonts that +have @samp{song ti} or @samp{fangsong ti} in @var{family} field. In +such a case, @samp{Fontset-@var{n}} can be specified as below: + +@smallexample +Emacs.Fontset-0: -*-fixed-medium-r-normal-*-24-*-*-*-*-*-fontset-24,\ + chinese-gb2312:-*-*-medium-r-normal-*-24-*-gb2312*-* +@end smallexample + +@noindent +Then, the font specifications for all but Chinese GB2312 characters have +@samp{fixed} in the @var{family} field, and the font specification for +Chinese GB2312 characters has a wild card @samp{*} in the @var{family} +field. + +@findex create-fontset-from-fontset-spec + The function that processes the fontset resource value to create the +fontset is called @code{create-fontset-from-fontset-spec}. You can also +call this function explicitly to create a fontset. + + @xref{Font X}, for more information about font naming in X. + +@node Undisplayable Characters +@section Undisplayable Characters + + There may be a some non-@acronym{ASCII} characters that your terminal cannot +display. Most text-only terminals support just a single character +set (use the variable @code{default-terminal-coding-system} +(@pxref{Terminal Coding}) to tell Emacs which one); characters which +can't be encoded in that coding system are displayed as @samp{?} by +default. + + Graphical displays can display a broader range of characters, but +you may not have fonts installed for all of them; characters that have +no font appear as a hollow box. + + If you use Latin-1 characters but your terminal can't display +Latin-1, you can arrange to display mnemonic @acronym{ASCII} sequences +instead, e.g.@: @samp{"o} for o-umlaut. Load the library +@file{iso-ascii} to do this. + +@vindex latin1-display + If your terminal can display Latin-1, you can display characters +from other European character sets using a mixture of equivalent +Latin-1 characters and @acronym{ASCII} mnemonics. Customize the variable +@code{latin1-display} to enable this. The mnemonic @acronym{ASCII} +sequences mostly correspond to those of the prefix input methods. + +@node Unibyte Mode +@section Unibyte Editing Mode + +@cindex European character sets +@cindex accented characters +@cindex ISO Latin character sets +@cindex Unibyte operation + The ISO 8859 Latin-@var{n} character sets define character codes in +the range 0240 to 0377 octal (160 to 255 decimal) to handle the +accented letters and punctuation needed by various European languages +(and some non-European ones). If you disable multibyte characters, +Emacs can still handle @emph{one} of these character codes at a time. +To specify @emph{which} of these codes to use, invoke @kbd{M-x +set-language-environment} and specify a suitable language environment +such as @samp{Latin-@var{n}}. + + For more information about unibyte operation, see @ref{Enabling +Multibyte}. Note particularly that you probably want to ensure that +your initialization files are read as unibyte if they contain +non-@acronym{ASCII} characters. + +@vindex unibyte-display-via-language-environment + Emacs can also display those characters, provided the terminal or font +in use supports them. This works automatically. Alternatively, on a +graphical display, Emacs can also display single-byte characters +through fontsets, in effect by displaying the equivalent multibyte +characters according to the current language environment. To request +this, set the variable @code{unibyte-display-via-language-environment} +to a non-@code{nil} value. + +@cindex @code{iso-ascii} library + If your terminal does not support display of the Latin-1 character +set, Emacs can display these characters as @acronym{ASCII} sequences which at +least give you a clear idea of what the characters are. To do this, +load the library @code{iso-ascii}. Similar libraries for other +Latin-@var{n} character sets could be implemented, but we don't have +them yet. + +@findex standard-display-8bit +@cindex 8-bit display + Normally non-ISO-8859 characters (decimal codes between 128 and 159 +inclusive) are displayed as octal escapes. You can change this for +non-standard ``extended'' versions of ISO-8859 character sets by using the +function @code{standard-display-8bit} in the @code{disp-table} library. + + There are two ways to input single-byte non-@acronym{ASCII} +characters: + +@itemize @bullet +@cindex 8-bit input +@item +You can use an input method for the selected language environment. +@xref{Input Methods}. When you use an input method in a unibyte buffer, +the non-@acronym{ASCII} character you specify with it is converted to unibyte. + +@item +If your keyboard can generate character codes 128 (decimal) and up, +representing non-@acronym{ASCII} characters, you can type those character codes +directly. + +On a graphical display, you should not need to do anything special to use +these keys; they should simply work. On a text-only terminal, you +should use the command @code{M-x set-keyboard-coding-system} or the +variable @code{keyboard-coding-system} to specify which coding system +your keyboard uses (@pxref{Terminal Coding}). Enabling this feature +will probably require you to use @kbd{ESC} to type Meta characters; +however, on a console terminal or in @code{xterm}, you can arrange for +Meta to be converted to @kbd{ESC} and still be able type 8-bit +characters present directly on the keyboard or using @kbd{Compose} or +@kbd{AltGr} keys. @xref{User Input}. + +@kindex C-x 8 +@cindex @code{iso-transl} library +@cindex compose character +@cindex dead character +@item +For Latin-1 only, you can use the key @kbd{C-x 8} as a ``compose +character'' prefix for entry of non-@acronym{ASCII} Latin-1 printing +characters. @kbd{C-x 8} is good for insertion (in the minibuffer as +well as other buffers), for searching, and in any other context where +a key sequence is allowed. + +@kbd{C-x 8} works by loading the @code{iso-transl} library. Once that +library is loaded, the @key{ALT} modifier key, if the keyboard has +one, serves the same purpose as @kbd{C-x 8}: use @key{ALT} together +with an accent character to modify the following letter. In addition, +if the keyboard has keys for the Latin-1 ``dead accent characters,'' +they too are defined to compose with the following character, once +@code{iso-transl} is loaded. + +Use @kbd{C-x 8 C-h} to list all the available @kbd{C-x 8} translations. +@end itemize + +@node Charsets +@section Charsets +@cindex charsets + + Emacs groups all supported characters into disjoint @dfn{charsets}. +Each character code belongs to one and only one charset. For +historical reasons, Emacs typically divides an 8-bit character code +for an extended version of @acronym{ASCII} into two charsets: +@acronym{ASCII}, which covers the codes 0 through 127, plus another +charset which covers the ``right-hand part'' (the codes 128 and up). +For instance, the characters of Latin-1 include the Emacs charset +@code{ascii} plus the Emacs charset @code{latin-iso8859-1}. + + Emacs characters belonging to different charsets may look the same, +but they are still different characters. For example, the letter +@samp{o} with acute accent in charset @code{latin-iso8859-1}, used for +Latin-1, is different from the letter @samp{o} with acute accent in +charset @code{latin-iso8859-2}, used for Latin-2. + +@findex list-charset-chars +@cindex characters in a certain charset +@findex describe-character-set + There are two commands for obtaining information about Emacs +charsets. The command @kbd{M-x list-charset-chars} prompts for a name +of a character set, and displays all the characters in that character +set. The command @kbd{M-x describe-character-set} prompts for a +charset name and displays information about that charset, including +its internal representation within Emacs. + + To find out which charset a character in the buffer belongs to, +put point before it and type @kbd{C-u C-x =}. + +@ignore + arch-tag: 310ba60d-31ef-4ce7-91f1-f282dd57b6b3 +@end ignore |