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1 | @c This is part of the Emacs manual. |
2 | @c Copyright (C) 1997, 1999, 2000, 2001, 2002, 2003, 2004, | |
3 | @c 2005, 2006, 2007 Free Software Foundation, Inc. | |
4 | @c See file emacs.texi for copying conditions. | |
5 | @node International, Major Modes, Frames, Top | |
6 | @chapter International Character Set Support | |
7 | @cindex MULE | |
8 | @cindex international scripts | |
9 | @cindex multibyte characters | |
10 | @cindex encoding of characters | |
11 | ||
12 | @cindex Celtic | |
13 | @cindex Chinese | |
14 | @cindex Cyrillic | |
15 | @cindex Czech | |
16 | @cindex Devanagari | |
17 | @cindex Hindi | |
18 | @cindex Marathi | |
19 | @cindex Ethiopic | |
20 | @cindex German | |
21 | @cindex Greek | |
22 | @cindex Hebrew | |
23 | @cindex IPA | |
24 | @cindex Japanese | |
25 | @cindex Korean | |
26 | @cindex Lao | |
27 | @cindex Latin | |
28 | @cindex Polish | |
29 | @cindex Romanian | |
30 | @cindex Slovak | |
31 | @cindex Slovenian | |
32 | @cindex Thai | |
33 | @cindex Tibetan | |
34 | @cindex Turkish | |
35 | @cindex Vietnamese | |
36 | @cindex Dutch | |
37 | @cindex Spanish | |
38 | Emacs supports a wide variety of international character sets, | |
39 | including European and Vietnamese variants of the Latin alphabet, as | |
40 | well as Cyrillic, Devanagari (for Hindi and Marathi), Ethiopic, Greek, | |
41 | Han (for Chinese and Japanese), Hangul (for Korean), Hebrew, IPA, | |
42 | Kannada, Lao, Malayalam, Tamil, Thai, Tibetan, and Vietnamese scripts. | |
43 | Emacs also supports various encodings of these characters used by | |
44 | other internationalized software, such as word processors and mailers. | |
45 | ||
46 | Emacs allows editing text with international characters by supporting | |
47 | all the related activities: | |
48 | ||
49 | @itemize @bullet | |
50 | @item | |
51 | You can visit files with non-@acronym{ASCII} characters, save non-@acronym{ASCII} text, and | |
52 | pass non-@acronym{ASCII} text between Emacs and programs it invokes (such as | |
53 | compilers, spell-checkers, and mailers). Setting your language | |
54 | environment (@pxref{Language Environments}) takes care of setting up the | |
55 | coding systems and other options for a specific language or culture. | |
56 | Alternatively, you can specify how Emacs should encode or decode text | |
57 | for each command; see @ref{Text Coding}. | |
58 | ||
59 | @item | |
60 | You can display non-@acronym{ASCII} characters encoded by the various | |
61 | scripts. This works by using appropriate fonts on graphics displays | |
62 | (@pxref{Defining Fontsets}), and by sending special codes to text-only | |
63 | displays (@pxref{Terminal Coding}). If some characters are displayed | |
64 | incorrectly, refer to @ref{Undisplayable Characters}, which describes | |
65 | possible problems and explains how to solve them. | |
66 | ||
67 | @item | |
68 | You can insert non-@acronym{ASCII} characters or search for them. To do that, | |
69 | you can specify an input method (@pxref{Select Input Method}) suitable | |
70 | for your language, or use the default input method set up when you set | |
71 | your language environment. If | |
72 | your keyboard can produce non-@acronym{ASCII} characters, you can select an | |
73 | appropriate keyboard coding system (@pxref{Terminal Coding}), and Emacs | |
74 | will accept those characters. Latin-1 characters can also be input by | |
75 | using the @kbd{C-x 8} prefix, see @ref{Unibyte Mode}. | |
76 | ||
77 | On X Window systems, your locale should be set to an appropriate value | |
78 | to make sure Emacs interprets keyboard input correctly; see | |
79 | @ref{Language Environments, locales}. | |
80 | @end itemize | |
81 | ||
82 | The rest of this chapter describes these issues in detail. | |
83 | ||
84 | @menu | |
85 | * International Chars:: Basic concepts of multibyte characters. | |
86 | * Enabling Multibyte:: Controlling whether to use multibyte characters. | |
87 | * Language Environments:: Setting things up for the language you use. | |
88 | * Input Methods:: Entering text characters not on your keyboard. | |
89 | * Select Input Method:: Specifying your choice of input methods. | |
90 | * Multibyte Conversion:: How single-byte characters convert to multibyte. | |
91 | * Coding Systems:: Character set conversion when you read and | |
92 | write files, and so on. | |
93 | * Recognize Coding:: How Emacs figures out which conversion to use. | |
94 | * Specify Coding:: Specifying a file's coding system explicitly. | |
95 | * Output Coding:: Choosing coding systems for output. | |
96 | * Text Coding:: Choosing conversion to use for file text. | |
97 | * Communication Coding:: Coding systems for interprocess communication. | |
98 | * File Name Coding:: Coding systems for file @emph{names}. | |
99 | * Terminal Coding:: Specifying coding systems for converting | |
100 | terminal input and output. | |
101 | * Fontsets:: Fontsets are collections of fonts | |
102 | that cover the whole spectrum of characters. | |
103 | * Defining Fontsets:: Defining a new fontset. | |
104 | * Undisplayable Characters:: When characters don't display. | |
105 | * Unibyte Mode:: You can pick one European character set | |
106 | to use without multibyte characters. | |
107 | * Charsets:: How Emacs groups its internal character codes. | |
108 | @end menu | |
109 | ||
110 | @node International Chars | |
111 | @section Introduction to International Character Sets | |
112 | ||
113 | The users of international character sets and scripts have | |
114 | established many more-or-less standard coding systems for storing | |
115 | files. Emacs internally uses a single multibyte character encoding, | |
116 | so that it can intermix characters from all these scripts in a single | |
117 | buffer or string. This encoding represents each non-@acronym{ASCII} | |
118 | character as a sequence of bytes in the range 0200 through 0377. | |
119 | Emacs translates between the multibyte character encoding and various | |
120 | other coding systems when reading and writing files, when exchanging | |
121 | data with subprocesses, and (in some cases) in the @kbd{C-q} command | |
122 | (@pxref{Multibyte Conversion}). | |
123 | ||
124 | @kindex C-h h | |
125 | @findex view-hello-file | |
126 | @cindex undisplayable characters | |
127 | @cindex @samp{?} in display | |
128 | The command @kbd{C-h h} (@code{view-hello-file}) displays the file | |
129 | @file{etc/HELLO}, which shows how to say ``hello'' in many languages. | |
130 | This illustrates various scripts. If some characters can't be | |
131 | displayed on your terminal, they appear as @samp{?} or as hollow boxes | |
132 | (@pxref{Undisplayable Characters}). | |
133 | ||
134 | Keyboards, even in the countries where these character sets are used, | |
135 | generally don't have keys for all the characters in them. So Emacs | |
136 | supports various @dfn{input methods}, typically one for each script or | |
137 | language, to make it convenient to type them. | |
138 | ||
139 | @kindex C-x RET | |
140 | The prefix key @kbd{C-x @key{RET}} is used for commands that pertain | |
141 | to multibyte characters, coding systems, and input methods. | |
142 | ||
143 | @node Enabling Multibyte | |
144 | @section Enabling Multibyte Characters | |
145 | ||
146 | By default, Emacs starts in multibyte mode, because that allows you to | |
147 | use all the supported languages and scripts without limitations. | |
148 | ||
149 | @cindex turn multibyte support on or off | |
150 | You can enable or disable multibyte character support, either for | |
151 | Emacs as a whole, or for a single buffer. When multibyte characters | |
152 | are disabled in a buffer, we call that @dfn{unibyte mode}. Then each | |
153 | byte in that buffer represents a character, even codes 0200 through | |
154 | 0377. | |
155 | ||
156 | The old features for supporting the European character sets, ISO | |
157 | Latin-1 and ISO Latin-2, work in unibyte mode as they did in Emacs 19 | |
158 | and also work for the other ISO 8859 character sets. However, there | |
159 | is no need to turn off multibyte character support to use ISO Latin; | |
160 | the Emacs multibyte character set includes all the characters in these | |
161 | character sets, and Emacs can translate automatically to and from the | |
162 | ISO codes. | |
163 | ||
164 | To edit a particular file in unibyte representation, visit it using | |
165 | @code{find-file-literally}. @xref{Visiting}. To convert a buffer in | |
166 | multibyte representation into a single-byte representation of the same | |
167 | characters, the easiest way is to save the contents in a file, kill the | |
168 | buffer, and find the file again with @code{find-file-literally}. You | |
169 | can also use @kbd{C-x @key{RET} c} | |
170 | (@code{universal-coding-system-argument}) and specify @samp{raw-text} as | |
171 | the coding system with which to find or save a file. @xref{Text | |
172 | Coding}. Finding a file as @samp{raw-text} doesn't disable format | |
173 | conversion, uncompression and auto mode selection as | |
174 | @code{find-file-literally} does. | |
175 | ||
176 | @vindex enable-multibyte-characters | |
177 | @vindex default-enable-multibyte-characters | |
178 | To turn off multibyte character support by default, start Emacs with | |
179 | the @samp{--unibyte} option (@pxref{Initial Options}), or set the | |
180 | environment variable @env{EMACS_UNIBYTE}. You can also customize | |
181 | @code{enable-multibyte-characters} or, equivalently, directly set the | |
182 | variable @code{default-enable-multibyte-characters} to @code{nil} in | |
183 | your init file to have basically the same effect as @samp{--unibyte}. | |
184 | ||
185 | @findex toggle-enable-multibyte-characters | |
186 | To convert a unibyte session to a multibyte session, set | |
187 | @code{default-enable-multibyte-characters} to @code{t}. Buffers which | |
188 | were created in the unibyte session before you turn on multibyte support | |
189 | will stay unibyte. You can turn on multibyte support in a specific | |
190 | buffer by invoking the command @code{toggle-enable-multibyte-characters} | |
191 | in that buffer. | |
192 | ||
193 | @cindex Lisp files, and multibyte operation | |
194 | @cindex multibyte operation, and Lisp files | |
195 | @cindex unibyte operation, and Lisp files | |
196 | @cindex init file, and non-@acronym{ASCII} characters | |
197 | @cindex environment variables, and non-@acronym{ASCII} characters | |
198 | With @samp{--unibyte}, multibyte strings are not created during | |
199 | initialization from the values of environment variables, | |
200 | @file{/etc/passwd} entries etc.@: that contain non-@acronym{ASCII} 8-bit | |
201 | characters. | |
202 | ||
203 | Emacs normally loads Lisp files as multibyte, regardless of whether | |
204 | you used @samp{--unibyte}. This includes the Emacs initialization file, | |
205 | @file{.emacs}, and the initialization files of Emacs packages such as | |
206 | Gnus. However, you can specify unibyte loading for a particular Lisp | |
207 | file, by putting @w{@samp{-*-unibyte: t;-*-}} in a comment on the first | |
208 | line (@pxref{File Variables}). Then that file is always loaded as | |
209 | unibyte text, even if you did not start Emacs with @samp{--unibyte}. | |
210 | The motivation for these conventions is that it is more reliable to | |
211 | always load any particular Lisp file in the same way. However, you can | |
212 | load a Lisp file as unibyte, on any one occasion, by typing @kbd{C-x | |
213 | @key{RET} c raw-text @key{RET}} immediately before loading it. | |
214 | ||
215 | The mode line indicates whether multibyte character support is | |
216 | enabled in the current buffer. If it is, there are two or more | |
217 | characters (most often two dashes) near the beginning of the mode | |
218 | line, before the indication of the visited file's end-of-line | |
219 | convention (colon, backslash, etc.). When multibyte characters | |
220 | are not enabled, nothing precedes the colon except a single dash. | |
221 | @xref{Mode Line}, for more details about this. | |
222 | ||
223 | @node Language Environments | |
224 | @section Language Environments | |
225 | @cindex language environments | |
226 | ||
227 | All supported character sets are supported in Emacs buffers whenever | |
228 | multibyte characters are enabled; there is no need to select a | |
229 | particular language in order to display its characters in an Emacs | |
230 | buffer. However, it is important to select a @dfn{language environment} | |
231 | in order to set various defaults. The language environment really | |
232 | represents a choice of preferred script (more or less) rather than a | |
233 | choice of language. | |
234 | ||
235 | The language environment controls which coding systems to recognize | |
236 | when reading text (@pxref{Recognize Coding}). This applies to files, | |
237 | incoming mail, netnews, and any other text you read into Emacs. It may | |
238 | also specify the default coding system to use when you create a file. | |
239 | Each language environment also specifies a default input method. | |
240 | ||
241 | @findex set-language-environment | |
242 | @vindex current-language-environment | |
243 | To select a language environment, you can customize the variable | |
244 | @code{current-language-environment} or use the command @kbd{M-x | |
245 | set-language-environment}. It makes no difference which buffer is | |
246 | current when you use this command, because the effects apply globally to | |
247 | the Emacs session. The supported language environments include: | |
248 | ||
249 | @cindex Euro sign | |
250 | @cindex UTF-8 | |
251 | @quotation | |
252 | ASCII, Belarusian, Brazilian Portuguese, Bulgarian, Chinese-BIG5, | |
253 | Chinese-CNS, Chinese-EUC-TW, Chinese-GB, Croatian, Cyrillic-ALT, | |
254 | Cyrillic-ISO, Cyrillic-KOI8, Czech, Devanagari, Dutch, English, | |
255 | Esperanto, Ethiopic, French, Georgian, German, Greek, Hebrew, IPA, | |
256 | Italian, Japanese, Kannada, Korean, Lao, Latin-1, Latin-2, Latin-3, | |
257 | Latin-4, Latin-5, Latin-6, Latin-7, Latin-8 (Celtic), Latin-9 (updated | |
258 | Latin-1 with the Euro sign), Latvian, Lithuanian, Malayalam, Polish, | |
259 | Romanian, Russian, Slovak, Slovenian, Spanish, Swedish, Tajik, Tamil, | |
260 | Thai, Tibetan, Turkish, UTF-8 (for a setup which prefers Unicode | |
261 | characters and files encoded in UTF-8), Ukrainian, Vietnamese, Welsh, | |
262 | and Windows-1255 (for a setup which prefers Cyrillic characters and | |
263 | files encoded in Windows-1255). | |
264 | @tex | |
265 | \hbadness=10000\par % just avoid underfull hbox warning | |
266 | @end tex | |
267 | @end quotation | |
268 | ||
269 | @cindex fonts for various scripts | |
270 | @cindex Intlfonts package, installation | |
271 | To display the script(s) used by your language environment on a | |
272 | graphical display, you need to have a suitable font. If some of the | |
273 | characters appear as empty boxes, you should install the GNU Intlfonts | |
274 | package, which includes fonts for most supported scripts.@footnote{If | |
275 | you run Emacs on X, you need to inform the X server about the location | |
276 | of the newly installed fonts with the following commands: | |
277 | ||
278 | @example | |
279 | xset fp+ /usr/local/share/emacs/fonts | |
280 | xset fp rehash | |
281 | @end example | |
282 | } | |
283 | @xref{Fontsets}, for more details about setting up your fonts. | |
284 | ||
285 | @findex set-locale-environment | |
286 | @vindex locale-language-names | |
287 | @vindex locale-charset-language-names | |
288 | @cindex locales | |
289 | Some operating systems let you specify the character-set locale you | |
290 | are using by setting the locale environment variables @env{LC_ALL}, | |
291 | @env{LC_CTYPE}, or @env{LANG}.@footnote{If more than one of these is | |
292 | set, the first one that is nonempty specifies your locale for this | |
293 | purpose.} During startup, Emacs looks up your character-set locale's | |
294 | name in the system locale alias table, matches its canonical name | |
295 | against entries in the value of the variables | |
296 | @code{locale-charset-language-names} and @code{locale-language-names}, | |
297 | and selects the corresponding language environment if a match is found. | |
298 | (The former variable overrides the latter.) It also adjusts the display | |
299 | table and terminal coding system, the locale coding system, the | |
300 | preferred coding system as needed for the locale, and---last but not | |
301 | least---the way Emacs decodes non-@acronym{ASCII} characters sent by your keyboard. | |
302 | ||
303 | If you modify the @env{LC_ALL}, @env{LC_CTYPE}, or @env{LANG} | |
304 | environment variables while running Emacs, you may want to invoke the | |
305 | @code{set-locale-environment} function afterwards to readjust the | |
306 | language environment from the new locale. | |
307 | ||
308 | @vindex locale-preferred-coding-systems | |
309 | The @code{set-locale-environment} function normally uses the preferred | |
310 | coding system established by the language environment to decode system | |
311 | messages. But if your locale matches an entry in the variable | |
312 | @code{locale-preferred-coding-systems}, Emacs uses the corresponding | |
313 | coding system instead. For example, if the locale @samp{ja_JP.PCK} | |
314 | matches @code{japanese-shift-jis} in | |
315 | @code{locale-preferred-coding-systems}, Emacs uses that encoding even | |
316 | though it might normally use @code{japanese-iso-8bit}. | |
317 | ||
318 | You can override the language environment chosen at startup with | |
319 | explicit use of the command @code{set-language-environment}, or with | |
320 | customization of @code{current-language-environment} in your init | |
321 | file. | |
322 | ||
323 | @kindex C-h L | |
324 | @findex describe-language-environment | |
325 | To display information about the effects of a certain language | |
326 | environment @var{lang-env}, use the command @kbd{C-h L @var{lang-env} | |
327 | @key{RET}} (@code{describe-language-environment}). This tells you | |
328 | which languages this language environment is useful for, and lists the | |
329 | character sets, coding systems, and input methods that go with it. It | |
330 | also shows some sample text to illustrate scripts used in this | |
331 | language environment. If you give an empty input for @var{lang-env}, | |
332 | this command describes the chosen language environment. | |
333 | ||
334 | @vindex set-language-environment-hook | |
335 | You can customize any language environment with the normal hook | |
336 | @code{set-language-environment-hook}. The command | |
337 | @code{set-language-environment} runs that hook after setting up the new | |
338 | language environment. The hook functions can test for a specific | |
339 | language environment by checking the variable | |
340 | @code{current-language-environment}. This hook is where you should | |
341 | put non-default settings for specific language environment, such as | |
342 | coding systems for keyboard input and terminal output, the default | |
343 | input method, etc. | |
344 | ||
345 | @vindex exit-language-environment-hook | |
346 | Before it starts to set up the new language environment, | |
347 | @code{set-language-environment} first runs the hook | |
348 | @code{exit-language-environment-hook}. This hook is useful for undoing | |
349 | customizations that were made with @code{set-language-environment-hook}. | |
350 | For instance, if you set up a special key binding in a specific language | |
351 | environment using @code{set-language-environment-hook}, you should set | |
352 | up @code{exit-language-environment-hook} to restore the normal binding | |
353 | for that key. | |
354 | ||
355 | @node Input Methods | |
356 | @section Input Methods | |
357 | ||
358 | @cindex input methods | |
359 | An @dfn{input method} is a kind of character conversion designed | |
360 | specifically for interactive input. In Emacs, typically each language | |
361 | has its own input method; sometimes several languages which use the same | |
362 | characters can share one input method. A few languages support several | |
363 | input methods. | |
364 | ||
365 | The simplest kind of input method works by mapping @acronym{ASCII} letters | |
366 | into another alphabet; this allows you to use one other alphabet | |
367 | instead of @acronym{ASCII}. The Greek and Russian input methods | |
368 | work this way. | |
369 | ||
370 | A more powerful technique is composition: converting sequences of | |
371 | characters into one letter. Many European input methods use composition | |
372 | to produce a single non-@acronym{ASCII} letter from a sequence that consists of a | |
373 | letter followed by accent characters (or vice versa). For example, some | |
374 | methods convert the sequence @kbd{a'} into a single accented letter. | |
375 | These input methods have no special commands of their own; all they do | |
376 | is compose sequences of printing characters. | |
377 | ||
378 | The input methods for syllabic scripts typically use mapping followed | |
379 | by composition. The input methods for Thai and Korean work this way. | |
380 | First, letters are mapped into symbols for particular sounds or tone | |
381 | marks; then, sequences of these which make up a whole syllable are | |
382 | mapped into one syllable sign. | |
383 | ||
384 | Chinese and Japanese require more complex methods. In Chinese input | |
385 | methods, first you enter the phonetic spelling of a Chinese word (in | |
386 | input method @code{chinese-py}, among others), or a sequence of | |
387 | portions of the character (input methods @code{chinese-4corner} and | |
388 | @code{chinese-sw}, and others). One input sequence typically | |
389 | corresponds to many possible Chinese characters. You select the one | |
390 | you mean using keys such as @kbd{C-f}, @kbd{C-b}, @kbd{C-n}, | |
391 | @kbd{C-p}, and digits, which have special meanings in this situation. | |
392 | ||
393 | The possible characters are conceptually arranged in several rows, | |
394 | with each row holding up to 10 alternatives. Normally, Emacs displays | |
395 | just one row at a time, in the echo area; @code{(@var{i}/@var{j})} | |
396 | appears at the beginning, to indicate that this is the @var{i}th row | |
397 | out of a total of @var{j} rows. Type @kbd{C-n} or @kbd{C-p} to | |
398 | display the next row or the previous row. | |
399 | ||
400 | Type @kbd{C-f} and @kbd{C-b} to move forward and backward among | |
401 | the alternatives in the current row. As you do this, Emacs highlights | |
402 | the current alternative with a special color; type @code{C-@key{SPC}} | |
403 | to select the current alternative and use it as input. The | |
404 | alternatives in the row are also numbered; the number appears before | |
405 | the alternative. Typing a digit @var{n} selects the @var{n}th | |
406 | alternative of the current row and uses it as input. | |
407 | ||
408 | @key{TAB} in these Chinese input methods displays a buffer showing | |
409 | all the possible characters at once; then clicking @kbd{Mouse-2} on | |
410 | one of them selects that alternative. The keys @kbd{C-f}, @kbd{C-b}, | |
411 | @kbd{C-n}, @kbd{C-p}, and digits continue to work as usual, but they | |
412 | do the highlighting in the buffer showing the possible characters, | |
413 | rather than in the echo area. | |
414 | ||
415 | In Japanese input methods, first you input a whole word using | |
416 | phonetic spelling; then, after the word is in the buffer, Emacs | |
417 | converts it into one or more characters using a large dictionary. One | |
418 | phonetic spelling corresponds to a number of different Japanese words; | |
419 | to select one of them, use @kbd{C-n} and @kbd{C-p} to cycle through | |
420 | the alternatives. | |
421 | ||
422 | Sometimes it is useful to cut off input method processing so that the | |
423 | characters you have just entered will not combine with subsequent | |
424 | characters. For example, in input method @code{latin-1-postfix}, the | |
425 | sequence @kbd{e '} combines to form an @samp{e} with an accent. What if | |
426 | you want to enter them as separate characters? | |
427 | ||
428 | One way is to type the accent twice; this is a special feature for | |
429 | entering the separate letter and accent. For example, @kbd{e ' '} gives | |
430 | you the two characters @samp{e'}. Another way is to type another letter | |
431 | after the @kbd{e}---something that won't combine with that---and | |
432 | immediately delete it. For example, you could type @kbd{e e @key{DEL} | |
433 | '} to get separate @samp{e} and @samp{'}. | |
434 | ||
435 | Another method, more general but not quite as easy to type, is to use | |
436 | @kbd{C-\ C-\} between two characters to stop them from combining. This | |
437 | is the command @kbd{C-\} (@code{toggle-input-method}) used twice. | |
438 | @ifnottex | |
439 | @xref{Select Input Method}. | |
440 | @end ifnottex | |
441 | ||
442 | @cindex incremental search, input method interference | |
443 | @kbd{C-\ C-\} is especially useful inside an incremental search, | |
444 | because it stops waiting for more characters to combine, and starts | |
445 | searching for what you have already entered. | |
446 | ||
447 | To find out how to input the character after point using the current | |
448 | input method, type @kbd{C-u C-x =}. @xref{Position Info}. | |
449 | ||
450 | @vindex input-method-verbose-flag | |
451 | @vindex input-method-highlight-flag | |
452 | The variables @code{input-method-highlight-flag} and | |
453 | @code{input-method-verbose-flag} control how input methods explain | |
454 | what is happening. If @code{input-method-highlight-flag} is | |
455 | non-@code{nil}, the partial sequence is highlighted in the buffer (for | |
456 | most input methods---some disable this feature). If | |
457 | @code{input-method-verbose-flag} is non-@code{nil}, the list of | |
458 | possible characters to type next is displayed in the echo area (but | |
459 | not when you are in the minibuffer). | |
460 | ||
461 | @node Select Input Method | |
462 | @section Selecting an Input Method | |
463 | ||
464 | @table @kbd | |
465 | @item C-\ | |
466 | Enable or disable use of the selected input method. | |
467 | ||
468 | @item C-x @key{RET} C-\ @var{method} @key{RET} | |
469 | Select a new input method for the current buffer. | |
470 | ||
471 | @item C-h I @var{method} @key{RET} | |
472 | @itemx C-h C-\ @var{method} @key{RET} | |
473 | @findex describe-input-method | |
474 | @kindex C-h I | |
475 | @kindex C-h C-\ | |
476 | Describe the input method @var{method} (@code{describe-input-method}). | |
477 | By default, it describes the current input method (if any). This | |
478 | description should give you the full details of how to use any | |
479 | particular input method. | |
480 | ||
481 | @item M-x list-input-methods | |
482 | Display a list of all the supported input methods. | |
483 | @end table | |
484 | ||
485 | @findex set-input-method | |
486 | @vindex current-input-method | |
487 | @kindex C-x RET C-\ | |
488 | To choose an input method for the current buffer, use @kbd{C-x | |
489 | @key{RET} C-\} (@code{set-input-method}). This command reads the | |
490 | input method name from the minibuffer; the name normally starts with the | |
491 | language environment that it is meant to be used with. The variable | |
492 | @code{current-input-method} records which input method is selected. | |
493 | ||
494 | @findex toggle-input-method | |
495 | @kindex C-\ | |
496 | Input methods use various sequences of @acronym{ASCII} characters to | |
497 | stand for non-@acronym{ASCII} characters. Sometimes it is useful to | |
498 | turn off the input method temporarily. To do this, type @kbd{C-\} | |
499 | (@code{toggle-input-method}). To reenable the input method, type | |
500 | @kbd{C-\} again. | |
501 | ||
502 | If you type @kbd{C-\} and you have not yet selected an input method, | |
503 | it prompts for you to specify one. This has the same effect as using | |
504 | @kbd{C-x @key{RET} C-\} to specify an input method. | |
505 | ||
506 | When invoked with a numeric argument, as in @kbd{C-u C-\}, | |
507 | @code{toggle-input-method} always prompts you for an input method, | |
508 | suggesting the most recently selected one as the default. | |
509 | ||
510 | @vindex default-input-method | |
511 | Selecting a language environment specifies a default input method for | |
512 | use in various buffers. When you have a default input method, you can | |
513 | select it in the current buffer by typing @kbd{C-\}. The variable | |
514 | @code{default-input-method} specifies the default input method | |
515 | (@code{nil} means there is none). | |
516 | ||
517 | In some language environments, which support several different input | |
518 | methods, you might want to use an input method different from the | |
519 | default chosen by @code{set-language-environment}. You can instruct | |
520 | Emacs to select a different default input method for a certain | |
521 | language environment, if you wish, by using | |
522 | @code{set-language-environment-hook} (@pxref{Language Environments, | |
523 | set-language-environment-hook}). For example: | |
524 | ||
525 | @lisp | |
526 | (defun my-chinese-setup () | |
527 | "Set up my private Chinese environment." | |
528 | (if (equal current-language-environment "Chinese-GB") | |
529 | (setq default-input-method "chinese-tonepy"))) | |
530 | (add-hook 'set-language-environment-hook 'my-chinese-setup) | |
531 | @end lisp | |
532 | ||
533 | @noindent | |
534 | This sets the default input method to be @code{chinese-tonepy} | |
535 | whenever you choose a Chinese-GB language environment. | |
536 | ||
537 | @findex quail-set-keyboard-layout | |
538 | Some input methods for alphabetic scripts work by (in effect) | |
539 | remapping the keyboard to emulate various keyboard layouts commonly used | |
540 | for those scripts. How to do this remapping properly depends on your | |
541 | actual keyboard layout. To specify which layout your keyboard has, use | |
542 | the command @kbd{M-x quail-set-keyboard-layout}. | |
543 | ||
544 | @findex quail-show-key | |
545 | You can use the command @kbd{M-x quail-show-key} to show what key (or | |
546 | key sequence) to type in order to input the character following point, | |
547 | using the selected keyboard layout. The command @kbd{C-u C-x =} also | |
548 | shows that information in addition to the other information about the | |
549 | character. | |
550 | ||
551 | @findex list-input-methods | |
552 | To see a list of all the supported input methods, type @kbd{M-x | |
553 | list-input-methods}. The list gives information about each input | |
554 | method, including the string that stands for it in the mode line. | |
555 | ||
556 | @node Multibyte Conversion | |
557 | @section Unibyte and Multibyte Non-@acronym{ASCII} characters | |
558 | ||
559 | When multibyte characters are enabled, character codes 0240 (octal) | |
560 | through 0377 (octal) are not really legitimate in the buffer. The valid | |
561 | non-@acronym{ASCII} printing characters have codes that start from 0400. | |
562 | ||
563 | If you type a self-inserting character in the range 0240 through | |
564 | 0377, or if you use @kbd{C-q} to insert one, Emacs assumes you | |
565 | intended to use one of the ISO Latin-@var{n} character sets, and | |
566 | converts it to the Emacs code representing that Latin-@var{n} | |
567 | character. You select @emph{which} ISO Latin character set to use | |
568 | through your choice of language environment | |
569 | @iftex | |
570 | (see above). | |
571 | @end iftex | |
572 | @ifnottex | |
573 | (@pxref{Language Environments}). | |
574 | @end ifnottex | |
575 | If you do not specify a choice, the default is Latin-1. | |
576 | ||
577 | If you insert a character in the range 0200 through 0237, which | |
578 | forms the @code{eight-bit-control} character set, it is inserted | |
579 | literally. You should normally avoid doing this since buffers | |
580 | containing such characters have to be written out in either the | |
581 | @code{emacs-mule} or @code{raw-text} coding system, which is usually | |
582 | not what you want. | |
583 | ||
584 | @node Coding Systems | |
585 | @section Coding Systems | |
586 | @cindex coding systems | |
587 | ||
588 | Users of various languages have established many more-or-less standard | |
589 | coding systems for representing them. Emacs does not use these coding | |
590 | systems internally; instead, it converts from various coding systems to | |
591 | its own system when reading data, and converts the internal coding | |
592 | system to other coding systems when writing data. Conversion is | |
593 | possible in reading or writing files, in sending or receiving from the | |
594 | terminal, and in exchanging data with subprocesses. | |
595 | ||
596 | Emacs assigns a name to each coding system. Most coding systems are | |
597 | used for one language, and the name of the coding system starts with the | |
598 | language name. Some coding systems are used for several languages; | |
599 | their names usually start with @samp{iso}. There are also special | |
600 | coding systems @code{no-conversion}, @code{raw-text} and | |
601 | @code{emacs-mule} which do not convert printing characters at all. | |
602 | ||
603 | @cindex international files from DOS/Windows systems | |
604 | A special class of coding systems, collectively known as | |
605 | @dfn{codepages}, is designed to support text encoded by MS-Windows and | |
606 | MS-DOS software. The names of these coding systems are | |
607 | @code{cp@var{nnnn}}, where @var{nnnn} is a 3- or 4-digit number of the | |
608 | codepage. You can use these encodings just like any other coding | |
609 | system; for example, to visit a file encoded in codepage 850, type | |
610 | @kbd{C-x @key{RET} c cp850 @key{RET} C-x C-f @var{filename} | |
611 | @key{RET}}@footnote{ | |
612 | In the MS-DOS port of Emacs, you need to create a @code{cp@var{nnn}} | |
613 | coding system with @kbd{M-x codepage-setup}, before you can use it. | |
614 | @iftex | |
615 | @xref{MS-DOS and MULE,,,emacs-extra,Specialized Emacs Features}. | |
616 | @end iftex | |
617 | @ifnottex | |
618 | @xref{MS-DOS and MULE}. | |
619 | @end ifnottex | |
620 | }. | |
621 | ||
622 | In addition to converting various representations of non-@acronym{ASCII} | |
623 | characters, a coding system can perform end-of-line conversion. Emacs | |
624 | handles three different conventions for how to separate lines in a file: | |
625 | newline, carriage-return linefeed, and just carriage-return. | |
626 | ||
627 | @table @kbd | |
628 | @item C-h C @var{coding} @key{RET} | |
629 | Describe coding system @var{coding}. | |
630 | ||
631 | @item C-h C @key{RET} | |
632 | Describe the coding systems currently in use. | |
633 | ||
634 | @item M-x list-coding-systems | |
635 | Display a list of all the supported coding systems. | |
636 | @end table | |
637 | ||
638 | @kindex C-h C | |
639 | @findex describe-coding-system | |
640 | The command @kbd{C-h C} (@code{describe-coding-system}) displays | |
641 | information about particular coding systems, including the end-of-line | |
642 | conversion specified by those coding systems. You can specify a coding | |
643 | system name as the argument; alternatively, with an empty argument, it | |
644 | describes the coding systems currently selected for various purposes, | |
645 | both in the current buffer and as the defaults, and the priority list | |
646 | for recognizing coding systems (@pxref{Recognize Coding}). | |
647 | ||
648 | @findex list-coding-systems | |
649 | To display a list of all the supported coding systems, type @kbd{M-x | |
650 | list-coding-systems}. The list gives information about each coding | |
651 | system, including the letter that stands for it in the mode line | |
652 | (@pxref{Mode Line}). | |
653 | ||
654 | @cindex end-of-line conversion | |
655 | @cindex line endings | |
656 | @cindex MS-DOS end-of-line conversion | |
657 | @cindex Macintosh end-of-line conversion | |
658 | Each of the coding systems that appear in this list---except for | |
659 | @code{no-conversion}, which means no conversion of any kind---specifies | |
660 | how and whether to convert printing characters, but leaves the choice of | |
661 | end-of-line conversion to be decided based on the contents of each file. | |
662 | For example, if the file appears to use the sequence carriage-return | |
663 | linefeed to separate lines, DOS end-of-line conversion will be used. | |
664 | ||
665 | Each of the listed coding systems has three variants which specify | |
666 | exactly what to do for end-of-line conversion: | |
667 | ||
668 | @table @code | |
669 | @item @dots{}-unix | |
670 | Don't do any end-of-line conversion; assume the file uses | |
671 | newline to separate lines. (This is the convention normally used | |
672 | on Unix and GNU systems.) | |
673 | ||
674 | @item @dots{}-dos | |
675 | Assume the file uses carriage-return linefeed to separate lines, and do | |
676 | the appropriate conversion. (This is the convention normally used on | |
677 | Microsoft systems.@footnote{It is also specified for MIME @samp{text/*} | |
678 | bodies and in other network transport contexts. It is different | |
679 | from the SGML reference syntax record-start/record-end format which | |
680 | Emacs doesn't support directly.}) | |
681 | ||
682 | @item @dots{}-mac | |
683 | Assume the file uses carriage-return to separate lines, and do the | |
684 | appropriate conversion. (This is the convention normally used on the | |
685 | Macintosh system.) | |
686 | @end table | |
687 | ||
688 | These variant coding systems are omitted from the | |
689 | @code{list-coding-systems} display for brevity, since they are entirely | |
690 | predictable. For example, the coding system @code{iso-latin-1} has | |
691 | variants @code{iso-latin-1-unix}, @code{iso-latin-1-dos} and | |
692 | @code{iso-latin-1-mac}. | |
693 | ||
694 | @cindex @code{undecided}, coding system | |
695 | The coding systems @code{unix}, @code{dos}, and @code{mac} are | |
696 | aliases for @code{undecided-unix}, @code{undecided-dos}, and | |
697 | @code{undecided-mac}, respectively. These coding systems specify only | |
698 | the end-of-line conversion, and leave the character code conversion to | |
699 | be deduced from the text itself. | |
700 | ||
701 | The coding system @code{raw-text} is good for a file which is mainly | |
702 | @acronym{ASCII} text, but may contain byte values above 127 which are | |
703 | not meant to encode non-@acronym{ASCII} characters. With | |
704 | @code{raw-text}, Emacs copies those byte values unchanged, and sets | |
705 | @code{enable-multibyte-characters} to @code{nil} in the current buffer | |
706 | so that they will be interpreted properly. @code{raw-text} handles | |
707 | end-of-line conversion in the usual way, based on the data | |
708 | encountered, and has the usual three variants to specify the kind of | |
709 | end-of-line conversion to use. | |
710 | ||
711 | In contrast, the coding system @code{no-conversion} specifies no | |
712 | character code conversion at all---none for non-@acronym{ASCII} byte values and | |
713 | none for end of line. This is useful for reading or writing binary | |
714 | files, tar files, and other files that must be examined verbatim. It, | |
715 | too, sets @code{enable-multibyte-characters} to @code{nil}. | |
716 | ||
717 | The easiest way to edit a file with no conversion of any kind is with | |
718 | the @kbd{M-x find-file-literally} command. This uses | |
719 | @code{no-conversion}, and also suppresses other Emacs features that | |
720 | might convert the file contents before you see them. @xref{Visiting}. | |
721 | ||
722 | The coding system @code{emacs-mule} means that the file contains | |
723 | non-@acronym{ASCII} characters stored with the internal Emacs encoding. It | |
724 | handles end-of-line conversion based on the data encountered, and has | |
725 | the usual three variants to specify the kind of end-of-line conversion. | |
726 | ||
727 | @findex unify-8859-on-decoding-mode | |
728 | @anchor{Character Translation} | |
729 | The @dfn{character translation} feature can modify the effect of | |
730 | various coding systems, by changing the internal Emacs codes that | |
731 | decoding produces. For instance, the command | |
732 | @code{unify-8859-on-decoding-mode} enables a mode that ``unifies'' the | |
733 | Latin alphabets when decoding text. This works by converting all | |
734 | non-@acronym{ASCII} Latin-@var{n} characters to either Latin-1 or | |
735 | Unicode characters. This way it is easier to use various | |
736 | Latin-@var{n} alphabets together. (In a future Emacs version we hope | |
737 | to move towards full Unicode support and complete unification of | |
738 | character sets.) | |
739 | ||
740 | @vindex enable-character-translation | |
741 | If you set the variable @code{enable-character-translation} to | |
742 | @code{nil}, that disables all character translation (including | |
743 | @code{unify-8859-on-decoding-mode}). | |
744 | ||
745 | @node Recognize Coding | |
746 | @section Recognizing Coding Systems | |
747 | ||
748 | Emacs tries to recognize which coding system to use for a given text | |
749 | as an integral part of reading that text. (This applies to files | |
750 | being read, output from subprocesses, text from X selections, etc.) | |
751 | Emacs can select the right coding system automatically most of the | |
752 | time---once you have specified your preferences. | |
753 | ||
754 | Some coding systems can be recognized or distinguished by which byte | |
755 | sequences appear in the data. However, there are coding systems that | |
756 | cannot be distinguished, not even potentially. For example, there is no | |
757 | way to distinguish between Latin-1 and Latin-2; they use the same byte | |
758 | values with different meanings. | |
759 | ||
760 | Emacs handles this situation by means of a priority list of coding | |
761 | systems. Whenever Emacs reads a file, if you do not specify the coding | |
762 | system to use, Emacs checks the data against each coding system, | |
763 | starting with the first in priority and working down the list, until it | |
764 | finds a coding system that fits the data. Then it converts the file | |
765 | contents assuming that they are represented in this coding system. | |
766 | ||
767 | The priority list of coding systems depends on the selected language | |
768 | environment (@pxref{Language Environments}). For example, if you use | |
769 | French, you probably want Emacs to prefer Latin-1 to Latin-2; if you use | |
770 | Czech, you probably want Latin-2 to be preferred. This is one of the | |
771 | reasons to specify a language environment. | |
772 | ||
773 | @findex prefer-coding-system | |
774 | However, you can alter the coding system priority list in detail | |
775 | with the command @kbd{M-x prefer-coding-system}. This command reads | |
776 | the name of a coding system from the minibuffer, and adds it to the | |
777 | front of the priority list, so that it is preferred to all others. If | |
778 | you use this command several times, each use adds one element to the | |
779 | front of the priority list. | |
780 | ||
781 | If you use a coding system that specifies the end-of-line conversion | |
782 | type, such as @code{iso-8859-1-dos}, what this means is that Emacs | |
783 | should attempt to recognize @code{iso-8859-1} with priority, and should | |
784 | use DOS end-of-line conversion when it does recognize @code{iso-8859-1}. | |
785 | ||
786 | @vindex file-coding-system-alist | |
787 | Sometimes a file name indicates which coding system to use for the | |
788 | file. The variable @code{file-coding-system-alist} specifies this | |
789 | correspondence. There is a special function | |
790 | @code{modify-coding-system-alist} for adding elements to this list. For | |
791 | example, to read and write all @samp{.txt} files using the coding system | |
792 | @code{chinese-iso-8bit}, you can execute this Lisp expression: | |
793 | ||
794 | @smallexample | |
795 | (modify-coding-system-alist 'file "\\.txt\\'" 'chinese-iso-8bit) | |
796 | @end smallexample | |
797 | ||
798 | @noindent | |
799 | The first argument should be @code{file}, the second argument should be | |
800 | a regular expression that determines which files this applies to, and | |
801 | the third argument says which coding system to use for these files. | |
802 | ||
803 | @vindex inhibit-eol-conversion | |
804 | @cindex DOS-style end-of-line display | |
805 | Emacs recognizes which kind of end-of-line conversion to use based on | |
806 | the contents of the file: if it sees only carriage-returns, or only | |
807 | carriage-return linefeed sequences, then it chooses the end-of-line | |
808 | conversion accordingly. You can inhibit the automatic use of | |
809 | end-of-line conversion by setting the variable @code{inhibit-eol-conversion} | |
810 | to non-@code{nil}. If you do that, DOS-style files will be displayed | |
811 | with the @samp{^M} characters visible in the buffer; some people | |
812 | prefer this to the more subtle @samp{(DOS)} end-of-line type | |
813 | indication near the left edge of the mode line (@pxref{Mode Line, | |
814 | eol-mnemonic}). | |
815 | ||
816 | @vindex inhibit-iso-escape-detection | |
817 | @cindex escape sequences in files | |
818 | By default, the automatic detection of coding system is sensitive to | |
819 | escape sequences. If Emacs sees a sequence of characters that begin | |
820 | with an escape character, and the sequence is valid as an ISO-2022 | |
821 | code, that tells Emacs to use one of the ISO-2022 encodings to decode | |
822 | the file. | |
823 | ||
824 | However, there may be cases that you want to read escape sequences | |
825 | in a file as is. In such a case, you can set the variable | |
826 | @code{inhibit-iso-escape-detection} to non-@code{nil}. Then the code | |
827 | detection ignores any escape sequences, and never uses an ISO-2022 | |
828 | encoding. The result is that all escape sequences become visible in | |
829 | the buffer. | |
830 | ||
831 | The default value of @code{inhibit-iso-escape-detection} is | |
832 | @code{nil}. We recommend that you not change it permanently, only for | |
833 | one specific operation. That's because many Emacs Lisp source files | |
834 | in the Emacs distribution contain non-@acronym{ASCII} characters encoded in the | |
835 | coding system @code{iso-2022-7bit}, and they won't be | |
836 | decoded correctly when you visit those files if you suppress the | |
837 | escape sequence detection. | |
838 | ||
839 | @vindex auto-coding-alist | |
840 | @vindex auto-coding-regexp-alist | |
841 | @vindex auto-coding-functions | |
842 | The variables @code{auto-coding-alist}, | |
843 | @code{auto-coding-regexp-alist} and @code{auto-coding-functions} are | |
844 | the strongest way to specify the coding system for certain patterns of | |
845 | file names, or for files containing certain patterns; these variables | |
846 | even override @samp{-*-coding:-*-} tags in the file itself. Emacs | |
847 | uses @code{auto-coding-alist} for tar and archive files, to prevent it | |
848 | from being confused by a @samp{-*-coding:-*-} tag in a member of the | |
849 | archive and thinking it applies to the archive file as a whole. | |
850 | Likewise, Emacs uses @code{auto-coding-regexp-alist} to ensure that | |
851 | RMAIL files, whose names in general don't match any particular | |
852 | pattern, are decoded correctly. One of the builtin | |
853 | @code{auto-coding-functions} detects the encoding for XML files. | |
854 | ||
855 | @vindex rmail-decode-mime-charset | |
856 | When you get new mail in Rmail, each message is translated | |
857 | automatically from the coding system it is written in, as if it were a | |
858 | separate file. This uses the priority list of coding systems that you | |
859 | have specified. If a MIME message specifies a character set, Rmail | |
860 | obeys that specification, unless @code{rmail-decode-mime-charset} is | |
861 | @code{nil}. | |
862 | ||
863 | @vindex rmail-file-coding-system | |
864 | For reading and saving Rmail files themselves, Emacs uses the coding | |
865 | system specified by the variable @code{rmail-file-coding-system}. The | |
866 | default value is @code{nil}, which means that Rmail files are not | |
867 | translated (they are read and written in the Emacs internal character | |
868 | code). | |
869 | ||
870 | @node Specify Coding | |
871 | @section Specifying a File's Coding System | |
872 | ||
873 | If Emacs recognizes the encoding of a file incorrectly, you can | |
874 | reread the file using the correct coding system by typing @kbd{C-x | |
875 | @key{RET} r @var{coding-system} @key{RET}}. To see what coding system | |
876 | Emacs actually used to decode the file, look at the coding system | |
877 | mnemonic letter near the left edge of the mode line (@pxref{Mode | |
878 | Line}), or type @kbd{C-h C @key{RET}}. | |
879 | ||
880 | @vindex coding | |
881 | You can specify the coding system for a particular file in the file | |
882 | itself, using the @w{@samp{-*-@dots{}-*-}} construct at the beginning, | |
883 | or a local variables list at the end (@pxref{File Variables}). You do | |
884 | this by defining a value for the ``variable'' named @code{coding}. | |
885 | Emacs does not really have a variable @code{coding}; instead of | |
886 | setting a variable, this uses the specified coding system for the | |
887 | file. For example, @samp{-*-mode: C; coding: latin-1;-*-} specifies | |
888 | use of the Latin-1 coding system, as well as C mode. When you specify | |
889 | the coding explicitly in the file, that overrides | |
890 | @code{file-coding-system-alist}. | |
891 | ||
892 | If you add the character @samp{!} at the end of the coding system | |
893 | name in @code{coding}, it disables any character translation | |
894 | (@pxref{Character Translation}) while decoding the file. This is | |
895 | useful when you need to make sure that the character codes in the | |
896 | Emacs buffer will not vary due to changes in user settings; for | |
897 | instance, for the sake of strings in Emacs Lisp source files. | |
898 | ||
899 | @node Output Coding | |
900 | @section Choosing Coding Systems for Output | |
901 | ||
902 | @vindex buffer-file-coding-system | |
903 | Once Emacs has chosen a coding system for a buffer, it stores that | |
904 | coding system in @code{buffer-file-coding-system}. That makes it the | |
905 | default for operations that write from this buffer into a file, such | |
906 | as @code{save-buffer} and @code{write-region}. You can specify a | |
907 | different coding system for further file output from the buffer using | |
908 | @code{set-buffer-file-coding-system} (@pxref{Text Coding}). | |
909 | ||
910 | You can insert any character Emacs supports into any Emacs buffer, | |
911 | but most coding systems can only handle a subset of these characters. | |
912 | Therefore, you can insert characters that cannot be encoded with the | |
913 | coding system that will be used to save the buffer. For example, you | |
914 | could start with an @acronym{ASCII} file and insert a few Latin-1 | |
915 | characters into it, or you could edit a text file in Polish encoded in | |
916 | @code{iso-8859-2} and add some Russian words to it. When you save | |
917 | that buffer, Emacs cannot use the current value of | |
918 | @code{buffer-file-coding-system}, because the characters you added | |
919 | cannot be encoded by that coding system. | |
920 | ||
921 | When that happens, Emacs tries the most-preferred coding system (set | |
922 | by @kbd{M-x prefer-coding-system} or @kbd{M-x | |
923 | set-language-environment}), and if that coding system can safely | |
924 | encode all of the characters in the buffer, Emacs uses it, and stores | |
925 | its value in @code{buffer-file-coding-system}. Otherwise, Emacs | |
926 | displays a list of coding systems suitable for encoding the buffer's | |
927 | contents, and asks you to choose one of those coding systems. | |
928 | ||
929 | If you insert the unsuitable characters in a mail message, Emacs | |
930 | behaves a bit differently. It additionally checks whether the | |
931 | most-preferred coding system is recommended for use in MIME messages; | |
932 | if not, Emacs tells you that the most-preferred coding system is not | |
933 | recommended and prompts you for another coding system. This is so you | |
934 | won't inadvertently send a message encoded in a way that your | |
935 | recipient's mail software will have difficulty decoding. (You can | |
936 | still use an unsuitable coding system if you type its name in response | |
937 | to the question.) | |
938 | ||
939 | @vindex sendmail-coding-system | |
940 | When you send a message with Mail mode (@pxref{Sending Mail}), Emacs has | |
941 | four different ways to determine the coding system to use for encoding | |
942 | the message text. It tries the buffer's own value of | |
943 | @code{buffer-file-coding-system}, if that is non-@code{nil}. Otherwise, | |
944 | it uses the value of @code{sendmail-coding-system}, if that is | |
945 | non-@code{nil}. The third way is to use the default coding system for | |
946 | new files, which is controlled by your choice of language environment, | |
947 | if that is non-@code{nil}. If all of these three values are @code{nil}, | |
948 | Emacs encodes outgoing mail using the Latin-1 coding system. | |
949 | ||
950 | @node Text Coding | |
951 | @section Specifying a Coding System for File Text | |
952 | ||
953 | In cases where Emacs does not automatically choose the right coding | |
954 | system for a file's contents, you can use these commands to specify | |
955 | one: | |
956 | ||
957 | @table @kbd | |
958 | @item C-x @key{RET} f @var{coding} @key{RET} | |
959 | Use coding system @var{coding} for saving or revisiting the visited | |
960 | file in the current buffer. | |
961 | ||
962 | @item C-x @key{RET} c @var{coding} @key{RET} | |
963 | Specify coding system @var{coding} for the immediately following | |
964 | command. | |
965 | ||
966 | @item C-x @key{RET} r @var{coding} @key{RET} | |
967 | Revisit the current file using the coding system @var{coding}. | |
968 | ||
969 | @item M-x recode-region @key{RET} @var{right} @key{RET} @var{wrong} @key{RET} | |
970 | Convert a region that was decoded using coding system @var{wrong}, | |
971 | decoding it using coding system @var{right} instead. | |
972 | @end table | |
973 | ||
974 | @kindex C-x RET f | |
975 | @findex set-buffer-file-coding-system | |
976 | The command @kbd{C-x @key{RET} f} | |
977 | (@code{set-buffer-file-coding-system}) sets the file coding system for | |
978 | the current buffer---in other words, it says which coding system to | |
979 | use when saving or reverting the visited file. You specify which | |
980 | coding system using the minibuffer. If you specify a coding system | |
981 | that cannot handle all of the characters in the buffer, Emacs warns | |
982 | you about the troublesome characters when you actually save the | |
983 | buffer. | |
984 | ||
985 | @cindex specify end-of-line conversion | |
986 | You can also use this command to specify the end-of-line conversion | |
987 | (@pxref{Coding Systems, end-of-line conversion}) for encoding the | |
988 | current buffer. For example, @kbd{C-x @key{RET} f dos @key{RET}} will | |
989 | cause Emacs to save the current buffer's text with DOS-style CRLF line | |
990 | endings. | |
991 | ||
992 | @kindex C-x RET c | |
993 | @findex universal-coding-system-argument | |
994 | Another way to specify the coding system for a file is when you visit | |
995 | the file. First use the command @kbd{C-x @key{RET} c} | |
996 | (@code{universal-coding-system-argument}); this command uses the | |
997 | minibuffer to read a coding system name. After you exit the minibuffer, | |
998 | the specified coding system is used for @emph{the immediately following | |
999 | command}. | |
1000 | ||
1001 | So if the immediately following command is @kbd{C-x C-f}, for example, | |
1002 | it reads the file using that coding system (and records the coding | |
1003 | system for when you later save the file). Or if the immediately following | |
1004 | command is @kbd{C-x C-w}, it writes the file using that coding system. | |
1005 | When you specify the coding system for saving in this way, instead | |
1006 | of with @kbd{C-x @key{RET} f}, there is no warning if the buffer | |
1007 | contains characters that the coding system cannot handle. | |
1008 | ||
1009 | Other file commands affected by a specified coding system include | |
1010 | @kbd{C-x i} and @kbd{C-x C-v}, as well as the other-window variants | |
1011 | of @kbd{C-x C-f}. @kbd{C-x @key{RET} c} also affects commands that | |
1012 | start subprocesses, including @kbd{M-x shell} (@pxref{Shell}). If the | |
1013 | immediately following command does not use the coding system, then | |
1014 | @kbd{C-x @key{RET} c} ultimately has no effect. | |
1015 | ||
1016 | An easy way to visit a file with no conversion is with the @kbd{M-x | |
1017 | find-file-literally} command. @xref{Visiting}. | |
1018 | ||
1019 | @vindex default-buffer-file-coding-system | |
1020 | The variable @code{default-buffer-file-coding-system} specifies the | |
1021 | choice of coding system to use when you create a new file. It applies | |
1022 | when you find a new file, and when you create a buffer and then save it | |
1023 | in a file. Selecting a language environment typically sets this | |
1024 | variable to a good choice of default coding system for that language | |
1025 | environment. | |
1026 | ||
1027 | @kindex C-x RET r | |
1028 | @findex revert-buffer-with-coding-system | |
1029 | If you visit a file with a wrong coding system, you can correct this | |
1030 | with @kbd{C-x @key{RET} r} (@code{revert-buffer-with-coding-system}). | |
1031 | This visits the current file again, using a coding system you specify. | |
1032 | ||
1033 | @findex recode-region | |
1034 | If a piece of text has already been inserted into a buffer using the | |
1035 | wrong coding system, you can redo the decoding of it using @kbd{M-x | |
1036 | recode-region}. This prompts you for the proper coding system, then | |
1037 | for the wrong coding system that was actually used, and does the | |
1038 | conversion. It first encodes the region using the wrong coding system, | |
1039 | then decodes it again using the proper coding system. | |
1040 | ||
1041 | @node Communication Coding | |
1042 | @section Coding Systems for Interprocess Communication | |
1043 | ||
1044 | This section explains how to specify coding systems for use | |
1045 | in communication with other processes. | |
1046 | ||
1047 | @table @kbd | |
1048 | @item C-x @key{RET} x @var{coding} @key{RET} | |
1049 | Use coding system @var{coding} for transferring selections to and from | |
1050 | other window-based applications. | |
1051 | ||
1052 | @item C-x @key{RET} X @var{coding} @key{RET} | |
1053 | Use coding system @var{coding} for transferring @emph{one} | |
1054 | selection---the next one---to or from another window-based application. | |
1055 | ||
1056 | @item C-x @key{RET} p @var{input-coding} @key{RET} @var{output-coding} @key{RET} | |
1057 | Use coding systems @var{input-coding} and @var{output-coding} for | |
1058 | subprocess input and output in the current buffer. | |
1059 | ||
1060 | @item C-x @key{RET} c @var{coding} @key{RET} | |
1061 | Specify coding system @var{coding} for the immediately following | |
1062 | command. | |
1063 | @end table | |
1064 | ||
1065 | @kindex C-x RET x | |
1066 | @kindex C-x RET X | |
1067 | @findex set-selection-coding-system | |
1068 | @findex set-next-selection-coding-system | |
1069 | The command @kbd{C-x @key{RET} x} (@code{set-selection-coding-system}) | |
1070 | specifies the coding system for sending selected text to other windowing | |
1071 | applications, and for receiving the text of selections made in other | |
1072 | applications. This command applies to all subsequent selections, until | |
1073 | you override it by using the command again. The command @kbd{C-x | |
1074 | @key{RET} X} (@code{set-next-selection-coding-system}) specifies the | |
1075 | coding system for the next selection made in Emacs or read by Emacs. | |
1076 | ||
1077 | @kindex C-x RET p | |
1078 | @findex set-buffer-process-coding-system | |
1079 | The command @kbd{C-x @key{RET} p} (@code{set-buffer-process-coding-system}) | |
1080 | specifies the coding system for input and output to a subprocess. This | |
1081 | command applies to the current buffer; normally, each subprocess has its | |
1082 | own buffer, and thus you can use this command to specify translation to | |
1083 | and from a particular subprocess by giving the command in the | |
1084 | corresponding buffer. | |
1085 | ||
1086 | You can also use @kbd{C-x @key{RET} c} just before the command that | |
1087 | runs or starts a subprocess, to specify the coding system to use for | |
1088 | communication with that subprocess. | |
1089 | ||
1090 | The default for translation of process input and output depends on the | |
1091 | current language environment. | |
1092 | ||
1093 | @vindex locale-coding-system | |
1094 | @cindex decoding non-@acronym{ASCII} keyboard input on X | |
1095 | The variable @code{locale-coding-system} specifies a coding system | |
1096 | to use when encoding and decoding system strings such as system error | |
1097 | messages and @code{format-time-string} formats and time stamps. That | |
1098 | coding system is also used for decoding non-@acronym{ASCII} keyboard input on X | |
1099 | Window systems. You should choose a coding system that is compatible | |
1100 | with the underlying system's text representation, which is normally | |
1101 | specified by one of the environment variables @env{LC_ALL}, | |
1102 | @env{LC_CTYPE}, and @env{LANG}. (The first one, in the order | |
1103 | specified above, whose value is nonempty is the one that determines | |
1104 | the text representation.) | |
1105 | ||
1106 | @node File Name Coding | |
1107 | @section Coding Systems for File Names | |
1108 | ||
1109 | @table @kbd | |
1110 | @item C-x @key{RET} F @var{coding} @key{RET} | |
1111 | Use coding system @var{coding} for encoding and decoding file | |
1112 | @emph{names}. | |
1113 | @end table | |
1114 | ||
1115 | @vindex file-name-coding-system | |
1116 | @cindex file names with non-@acronym{ASCII} characters | |
1117 | The variable @code{file-name-coding-system} specifies a coding | |
1118 | system to use for encoding file names. It has no effect on reading | |
1119 | and writing the @emph{contents} of files. | |
1120 | ||
1121 | @findex set-file-name-coding-system | |
1122 | @kindex C-x @key{RET} F | |
1123 | If you set the variable to a coding system name (as a Lisp symbol or | |
1124 | a string), Emacs encodes file names using that coding system for all | |
1125 | file operations. This makes it possible to use non-@acronym{ASCII} | |
1126 | characters in file names---or, at least, those non-@acronym{ASCII} | |
1127 | characters which the specified coding system can encode. Use @kbd{C-x | |
1128 | @key{RET} F} (@code{set-file-name-coding-system}) to specify this | |
1129 | interactively. | |
1130 | ||
1131 | If @code{file-name-coding-system} is @code{nil}, Emacs uses a | |
1132 | default coding system determined by the selected language environment. | |
1133 | In the default language environment, any non-@acronym{ASCII} | |
1134 | characters in file names are not encoded specially; they appear in the | |
1135 | file system using the internal Emacs representation. | |
1136 | ||
1137 | @strong{Warning:} if you change @code{file-name-coding-system} (or the | |
1138 | language environment) in the middle of an Emacs session, problems can | |
1139 | result if you have already visited files whose names were encoded using | |
1140 | the earlier coding system and cannot be encoded (or are encoded | |
1141 | differently) under the new coding system. If you try to save one of | |
1142 | these buffers under the visited file name, saving may use the wrong file | |
1143 | name, or it may get an error. If such a problem happens, use @kbd{C-x | |
1144 | C-w} to specify a new file name for that buffer. | |
1145 | ||
1146 | @findex recode-file-name | |
1147 | If a mistake occurs when encoding a file name, use the command | |
1148 | @kbd{M-x recode-file-name} to change the file name's coding | |
1149 | system. This prompts for an existing file name, its old coding | |
1150 | system, and the coding system to which you wish to convert. | |
1151 | ||
1152 | @node Terminal Coding | |
1153 | @section Coding Systems for Terminal I/O | |
1154 | ||
1155 | @table @kbd | |
1156 | @item C-x @key{RET} k @var{coding} @key{RET} | |
1157 | Use coding system @var{coding} for keyboard input. | |
1158 | ||
1159 | @item C-x @key{RET} t @var{coding} @key{RET} | |
1160 | Use coding system @var{coding} for terminal output. | |
1161 | @end table | |
1162 | ||
1163 | @kindex C-x RET t | |
1164 | @findex set-terminal-coding-system | |
1165 | The command @kbd{C-x @key{RET} t} (@code{set-terminal-coding-system}) | |
1166 | specifies the coding system for terminal output. If you specify a | |
1167 | character code for terminal output, all characters output to the | |
1168 | terminal are translated into that coding system. | |
1169 | ||
1170 | This feature is useful for certain character-only terminals built to | |
1171 | support specific languages or character sets---for example, European | |
1172 | terminals that support one of the ISO Latin character sets. You need to | |
1173 | specify the terminal coding system when using multibyte text, so that | |
1174 | Emacs knows which characters the terminal can actually handle. | |
1175 | ||
1176 | By default, output to the terminal is not translated at all, unless | |
1177 | Emacs can deduce the proper coding system from your terminal type or | |
1178 | your locale specification (@pxref{Language Environments}). | |
1179 | ||
1180 | @kindex C-x RET k | |
1181 | @findex set-keyboard-coding-system | |
1182 | @vindex keyboard-coding-system | |
1183 | The command @kbd{C-x @key{RET} k} (@code{set-keyboard-coding-system}) | |
1184 | or the variable @code{keyboard-coding-system} specifies the coding | |
1185 | system for keyboard input. Character-code translation of keyboard | |
1186 | input is useful for terminals with keys that send non-@acronym{ASCII} | |
1187 | graphic characters---for example, some terminals designed for ISO | |
1188 | Latin-1 or subsets of it. | |
1189 | ||
1190 | By default, keyboard input is translated based on your system locale | |
1191 | setting. If your terminal does not really support the encoding | |
1192 | implied by your locale (for example, if you find it inserts a | |
1193 | non-@acronym{ASCII} character if you type @kbd{M-i}), you will need to set | |
1194 | @code{keyboard-coding-system} to @code{nil} to turn off encoding. | |
1195 | You can do this by putting | |
1196 | ||
1197 | @lisp | |
1198 | (set-keyboard-coding-system nil) | |
1199 | @end lisp | |
1200 | ||
1201 | @noindent | |
1202 | in your @file{~/.emacs} file. | |
1203 | ||
1204 | There is a similarity between using a coding system translation for | |
1205 | keyboard input, and using an input method: both define sequences of | |
1206 | keyboard input that translate into single characters. However, input | |
1207 | methods are designed to be convenient for interactive use by humans, and | |
1208 | the sequences that are translated are typically sequences of @acronym{ASCII} | |
1209 | printing characters. Coding systems typically translate sequences of | |
1210 | non-graphic characters. | |
1211 | ||
1212 | @node Fontsets | |
1213 | @section Fontsets | |
1214 | @cindex fontsets | |
1215 | ||
1216 | A font typically defines shapes for a single alphabet or script. | |
1217 | Therefore, displaying the entire range of scripts that Emacs supports | |
1218 | requires a collection of many fonts. In Emacs, such a collection is | |
1219 | called a @dfn{fontset}. A fontset is defined by a list of fonts, each | |
1220 | assigned to handle a range of character codes. | |
1221 | ||
1222 | Each fontset has a name, like a font. However, while fonts are | |
1223 | stored in the system and the available font names are defined by the | |
1224 | system, fontsets are defined within Emacs itself. Once you have | |
1225 | defined a fontset, you can use it within Emacs by specifying its name, | |
1226 | anywhere that you could use a single font. Of course, Emacs fontsets | |
1227 | can use only the fonts that the system supports; if certain characters | |
1228 | appear on the screen as hollow boxes, this means that the fontset in | |
1229 | use for them has no font for those characters.@footnote{The Emacs | |
1230 | installation instructions have information on additional font | |
1231 | support.} | |
1232 | ||
1233 | Emacs creates two fontsets automatically: the @dfn{standard fontset} | |
1234 | and the @dfn{startup fontset}. The standard fontset is most likely to | |
1235 | have fonts for a wide variety of non-@acronym{ASCII} characters; | |
1236 | however, this is not the default for Emacs to use. (By default, Emacs | |
1237 | tries to find a font that has bold and italic variants.) You can | |
1238 | specify use of the standard fontset with the @samp{-fn} option. For | |
1239 | example, | |
1240 | ||
1241 | @example | |
1242 | emacs -fn fontset-standard | |
1243 | @end example | |
1244 | ||
1245 | @noindent | |
1246 | You can also specify a fontset with the @samp{Font} resource (@pxref{X | |
1247 | Resources}). | |
1248 | ||
1249 | A fontset does not necessarily specify a font for every character | |
1250 | code. If a fontset specifies no font for a certain character, or if it | |
1251 | specifies a font that does not exist on your system, then it cannot | |
1252 | display that character properly. It will display that character as an | |
1253 | empty box instead. | |
1254 | ||
1255 | @node Defining Fontsets | |
1256 | @section Defining fontsets | |
1257 | ||
1258 | @vindex standard-fontset-spec | |
1259 | @cindex standard fontset | |
1260 | Emacs creates a standard fontset automatically according to the value | |
1261 | of @code{standard-fontset-spec}. This fontset's name is | |
1262 | ||
1263 | @example | |
1264 | -*-fixed-medium-r-normal-*-16-*-*-*-*-*-fontset-standard | |
1265 | @end example | |
1266 | ||
1267 | @noindent | |
1268 | or just @samp{fontset-standard} for short. | |
1269 | ||
1270 | Bold, italic, and bold-italic variants of the standard fontset are | |
1271 | created automatically. Their names have @samp{bold} instead of | |
1272 | @samp{medium}, or @samp{i} instead of @samp{r}, or both. | |
1273 | ||
1274 | @cindex startup fontset | |
1275 | If you specify a default @acronym{ASCII} font with the @samp{Font} resource or | |
1276 | the @samp{-fn} argument, Emacs generates a fontset from it | |
1277 | automatically. This is the @dfn{startup fontset} and its name is | |
1278 | @code{fontset-startup}. It does this by replacing the @var{foundry}, | |
1279 | @var{family}, @var{add_style}, and @var{average_width} fields of the | |
1280 | font name with @samp{*}, replacing @var{charset_registry} field with | |
1281 | @samp{fontset}, and replacing @var{charset_encoding} field with | |
1282 | @samp{startup}, then using the resulting string to specify a fontset. | |
1283 | ||
1284 | For instance, if you start Emacs this way, | |
1285 | ||
1286 | @example | |
1287 | emacs -fn "*courier-medium-r-normal--14-140-*-iso8859-1" | |
1288 | @end example | |
1289 | ||
1290 | @noindent | |
1291 | Emacs generates the following fontset and uses it for the initial X | |
1292 | window frame: | |
1293 | ||
1294 | @example | |
1295 | -*-*-medium-r-normal-*-14-140-*-*-*-*-fontset-startup | |
1296 | @end example | |
1297 | ||
1298 | With the X resource @samp{Emacs.Font}, you can specify a fontset name | |
1299 | just like an actual font name. But be careful not to specify a fontset | |
1300 | name in a wildcard resource like @samp{Emacs*Font}---that wildcard | |
1301 | specification matches various other resources, such as for menus, and | |
1302 | menus cannot handle fontsets. | |
1303 | ||
1304 | You can specify additional fontsets using X resources named | |
1305 | @samp{Fontset-@var{n}}, where @var{n} is an integer starting from 0. | |
1306 | The resource value should have this form: | |
1307 | ||
1308 | @smallexample | |
1309 | @var{fontpattern}, @r{[}@var{charset}:@var{font}@r{]@dots{}} | |
1310 | @end smallexample | |
1311 | ||
1312 | @noindent | |
1313 | @var{fontpattern} should have the form of a standard X font name, except | |
1314 | for the last two fields. They should have the form | |
1315 | @samp{fontset-@var{alias}}. | |
1316 | ||
1317 | The fontset has two names, one long and one short. The long name is | |
1318 | @var{fontpattern}. The short name is @samp{fontset-@var{alias}}. You | |
1319 | can refer to the fontset by either name. | |
1320 | ||
1321 | The construct @samp{@var{charset}:@var{font}} specifies which font to | |
1322 | use (in this fontset) for one particular character set. Here, | |
1323 | @var{charset} is the name of a character set, and @var{font} is the | |
1324 | font to use for that character set. You can use this construct any | |
1325 | number of times in defining one fontset. | |
1326 | ||
1327 | For the other character sets, Emacs chooses a font based on | |
1328 | @var{fontpattern}. It replaces @samp{fontset-@var{alias}} with values | |
1329 | that describe the character set. For the @acronym{ASCII} character font, | |
1330 | @samp{fontset-@var{alias}} is replaced with @samp{ISO8859-1}. | |
1331 | ||
1332 | In addition, when several consecutive fields are wildcards, Emacs | |
1333 | collapses them into a single wildcard. This is to prevent use of | |
1334 | auto-scaled fonts. Fonts made by scaling larger fonts are not usable | |
1335 | for editing, and scaling a smaller font is not useful because it is | |
1336 | better to use the smaller font in its own size, which is what Emacs | |
1337 | does. | |
1338 | ||
1339 | Thus if @var{fontpattern} is this, | |
1340 | ||
1341 | @example | |
1342 | -*-fixed-medium-r-normal-*-24-*-*-*-*-*-fontset-24 | |
1343 | @end example | |
1344 | ||
1345 | @noindent | |
1346 | the font specification for @acronym{ASCII} characters would be this: | |
1347 | ||
1348 | @example | |
1349 | -*-fixed-medium-r-normal-*-24-*-ISO8859-1 | |
1350 | @end example | |
1351 | ||
1352 | @noindent | |
1353 | and the font specification for Chinese GB2312 characters would be this: | |
1354 | ||
1355 | @example | |
1356 | -*-fixed-medium-r-normal-*-24-*-gb2312*-* | |
1357 | @end example | |
1358 | ||
1359 | You may not have any Chinese font matching the above font | |
1360 | specification. Most X distributions include only Chinese fonts that | |
1361 | have @samp{song ti} or @samp{fangsong ti} in @var{family} field. In | |
1362 | such a case, @samp{Fontset-@var{n}} can be specified as below: | |
1363 | ||
1364 | @smallexample | |
1365 | Emacs.Fontset-0: -*-fixed-medium-r-normal-*-24-*-*-*-*-*-fontset-24,\ | |
1366 | chinese-gb2312:-*-*-medium-r-normal-*-24-*-gb2312*-* | |
1367 | @end smallexample | |
1368 | ||
1369 | @noindent | |
1370 | Then, the font specifications for all but Chinese GB2312 characters have | |
1371 | @samp{fixed} in the @var{family} field, and the font specification for | |
1372 | Chinese GB2312 characters has a wild card @samp{*} in the @var{family} | |
1373 | field. | |
1374 | ||
1375 | @findex create-fontset-from-fontset-spec | |
1376 | The function that processes the fontset resource value to create the | |
1377 | fontset is called @code{create-fontset-from-fontset-spec}. You can also | |
1378 | call this function explicitly to create a fontset. | |
1379 | ||
1380 | @xref{Font X}, for more information about font naming in X. | |
1381 | ||
1382 | @node Undisplayable Characters | |
1383 | @section Undisplayable Characters | |
1384 | ||
1385 | There may be a some non-@acronym{ASCII} characters that your terminal cannot | |
1386 | display. Most text-only terminals support just a single character | |
1387 | set (use the variable @code{default-terminal-coding-system} | |
1388 | (@pxref{Terminal Coding}) to tell Emacs which one); characters which | |
1389 | can't be encoded in that coding system are displayed as @samp{?} by | |
1390 | default. | |
1391 | ||
1392 | Graphical displays can display a broader range of characters, but | |
1393 | you may not have fonts installed for all of them; characters that have | |
1394 | no font appear as a hollow box. | |
1395 | ||
1396 | If you use Latin-1 characters but your terminal can't display | |
1397 | Latin-1, you can arrange to display mnemonic @acronym{ASCII} sequences | |
1398 | instead, e.g.@: @samp{"o} for o-umlaut. Load the library | |
1399 | @file{iso-ascii} to do this. | |
1400 | ||
1401 | @vindex latin1-display | |
1402 | If your terminal can display Latin-1, you can display characters | |
1403 | from other European character sets using a mixture of equivalent | |
1404 | Latin-1 characters and @acronym{ASCII} mnemonics. Customize the variable | |
1405 | @code{latin1-display} to enable this. The mnemonic @acronym{ASCII} | |
1406 | sequences mostly correspond to those of the prefix input methods. | |
1407 | ||
1408 | @node Unibyte Mode | |
1409 | @section Unibyte Editing Mode | |
1410 | ||
1411 | @cindex European character sets | |
1412 | @cindex accented characters | |
1413 | @cindex ISO Latin character sets | |
1414 | @cindex Unibyte operation | |
1415 | The ISO 8859 Latin-@var{n} character sets define character codes in | |
1416 | the range 0240 to 0377 octal (160 to 255 decimal) to handle the | |
1417 | accented letters and punctuation needed by various European languages | |
1418 | (and some non-European ones). If you disable multibyte characters, | |
1419 | Emacs can still handle @emph{one} of these character codes at a time. | |
1420 | To specify @emph{which} of these codes to use, invoke @kbd{M-x | |
1421 | set-language-environment} and specify a suitable language environment | |
1422 | such as @samp{Latin-@var{n}}. | |
1423 | ||
1424 | For more information about unibyte operation, see @ref{Enabling | |
1425 | Multibyte}. Note particularly that you probably want to ensure that | |
1426 | your initialization files are read as unibyte if they contain | |
1427 | non-@acronym{ASCII} characters. | |
1428 | ||
1429 | @vindex unibyte-display-via-language-environment | |
1430 | Emacs can also display those characters, provided the terminal or font | |
1431 | in use supports them. This works automatically. Alternatively, on a | |
1432 | graphical display, Emacs can also display single-byte characters | |
1433 | through fontsets, in effect by displaying the equivalent multibyte | |
1434 | characters according to the current language environment. To request | |
1435 | this, set the variable @code{unibyte-display-via-language-environment} | |
1436 | to a non-@code{nil} value. | |
1437 | ||
1438 | @cindex @code{iso-ascii} library | |
1439 | If your terminal does not support display of the Latin-1 character | |
1440 | set, Emacs can display these characters as @acronym{ASCII} sequences which at | |
1441 | least give you a clear idea of what the characters are. To do this, | |
1442 | load the library @code{iso-ascii}. Similar libraries for other | |
1443 | Latin-@var{n} character sets could be implemented, but we don't have | |
1444 | them yet. | |
1445 | ||
1446 | @findex standard-display-8bit | |
1447 | @cindex 8-bit display | |
1448 | Normally non-ISO-8859 characters (decimal codes between 128 and 159 | |
1449 | inclusive) are displayed as octal escapes. You can change this for | |
1450 | non-standard ``extended'' versions of ISO-8859 character sets by using the | |
1451 | function @code{standard-display-8bit} in the @code{disp-table} library. | |
1452 | ||
1453 | There are two ways to input single-byte non-@acronym{ASCII} | |
1454 | characters: | |
1455 | ||
1456 | @itemize @bullet | |
1457 | @cindex 8-bit input | |
1458 | @item | |
1459 | You can use an input method for the selected language environment. | |
1460 | @xref{Input Methods}. When you use an input method in a unibyte buffer, | |
1461 | the non-@acronym{ASCII} character you specify with it is converted to unibyte. | |
1462 | ||
1463 | @item | |
1464 | If your keyboard can generate character codes 128 (decimal) and up, | |
1465 | representing non-@acronym{ASCII} characters, you can type those character codes | |
1466 | directly. | |
1467 | ||
1468 | On a graphical display, you should not need to do anything special to use | |
1469 | these keys; they should simply work. On a text-only terminal, you | |
1470 | should use the command @code{M-x set-keyboard-coding-system} or the | |
1471 | variable @code{keyboard-coding-system} to specify which coding system | |
1472 | your keyboard uses (@pxref{Terminal Coding}). Enabling this feature | |
1473 | will probably require you to use @kbd{ESC} to type Meta characters; | |
1474 | however, on a console terminal or in @code{xterm}, you can arrange for | |
1475 | Meta to be converted to @kbd{ESC} and still be able type 8-bit | |
1476 | characters present directly on the keyboard or using @kbd{Compose} or | |
1477 | @kbd{AltGr} keys. @xref{User Input}. | |
1478 | ||
1479 | @kindex C-x 8 | |
1480 | @cindex @code{iso-transl} library | |
1481 | @cindex compose character | |
1482 | @cindex dead character | |
1483 | @item | |
1484 | For Latin-1 only, you can use the key @kbd{C-x 8} as a ``compose | |
1485 | character'' prefix for entry of non-@acronym{ASCII} Latin-1 printing | |
1486 | characters. @kbd{C-x 8} is good for insertion (in the minibuffer as | |
1487 | well as other buffers), for searching, and in any other context where | |
1488 | a key sequence is allowed. | |
1489 | ||
1490 | @kbd{C-x 8} works by loading the @code{iso-transl} library. Once that | |
1491 | library is loaded, the @key{ALT} modifier key, if the keyboard has | |
1492 | one, serves the same purpose as @kbd{C-x 8}: use @key{ALT} together | |
1493 | with an accent character to modify the following letter. In addition, | |
1494 | if the keyboard has keys for the Latin-1 ``dead accent characters,'' | |
1495 | they too are defined to compose with the following character, once | |
1496 | @code{iso-transl} is loaded. | |
1497 | ||
1498 | Use @kbd{C-x 8 C-h} to list all the available @kbd{C-x 8} translations. | |
1499 | @end itemize | |
1500 | ||
1501 | @node Charsets | |
1502 | @section Charsets | |
1503 | @cindex charsets | |
1504 | ||
1505 | Emacs groups all supported characters into disjoint @dfn{charsets}. | |
1506 | Each character code belongs to one and only one charset. For | |
1507 | historical reasons, Emacs typically divides an 8-bit character code | |
1508 | for an extended version of @acronym{ASCII} into two charsets: | |
1509 | @acronym{ASCII}, which covers the codes 0 through 127, plus another | |
1510 | charset which covers the ``right-hand part'' (the codes 128 and up). | |
1511 | For instance, the characters of Latin-1 include the Emacs charset | |
1512 | @code{ascii} plus the Emacs charset @code{latin-iso8859-1}. | |
1513 | ||
1514 | Emacs characters belonging to different charsets may look the same, | |
1515 | but they are still different characters. For example, the letter | |
1516 | @samp{o} with acute accent in charset @code{latin-iso8859-1}, used for | |
1517 | Latin-1, is different from the letter @samp{o} with acute accent in | |
1518 | charset @code{latin-iso8859-2}, used for Latin-2. | |
1519 | ||
1520 | @findex list-charset-chars | |
1521 | @cindex characters in a certain charset | |
1522 | @findex describe-character-set | |
1523 | There are two commands for obtaining information about Emacs | |
1524 | charsets. The command @kbd{M-x list-charset-chars} prompts for a name | |
1525 | of a character set, and displays all the characters in that character | |
1526 | set. The command @kbd{M-x describe-character-set} prompts for a | |
1527 | charset name and displays information about that charset, including | |
1528 | its internal representation within Emacs. | |
1529 | ||
1530 | To find out which charset a character in the buffer belongs to, | |
1531 | put point before it and type @kbd{C-u C-x =}. | |
1532 | ||
1533 | @ignore | |
1534 | arch-tag: 310ba60d-31ef-4ce7-91f1-f282dd57b6b3 | |
1535 | @end ignore |