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8cf51b2c | 1 | @c This is part of the Emacs manual. |
66ecdc9e | 2 | @c Copyright (C) 1997, 1999-2012 Free Software Foundation, Inc. |
8cf51b2c | 3 | @c See file emacs.texi for copying conditions. |
8875da1e | 4 | @node International, Modes, Frames, Top |
8cf51b2c | 5 | @chapter International Character Set Support |
59eda47f RS |
6 | @c This node is referenced in the tutorial. When renaming or deleting |
7 | @c it, the tutorial needs to be adjusted. (TUTORIAL.de) | |
8cf51b2c GM |
8 | @cindex MULE |
9 | @cindex international scripts | |
10 | @cindex multibyte characters | |
11 | @cindex encoding of characters | |
12 | ||
13 | @cindex Celtic | |
14 | @cindex Chinese | |
15 | @cindex Cyrillic | |
16 | @cindex Czech | |
17 | @cindex Devanagari | |
18 | @cindex Hindi | |
19 | @cindex Marathi | |
20 | @cindex Ethiopic | |
21 | @cindex German | |
22 | @cindex Greek | |
23 | @cindex Hebrew | |
24 | @cindex IPA | |
25 | @cindex Japanese | |
26 | @cindex Korean | |
27 | @cindex Lao | |
28 | @cindex Latin | |
29 | @cindex Polish | |
30 | @cindex Romanian | |
31 | @cindex Slovak | |
32 | @cindex Slovenian | |
33 | @cindex Thai | |
34 | @cindex Tibetan | |
35 | @cindex Turkish | |
36 | @cindex Vietnamese | |
37 | @cindex Dutch | |
38 | @cindex Spanish | |
39 | Emacs supports a wide variety of international character sets, | |
40 | including European and Vietnamese variants of the Latin alphabet, as | |
41 | well as Cyrillic, Devanagari (for Hindi and Marathi), Ethiopic, Greek, | |
42 | Han (for Chinese and Japanese), Hangul (for Korean), Hebrew, IPA, | |
43 | Kannada, Lao, Malayalam, Tamil, Thai, Tibetan, and Vietnamese scripts. | |
8edb942b | 44 | Emacs also supports various encodings of these characters that are used by |
8cf51b2c GM |
45 | other internationalized software, such as word processors and mailers. |
46 | ||
47 | Emacs allows editing text with international characters by supporting | |
48 | all the related activities: | |
49 | ||
50 | @itemize @bullet | |
51 | @item | |
52 | You can visit files with non-@acronym{ASCII} characters, save non-@acronym{ASCII} text, and | |
53 | pass non-@acronym{ASCII} text between Emacs and programs it invokes (such as | |
54 | compilers, spell-checkers, and mailers). Setting your language | |
55 | environment (@pxref{Language Environments}) takes care of setting up the | |
56 | coding systems and other options for a specific language or culture. | |
57 | Alternatively, you can specify how Emacs should encode or decode text | |
58 | for each command; see @ref{Text Coding}. | |
59 | ||
60 | @item | |
61 | You can display non-@acronym{ASCII} characters encoded by the various | |
62 | scripts. This works by using appropriate fonts on graphics displays | |
0be641c0 | 63 | (@pxref{Defining Fontsets}), and by sending special codes to text |
8cf51b2c GM |
64 | displays (@pxref{Terminal Coding}). If some characters are displayed |
65 | incorrectly, refer to @ref{Undisplayable Characters}, which describes | |
66 | possible problems and explains how to solve them. | |
67 | ||
f4b6ba46 EZ |
68 | @item |
69 | Characters from scripts whose natural ordering of text is from right | |
70 | to left are reordered for display (@pxref{Bidirectional Editing}). | |
71 | These scripts include Arabic, Hebrew, Syriac, Thaana, and a few | |
72 | others. | |
73 | ||
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74 | @item |
75 | You can insert non-@acronym{ASCII} characters or search for them. To do that, | |
76 | you can specify an input method (@pxref{Select Input Method}) suitable | |
8edb942b | 77 | for your language, or use the default input method set up when you chose |
8cf51b2c GM |
78 | your language environment. If |
79 | your keyboard can produce non-@acronym{ASCII} characters, you can select an | |
80 | appropriate keyboard coding system (@pxref{Terminal Coding}), and Emacs | |
81 | will accept those characters. Latin-1 characters can also be input by | |
82 | using the @kbd{C-x 8} prefix, see @ref{Unibyte Mode}. | |
83 | ||
8edb942b | 84 | With the X Window System, your locale should be set to an appropriate |
50b063c3 | 85 | value to make sure Emacs interprets keyboard input correctly; see |
8cf51b2c GM |
86 | @ref{Language Environments, locales}. |
87 | @end itemize | |
88 | ||
89 | The rest of this chapter describes these issues in detail. | |
90 | ||
91 | @menu | |
92 | * International Chars:: Basic concepts of multibyte characters. | |
8edb942b | 93 | * Disabling Multibyte:: Controlling whether to use multibyte characters. |
8cf51b2c GM |
94 | * Language Environments:: Setting things up for the language you use. |
95 | * Input Methods:: Entering text characters not on your keyboard. | |
96 | * Select Input Method:: Specifying your choice of input methods. | |
8cf51b2c GM |
97 | * Coding Systems:: Character set conversion when you read and |
98 | write files, and so on. | |
99 | * Recognize Coding:: How Emacs figures out which conversion to use. | |
100 | * Specify Coding:: Specifying a file's coding system explicitly. | |
101 | * Output Coding:: Choosing coding systems for output. | |
102 | * Text Coding:: Choosing conversion to use for file text. | |
103 | * Communication Coding:: Coding systems for interprocess communication. | |
104 | * File Name Coding:: Coding systems for file @emph{names}. | |
105 | * Terminal Coding:: Specifying coding systems for converting | |
106 | terminal input and output. | |
107 | * Fontsets:: Fontsets are collections of fonts | |
108 | that cover the whole spectrum of characters. | |
109 | * Defining Fontsets:: Defining a new fontset. | |
70bb6cac | 110 | * Modifying Fontsets:: Modifying an existing fontset. |
8cf51b2c GM |
111 | * Undisplayable Characters:: When characters don't display. |
112 | * Unibyte Mode:: You can pick one European character set | |
113 | to use without multibyte characters. | |
114 | * Charsets:: How Emacs groups its internal character codes. | |
f4b6ba46 | 115 | * Bidirectional Editing:: Support for right-to-left scripts. |
8cf51b2c GM |
116 | @end menu |
117 | ||
118 | @node International Chars | |
119 | @section Introduction to International Character Sets | |
120 | ||
121 | The users of international character sets and scripts have | |
122 | established many more-or-less standard coding systems for storing | |
ad36c422 CY |
123 | files. These coding systems are typically @dfn{multibyte}, meaning |
124 | that sequences of two or more bytes are used to represent individual | |
125 | non-@acronym{ASCII} characters. | |
126 | ||
127 | @cindex Unicode | |
128 | Internally, Emacs uses its own multibyte character encoding, which | |
129 | is a superset of the @dfn{Unicode} standard. This internal encoding | |
130 | allows characters from almost every known script to be intermixed in a | |
131 | single buffer or string. Emacs translates between the multibyte | |
132 | character encoding and various other coding systems when reading and | |
133 | writing files, and when exchanging data with subprocesses. | |
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134 | |
135 | @kindex C-h h | |
136 | @findex view-hello-file | |
137 | @cindex undisplayable characters | |
138 | @cindex @samp{?} in display | |
139 | The command @kbd{C-h h} (@code{view-hello-file}) displays the file | |
66ecdc9e GM |
140 | @file{etc/HELLO}, which illustrates various scripts by showing |
141 | how to say ``hello'' in many languages. If some characters can't be | |
8cf51b2c GM |
142 | displayed on your terminal, they appear as @samp{?} or as hollow boxes |
143 | (@pxref{Undisplayable Characters}). | |
144 | ||
ad36c422 CY |
145 | Keyboards, even in the countries where these character sets are |
146 | used, generally don't have keys for all the characters in them. You | |
147 | can insert characters that your keyboard does not support, using | |
148 | @kbd{C-q} (@code{quoted-insert}) or @kbd{C-x 8 @key{RET}} | |
149 | (@code{ucs-insert}). @xref{Inserting Text}. Emacs also supports | |
150 | various @dfn{input methods}, typically one for each script or | |
151 | language, which make it easier to type characters in the script. | |
152 | @xref{Input Methods}. | |
8cf51b2c GM |
153 | |
154 | @kindex C-x RET | |
155 | The prefix key @kbd{C-x @key{RET}} is used for commands that pertain | |
156 | to multibyte characters, coding systems, and input methods. | |
157 | ||
8087d399 CY |
158 | @kindex C-x = |
159 | @findex what-cursor-position | |
160 | The command @kbd{C-x =} (@code{what-cursor-position}) shows | |
161 | information about the character at point. In addition to the | |
162 | character position, which was described in @ref{Position Info}, this | |
163 | command displays how the character is encoded. For instance, it | |
164 | displays the following line in the echo area for the character | |
165 | @samp{c}: | |
166 | ||
167 | @smallexample | |
168 | Char: c (99, #o143, #x63) point=28062 of 36168 (78%) column=53 | |
169 | @end smallexample | |
170 | ||
171 | The four values after @samp{Char:} describe the character that | |
172 | follows point, first by showing it and then by giving its character | |
173 | code in decimal, octal and hex. For a non-@acronym{ASCII} multibyte | |
174 | character, these are followed by @samp{file} and the character's | |
175 | representation, in hex, in the buffer's coding system, if that coding | |
176 | system encodes the character safely and with a single byte | |
177 | (@pxref{Coding Systems}). If the character's encoding is longer than | |
178 | one byte, Emacs shows @samp{file ...}. | |
179 | ||
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180 | As a special case, if the character lies in the range 128 (0200 |
181 | octal) through 159 (0237 octal), it stands for a ``raw'' byte that | |
182 | does not correspond to any specific displayable character. Such a | |
183 | ``character'' lies within the @code{eight-bit-control} character set, | |
184 | and is displayed as an escaped octal character code. In this case, | |
185 | @kbd{C-x =} shows @samp{part of display ...} instead of @samp{file}. | |
8087d399 CY |
186 | |
187 | @cindex character set of character at point | |
188 | @cindex font of character at point | |
189 | @cindex text properties at point | |
190 | @cindex face at point | |
191 | With a prefix argument (@kbd{C-u C-x =}), this command displays a | |
192 | detailed description of the character in a window: | |
193 | ||
194 | @itemize @bullet | |
195 | @item | |
196 | The character set name, and the codes that identify the character | |
197 | within that character set; @acronym{ASCII} characters are identified | |
198 | as belonging to the @code{ascii} character set. | |
199 | ||
200 | @item | |
201 | The character's syntax and categories. | |
202 | ||
203 | @item | |
204 | The character's encodings, both internally in the buffer, and externally | |
205 | if you were to save the file. | |
206 | ||
207 | @item | |
208 | What keys to type to input the character in the current input method | |
209 | (if it supports the character). | |
210 | ||
211 | @item | |
212 | If you are running Emacs on a graphical display, the font name and | |
0be641c0 | 213 | glyph code for the character. If you are running Emacs on a text |
8087d399 CY |
214 | terminal, the code(s) sent to the terminal. |
215 | ||
216 | @item | |
217 | The character's text properties (@pxref{Text Properties,,, | |
218 | elisp, the Emacs Lisp Reference Manual}), including any non-default | |
219 | faces used to display the character, and any overlays containing it | |
220 | (@pxref{Overlays,,, elisp, the same manual}). | |
221 | @end itemize | |
222 | ||
223 | Here's an example showing the Latin-1 character A with grave accent, | |
224 | in a buffer whose coding system is @code{utf-8-unix}: | |
225 | ||
226 | @smallexample | |
8edb942b GM |
227 | position: 1 of 1 (0%), column: 0 |
228 | character: @`A (displayed as @`A) (codepoint 192, #o300, #xc0) | |
229 | preferred charset: unicode (Unicode (ISO10646)) | |
230 | code point in charset: 0xC0 | |
231 | syntax: w which means: word | |
232 | category: .:Base, L:Left-to-right (strong), | |
233 | j:Japanese, l:Latin, v:Viet | |
234 | buffer code: #xC3 #x80 | |
235 | file code: not encodable by coding system undecided-unix | |
236 | display: by this font (glyph code) | |
ae742cb5 CY |
237 | xft:-unknown-DejaVu Sans Mono-normal-normal- |
238 | normal-*-13-*-*-*-m-0-iso10646-1 (#x82) | |
8087d399 CY |
239 | |
240 | Character code properties: customize what to show | |
241 | name: LATIN CAPITAL LETTER A WITH GRAVE | |
8edb942b | 242 | old-name: LATIN CAPITAL LETTER A GRAVE |
8087d399 | 243 | general-category: Lu (Letter, Uppercase) |
62d94509 | 244 | decomposition: (65 768) ('A' '`') |
8087d399 CY |
245 | @end smallexample |
246 | ||
8edb942b GM |
247 | @c FIXME? Does this section even belong in the user manual? |
248 | @c Seems more appropriate to the lispref? | |
249 | @node Disabling Multibyte | |
250 | @section Disabling Multibyte Characters | |
8cf51b2c | 251 | |
ad36c422 CY |
252 | By default, Emacs starts in multibyte mode: it stores the contents |
253 | of buffers and strings using an internal encoding that represents | |
254 | non-@acronym{ASCII} characters using multi-byte sequences. Multibyte | |
255 | mode allows you to use all the supported languages and scripts without | |
256 | limitations. | |
8cf51b2c GM |
257 | |
258 | @cindex turn multibyte support on or off | |
ad36c422 | 259 | Under very special circumstances, you may want to disable multibyte |
82e98df4 SM |
260 | character support, for a specific buffer. |
261 | When multibyte characters are disabled in a buffer, we call | |
ad36c422 CY |
262 | that @dfn{unibyte mode}. In unibyte mode, each character in the |
263 | buffer has a character code ranging from 0 through 255 (0377 octal); 0 | |
264 | through 127 (0177 octal) represent @acronym{ASCII} characters, and 128 | |
265 | (0200 octal) through 255 (0377 octal) represent non-@acronym{ASCII} | |
266 | characters. | |
8cf51b2c GM |
267 | |
268 | To edit a particular file in unibyte representation, visit it using | |
ad36c422 CY |
269 | @code{find-file-literally}. @xref{Visiting}. You can convert a |
270 | multibyte buffer to unibyte by saving it to a file, killing the | |
271 | buffer, and visiting the file again with @code{find-file-literally}. | |
272 | Alternatively, you can use @kbd{C-x @key{RET} c} | |
273 | (@code{universal-coding-system-argument}) and specify @samp{raw-text} | |
274 | as the coding system with which to visit or save a file. @xref{Text | |
275 | Coding}. Unlike @code{find-file-literally}, finding a file as | |
276 | @samp{raw-text} doesn't disable format conversion, uncompression, or | |
277 | auto mode selection. | |
8cf51b2c | 278 | |
8edb942b GM |
279 | @c Not a single file in Emacs uses this feature. Is it really worth |
280 | @c mentioning in the _user_ manual? Also, this duplicates somewhat | |
281 | @c "Loading Non-ASCII" from the lispref. | |
8cf51b2c GM |
282 | @cindex Lisp files, and multibyte operation |
283 | @cindex multibyte operation, and Lisp files | |
284 | @cindex unibyte operation, and Lisp files | |
285 | @cindex init file, and non-@acronym{ASCII} characters | |
82e98df4 SM |
286 | Emacs normally loads Lisp files as multibyte. |
287 | This includes the Emacs initialization | |
8edb942b | 288 | file, @file{.emacs}, and the initialization files of packages |
ad36c422 | 289 | such as Gnus. However, you can specify unibyte loading for a |
8edb942b GM |
290 | particular Lisp file, by adding an entry @samp{unibyte: t} in a file |
291 | local variables section (@pxref{File Variables}). Then that file is | |
292 | always loaded as unibyte text. Note that this does not represent a | |
293 | real @code{unibyte} variable, rather it just acts as an indicator | |
294 | to Emacs in the same way as @code{coding} does (@pxref{Specify Coding}). | |
295 | @ignore | |
296 | @c I don't see the point of this statement: | |
297 | The motivation for these conventions is that it is more reliable to | |
298 | always load any particular Lisp file in the same way. | |
299 | @end ignore | |
300 | Note also that this feature only applies to @emph{loading} Lisp files | |
301 | for evaluation, not to visiting them for editing. You can also load a | |
302 | Lisp file as unibyte, on any one occasion, by typing @kbd{C-x | |
303 | @key{RET} c raw-text @key{RET}} immediately before loading it. | |
304 | ||
305 | @c See http://debbugs.gnu.org/11226 for lack of unibyte tooltip. | |
306 | @vindex enable-multibyte-characters | |
307 | The buffer-local variable @code{enable-multibyte-characters} is | |
308 | non-@code{nil} in multibyte buffers, and @code{nil} in unibyte ones. | |
309 | The mode line also indicates whether a buffer is multibyte or not. | |
310 | @xref{Mode Line}. With a graphical display, in a multibyte buffer, | |
311 | the portion of the mode line that indicates the character set has a | |
312 | tooltip that (amongst other things) says that the buffer is multibyte. | |
313 | In a unibyte buffer, the character set indicator is absent. Thus, in | |
314 | a unibyte buffer (when using a graphical display) there is normally | |
315 | nothing before the indication of the visited file's end-of-line | |
316 | convention (colon, backslash, etc.), unless you are using an input | |
317 | method. | |
8cf51b2c | 318 | |
ad36c422 | 319 | @findex toggle-enable-multibyte-characters |
8edb942b | 320 | You can turn off multibyte support in a specific buffer by invoking the |
4e3b4528 | 321 | command @code{toggle-enable-multibyte-characters} in that buffer. |
ad36c422 | 322 | |
8cf51b2c GM |
323 | @node Language Environments |
324 | @section Language Environments | |
325 | @cindex language environments | |
326 | ||
327 | All supported character sets are supported in Emacs buffers whenever | |
328 | multibyte characters are enabled; there is no need to select a | |
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329 | particular language in order to display its characters. |
330 | However, it is important to select a @dfn{language | |
ad36c422 CY |
331 | environment} in order to set various defaults. Roughly speaking, the |
332 | language environment represents a choice of preferred script rather | |
333 | than a choice of language. | |
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334 | |
335 | The language environment controls which coding systems to recognize | |
336 | when reading text (@pxref{Recognize Coding}). This applies to files, | |
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337 | incoming mail, and any other text you read into Emacs. It may also |
338 | specify the default coding system to use when you create a file. Each | |
339 | language environment also specifies a default input method. | |
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340 | |
341 | @findex set-language-environment | |
342 | @vindex current-language-environment | |
ae742cb5 | 343 | To select a language environment, customize |
8cf51b2c GM |
344 | @code{current-language-environment} or use the command @kbd{M-x |
345 | set-language-environment}. It makes no difference which buffer is | |
ad36c422 | 346 | current when you use this command, because the effects apply globally |
e0550cae GM |
347 | to the Emacs session. The supported language environments |
348 | (see the variable @code{language-info-alist}) include: | |
8cf51b2c GM |
349 | |
350 | @cindex Euro sign | |
351 | @cindex UTF-8 | |
352 | @quotation | |
9eb25ee8 | 353 | ASCII, Belarusian, Bengali, Brazilian Portuguese, Bulgarian, Cham, |
ad36c422 CY |
354 | Chinese-BIG5, Chinese-CNS, Chinese-EUC-TW, Chinese-GB, Chinese-GBK, |
355 | Chinese-GB18030, Croatian, Cyrillic-ALT, Cyrillic-ISO, Cyrillic-KOI8, | |
356 | Czech, Devanagari, Dutch, English, Esperanto, Ethiopic, French, | |
357 | Georgian, German, Greek, Gujarati, Hebrew, IPA, Italian, Japanese, | |
358 | Kannada, Khmer, Korean, Lao, Latin-1, Latin-2, Latin-3, Latin-4, | |
359 | Latin-5, Latin-6, Latin-7, Latin-8 (Celtic), Latin-9 (updated Latin-1 | |
360 | with the Euro sign), Latvian, Lithuanian, Malayalam, Oriya, Polish, | |
361 | Punjabi, Romanian, Russian, Sinhala, Slovak, Slovenian, Spanish, | |
362 | Swedish, TaiViet, Tajik, Tamil, Telugu, Thai, Tibetan, Turkish, UTF-8 | |
363 | (for a setup which prefers Unicode characters and files encoded in | |
364 | UTF-8), Ukrainian, Vietnamese, Welsh, and Windows-1255 (for a setup | |
365 | which prefers Cyrillic characters and files encoded in Windows-1255). | |
8cf51b2c GM |
366 | @end quotation |
367 | ||
8cf51b2c | 368 | To display the script(s) used by your language environment on a |
05806f43 | 369 | graphical display, you need to have suitable fonts. |
8cf51b2c GM |
370 | @xref{Fontsets}, for more details about setting up your fonts. |
371 | ||
372 | @findex set-locale-environment | |
373 | @vindex locale-language-names | |
374 | @vindex locale-charset-language-names | |
375 | @cindex locales | |
376 | Some operating systems let you specify the character-set locale you | |
377 | are using by setting the locale environment variables @env{LC_ALL}, | |
e0550cae | 378 | @env{LC_CTYPE}, or @env{LANG}. (If more than one of these is |
8cf51b2c | 379 | set, the first one that is nonempty specifies your locale for this |
e0550cae | 380 | purpose.) During startup, Emacs looks up your character-set locale's |
8cf51b2c GM |
381 | name in the system locale alias table, matches its canonical name |
382 | against entries in the value of the variables | |
e0550cae GM |
383 | @code{locale-charset-language-names} and @code{locale-language-names} |
384 | (the former overrides the latter), | |
8cf51b2c | 385 | and selects the corresponding language environment if a match is found. |
e0550cae | 386 | It also adjusts the display |
8cf51b2c GM |
387 | table and terminal coding system, the locale coding system, the |
388 | preferred coding system as needed for the locale, and---last but not | |
389 | least---the way Emacs decodes non-@acronym{ASCII} characters sent by your keyboard. | |
390 | ||
e0550cae | 391 | @c This seems unlikely, doesn't it? |
8cf51b2c | 392 | If you modify the @env{LC_ALL}, @env{LC_CTYPE}, or @env{LANG} |
e0550cae GM |
393 | environment variables while running Emacs (by using @kbd{M-x setenv}), |
394 | you may want to invoke the @code{set-locale-environment} | |
395 | function afterwards to readjust the language environment from the new | |
396 | locale. | |
8cf51b2c GM |
397 | |
398 | @vindex locale-preferred-coding-systems | |
399 | The @code{set-locale-environment} function normally uses the preferred | |
400 | coding system established by the language environment to decode system | |
401 | messages. But if your locale matches an entry in the variable | |
402 | @code{locale-preferred-coding-systems}, Emacs uses the corresponding | |
403 | coding system instead. For example, if the locale @samp{ja_JP.PCK} | |
404 | matches @code{japanese-shift-jis} in | |
405 | @code{locale-preferred-coding-systems}, Emacs uses that encoding even | |
406 | though it might normally use @code{japanese-iso-8bit}. | |
407 | ||
408 | You can override the language environment chosen at startup with | |
409 | explicit use of the command @code{set-language-environment}, or with | |
410 | customization of @code{current-language-environment} in your init | |
411 | file. | |
412 | ||
413 | @kindex C-h L | |
414 | @findex describe-language-environment | |
415 | To display information about the effects of a certain language | |
416 | environment @var{lang-env}, use the command @kbd{C-h L @var{lang-env} | |
417 | @key{RET}} (@code{describe-language-environment}). This tells you | |
418 | which languages this language environment is useful for, and lists the | |
419 | character sets, coding systems, and input methods that go with it. It | |
420 | also shows some sample text to illustrate scripts used in this | |
421 | language environment. If you give an empty input for @var{lang-env}, | |
422 | this command describes the chosen language environment. | |
d2fac4a9 | 423 | @anchor{Describe Language Environment} |
8cf51b2c GM |
424 | |
425 | @vindex set-language-environment-hook | |
426 | You can customize any language environment with the normal hook | |
427 | @code{set-language-environment-hook}. The command | |
428 | @code{set-language-environment} runs that hook after setting up the new | |
429 | language environment. The hook functions can test for a specific | |
430 | language environment by checking the variable | |
431 | @code{current-language-environment}. This hook is where you should | |
e0550cae | 432 | put non-default settings for specific language environments, such as |
8cf51b2c GM |
433 | coding systems for keyboard input and terminal output, the default |
434 | input method, etc. | |
435 | ||
436 | @vindex exit-language-environment-hook | |
437 | Before it starts to set up the new language environment, | |
438 | @code{set-language-environment} first runs the hook | |
439 | @code{exit-language-environment-hook}. This hook is useful for undoing | |
440 | customizations that were made with @code{set-language-environment-hook}. | |
441 | For instance, if you set up a special key binding in a specific language | |
442 | environment using @code{set-language-environment-hook}, you should set | |
443 | up @code{exit-language-environment-hook} to restore the normal binding | |
444 | for that key. | |
445 | ||
446 | @node Input Methods | |
447 | @section Input Methods | |
448 | ||
449 | @cindex input methods | |
450 | An @dfn{input method} is a kind of character conversion designed | |
451 | specifically for interactive input. In Emacs, typically each language | |
893585f4 | 452 | has its own input method; sometimes several languages that use the same |
8cf51b2c GM |
453 | characters can share one input method. A few languages support several |
454 | input methods. | |
455 | ||
456 | The simplest kind of input method works by mapping @acronym{ASCII} letters | |
457 | into another alphabet; this allows you to use one other alphabet | |
458 | instead of @acronym{ASCII}. The Greek and Russian input methods | |
459 | work this way. | |
460 | ||
461 | A more powerful technique is composition: converting sequences of | |
462 | characters into one letter. Many European input methods use composition | |
463 | to produce a single non-@acronym{ASCII} letter from a sequence that consists of a | |
464 | letter followed by accent characters (or vice versa). For example, some | |
893585f4 | 465 | methods convert the sequence @kbd{o ^} into a single accented letter. |
8cf51b2c GM |
466 | These input methods have no special commands of their own; all they do |
467 | is compose sequences of printing characters. | |
468 | ||
469 | The input methods for syllabic scripts typically use mapping followed | |
470 | by composition. The input methods for Thai and Korean work this way. | |
471 | First, letters are mapped into symbols for particular sounds or tone | |
893585f4 | 472 | marks; then, sequences of these that make up a whole syllable are |
8cf51b2c GM |
473 | mapped into one syllable sign. |
474 | ||
475 | Chinese and Japanese require more complex methods. In Chinese input | |
476 | methods, first you enter the phonetic spelling of a Chinese word (in | |
477 | input method @code{chinese-py}, among others), or a sequence of | |
478 | portions of the character (input methods @code{chinese-4corner} and | |
479 | @code{chinese-sw}, and others). One input sequence typically | |
480 | corresponds to many possible Chinese characters. You select the one | |
481 | you mean using keys such as @kbd{C-f}, @kbd{C-b}, @kbd{C-n}, | |
893585f4 GM |
482 | @kbd{C-p} (or the arrow keys), and digits, which have special meanings |
483 | in this situation. | |
8cf51b2c GM |
484 | |
485 | The possible characters are conceptually arranged in several rows, | |
486 | with each row holding up to 10 alternatives. Normally, Emacs displays | |
487 | just one row at a time, in the echo area; @code{(@var{i}/@var{j})} | |
488 | appears at the beginning, to indicate that this is the @var{i}th row | |
489 | out of a total of @var{j} rows. Type @kbd{C-n} or @kbd{C-p} to | |
490 | display the next row or the previous row. | |
491 | ||
492 | Type @kbd{C-f} and @kbd{C-b} to move forward and backward among | |
493 | the alternatives in the current row. As you do this, Emacs highlights | |
494 | the current alternative with a special color; type @code{C-@key{SPC}} | |
495 | to select the current alternative and use it as input. The | |
496 | alternatives in the row are also numbered; the number appears before | |
893585f4 GM |
497 | the alternative. Typing a number selects the associated alternative |
498 | of the current row and uses it as input. | |
8cf51b2c GM |
499 | |
500 | @key{TAB} in these Chinese input methods displays a buffer showing | |
501 | all the possible characters at once; then clicking @kbd{Mouse-2} on | |
502 | one of them selects that alternative. The keys @kbd{C-f}, @kbd{C-b}, | |
503 | @kbd{C-n}, @kbd{C-p}, and digits continue to work as usual, but they | |
504 | do the highlighting in the buffer showing the possible characters, | |
505 | rather than in the echo area. | |
506 | ||
507 | In Japanese input methods, first you input a whole word using | |
508 | phonetic spelling; then, after the word is in the buffer, Emacs | |
509 | converts it into one or more characters using a large dictionary. One | |
510 | phonetic spelling corresponds to a number of different Japanese words; | |
511 | to select one of them, use @kbd{C-n} and @kbd{C-p} to cycle through | |
512 | the alternatives. | |
513 | ||
514 | Sometimes it is useful to cut off input method processing so that the | |
515 | characters you have just entered will not combine with subsequent | |
516 | characters. For example, in input method @code{latin-1-postfix}, the | |
893585f4 | 517 | sequence @kbd{o ^} combines to form an @samp{o} with an accent. What if |
8cf51b2c GM |
518 | you want to enter them as separate characters? |
519 | ||
520 | One way is to type the accent twice; this is a special feature for | |
893585f4 GM |
521 | entering the separate letter and accent. For example, @kbd{o ^ ^} gives |
522 | you the two characters @samp{o^}. Another way is to type another letter | |
523 | after the @kbd{o}---something that won't combine with that---and | |
524 | immediately delete it. For example, you could type @kbd{o o @key{DEL} | |
525 | ^} to get separate @samp{o} and @samp{^}. | |
8cf51b2c GM |
526 | |
527 | Another method, more general but not quite as easy to type, is to use | |
528 | @kbd{C-\ C-\} between two characters to stop them from combining. This | |
529 | is the command @kbd{C-\} (@code{toggle-input-method}) used twice. | |
530 | @ifnottex | |
531 | @xref{Select Input Method}. | |
532 | @end ifnottex | |
533 | ||
534 | @cindex incremental search, input method interference | |
535 | @kbd{C-\ C-\} is especially useful inside an incremental search, | |
536 | because it stops waiting for more characters to combine, and starts | |
537 | searching for what you have already entered. | |
538 | ||
539 | To find out how to input the character after point using the current | |
540 | input method, type @kbd{C-u C-x =}. @xref{Position Info}. | |
541 | ||
542 | @vindex input-method-verbose-flag | |
543 | @vindex input-method-highlight-flag | |
544 | The variables @code{input-method-highlight-flag} and | |
545 | @code{input-method-verbose-flag} control how input methods explain | |
546 | what is happening. If @code{input-method-highlight-flag} is | |
547 | non-@code{nil}, the partial sequence is highlighted in the buffer (for | |
548 | most input methods---some disable this feature). If | |
549 | @code{input-method-verbose-flag} is non-@code{nil}, the list of | |
550 | possible characters to type next is displayed in the echo area (but | |
551 | not when you are in the minibuffer). | |
552 | ||
ce79424f | 553 | Another facility for typing characters not on your keyboard is by |
893585f4 | 554 | using @kbd{C-x 8 @key{RET}} (@code{ucs-insert}) to insert a single |
ce79424f EZ |
555 | character based on its Unicode name or code-point; see @ref{Inserting |
556 | Text}. | |
557 | ||
8cf51b2c GM |
558 | @node Select Input Method |
559 | @section Selecting an Input Method | |
560 | ||
561 | @table @kbd | |
562 | @item C-\ | |
71cd7772 | 563 | Enable or disable use of the selected input method (@code{toggle-input-method}). |
8cf51b2c GM |
564 | |
565 | @item C-x @key{RET} C-\ @var{method} @key{RET} | |
71cd7772 | 566 | Select a new input method for the current buffer (@code{set-input-method}). |
8cf51b2c GM |
567 | |
568 | @item C-h I @var{method} @key{RET} | |
569 | @itemx C-h C-\ @var{method} @key{RET} | |
570 | @findex describe-input-method | |
571 | @kindex C-h I | |
572 | @kindex C-h C-\ | |
573 | Describe the input method @var{method} (@code{describe-input-method}). | |
574 | By default, it describes the current input method (if any). This | |
575 | description should give you the full details of how to use any | |
576 | particular input method. | |
577 | ||
578 | @item M-x list-input-methods | |
579 | Display a list of all the supported input methods. | |
580 | @end table | |
581 | ||
582 | @findex set-input-method | |
583 | @vindex current-input-method | |
584 | @kindex C-x RET C-\ | |
585 | To choose an input method for the current buffer, use @kbd{C-x | |
586 | @key{RET} C-\} (@code{set-input-method}). This command reads the | |
587 | input method name from the minibuffer; the name normally starts with the | |
588 | language environment that it is meant to be used with. The variable | |
589 | @code{current-input-method} records which input method is selected. | |
590 | ||
591 | @findex toggle-input-method | |
592 | @kindex C-\ | |
593 | Input methods use various sequences of @acronym{ASCII} characters to | |
594 | stand for non-@acronym{ASCII} characters. Sometimes it is useful to | |
595 | turn off the input method temporarily. To do this, type @kbd{C-\} | |
596 | (@code{toggle-input-method}). To reenable the input method, type | |
597 | @kbd{C-\} again. | |
598 | ||
599 | If you type @kbd{C-\} and you have not yet selected an input method, | |
05f7d0d3 | 600 | it prompts you to specify one. This has the same effect as using |
8cf51b2c GM |
601 | @kbd{C-x @key{RET} C-\} to specify an input method. |
602 | ||
603 | When invoked with a numeric argument, as in @kbd{C-u C-\}, | |
604 | @code{toggle-input-method} always prompts you for an input method, | |
605 | suggesting the most recently selected one as the default. | |
606 | ||
607 | @vindex default-input-method | |
608 | Selecting a language environment specifies a default input method for | |
609 | use in various buffers. When you have a default input method, you can | |
610 | select it in the current buffer by typing @kbd{C-\}. The variable | |
611 | @code{default-input-method} specifies the default input method | |
612 | (@code{nil} means there is none). | |
613 | ||
614 | In some language environments, which support several different input | |
615 | methods, you might want to use an input method different from the | |
616 | default chosen by @code{set-language-environment}. You can instruct | |
617 | Emacs to select a different default input method for a certain | |
618 | language environment, if you wish, by using | |
619 | @code{set-language-environment-hook} (@pxref{Language Environments, | |
620 | set-language-environment-hook}). For example: | |
621 | ||
622 | @lisp | |
623 | (defun my-chinese-setup () | |
624 | "Set up my private Chinese environment." | |
625 | (if (equal current-language-environment "Chinese-GB") | |
626 | (setq default-input-method "chinese-tonepy"))) | |
627 | (add-hook 'set-language-environment-hook 'my-chinese-setup) | |
628 | @end lisp | |
629 | ||
630 | @noindent | |
631 | This sets the default input method to be @code{chinese-tonepy} | |
632 | whenever you choose a Chinese-GB language environment. | |
633 | ||
0cf8a906 KH |
634 | You can instruct Emacs to activate a certain input method |
635 | automatically. For example: | |
636 | ||
637 | @lisp | |
638 | (add-hook 'text-mode-hook | |
639 | (lambda () (set-input-method "german-prefix"))) | |
640 | @end lisp | |
641 | ||
642 | @noindent | |
05f7d0d3 | 643 | This automatically activates the input method ``german-prefix'' in |
0cf8a906 KH |
644 | Text mode. |
645 | ||
8cf51b2c GM |
646 | @findex quail-set-keyboard-layout |
647 | Some input methods for alphabetic scripts work by (in effect) | |
648 | remapping the keyboard to emulate various keyboard layouts commonly used | |
649 | for those scripts. How to do this remapping properly depends on your | |
650 | actual keyboard layout. To specify which layout your keyboard has, use | |
651 | the command @kbd{M-x quail-set-keyboard-layout}. | |
652 | ||
653 | @findex quail-show-key | |
654 | You can use the command @kbd{M-x quail-show-key} to show what key (or | |
655 | key sequence) to type in order to input the character following point, | |
656 | using the selected keyboard layout. The command @kbd{C-u C-x =} also | |
05f7d0d3 | 657 | shows that information, in addition to other information about the |
8cf51b2c GM |
658 | character. |
659 | ||
660 | @findex list-input-methods | |
ae742cb5 CY |
661 | @kbd{M-x list-input-methods} displays a list of all the supported |
662 | input methods. The list gives information about each input method, | |
663 | including the string that stands for it in the mode line. | |
8cf51b2c | 664 | |
8cf51b2c GM |
665 | @node Coding Systems |
666 | @section Coding Systems | |
667 | @cindex coding systems | |
668 | ||
669 | Users of various languages have established many more-or-less standard | |
670 | coding systems for representing them. Emacs does not use these coding | |
671 | systems internally; instead, it converts from various coding systems to | |
672 | its own system when reading data, and converts the internal coding | |
673 | system to other coding systems when writing data. Conversion is | |
674 | possible in reading or writing files, in sending or receiving from the | |
675 | terminal, and in exchanging data with subprocesses. | |
676 | ||
677 | Emacs assigns a name to each coding system. Most coding systems are | |
ad36c422 CY |
678 | used for one language, and the name of the coding system starts with |
679 | the language name. Some coding systems are used for several | |
680 | languages; their names usually start with @samp{iso}. There are also | |
681 | special coding systems, such as @code{no-conversion}, @code{raw-text}, | |
682 | and @code{emacs-internal}. | |
8cf51b2c GM |
683 | |
684 | @cindex international files from DOS/Windows systems | |
685 | A special class of coding systems, collectively known as | |
686 | @dfn{codepages}, is designed to support text encoded by MS-Windows and | |
687 | MS-DOS software. The names of these coding systems are | |
688 | @code{cp@var{nnnn}}, where @var{nnnn} is a 3- or 4-digit number of the | |
689 | codepage. You can use these encodings just like any other coding | |
690 | system; for example, to visit a file encoded in codepage 850, type | |
691 | @kbd{C-x @key{RET} c cp850 @key{RET} C-x C-f @var{filename} | |
f68eb991 | 692 | @key{RET}}. |
8cf51b2c GM |
693 | |
694 | In addition to converting various representations of non-@acronym{ASCII} | |
695 | characters, a coding system can perform end-of-line conversion. Emacs | |
696 | handles three different conventions for how to separate lines in a file: | |
05f7d0d3 GM |
697 | newline (``unix''), carriage-return linefeed (``dos''), and just |
698 | carriage-return (``mac''). | |
8cf51b2c GM |
699 | |
700 | @table @kbd | |
701 | @item C-h C @var{coding} @key{RET} | |
71cd7772 | 702 | Describe coding system @var{coding} (@code{describe-coding-system}). |
8cf51b2c GM |
703 | |
704 | @item C-h C @key{RET} | |
705 | Describe the coding systems currently in use. | |
706 | ||
707 | @item M-x list-coding-systems | |
708 | Display a list of all the supported coding systems. | |
709 | @end table | |
710 | ||
711 | @kindex C-h C | |
712 | @findex describe-coding-system | |
713 | The command @kbd{C-h C} (@code{describe-coding-system}) displays | |
714 | information about particular coding systems, including the end-of-line | |
715 | conversion specified by those coding systems. You can specify a coding | |
716 | system name as the argument; alternatively, with an empty argument, it | |
717 | describes the coding systems currently selected for various purposes, | |
718 | both in the current buffer and as the defaults, and the priority list | |
719 | for recognizing coding systems (@pxref{Recognize Coding}). | |
720 | ||
721 | @findex list-coding-systems | |
722 | To display a list of all the supported coding systems, type @kbd{M-x | |
723 | list-coding-systems}. The list gives information about each coding | |
724 | system, including the letter that stands for it in the mode line | |
725 | (@pxref{Mode Line}). | |
726 | ||
727 | @cindex end-of-line conversion | |
728 | @cindex line endings | |
729 | @cindex MS-DOS end-of-line conversion | |
730 | @cindex Macintosh end-of-line conversion | |
731 | Each of the coding systems that appear in this list---except for | |
732 | @code{no-conversion}, which means no conversion of any kind---specifies | |
733 | how and whether to convert printing characters, but leaves the choice of | |
734 | end-of-line conversion to be decided based on the contents of each file. | |
735 | For example, if the file appears to use the sequence carriage-return | |
736 | linefeed to separate lines, DOS end-of-line conversion will be used. | |
737 | ||
05f7d0d3 | 738 | Each of the listed coding systems has three variants, which specify |
8cf51b2c GM |
739 | exactly what to do for end-of-line conversion: |
740 | ||
741 | @table @code | |
742 | @item @dots{}-unix | |
743 | Don't do any end-of-line conversion; assume the file uses | |
744 | newline to separate lines. (This is the convention normally used | |
05f7d0d3 | 745 | on Unix and GNU systems, and Mac OS X.) |
8cf51b2c GM |
746 | |
747 | @item @dots{}-dos | |
748 | Assume the file uses carriage-return linefeed to separate lines, and do | |
749 | the appropriate conversion. (This is the convention normally used on | |
750 | Microsoft systems.@footnote{It is also specified for MIME @samp{text/*} | |
751 | bodies and in other network transport contexts. It is different | |
05f7d0d3 | 752 | from the SGML reference syntax record-start/record-end format, which |
8cf51b2c GM |
753 | Emacs doesn't support directly.}) |
754 | ||
755 | @item @dots{}-mac | |
756 | Assume the file uses carriage-return to separate lines, and do the | |
05f7d0d3 GM |
757 | appropriate conversion. (This was the convention used on the |
758 | Macintosh system prior to OS X.) | |
8cf51b2c GM |
759 | @end table |
760 | ||
761 | These variant coding systems are omitted from the | |
762 | @code{list-coding-systems} display for brevity, since they are entirely | |
763 | predictable. For example, the coding system @code{iso-latin-1} has | |
764 | variants @code{iso-latin-1-unix}, @code{iso-latin-1-dos} and | |
765 | @code{iso-latin-1-mac}. | |
766 | ||
767 | @cindex @code{undecided}, coding system | |
768 | The coding systems @code{unix}, @code{dos}, and @code{mac} are | |
769 | aliases for @code{undecided-unix}, @code{undecided-dos}, and | |
770 | @code{undecided-mac}, respectively. These coding systems specify only | |
771 | the end-of-line conversion, and leave the character code conversion to | |
772 | be deduced from the text itself. | |
773 | ||
978ff6c5 | 774 | @cindex @code{raw-text}, coding system |
8cf51b2c | 775 | The coding system @code{raw-text} is good for a file which is mainly |
05f7d0d3 | 776 | @acronym{ASCII} text, but may contain byte values above 127 that are |
8cf51b2c GM |
777 | not meant to encode non-@acronym{ASCII} characters. With |
778 | @code{raw-text}, Emacs copies those byte values unchanged, and sets | |
779 | @code{enable-multibyte-characters} to @code{nil} in the current buffer | |
780 | so that they will be interpreted properly. @code{raw-text} handles | |
781 | end-of-line conversion in the usual way, based on the data | |
782 | encountered, and has the usual three variants to specify the kind of | |
783 | end-of-line conversion to use. | |
784 | ||
978ff6c5 | 785 | @cindex @code{no-conversion}, coding system |
8cf51b2c GM |
786 | In contrast, the coding system @code{no-conversion} specifies no |
787 | character code conversion at all---none for non-@acronym{ASCII} byte values and | |
788 | none for end of line. This is useful for reading or writing binary | |
789 | files, tar files, and other files that must be examined verbatim. It, | |
790 | too, sets @code{enable-multibyte-characters} to @code{nil}. | |
791 | ||
792 | The easiest way to edit a file with no conversion of any kind is with | |
793 | the @kbd{M-x find-file-literally} command. This uses | |
794 | @code{no-conversion}, and also suppresses other Emacs features that | |
795 | might convert the file contents before you see them. @xref{Visiting}. | |
796 | ||
978ff6c5 | 797 | @cindex @code{emacs-internal}, coding system |
ad36c422 CY |
798 | The coding system @code{emacs-internal} (or @code{utf-8-emacs}, |
799 | which is equivalent) means that the file contains non-@acronym{ASCII} | |
800 | characters stored with the internal Emacs encoding. This coding | |
801 | system handles end-of-line conversion based on the data encountered, | |
802 | and has the usual three variants to specify the kind of end-of-line | |
803 | conversion. | |
8cf51b2c GM |
804 | |
805 | @node Recognize Coding | |
806 | @section Recognizing Coding Systems | |
807 | ||
ad36c422 CY |
808 | Whenever Emacs reads a given piece of text, it tries to recognize |
809 | which coding system to use. This applies to files being read, output | |
810 | from subprocesses, text from X selections, etc. Emacs can select the | |
811 | right coding system automatically most of the time---once you have | |
812 | specified your preferences. | |
8cf51b2c GM |
813 | |
814 | Some coding systems can be recognized or distinguished by which byte | |
815 | sequences appear in the data. However, there are coding systems that | |
816 | cannot be distinguished, not even potentially. For example, there is no | |
817 | way to distinguish between Latin-1 and Latin-2; they use the same byte | |
818 | values with different meanings. | |
819 | ||
820 | Emacs handles this situation by means of a priority list of coding | |
821 | systems. Whenever Emacs reads a file, if you do not specify the coding | |
822 | system to use, Emacs checks the data against each coding system, | |
823 | starting with the first in priority and working down the list, until it | |
824 | finds a coding system that fits the data. Then it converts the file | |
825 | contents assuming that they are represented in this coding system. | |
826 | ||
827 | The priority list of coding systems depends on the selected language | |
828 | environment (@pxref{Language Environments}). For example, if you use | |
829 | French, you probably want Emacs to prefer Latin-1 to Latin-2; if you use | |
830 | Czech, you probably want Latin-2 to be preferred. This is one of the | |
831 | reasons to specify a language environment. | |
832 | ||
833 | @findex prefer-coding-system | |
834 | However, you can alter the coding system priority list in detail | |
835 | with the command @kbd{M-x prefer-coding-system}. This command reads | |
836 | the name of a coding system from the minibuffer, and adds it to the | |
837 | front of the priority list, so that it is preferred to all others. If | |
838 | you use this command several times, each use adds one element to the | |
839 | front of the priority list. | |
840 | ||
841 | If you use a coding system that specifies the end-of-line conversion | |
842 | type, such as @code{iso-8859-1-dos}, what this means is that Emacs | |
843 | should attempt to recognize @code{iso-8859-1} with priority, and should | |
844 | use DOS end-of-line conversion when it does recognize @code{iso-8859-1}. | |
845 | ||
846 | @vindex file-coding-system-alist | |
847 | Sometimes a file name indicates which coding system to use for the | |
848 | file. The variable @code{file-coding-system-alist} specifies this | |
849 | correspondence. There is a special function | |
850 | @code{modify-coding-system-alist} for adding elements to this list. For | |
851 | example, to read and write all @samp{.txt} files using the coding system | |
852 | @code{chinese-iso-8bit}, you can execute this Lisp expression: | |
853 | ||
854 | @smallexample | |
855 | (modify-coding-system-alist 'file "\\.txt\\'" 'chinese-iso-8bit) | |
856 | @end smallexample | |
857 | ||
858 | @noindent | |
859 | The first argument should be @code{file}, the second argument should be | |
860 | a regular expression that determines which files this applies to, and | |
861 | the third argument says which coding system to use for these files. | |
862 | ||
863 | @vindex inhibit-eol-conversion | |
864 | @cindex DOS-style end-of-line display | |
865 | Emacs recognizes which kind of end-of-line conversion to use based on | |
866 | the contents of the file: if it sees only carriage-returns, or only | |
867 | carriage-return linefeed sequences, then it chooses the end-of-line | |
868 | conversion accordingly. You can inhibit the automatic use of | |
869 | end-of-line conversion by setting the variable @code{inhibit-eol-conversion} | |
870 | to non-@code{nil}. If you do that, DOS-style files will be displayed | |
871 | with the @samp{^M} characters visible in the buffer; some people | |
872 | prefer this to the more subtle @samp{(DOS)} end-of-line type | |
873 | indication near the left edge of the mode line (@pxref{Mode Line, | |
874 | eol-mnemonic}). | |
875 | ||
876 | @vindex inhibit-iso-escape-detection | |
877 | @cindex escape sequences in files | |
878 | By default, the automatic detection of coding system is sensitive to | |
879 | escape sequences. If Emacs sees a sequence of characters that begin | |
880 | with an escape character, and the sequence is valid as an ISO-2022 | |
881 | code, that tells Emacs to use one of the ISO-2022 encodings to decode | |
882 | the file. | |
883 | ||
884 | However, there may be cases that you want to read escape sequences | |
885 | in a file as is. In such a case, you can set the variable | |
886 | @code{inhibit-iso-escape-detection} to non-@code{nil}. Then the code | |
887 | detection ignores any escape sequences, and never uses an ISO-2022 | |
888 | encoding. The result is that all escape sequences become visible in | |
889 | the buffer. | |
890 | ||
891 | The default value of @code{inhibit-iso-escape-detection} is | |
892 | @code{nil}. We recommend that you not change it permanently, only for | |
05f7d0d3 | 893 | one specific operation. That's because some Emacs Lisp source files |
8cf51b2c GM |
894 | in the Emacs distribution contain non-@acronym{ASCII} characters encoded in the |
895 | coding system @code{iso-2022-7bit}, and they won't be | |
896 | decoded correctly when you visit those files if you suppress the | |
897 | escape sequence detection. | |
05f7d0d3 | 898 | @c I count a grand total of 3 such files, so is the above really true? |
8cf51b2c GM |
899 | |
900 | @vindex auto-coding-alist | |
901 | @vindex auto-coding-regexp-alist | |
05f7d0d3 GM |
902 | The variables @code{auto-coding-alist} and |
903 | @code{auto-coding-regexp-alist} are | |
8cf51b2c | 904 | the strongest way to specify the coding system for certain patterns of |
05f7d0d3 GM |
905 | file names, or for files containing certain patterns, respectively. |
906 | These variables even override @samp{-*-coding:-*-} tags in the file | |
71cd7772 | 907 | itself (@pxref{Specify Coding}). For example, Emacs |
8cf51b2c GM |
908 | uses @code{auto-coding-alist} for tar and archive files, to prevent it |
909 | from being confused by a @samp{-*-coding:-*-} tag in a member of the | |
910 | archive and thinking it applies to the archive file as a whole. | |
05f7d0d3 GM |
911 | @ignore |
912 | @c This describes old-style BABYL files, which are no longer relevant. | |
8cf51b2c GM |
913 | Likewise, Emacs uses @code{auto-coding-regexp-alist} to ensure that |
914 | RMAIL files, whose names in general don't match any particular | |
05f7d0d3 GM |
915 | pattern, are decoded correctly. |
916 | @end ignore | |
917 | ||
918 | @vindex auto-coding-functions | |
919 | Another way to specify a coding system is with the variable | |
920 | @code{auto-coding-functions}. For example, one of the builtin | |
8cf51b2c | 921 | @code{auto-coding-functions} detects the encoding for XML files. |
05f7d0d3 GM |
922 | Unlike the previous two, this variable does not override any |
923 | @samp{-*-coding:-*-} tag. | |
8cf51b2c | 924 | |
05f7d0d3 | 925 | @c FIXME? This seems somewhat out of place. Move to the Rmail section? |
8cf51b2c | 926 | @vindex rmail-decode-mime-charset |
ad36c422 | 927 | @vindex rmail-file-coding-system |
8cf51b2c GM |
928 | When you get new mail in Rmail, each message is translated |
929 | automatically from the coding system it is written in, as if it were a | |
930 | separate file. This uses the priority list of coding systems that you | |
931 | have specified. If a MIME message specifies a character set, Rmail | |
05f7d0d3 GM |
932 | obeys that specification. For reading and saving Rmail files |
933 | themselves, Emacs uses the coding system specified by the variable | |
ad36c422 CY |
934 | @code{rmail-file-coding-system}. The default value is @code{nil}, |
935 | which means that Rmail files are not translated (they are read and | |
936 | written in the Emacs internal character code). | |
8cf51b2c GM |
937 | |
938 | @node Specify Coding | |
939 | @section Specifying a File's Coding System | |
940 | ||
941 | If Emacs recognizes the encoding of a file incorrectly, you can | |
313f790e CY |
942 | reread the file using the correct coding system with @kbd{C-x |
943 | @key{RET} r} (@code{revert-buffer-with-coding-system}). This command | |
944 | prompts for the coding system to use. To see what coding system Emacs | |
945 | actually used to decode the file, look at the coding system mnemonic | |
946 | letter near the left edge of the mode line (@pxref{Mode Line}), or | |
947 | type @kbd{C-h C} (@code{describe-coding-system}). | |
8cf51b2c GM |
948 | |
949 | @vindex coding | |
950 | You can specify the coding system for a particular file in the file | |
951 | itself, using the @w{@samp{-*-@dots{}-*-}} construct at the beginning, | |
952 | or a local variables list at the end (@pxref{File Variables}). You do | |
953 | this by defining a value for the ``variable'' named @code{coding}. | |
954 | Emacs does not really have a variable @code{coding}; instead of | |
955 | setting a variable, this uses the specified coding system for the | |
956 | file. For example, @samp{-*-mode: C; coding: latin-1;-*-} specifies | |
957 | use of the Latin-1 coding system, as well as C mode. When you specify | |
958 | the coding explicitly in the file, that overrides | |
959 | @code{file-coding-system-alist}. | |
960 | ||
8cf51b2c GM |
961 | @node Output Coding |
962 | @section Choosing Coding Systems for Output | |
963 | ||
964 | @vindex buffer-file-coding-system | |
965 | Once Emacs has chosen a coding system for a buffer, it stores that | |
966 | coding system in @code{buffer-file-coding-system}. That makes it the | |
967 | default for operations that write from this buffer into a file, such | |
968 | as @code{save-buffer} and @code{write-region}. You can specify a | |
969 | different coding system for further file output from the buffer using | |
970 | @code{set-buffer-file-coding-system} (@pxref{Text Coding}). | |
971 | ||
972 | You can insert any character Emacs supports into any Emacs buffer, | |
973 | but most coding systems can only handle a subset of these characters. | |
ad36c422 CY |
974 | Therefore, it's possible that the characters you insert cannot be |
975 | encoded with the coding system that will be used to save the buffer. | |
976 | For example, you could visit a text file in Polish, encoded in | |
977 | @code{iso-8859-2}, and add some Russian words to it. When you save | |
8cf51b2c GM |
978 | that buffer, Emacs cannot use the current value of |
979 | @code{buffer-file-coding-system}, because the characters you added | |
980 | cannot be encoded by that coding system. | |
981 | ||
982 | When that happens, Emacs tries the most-preferred coding system (set | |
983 | by @kbd{M-x prefer-coding-system} or @kbd{M-x | |
ad36c422 CY |
984 | set-language-environment}). If that coding system can safely encode |
985 | all of the characters in the buffer, Emacs uses it, and stores its | |
986 | value in @code{buffer-file-coding-system}. Otherwise, Emacs displays | |
987 | a list of coding systems suitable for encoding the buffer's contents, | |
988 | and asks you to choose one of those coding systems. | |
8cf51b2c GM |
989 | |
990 | If you insert the unsuitable characters in a mail message, Emacs | |
991 | behaves a bit differently. It additionally checks whether the | |
71cd7772 | 992 | @c What determines this? |
8cf51b2c GM |
993 | most-preferred coding system is recommended for use in MIME messages; |
994 | if not, Emacs tells you that the most-preferred coding system is not | |
995 | recommended and prompts you for another coding system. This is so you | |
996 | won't inadvertently send a message encoded in a way that your | |
997 | recipient's mail software will have difficulty decoding. (You can | |
998 | still use an unsuitable coding system if you type its name in response | |
999 | to the question.) | |
1000 | ||
71cd7772 GM |
1001 | @c It seems that select-message-coding-system does this. |
1002 | @c Both sendmail.el and smptmail.el call it; i.e. smtpmail.el still | |
1003 | @c obeys sendmail-coding-system. | |
8cf51b2c | 1004 | @vindex sendmail-coding-system |
71cd7772 | 1005 | When you send a mail message (@pxref{Sending Mail}), |
e73c2434 CY |
1006 | Emacs has four different ways to determine the coding system to use |
1007 | for encoding the message text. It tries the buffer's own value of | |
1008 | @code{buffer-file-coding-system}, if that is non-@code{nil}. | |
1009 | Otherwise, it uses the value of @code{sendmail-coding-system}, if that | |
1010 | is non-@code{nil}. The third way is to use the default coding system | |
1011 | for new files, which is controlled by your choice of language | |
71cd7772 | 1012 | @c i.e., default-sendmail-coding-system |
e73c2434 CY |
1013 | environment, if that is non-@code{nil}. If all of these three values |
1014 | are @code{nil}, Emacs encodes outgoing mail using the Latin-1 coding | |
1015 | system. | |
71cd7772 | 1016 | @c FIXME? Where does the Latin-1 default come in? |
8cf51b2c GM |
1017 | |
1018 | @node Text Coding | |
1019 | @section Specifying a Coding System for File Text | |
1020 | ||
1021 | In cases where Emacs does not automatically choose the right coding | |
1022 | system for a file's contents, you can use these commands to specify | |
1023 | one: | |
1024 | ||
1025 | @table @kbd | |
1026 | @item C-x @key{RET} f @var{coding} @key{RET} | |
71cd7772 GM |
1027 | Use coding system @var{coding} to save or revisit the file in |
1028 | the current buffer (@code{set-buffer-file-coding-system}). | |
8cf51b2c GM |
1029 | |
1030 | @item C-x @key{RET} c @var{coding} @key{RET} | |
1031 | Specify coding system @var{coding} for the immediately following | |
313f790e | 1032 | command (@code{universal-coding-system-argument}). |
8cf51b2c GM |
1033 | |
1034 | @item C-x @key{RET} r @var{coding} @key{RET} | |
313f790e CY |
1035 | Revisit the current file using the coding system @var{coding} |
1036 | (@code{revert-buffer-with-coding-system}). | |
8cf51b2c GM |
1037 | |
1038 | @item M-x recode-region @key{RET} @var{right} @key{RET} @var{wrong} @key{RET} | |
1039 | Convert a region that was decoded using coding system @var{wrong}, | |
1040 | decoding it using coding system @var{right} instead. | |
1041 | @end table | |
1042 | ||
1043 | @kindex C-x RET f | |
1044 | @findex set-buffer-file-coding-system | |
1045 | The command @kbd{C-x @key{RET} f} | |
1046 | (@code{set-buffer-file-coding-system}) sets the file coding system for | |
1047 | the current buffer---in other words, it says which coding system to | |
1048 | use when saving or reverting the visited file. You specify which | |
1049 | coding system using the minibuffer. If you specify a coding system | |
1050 | that cannot handle all of the characters in the buffer, Emacs warns | |
1051 | you about the troublesome characters when you actually save the | |
1052 | buffer. | |
1053 | ||
1054 | @cindex specify end-of-line conversion | |
1055 | You can also use this command to specify the end-of-line conversion | |
1056 | (@pxref{Coding Systems, end-of-line conversion}) for encoding the | |
1057 | current buffer. For example, @kbd{C-x @key{RET} f dos @key{RET}} will | |
71cd7772 GM |
1058 | cause Emacs to save the current buffer's text with DOS-style |
1059 | carriage-return linefeed line endings. | |
8cf51b2c GM |
1060 | |
1061 | @kindex C-x RET c | |
1062 | @findex universal-coding-system-argument | |
1063 | Another way to specify the coding system for a file is when you visit | |
1064 | the file. First use the command @kbd{C-x @key{RET} c} | |
1065 | (@code{universal-coding-system-argument}); this command uses the | |
1066 | minibuffer to read a coding system name. After you exit the minibuffer, | |
1067 | the specified coding system is used for @emph{the immediately following | |
1068 | command}. | |
1069 | ||
1070 | So if the immediately following command is @kbd{C-x C-f}, for example, | |
1071 | it reads the file using that coding system (and records the coding | |
1072 | system for when you later save the file). Or if the immediately following | |
1073 | command is @kbd{C-x C-w}, it writes the file using that coding system. | |
1074 | When you specify the coding system for saving in this way, instead | |
1075 | of with @kbd{C-x @key{RET} f}, there is no warning if the buffer | |
1076 | contains characters that the coding system cannot handle. | |
1077 | ||
1078 | Other file commands affected by a specified coding system include | |
1079 | @kbd{C-x i} and @kbd{C-x C-v}, as well as the other-window variants | |
1080 | of @kbd{C-x C-f}. @kbd{C-x @key{RET} c} also affects commands that | |
1081 | start subprocesses, including @kbd{M-x shell} (@pxref{Shell}). If the | |
1082 | immediately following command does not use the coding system, then | |
1083 | @kbd{C-x @key{RET} c} ultimately has no effect. | |
1084 | ||
1085 | An easy way to visit a file with no conversion is with the @kbd{M-x | |
1086 | find-file-literally} command. @xref{Visiting}. | |
1087 | ||
4e3b4528 SM |
1088 | The default value of the variable @code{buffer-file-coding-system} |
1089 | specifies the choice of coding system to use when you create a new file. | |
1090 | It applies when you find a new file, and when you create a buffer and | |
1091 | then save it in a file. Selecting a language environment typically sets | |
1092 | this variable to a good choice of default coding system for that language | |
8cf51b2c GM |
1093 | environment. |
1094 | ||
1095 | @kindex C-x RET r | |
1096 | @findex revert-buffer-with-coding-system | |
1097 | If you visit a file with a wrong coding system, you can correct this | |
1098 | with @kbd{C-x @key{RET} r} (@code{revert-buffer-with-coding-system}). | |
1099 | This visits the current file again, using a coding system you specify. | |
1100 | ||
1101 | @findex recode-region | |
1102 | If a piece of text has already been inserted into a buffer using the | |
1103 | wrong coding system, you can redo the decoding of it using @kbd{M-x | |
1104 | recode-region}. This prompts you for the proper coding system, then | |
1105 | for the wrong coding system that was actually used, and does the | |
1106 | conversion. It first encodes the region using the wrong coding system, | |
1107 | then decodes it again using the proper coding system. | |
1108 | ||
1109 | @node Communication Coding | |
1110 | @section Coding Systems for Interprocess Communication | |
1111 | ||
1112 | This section explains how to specify coding systems for use | |
1113 | in communication with other processes. | |
1114 | ||
1115 | @table @kbd | |
1116 | @item C-x @key{RET} x @var{coding} @key{RET} | |
1117 | Use coding system @var{coding} for transferring selections to and from | |
313f790e | 1118 | other window-based applications (@code{set-selection-coding-system}). |
8cf51b2c GM |
1119 | |
1120 | @item C-x @key{RET} X @var{coding} @key{RET} | |
1121 | Use coding system @var{coding} for transferring @emph{one} | |
313f790e CY |
1122 | selection---the next one---to or from another window-based application |
1123 | (@code{set-next-selection-coding-system}). | |
8cf51b2c GM |
1124 | |
1125 | @item C-x @key{RET} p @var{input-coding} @key{RET} @var{output-coding} @key{RET} | |
1126 | Use coding systems @var{input-coding} and @var{output-coding} for | |
313f790e CY |
1127 | subprocess input and output in the current buffer |
1128 | (@code{set-buffer-process-coding-system}). | |
8cf51b2c GM |
1129 | @end table |
1130 | ||
1131 | @kindex C-x RET x | |
1132 | @kindex C-x RET X | |
1133 | @findex set-selection-coding-system | |
1134 | @findex set-next-selection-coding-system | |
1135 | The command @kbd{C-x @key{RET} x} (@code{set-selection-coding-system}) | |
1136 | specifies the coding system for sending selected text to other windowing | |
1137 | applications, and for receiving the text of selections made in other | |
1138 | applications. This command applies to all subsequent selections, until | |
1139 | you override it by using the command again. The command @kbd{C-x | |
1140 | @key{RET} X} (@code{set-next-selection-coding-system}) specifies the | |
1141 | coding system for the next selection made in Emacs or read by Emacs. | |
1142 | ||
53b7759e | 1143 | @vindex x-select-request-type |
221bb7f6 EZ |
1144 | The variable @code{x-select-request-type} specifies the data type to |
1145 | request from the X Window System for receiving text selections from | |
1146 | other applications. If the value is @code{nil} (the default), Emacs | |
71cd7772 | 1147 | tries @code{UTF8_STRING} and @code{COMPOUND_TEXT}, in this order, and |
221bb7f6 EZ |
1148 | uses various heuristics to choose the more appropriate of the two |
1149 | results; if none of these succeed, Emacs falls back on @code{STRING}. | |
1150 | If the value of @code{x-select-request-type} is one of the symbols | |
1151 | @code{COMPOUND_TEXT}, @code{UTF8_STRING}, @code{STRING}, or | |
1152 | @code{TEXT}, Emacs uses only that request type. If the value is a | |
1153 | list of some of these symbols, Emacs tries only the request types in | |
1154 | the list, in order, until one of them succeeds, or until the list is | |
1155 | exhausted. | |
53b7759e | 1156 | |
8cf51b2c GM |
1157 | @kindex C-x RET p |
1158 | @findex set-buffer-process-coding-system | |
1159 | The command @kbd{C-x @key{RET} p} (@code{set-buffer-process-coding-system}) | |
1160 | specifies the coding system for input and output to a subprocess. This | |
1161 | command applies to the current buffer; normally, each subprocess has its | |
1162 | own buffer, and thus you can use this command to specify translation to | |
1163 | and from a particular subprocess by giving the command in the | |
1164 | corresponding buffer. | |
1165 | ||
313f790e CY |
1166 | You can also use @kbd{C-x @key{RET} c} |
1167 | (@code{universal-coding-system-argument}) just before the command that | |
1168 | runs or starts a subprocess, to specify the coding system for | |
1169 | communicating with that subprocess. @xref{Text Coding}. | |
8cf51b2c GM |
1170 | |
1171 | The default for translation of process input and output depends on the | |
1172 | current language environment. | |
1173 | ||
1174 | @vindex locale-coding-system | |
1175 | @cindex decoding non-@acronym{ASCII} keyboard input on X | |
1176 | The variable @code{locale-coding-system} specifies a coding system | |
1177 | to use when encoding and decoding system strings such as system error | |
1178 | messages and @code{format-time-string} formats and time stamps. That | |
71cd7772 GM |
1179 | coding system is also used for decoding non-@acronym{ASCII} keyboard |
1180 | input on the X Window System. You should choose a coding system that is compatible | |
8cf51b2c GM |
1181 | with the underlying system's text representation, which is normally |
1182 | specified by one of the environment variables @env{LC_ALL}, | |
1183 | @env{LC_CTYPE}, and @env{LANG}. (The first one, in the order | |
1184 | specified above, whose value is nonempty is the one that determines | |
1185 | the text representation.) | |
1186 | ||
1187 | @node File Name Coding | |
1188 | @section Coding Systems for File Names | |
1189 | ||
1190 | @table @kbd | |
1191 | @item C-x @key{RET} F @var{coding} @key{RET} | |
1192 | Use coding system @var{coding} for encoding and decoding file | |
71cd7772 | 1193 | names (@code{set-file-name-coding-system}). |
8cf51b2c GM |
1194 | @end table |
1195 | ||
8cf51b2c GM |
1196 | @findex set-file-name-coding-system |
1197 | @kindex C-x @key{RET} F | |
71cd7772 GM |
1198 | @cindex file names with non-@acronym{ASCII} characters |
1199 | The command @kbd{C-x @key{RET} F} (@code{set-file-name-coding-system}) | |
1200 | specifies a coding system to use for encoding file @emph{names}. It | |
1201 | has no effect on reading and writing the @emph{contents} of files. | |
1202 | ||
1203 | @vindex file-name-coding-system | |
1204 | In fact, all this command does is set the value of the variable | |
1205 | @code{file-name-coding-system}. If you set the variable to a coding | |
1206 | system name (as a Lisp symbol or a string), Emacs encodes file names | |
1207 | using that coding system for all file operations. This makes it | |
1208 | possible to use non-@acronym{ASCII} characters in file names---or, at | |
1209 | least, those non-@acronym{ASCII} characters that the specified coding | |
1210 | system can encode. | |
8cf51b2c GM |
1211 | |
1212 | If @code{file-name-coding-system} is @code{nil}, Emacs uses a | |
71cd7772 GM |
1213 | default coding system determined by the selected language environment, |
1214 | and stored in the @code{default-file-name-coding-system} variable. | |
1215 | @c FIXME? Is this correct? What is the "default language environment"? | |
ad36c422 CY |
1216 | In the default language environment, non-@acronym{ASCII} characters in |
1217 | file names are not encoded specially; they appear in the file system | |
1218 | using the internal Emacs representation. | |
8cf51b2c GM |
1219 | |
1220 | @strong{Warning:} if you change @code{file-name-coding-system} (or the | |
1221 | language environment) in the middle of an Emacs session, problems can | |
1222 | result if you have already visited files whose names were encoded using | |
1223 | the earlier coding system and cannot be encoded (or are encoded | |
1224 | differently) under the new coding system. If you try to save one of | |
1225 | these buffers under the visited file name, saving may use the wrong file | |
71cd7772 | 1226 | name, or it may encounter an error. If such a problem happens, use @kbd{C-x |
8cf51b2c GM |
1227 | C-w} to specify a new file name for that buffer. |
1228 | ||
1229 | @findex recode-file-name | |
1230 | If a mistake occurs when encoding a file name, use the command | |
1231 | @kbd{M-x recode-file-name} to change the file name's coding | |
1232 | system. This prompts for an existing file name, its old coding | |
1233 | system, and the coding system to which you wish to convert. | |
1234 | ||
1235 | @node Terminal Coding | |
1236 | @section Coding Systems for Terminal I/O | |
1237 | ||
1238 | @table @kbd | |
8cf51b2c | 1239 | @item C-x @key{RET} t @var{coding} @key{RET} |
313f790e CY |
1240 | Use coding system @var{coding} for terminal output |
1241 | (@code{set-terminal-coding-system}). | |
71cd7772 GM |
1242 | |
1243 | @item C-x @key{RET} k @var{coding} @key{RET} | |
1244 | Use coding system @var{coding} for keyboard input | |
1245 | (@code{set-keyboard-coding-system}). | |
8cf51b2c GM |
1246 | @end table |
1247 | ||
1248 | @kindex C-x RET t | |
1249 | @findex set-terminal-coding-system | |
1250 | The command @kbd{C-x @key{RET} t} (@code{set-terminal-coding-system}) | |
1251 | specifies the coding system for terminal output. If you specify a | |
1252 | character code for terminal output, all characters output to the | |
1253 | terminal are translated into that coding system. | |
1254 | ||
1255 | This feature is useful for certain character-only terminals built to | |
1256 | support specific languages or character sets---for example, European | |
1257 | terminals that support one of the ISO Latin character sets. You need to | |
1258 | specify the terminal coding system when using multibyte text, so that | |
1259 | Emacs knows which characters the terminal can actually handle. | |
1260 | ||
1261 | By default, output to the terminal is not translated at all, unless | |
1262 | Emacs can deduce the proper coding system from your terminal type or | |
1263 | your locale specification (@pxref{Language Environments}). | |
1264 | ||
1265 | @kindex C-x RET k | |
1266 | @findex set-keyboard-coding-system | |
1267 | @vindex keyboard-coding-system | |
71cd7772 GM |
1268 | The command @kbd{C-x @key{RET} k} (@code{set-keyboard-coding-system}), |
1269 | or the variable @code{keyboard-coding-system}, specifies the coding | |
8cf51b2c GM |
1270 | system for keyboard input. Character-code translation of keyboard |
1271 | input is useful for terminals with keys that send non-@acronym{ASCII} | |
1272 | graphic characters---for example, some terminals designed for ISO | |
1273 | Latin-1 or subsets of it. | |
1274 | ||
1275 | By default, keyboard input is translated based on your system locale | |
1276 | setting. If your terminal does not really support the encoding | |
1277 | implied by your locale (for example, if you find it inserts a | |
1278 | non-@acronym{ASCII} character if you type @kbd{M-i}), you will need to set | |
1279 | @code{keyboard-coding-system} to @code{nil} to turn off encoding. | |
1280 | You can do this by putting | |
1281 | ||
1282 | @lisp | |
1283 | (set-keyboard-coding-system nil) | |
1284 | @end lisp | |
1285 | ||
1286 | @noindent | |
ad36c422 | 1287 | in your init file. |
8cf51b2c GM |
1288 | |
1289 | There is a similarity between using a coding system translation for | |
1290 | keyboard input, and using an input method: both define sequences of | |
1291 | keyboard input that translate into single characters. However, input | |
1292 | methods are designed to be convenient for interactive use by humans, and | |
1293 | the sequences that are translated are typically sequences of @acronym{ASCII} | |
1294 | printing characters. Coding systems typically translate sequences of | |
1295 | non-graphic characters. | |
1296 | ||
1297 | @node Fontsets | |
1298 | @section Fontsets | |
1299 | @cindex fontsets | |
1300 | ||
1301 | A font typically defines shapes for a single alphabet or script. | |
1302 | Therefore, displaying the entire range of scripts that Emacs supports | |
1303 | requires a collection of many fonts. In Emacs, such a collection is | |
05806f43 | 1304 | called a @dfn{fontset}. A fontset is defined by a list of font specifications, |
b545ff9c | 1305 | each assigned to handle a range of character codes, and may fall back |
05806f43 | 1306 | on another fontset for characters that are not covered by the fonts |
b545ff9c | 1307 | it specifies. |
8cf51b2c | 1308 | |
05806f43 GM |
1309 | @cindex fonts for various scripts |
1310 | @cindex Intlfonts package, installation | |
8cf51b2c GM |
1311 | Each fontset has a name, like a font. However, while fonts are |
1312 | stored in the system and the available font names are defined by the | |
1313 | system, fontsets are defined within Emacs itself. Once you have | |
1314 | defined a fontset, you can use it within Emacs by specifying its name, | |
1315 | anywhere that you could use a single font. Of course, Emacs fontsets | |
05806f43 GM |
1316 | can use only the fonts that the system supports. If some characters |
1317 | appear on the screen as empty boxes or hex codes, this means that the | |
1318 | fontset in use for them has no font for those characters. In this | |
1319 | case, or if the characters are shown, but not as well as you would | |
1320 | like, you may need to install extra fonts. Your operating system may | |
1321 | have optional fonts that you can install; or you can install the GNU | |
1322 | Intlfonts package, which includes fonts for most supported | |
1323 | scripts.@footnote{If you run Emacs on X, you may need to inform the X | |
1324 | server about the location of the newly installed fonts with commands | |
1325 | such as: | |
1326 | @c FIXME? I feel like this may be out of date. | |
1327 | @c Eg the intlfonts tarfile is ~ 10 years old. | |
1328 | ||
1329 | @example | |
1330 | xset fp+ /usr/local/share/emacs/fonts | |
1331 | xset fp rehash | |
1332 | @end example | |
1333 | } | |
8cf51b2c | 1334 | |
b545ff9c JR |
1335 | Emacs creates three fontsets automatically: the @dfn{standard |
1336 | fontset}, the @dfn{startup fontset} and the @dfn{default fontset}. | |
05806f43 GM |
1337 | @c FIXME? The doc of *standard*-fontset-spec says: |
1338 | @c "You have the biggest chance to display international characters | |
1339 | @c with correct glyphs by using the *standard* fontset." (my emphasis) | |
de649682 | 1340 | @c See http://lists.gnu.org/archive/html/emacs-devel/2012-04/msg00430.html |
b545ff9c | 1341 | The default fontset is most likely to have fonts for a wide variety of |
05806f43 | 1342 | non-@acronym{ASCII} characters, and is the default fallback for the |
b545ff9c | 1343 | other two fontsets, and if you set a default font rather than fontset. |
05806f43 | 1344 | However, it does not specify font family names, so results can be |
a4bead12 | 1345 | somewhat random if you use it directly. You can specify use of a |
05806f43 GM |
1346 | particular fontset by starting Emacs with the @samp{-fn} option. |
1347 | For example, | |
8cf51b2c GM |
1348 | |
1349 | @example | |
1350 | emacs -fn fontset-standard | |
1351 | @end example | |
1352 | ||
1353 | @noindent | |
1354 | You can also specify a fontset with the @samp{Font} resource (@pxref{X | |
1355 | Resources}). | |
1356 | ||
a4bead12 JR |
1357 | If no fontset is specified for use, then Emacs uses an |
1358 | @acronym{ASCII} font, with @samp{fontset-default} as a fallback for | |
1359 | characters the font does not cover. The standard fontset is only used if | |
1360 | explicitly requested, despite its name. | |
1361 | ||
8cf51b2c | 1362 | A fontset does not necessarily specify a font for every character |
0eb025fb EZ |
1363 | code. If a fontset specifies no font for a certain character, or if |
1364 | it specifies a font that does not exist on your system, then it cannot | |
1365 | display that character properly. It will display that character as a | |
0088729a | 1366 | hex code or thin space or an empty box instead. (@xref{Text Display, , |
0eb025fb | 1367 | glyphless characters}, for details.) |
8cf51b2c GM |
1368 | |
1369 | @node Defining Fontsets | |
1370 | @section Defining fontsets | |
1371 | ||
1372 | @vindex standard-fontset-spec | |
b545ff9c JR |
1373 | @vindex w32-standard-fontset-spec |
1374 | @vindex ns-standard-fontset-spec | |
8cf51b2c | 1375 | @cindex standard fontset |
b545ff9c | 1376 | When running on X, Emacs creates a standard fontset automatically according to the value |
8cf51b2c GM |
1377 | of @code{standard-fontset-spec}. This fontset's name is |
1378 | ||
1379 | @example | |
1380 | -*-fixed-medium-r-normal-*-16-*-*-*-*-*-fontset-standard | |
1381 | @end example | |
1382 | ||
1383 | @noindent | |
1384 | or just @samp{fontset-standard} for short. | |
1385 | ||
05806f43 GM |
1386 | On GNUstep and Mac OS X, the standard fontset is created using the value of |
1387 | @code{ns-standard-fontset-spec}, and on MS Windows it is | |
b545ff9c JR |
1388 | created using the value of @code{w32-standard-fontset-spec}. |
1389 | ||
05806f43 GM |
1390 | @c FIXME? How does one access these, or do anything with them? |
1391 | @c Does it matter? | |
8cf51b2c GM |
1392 | Bold, italic, and bold-italic variants of the standard fontset are |
1393 | created automatically. Their names have @samp{bold} instead of | |
1394 | @samp{medium}, or @samp{i} instead of @samp{r}, or both. | |
1395 | ||
1396 | @cindex startup fontset | |
b545ff9c JR |
1397 | Emacs generates a fontset automatically, based on any default |
1398 | @acronym{ASCII} font that you specify with the @samp{Font} resource or | |
1399 | the @samp{-fn} argument, or the default font that Emacs found when it | |
1400 | started. This is the @dfn{startup fontset} and its name is | |
1401 | @code{fontset-startup}. It does this by replacing the | |
1402 | @var{charset_registry} field with @samp{fontset}, and replacing | |
1403 | @var{charset_encoding} field with @samp{startup}, then using the | |
1404 | resulting string to specify a fontset. | |
8cf51b2c | 1405 | |
05806f43 | 1406 | For instance, if you start Emacs with a font of this form, |
8cf51b2c | 1407 | |
05806f43 GM |
1408 | @c FIXME? I think this is a little misleading, because you cannot (?) |
1409 | @c actually specify a font with wildcards, it has to be a complete spec. | |
1410 | @c Also, an X font specification of this form hasn't (?) been | |
1411 | @c mentioned before now, and is somewhat obsolete these days. | |
1412 | @c People are more likely to use a form like | |
1413 | @c emacs -fn "DejaVu Sans Mono-12" | |
1414 | @c How does any of this apply in that case? | |
8cf51b2c GM |
1415 | @example |
1416 | emacs -fn "*courier-medium-r-normal--14-140-*-iso8859-1" | |
1417 | @end example | |
1418 | ||
1419 | @noindent | |
1420 | Emacs generates the following fontset and uses it for the initial X | |
1421 | window frame: | |
1422 | ||
1423 | @example | |
b545ff9c | 1424 | -*-courier-medium-r-normal-*-14-140-*-*-*-*-fontset-startup |
8cf51b2c GM |
1425 | @end example |
1426 | ||
05806f43 GM |
1427 | The startup fontset will use the font that you specify, or a variant |
1428 | with a different registry and encoding, for all the characters that | |
b545ff9c JR |
1429 | are supported by that font, and fallback on @samp{fontset-default} for |
1430 | other characters. | |
1431 | ||
8cf51b2c GM |
1432 | With the X resource @samp{Emacs.Font}, you can specify a fontset name |
1433 | just like an actual font name. But be careful not to specify a fontset | |
1434 | name in a wildcard resource like @samp{Emacs*Font}---that wildcard | |
1435 | specification matches various other resources, such as for menus, and | |
05806f43 GM |
1436 | @c FIXME is this still true? |
1437 | menus cannot handle fontsets. @xref{X Resources}. | |
8cf51b2c GM |
1438 | |
1439 | You can specify additional fontsets using X resources named | |
1440 | @samp{Fontset-@var{n}}, where @var{n} is an integer starting from 0. | |
1441 | The resource value should have this form: | |
1442 | ||
1443 | @smallexample | |
1444 | @var{fontpattern}, @r{[}@var{charset}:@var{font}@r{]@dots{}} | |
1445 | @end smallexample | |
1446 | ||
1447 | @noindent | |
05806f43 GM |
1448 | @var{fontpattern} should have the form of a standard X font name (see |
1449 | the previous fontset-startup example), except | |
8cf51b2c GM |
1450 | for the last two fields. They should have the form |
1451 | @samp{fontset-@var{alias}}. | |
1452 | ||
1453 | The fontset has two names, one long and one short. The long name is | |
1454 | @var{fontpattern}. The short name is @samp{fontset-@var{alias}}. You | |
1455 | can refer to the fontset by either name. | |
1456 | ||
1457 | The construct @samp{@var{charset}:@var{font}} specifies which font to | |
1458 | use (in this fontset) for one particular character set. Here, | |
1459 | @var{charset} is the name of a character set, and @var{font} is the | |
1460 | font to use for that character set. You can use this construct any | |
1461 | number of times in defining one fontset. | |
1462 | ||
1463 | For the other character sets, Emacs chooses a font based on | |
1464 | @var{fontpattern}. It replaces @samp{fontset-@var{alias}} with values | |
1465 | that describe the character set. For the @acronym{ASCII} character font, | |
1466 | @samp{fontset-@var{alias}} is replaced with @samp{ISO8859-1}. | |
1467 | ||
1468 | In addition, when several consecutive fields are wildcards, Emacs | |
1469 | collapses them into a single wildcard. This is to prevent use of | |
1470 | auto-scaled fonts. Fonts made by scaling larger fonts are not usable | |
05806f43 | 1471 | for editing, and scaling a smaller font is not also useful, because it is |
8cf51b2c GM |
1472 | better to use the smaller font in its own size, which is what Emacs |
1473 | does. | |
1474 | ||
1475 | Thus if @var{fontpattern} is this, | |
1476 | ||
1477 | @example | |
1478 | -*-fixed-medium-r-normal-*-24-*-*-*-*-*-fontset-24 | |
1479 | @end example | |
1480 | ||
1481 | @noindent | |
1482 | the font specification for @acronym{ASCII} characters would be this: | |
1483 | ||
1484 | @example | |
1485 | -*-fixed-medium-r-normal-*-24-*-ISO8859-1 | |
1486 | @end example | |
1487 | ||
1488 | @noindent | |
1489 | and the font specification for Chinese GB2312 characters would be this: | |
1490 | ||
1491 | @example | |
1492 | -*-fixed-medium-r-normal-*-24-*-gb2312*-* | |
1493 | @end example | |
1494 | ||
1495 | You may not have any Chinese font matching the above font | |
1496 | specification. Most X distributions include only Chinese fonts that | |
05806f43 GM |
1497 | have @samp{song ti} or @samp{fangsong ti} in the @var{family} field. In |
1498 | such a case, @samp{Fontset-@var{n}} can be specified as: | |
8cf51b2c GM |
1499 | |
1500 | @smallexample | |
1501 | Emacs.Fontset-0: -*-fixed-medium-r-normal-*-24-*-*-*-*-*-fontset-24,\ | |
1502 | chinese-gb2312:-*-*-medium-r-normal-*-24-*-gb2312*-* | |
1503 | @end smallexample | |
1504 | ||
1505 | @noindent | |
1506 | Then, the font specifications for all but Chinese GB2312 characters have | |
1507 | @samp{fixed} in the @var{family} field, and the font specification for | |
1508 | Chinese GB2312 characters has a wild card @samp{*} in the @var{family} | |
1509 | field. | |
1510 | ||
1511 | @findex create-fontset-from-fontset-spec | |
1512 | The function that processes the fontset resource value to create the | |
1513 | fontset is called @code{create-fontset-from-fontset-spec}. You can also | |
1514 | call this function explicitly to create a fontset. | |
1515 | ||
d68eb23c | 1516 | @xref{Fonts}, for more information about font naming. |
8cf51b2c | 1517 | |
b545ff9c JR |
1518 | @node Modifying Fontsets |
1519 | @section Modifying Fontsets | |
1520 | @cindex fontsets, modifying | |
1521 | @findex set-fontset-font | |
1522 | ||
1523 | Fontsets do not always have to be created from scratch. If only | |
1524 | minor changes are required it may be easier to modify an existing | |
1525 | fontset. Modifying @samp{fontset-default} will also affect other | |
1526 | fontsets that use it as a fallback, so can be an effective way of | |
1527 | fixing problems with the fonts that Emacs chooses for a particular | |
1528 | script. | |
1529 | ||
1530 | Fontsets can be modified using the function @code{set-fontset-font}, | |
1531 | specifying a character, a charset, a script, or a range of characters | |
05806f43 GM |
1532 | to modify the font for, and a font specification for the font to be |
1533 | used. Some examples are: | |
b545ff9c JR |
1534 | |
1535 | @example | |
1536 | ;; Use Liberation Mono for latin-3 charset. | |
ae742cb5 CY |
1537 | (set-fontset-font "fontset-default" 'iso-8859-3 |
1538 | "Liberation Mono") | |
b545ff9c JR |
1539 | |
1540 | ;; Prefer a big5 font for han characters | |
ae742cb5 CY |
1541 | (set-fontset-font "fontset-default" |
1542 | 'han (font-spec :registry "big5") | |
b545ff9c JR |
1543 | nil 'prepend) |
1544 | ||
ae742cb5 CY |
1545 | ;; Use DejaVu Sans Mono as a fallback in fontset-startup |
1546 | ;; before resorting to fontset-default. | |
1547 | (set-fontset-font "fontset-startup" nil "DejaVu Sans Mono" | |
1548 | nil 'append) | |
b545ff9c JR |
1549 | |
1550 | ;; Use MyPrivateFont for the Unicode private use area. | |
ae742cb5 CY |
1551 | (set-fontset-font "fontset-default" '(#xe000 . #xf8ff) |
1552 | "MyPrivateFont") | |
b545ff9c JR |
1553 | |
1554 | @end example | |
1555 | ||
1556 | ||
8cf51b2c GM |
1557 | @node Undisplayable Characters |
1558 | @section Undisplayable Characters | |
1559 | ||
05806f43 | 1560 | There may be some non-@acronym{ASCII} characters that your |
0be641c0 CY |
1561 | terminal cannot display. Most text terminals support just a single |
1562 | character set (use the variable @code{default-terminal-coding-system} | |
05806f43 | 1563 | to tell Emacs which one, @ref{Terminal Coding}); characters that |
8cf51b2c GM |
1564 | can't be encoded in that coding system are displayed as @samp{?} by |
1565 | default. | |
1566 | ||
1567 | Graphical displays can display a broader range of characters, but | |
1568 | you may not have fonts installed for all of them; characters that have | |
1569 | no font appear as a hollow box. | |
1570 | ||
1571 | If you use Latin-1 characters but your terminal can't display | |
1572 | Latin-1, you can arrange to display mnemonic @acronym{ASCII} sequences | |
1573 | instead, e.g.@: @samp{"o} for o-umlaut. Load the library | |
1574 | @file{iso-ascii} to do this. | |
1575 | ||
1576 | @vindex latin1-display | |
1577 | If your terminal can display Latin-1, you can display characters | |
1578 | from other European character sets using a mixture of equivalent | |
1579 | Latin-1 characters and @acronym{ASCII} mnemonics. Customize the variable | |
1580 | @code{latin1-display} to enable this. The mnemonic @acronym{ASCII} | |
1581 | sequences mostly correspond to those of the prefix input methods. | |
1582 | ||
1583 | @node Unibyte Mode | |
1584 | @section Unibyte Editing Mode | |
1585 | ||
1586 | @cindex European character sets | |
1587 | @cindex accented characters | |
1588 | @cindex ISO Latin character sets | |
1589 | @cindex Unibyte operation | |
1590 | The ISO 8859 Latin-@var{n} character sets define character codes in | |
1591 | the range 0240 to 0377 octal (160 to 255 decimal) to handle the | |
1592 | accented letters and punctuation needed by various European languages | |
43b3b4d1 EZ |
1593 | (and some non-European ones). Note that Emacs considers bytes with |
1594 | codes in this range as raw bytes, not as characters, even in a unibyte | |
05806f43 | 1595 | buffer, i.e.@: if you disable multibyte characters. However, Emacs |
43b3b4d1 EZ |
1596 | can still handle these character codes as if they belonged to |
1597 | @emph{one} of the single-byte character sets at a time. To specify | |
1598 | @emph{which} of these codes to use, invoke @kbd{M-x | |
8cf51b2c GM |
1599 | set-language-environment} and specify a suitable language environment |
1600 | such as @samp{Latin-@var{n}}. | |
1601 | ||
faab108e GM |
1602 | For more information about unibyte operation, see |
1603 | @ref{Disabling Multibyte}. | |
8cf51b2c GM |
1604 | |
1605 | @vindex unibyte-display-via-language-environment | |
43b3b4d1 EZ |
1606 | Emacs can also display bytes in the range 160 to 255 as readable |
1607 | characters, provided the terminal or font in use supports them. This | |
1608 | works automatically. On a graphical display, Emacs can also display | |
1609 | single-byte characters through fontsets, in effect by displaying the | |
1610 | equivalent multibyte characters according to the current language | |
1611 | environment. To request this, set the variable | |
1612 | @code{unibyte-display-via-language-environment} to a non-@code{nil} | |
1613 | value. Note that setting this only affects how these bytes are | |
1614 | displayed, but does not change the fundamental fact that Emacs treats | |
1615 | them as raw bytes, not as characters. | |
8cf51b2c GM |
1616 | |
1617 | @cindex @code{iso-ascii} library | |
1618 | If your terminal does not support display of the Latin-1 character | |
1619 | set, Emacs can display these characters as @acronym{ASCII} sequences which at | |
1620 | least give you a clear idea of what the characters are. To do this, | |
1621 | load the library @code{iso-ascii}. Similar libraries for other | |
05806f43 GM |
1622 | Latin-@var{n} character sets could be implemented, but have not been |
1623 | so far. | |
8cf51b2c GM |
1624 | |
1625 | @findex standard-display-8bit | |
1626 | @cindex 8-bit display | |
1627 | Normally non-ISO-8859 characters (decimal codes between 128 and 159 | |
1628 | inclusive) are displayed as octal escapes. You can change this for | |
1629 | non-standard ``extended'' versions of ISO-8859 character sets by using the | |
1630 | function @code{standard-display-8bit} in the @code{disp-table} library. | |
1631 | ||
1632 | There are two ways to input single-byte non-@acronym{ASCII} | |
1633 | characters: | |
1634 | ||
1635 | @itemize @bullet | |
1636 | @cindex 8-bit input | |
1637 | @item | |
1638 | You can use an input method for the selected language environment. | |
1639 | @xref{Input Methods}. When you use an input method in a unibyte buffer, | |
1640 | the non-@acronym{ASCII} character you specify with it is converted to unibyte. | |
1641 | ||
1642 | @item | |
1643 | If your keyboard can generate character codes 128 (decimal) and up, | |
1644 | representing non-@acronym{ASCII} characters, you can type those character codes | |
1645 | directly. | |
1646 | ||
0be641c0 CY |
1647 | On a graphical display, you should not need to do anything special to |
1648 | use these keys; they should simply work. On a text terminal, you | |
05806f43 | 1649 | should use the command @code{M-x set-keyboard-coding-system} or customize the |
8cf51b2c GM |
1650 | variable @code{keyboard-coding-system} to specify which coding system |
1651 | your keyboard uses (@pxref{Terminal Coding}). Enabling this feature | |
1652 | will probably require you to use @kbd{ESC} to type Meta characters; | |
1653 | however, on a console terminal or in @code{xterm}, you can arrange for | |
1654 | Meta to be converted to @kbd{ESC} and still be able type 8-bit | |
1655 | characters present directly on the keyboard or using @kbd{Compose} or | |
1656 | @kbd{AltGr} keys. @xref{User Input}. | |
1657 | ||
1658 | @kindex C-x 8 | |
1659 | @cindex @code{iso-transl} library | |
1660 | @cindex compose character | |
1661 | @cindex dead character | |
1662 | @item | |
1663 | For Latin-1 only, you can use the key @kbd{C-x 8} as a ``compose | |
1664 | character'' prefix for entry of non-@acronym{ASCII} Latin-1 printing | |
1665 | characters. @kbd{C-x 8} is good for insertion (in the minibuffer as | |
1666 | well as other buffers), for searching, and in any other context where | |
1667 | a key sequence is allowed. | |
1668 | ||
1669 | @kbd{C-x 8} works by loading the @code{iso-transl} library. Once that | |
1670 | library is loaded, the @key{ALT} modifier key, if the keyboard has | |
1671 | one, serves the same purpose as @kbd{C-x 8}: use @key{ALT} together | |
1672 | with an accent character to modify the following letter. In addition, | |
8edb942b | 1673 | if the keyboard has keys for the Latin-1 ``dead accent characters'', |
8cf51b2c GM |
1674 | they too are defined to compose with the following character, once |
1675 | @code{iso-transl} is loaded. | |
1676 | ||
1677 | Use @kbd{C-x 8 C-h} to list all the available @kbd{C-x 8} translations. | |
1678 | @end itemize | |
1679 | ||
1680 | @node Charsets | |
1681 | @section Charsets | |
1682 | @cindex charsets | |
1683 | ||
18430066 CY |
1684 | In Emacs, @dfn{charset} is short for ``character set''. Emacs |
1685 | supports most popular charsets (such as @code{ascii}, | |
1686 | @code{iso-8859-1}, @code{cp1250}, @code{big5}, and @code{unicode}), in | |
1687 | addition to some charsets of its own (such as @code{emacs}, | |
1688 | @code{unicode-bmp}, and @code{eight-bit}). All supported characters | |
1689 | belong to one or more charsets. | |
1690 | ||
1691 | Emacs normally ``does the right thing'' with respect to charsets, so | |
1692 | that you don't have to worry about them. However, it is sometimes | |
1693 | helpful to know some of the underlying details about charsets. | |
1694 | ||
d68eb23c | 1695 | One example is font selection (@pxref{Fonts}). Each language |
18430066 CY |
1696 | environment (@pxref{Language Environments}) defines a ``priority |
1697 | list'' for the various charsets. When searching for a font, Emacs | |
1698 | initially attempts to find one that can display the highest-priority | |
1699 | charsets. For instance, in the Japanese language environment, the | |
1700 | charset @code{japanese-jisx0208} has the highest priority, so Emacs | |
1701 | tries to use a font whose @code{registry} property is | |
1702 | @samp{JISX0208.1983-0}. | |
8cf51b2c GM |
1703 | |
1704 | @findex list-charset-chars | |
1705 | @cindex characters in a certain charset | |
1706 | @findex describe-character-set | |
18430066 | 1707 | There are two commands that can be used to obtain information about |
3af970a0 KH |
1708 | charsets. The command @kbd{M-x list-charset-chars} prompts for a |
1709 | charset name, and displays all the characters in that character set. | |
1710 | The command @kbd{M-x describe-character-set} prompts for a charset | |
18430066 | 1711 | name, and displays information about that charset, including its |
3af970a0 KH |
1712 | internal representation within Emacs. |
1713 | ||
1714 | @findex list-character-sets | |
ae742cb5 CY |
1715 | @kbd{M-x list-character-sets} displays a list of all supported |
1716 | charsets. The list gives the names of charsets and additional | |
05806f43 GM |
1717 | information to identity each charset; see the |
1718 | @url{http://www.itscj.ipsj.or.jp/ISO-IR/, International Register of | |
1719 | Coded Character Sets} for more details. In this list, | |
18430066 CY |
1720 | charsets are divided into two categories: @dfn{normal charsets} are |
1721 | listed first, followed by @dfn{supplementary charsets}. A | |
1722 | supplementary charset is one that is used to define another charset | |
1723 | (as a parent or a subset), or to provide backward-compatibility for | |
1724 | older Emacs versions. | |
1725 | ||
1726 | To find out which charset a character in the buffer belongs to, put | |
1727 | point before it and type @kbd{C-u C-x =} (@pxref{International | |
1728 | Chars}). | |
8cf51b2c | 1729 | |
f4b6ba46 EZ |
1730 | @node Bidirectional Editing |
1731 | @section Bidirectional Editing | |
1732 | @cindex bidirectional editing | |
1733 | @cindex right-to-left text | |
1734 | ||
1735 | Emacs supports editing text written in scripts, such as Arabic and | |
1736 | Hebrew, whose natural ordering of horizontal text for display is from | |
1737 | right to left. However, digits and Latin text embedded in these | |
1738 | scripts are still displayed left to right. It is also not uncommon to | |
05806f43 GM |
1739 | have small portions of text in Arabic or Hebrew embedded in an otherwise |
1740 | Latin document; e.g., as comments and strings in a program source | |
f4b6ba46 EZ |
1741 | file. For these reasons, text that uses these scripts is actually |
1742 | @dfn{bidirectional}: a mixture of runs of left-to-right and | |
1743 | right-to-left characters. | |
1744 | ||
1745 | This section describes the facilities and options provided by Emacs | |
1746 | for editing bidirectional text. | |
1747 | ||
1748 | @cindex logical order | |
1749 | @cindex visual order | |
1750 | Emacs stores right-to-left and bidirectional text in the so-called | |
1751 | @dfn{logical} (or @dfn{reading}) order: the buffer or string position | |
1752 | of the first character you read precedes that of the next character. | |
1753 | Reordering of bidirectional text into the @dfn{visual} order happens | |
1754 | at display time. As result, character positions no longer increase | |
1755 | monotonically with their positions on display. Emacs implements the | |
1756 | Unicode Bidirectional Algorithm described in the Unicode Standard | |
1757 | Annex #9, for reordering of bidirectional text for display. | |
1758 | ||
1759 | @vindex bidi-display-reordering | |
1760 | The buffer-local variable @code{bidi-display-reordering} controls | |
1761 | whether text in the buffer is reordered for display. If its value is | |
1762 | non-@code{nil}, Emacs reorders characters that have right-to-left | |
1763 | directionality when they are displayed. The default value is | |
4cc60b9b | 1764 | @code{t}. |
f4b6ba46 | 1765 | |
84412f2c EZ |
1766 | @cindex base direction of paragraphs |
1767 | @cindex paragraph, base direction | |
f4b6ba46 EZ |
1768 | Each paragraph of bidirectional text can have its own @dfn{base |
1769 | direction}, either right-to-left or left-to-right. (Paragraph | |
05806f43 | 1770 | @c paragraph-separate etc have no influence on this? |
2d3fe5d7 | 1771 | boundaries are empty lines, i.e.@: lines consisting entirely of |
84412f2c EZ |
1772 | whitespace characters.) Text in left-to-right paragraphs begins on |
1773 | the screen at the left margin of the window and is truncated or | |
1774 | continued when it reaches the right margin. By contrast, text in | |
1775 | right-to-left paragraphs is displayed starting at the right margin and | |
1776 | is continued or truncated at the left margin. | |
f4b6ba46 EZ |
1777 | |
1778 | @vindex bidi-paragraph-direction | |
1779 | Emacs determines the base direction of each paragraph dynamically, | |
1780 | based on the text at the beginning of the paragraph. However, | |
1781 | sometimes a buffer may need to force a certain base direction for its | |
1782 | paragraphs. The variable @code{bidi-paragraph-direction}, if | |
1783 | non-@code{nil}, disables the dynamic determination of the base | |
1784 | direction, and instead forces all paragraphs in the buffer to have the | |
1785 | direction specified by its buffer-local value. The value can be either | |
1786 | @code{right-to-left} or @code{left-to-right}. Any other value is | |
1787 | interpreted as @code{nil}. | |
1788 | ||
1789 | @cindex LRM | |
1790 | @cindex RLM | |
1791 | Alternatively, you can control the base direction of a paragraph by | |
1792 | inserting special formatting characters in front of the paragraph. | |
1793 | The special character @code{RIGHT-TO-LEFT MARK}, or @sc{rlm}, forces | |
1794 | the right-to-left direction on the following paragraph, while | |
1795 | @code{LEFT-TO-RIGHT MARK}, or @sc{lrm} forces the left-to-right | |
1796 | direction. (You can use @kbd{C-x 8 RET} to insert these characters.) | |
2d3fe5d7 EZ |
1797 | In a GUI session, the @sc{lrm} and @sc{rlm} characters display as very |
1798 | thin blank characters; on text terminals they display as blanks. | |
f4b6ba46 EZ |
1799 | |
1800 | Because characters are reordered for display, Emacs commands that | |
1801 | operate in the logical order or on stretches of buffer positions may | |
1802 | produce unusual effects. For example, @kbd{C-f} and @kbd{C-b} | |
1803 | commands move point in the logical order, so the cursor will sometimes | |
1804 | jump when point traverses reordered bidirectional text. Similarly, a | |
1805 | highlighted region covering a contiguous range of character positions | |
1806 | may look discontinuous if the region spans reordered text. This is | |
05806f43 | 1807 | normal and similar to the behavior of other programs that support |
f4b6ba46 | 1808 | bidirectional text. |