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1 <?xml version='1.0' encoding="UTF-8"?>
2 <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/utf-8.xml,v 1.21 2005/06/20 17:25:06 neysx Exp $ -->
3 <!DOCTYPE guide SYSTEM "/dtd/guide.dtd">
5 <guide link="/doc/en/utf-8.xml">
6 <title>Using UTF-8 with Gentoo</title>
8 <author title="Author">
9 <mail link="slarti@gentoo.org">Thomas Martin</mail>
10 </author>
11 <author title="Contributor">
12 <mail link="devil@gentoo.org.ua">Alexander Simonov</mail>
13 </author>
14 <author title="Editor">
15 <mail link="fox2mike@gentoo.org">Shyam Mani</mail>
16 </author>
18 <abstract>
19 This guide shows you how to set up and use the UTF-8 Unicode character set with
20 your Gentoo Linux system, after explaining the benefits of Unicode and more
21 specifically UTF-8.
22 </abstract>
24 <!-- The content of this document is licensed under the CC-BY-SA license -->
25 <!-- See http://creativecommons.org/licenses/by-sa/2.5 -->
26 <license />
28 <version>2.3</version>
29 <date>2005-06-20</date>
31 <chapter>
32 <title>Character Encodings</title>
33 <section>
34 <title>What is a Character Encoding?</title>
35 <body>
37 <p>
38 Computers do not understand text themselves. Instead, every character is
39 represented by a number. Traditionally, each set of numbers used to represent
40 alphabets and characters (known as a coding system, encoding or character set)
41 was limited in size due to limitations in computer hardware.
42 </p>
44 </body>
45 </section>
46 <section>
47 <title>The History of Character Encodings</title>
48 <body>
50 <p>
51 The most common (or at least the most widely accepted) character set is
52 <b>ASCII</b> (American Standard Code for Information Interchange). It is widely
53 held that ASCII is the most successful software standard ever. Modern ASCII
54 was standardised in 1986 (ANSI X3.4, RFC 20, ISO/IEC 646:1991, ECMA-6) by the
55 American National Standards Institute.
56 </p>
58 <p>
59 ASCII is strictly seven-bit, meaning that it uses bit patterns representable
60 with seven binary digits, which provides a range of 0 to 127 in decimal. These
61 include 32 non-visible control characters, most between 0 and 31, with the
62 final control character, DEL or delete at 127. Characters 32 to 126 are
63 visible characters: a space, punctuation marks, Latin letters and numbers.
64 </p>
66 <p>
67 The eighth bit in ASCII was originally used as a parity bit for error checking.
68 If this is not desired, it is left as 0. This means that, with ASCII, each
69 character is represented by a single byte.
70 </p>
72 <p>
73 Although ASCII was enough for communication in modern English, in other
74 European languages that include accented characters, things were not so easy.
75 The ISO 8859 standards were developed to meet these needs. They were backwards
76 compatible with ASCII, but instead of leaving the eighth bit blank, they used
77 it to allow another 127 characters in each encoding. ISO 8859's limitations
78 soon came to light, and there are currently 15 variants of the ISO 8859
79 standard (8859-1 through to 8859-15). Outside of the ASCII-compatible byte
80 range of these character sets, there is often conflict between the letters
81 represented by each byte. To complicate interoperability between character
82 encodings further, Windows-1252 is used in some versions of Microsoft Windows
83 instead for Western European languages. This is a superset of ISO 8859-1,
84 however it is different in several ways. These sets do all retain ASCII
85 compatibility, however.
86 </p>
88 <p>
89 The necessary development of completely different single-byte encodings for
90 non-Latin alphabets, such as EUC (Extended Unix Coding) which is used for
91 Japanese and Korean (and to a lesser extent Chinese) created more confusion,
92 while other operating systems still used different character sets for the same
93 languages, for example, Shift-JIS and ISO-2022-JP. Users wishing to view
94 cyrillic glyphs had to choose between KOI8-R for Russian and Bulgarian or
95 KOI8-U for Ukrainian, as well as all the other cyrillic encodings such as the
96 unsuccessful ISO 8859-5, and the common Windows-1251 set. All of these
97 character sets broke most compatibility with ASCII (although KOI8 encodings
98 place cyrillic characters in Latin order, so in case the eighth bit is
99 stripped, text is still decipherable on an ASCII terminal through case-reversed
100 transliteration.)
101 </p>
103 <p>
104 This has led to confusion, and also to an almost total inability for
105 multilingual communication, especially across different alphabets. Enter
106 Unicode.
107 </p>
109 </body>
110 </section>
111 <section>
112 <title>What is Unicode?</title>
113 <body>
115 <p>
116 Unicode throws away the traditional single-byte limit of character sets. It
117 uses 17 "planes" of 65,536 code points to describe a maximum of 1,114,112
118 characters. As the first plane, aka. "Basic Multilingual Plane" or BMP,
119 contains almost everything you will ever use, many have made the wrong
120 assumption that Unicode was a 16-bit character set.
121 </p>
123 <p>
124 Unicode has been mapped in many different ways, but the two most common are
125 <b>UTF</b> (Unicode Transformation Format) and <b>UCS</b> (Universal Character
126 Set). A number after UTF indicates the number of bits in one unit, while the
127 number after UCS indicates the number of bytes. UTF-8 has become the most
128 widespread means for the interchange of Unicode text as a result of its
129 eight-bit clean nature, and it is the subject of this document.
130 </p>
132 </body>
133 </section>
134 <section>
135 <title>UTF-8</title>
136 <body>
138 <p>
139 UTF-8 is a variable-length character encoding, which in this instance means
140 that it uses 1 to 4 bytes per symbol. So, the first UTF-8 byte is used for
141 encoding ASCII, giving the character set full backwards compatibility with
142 ASCII. UTF-8 means that ASCII and Latin characters are interchangeable with
143 little increase in the size of the data, because only the first bit is used.
144 Users of Eastern alphabets such as Japanese, who have been assigned a higher
145 byte range are unhappy, as this results in as much as a 50% redundancy in their
146 data.
147 </p>
149 </body>
150 </section>
151 <section>
152 <title>What UTF-8 Can Do for You</title>
153 <body>
155 <p>
156 UTF-8 allows you to work in a standards-compliant and internationally accepted
157 multilingual environment, with a comparatively low data redundancy. UTF-8 is
158 the preferred way for transmitting non-ASCII characters over the Internet,
159 through Email, IRC or almost any other medium. Despite this, many people regard
160 UTF-8 in online communication as abusive. It is always best to be aware of the
161 attitude towards UTF-8 in a specific channel, mailing list or Usenet group
162 before using <e>non-ASCII</e> UTF-8.
163 </p>
165 </body>
166 </section>
167 </chapter>
169 <chapter>
170 <title>Setting up UTF-8 with Gentoo Linux</title>
171 <section>
172 <title>Finding or Creating UTF-8 Locales</title>
173 <body>
175 <p>
176 Now that you understand the principles behind Unicode, you're ready to start
177 using UTF-8 with your system.
178 </p>
180 <p>
181 The preliminary requirement for UTF-8 is to have a version of glibc installed
182 that has national language support. The recommend means to do this is the
183 <path>/etc/locales.build</path> file in combination with the <c>userlocales</c>
184 USE flag. It is beyond the scope of this document to explain the usage of this
185 file though, luckily, the usage of this file is well documented in the comments
186 within it. It is also explained in the <uri
187 link="/doc/en/guide-localization.xml#doc_chap3_sect3"> Gentoo Localisation
188 Guide</uri>.
189 </p>
191 <p>
192 Next, we'll need to decide whether a UTF-8 locale is already available for our
193 language, or whether we need to create one.
194 </p>
196 <pre caption="Checking for an existing UTF-8 locale">
197 <comment>(Replace "en_GB" with your desired locale setting)</comment>
198 # <i>locale -a | grep 'en_GB'</i>
199 en_GB
200 en_GB.UTF-8
201 </pre>
203 <p>
204 From the output of this command line, we need to take the result with a suffix
205 similar to <c>.UTF-8</c>. If there is no result with a suffix similar to
206 <c>.UTF-8</c>, we need to create a UTF-8 compatible locale.
207 </p>
209 <note>
210 Only execute the following code listing if you do not have a UTF-8 locale
211 available for your language.
212 </note>
214 <pre caption="Creating a UTF-8 locale">
215 <comment>(Replace "en_GB" with your desired locale setting)</comment>
216 # <i>localedef -i en_GB -f UTF-8 en_GB.UTF-8</i>
217 </pre>
219 <p>
220 Another way to include a UTF-8 locale is to add it to the
221 <path>/etc/locales.build</path> file and rebuild <c>glibc</c> with the
222 <c>userlocales</c> USE flag set.
223 </p>
225 <pre caption="Line in /etc/locales.build">
226 en_GB.UTF-8/UTF-8
227 </pre>
229 </body>
230 </section>
231 <section>
232 <title>Setting the Locale</title>
233 <body>
235 <p>
236 There is one environment variable that needs to be set in order to use
237 our new UTF-8 locales: <c>LC_ALL</c> (this variable overrides the <c>LANG</c>
238 setting as well). There are also many different ways to set it; some people
239 prefer to only have a UTF-8 environment for a specific user, in which case
240 they set them in their <path>~/.profile</path> (if you use <c>/bin/sh</c>),
241 <path>~/.bash_profile</path> or <path>~/.bashrc</path> (if you use
242 <c>/bin/bash</c>).
243 </p>
245 <p>
246 Others prefer to set the locale globally. One specific circumstance where
247 the author particularly recommends doing this is when
248 <path>/etc/init.d/xdm</path> is in use, because
249 this init script starts the display manager and desktop before any of the
250 aforementioned shell startup files are sourced, and so before any of the
251 variables are in the environment.
252 </p>
254 <p>
255 Setting the locale globally should be done using
256 <path>/etc/env.d/02locale</path>. The file should look something like the
257 following:
258 </p>
260 <pre caption="Demonstration /etc/env.d/02locale">
261 <comment>(As always, change "en_GB.UTF-8" to your locale)</comment>
262 LC_ALL="en_GB.UTF-8"
263 </pre>
265 <p>
266 Next, the environment must be updated with the change.
267 </p>
269 <pre caption="Updating the environment">
270 # <i>env-update</i>
271 >>> Regenerating /etc/ld.so.cache...
272 * Caching service dependencies ...
273 # <i>source /etc/profile</i>
274 </pre>
276 <p>
277 Now, run <c>locale</c> with no arguments to see if we have the correct
278 variables in our environment:
279 </p>
281 <pre caption="Checking if our new locale is in the environment">
282 # <i>locale</i>
283 LANG=
284 LC_CTYPE="en_GB.UTF-8"
285 LC_NUMERIC="en_GB.UTF-8"
286 LC_TIME="en_GB.UTF-8"
287 LC_COLLATE="en_GB.UTF-8"
290 LC_PAPER="en_GB.UTF-8"
291 LC_NAME="en_GB.UTF-8"
292 LC_ADDRESS="en_GB.UTF-8"
296 LC_ALL=en_GB.UTF-8
297 </pre>
299 <p>
300 That's everything. You are now using UTF-8 locales, and the next hurdle is the
301 configuration of the applications you use from day to day.
302 </p>
304 </body>
305 </section>
306 </chapter>
308 <chapter>
309 <title>Application Support</title>
310 <section>
311 <body>
313 <p>
314 When Unicode first started gaining momentum in the software world, multibyte
315 character sets were not well suited to languages like C, in which many of the
316 day-to-day programs people use are written. Even today, some programs are not
317 able to handle UTF-8 properly. Fortunately, most are!
318 </p>
320 </body>
321 </section>
322 <section>
323 <title>Filenames, NTFS, and FAT</title>
324 <body>
326 <p>
327 There are several NLS options in the Linux kernel configuration menu, but it is
328 important to not become confused! For the most part, the only thing you need to
329 do is to build UTF-8 NLS support into your kernel, and change the default NLS
330 option to utf8.
331 </p>
333 <pre caption="Kernel configuration steps for UTF-8 NLS">
334 File Systems --&gt;
335 Native Language Support --&gt;
336 (utf8) Default NLS Option
337 &lt;*&gt; NLS UTF8
338 <comment>(Also &lt;*&gt; other character sets that are in use in
339 your FAT filesystems or Joilet CD-ROMs.)</comment>
340 </pre>
342 <p>
343 If you plan on mounting NTFS partitions, you may need to specify an <c>nls=</c>
344 option with mount. For more information, see <c>man mount</c>.
345 </p>
347 <p>
348 For changing the encoding of filenames, <c>app-text/convmv</c> can be used.
349 </p>
351 <pre caption="Example usage of convmv">
352 # <i>emerge --ask app-text/convmv</i>
353 # <i>convmv -f current-encoding -t utf-8 filename</i>
354 </pre>
356 <p>
357 For changing the <e>contents</e> of files, use the <c>iconv</c> utility,
358 bundled with <c>glibc</c>:
359 </p>
361 <pre caption="Example usage of iconv">
362 <comment>(substitute iso-8859-1 with the charset you are converting from)</comment>
363 <comment>(Check the output is sane)</comment>
364 # <i>iconv -f iso-8859-1 -t utf-8 filename</i>
365 <comment>(Convert a file, you must create another file)</comment>
366 # <i>iconv -f iso-8859-1 -t utf-8 filename > newfile</i>
367 </pre>
369 <p>
370 <c>app-text/recode</c> can also be used for this purpose.
371 </p>
373 </body>
374 </section>
375 <section>
376 <title>The System Console</title>
377 <body>
379 <impo>
380 You need >=sys-apps/baselayout-1.11.9 for Unicode on the console.
381 </impo>
383 <p>
384 To enable UTF-8 on the console, you should edit <path>/etc/rc.conf</path> and
385 set <c>UNICODE="yes"</c>, and also read the comments in that file -- it is
386 important to have a font that has a good range of characters if you plan on
387 making the most of Unicode.
388 </p>
390 <p>
391 The <c>KEYMAP</c> variable, set in <path>/etc/conf.d/keymaps</path>, should
392 have a Unicode keymap specified. To do this, simply prepend the keymap already
393 specified there with -u.
394 </p>
396 <pre caption="Example /etc/conf.d/keymaps snippet">
397 <comment>(Change "uk" to your local layout)</comment>
398 KEYMAP="-u uk"
399 </pre>
401 </body>
402 </section>
403 <section>
404 <title>Ncurses and Slang</title>
405 <body>
407 <note>
408 Ignore any mention of Slang in this section if you do not have it installed or
409 do not use it.
410 </note>
412 <p>
413 It is wise to add <c>unicode</c> to your global USE flags in
414 <path>/etc/make.conf</path>, and then to remerge <c>sys-libs/ncurses</c> and
415 <c>sys-libs/slang</c> if appropriate:
416 </p>
418 <pre caption="Emerging ncurses and slang">
419 <comment>(We avoid putting these libraries in our world file with --oneshot)</comment>
420 # <i>emerge --oneshot sys-libs/ncurses sys-libs/slang</i>
421 </pre>
423 <p>
424 We also need to rebuild packages that link to these, now the USE changes have
425 been applied. The tool we use (<c>revdep-rebuild</c>) is part of the
426 <c>gentoolkit</c> package.
427 </p>
429 <pre caption="Rebuilding of programs that link to ncurses or slang">
430 # <i>revdep-rebuild --soname libncurses.so.5</i>
431 # <i>revdep-rebuild --soname libslang.so.1</i>
432 </pre>
434 </body>
435 </section>
436 <section>
437 <title>KDE, GNOME and Xfce</title>
438 <body>
440 <p>
441 All of the major desktop environments have full Unicode support, and will
442 require no further setup than what has already been covered in this guide. This
443 is because the underlying graphical toolkits (Qt or GTK+2) are UTF-8 aware.
444 Subsequently, all applications running on top of these toolkits should be
445 UTF-8-aware out of the box.
446 </p>
448 <p>
449 The exceptions to this rule come in Xlib and GTK+1. GTK+1 requires a
450 iso-10646-1 FontSpec in the ~/.gtkrc, for example
451 <c>-misc-fixed-*-*-*-*-*-*-*-*-*-*-iso10646-1</c>. Also, applications using
452 Xlib or Xaw will need to be given a similar FontSpec, otherwise they will not
453 work.
454 </p>
456 <note>
457 If you have a version of the gnome1 control center around, use that instead.
458 Pick any iso10646-1 font from there.
459 </note>
461 <pre caption="Example ~/.gtkrc (for GTK+1) that defines a Unicode compatible font">
462 style "user-font"
463 {
464 fontset="-misc-fixed-*-*-*-*-*-*-*-*-*-*-iso10646-1"
465 }
466 widget_class "*" style "user-font"
467 </pre>
469 <p>
470 If an application has support for both a Qt and GTK+2 GUI, the GTK+2 GUI will
471 generally give better results with Unicode.
472 </p>
474 </body>
475 </section>
476 <section>
477 <title>X11 and Fonts</title>
478 <body>
480 <impo>
481 <c>x11-base/xorg-x11</c> has far better support for Unicode than XFree86
482 and is <e>highly</e> recommended.
483 </impo>
485 <p>
486 TrueType fonts have support for Unicode, and most of the fonts that ship with
487 Xorg have impressive character support, although, obviously, not every single
488 glyph available in Unicode has been created for that font. To build fonts
489 (including the Bitstream Vera set) with support for East Asian letters with X,
490 make sure you have the <c>cjk</c> USE flag set. Many other applications utilise
491 this flag, so it may be worthwhile to add it as a permanent USE flag.
492 </p>
494 <p>
495 Also, several font packages in Portage are Unicode aware.
496 </p>
498 <pre caption="Optional: Install some more Unicode-aware fonts">
499 # <i>emerge terminus-font intlfonts freefonts cronyx-fonts corefonts</i>
500 </pre>
502 </body>
503 </section>
504 <section>
505 <title>Window Managers and Terminal Emulators</title>
506 <body>
508 <p>
509 Window managers not built on GTK or Qt generally have very good Unicode
510 support, as they often use the Xft library for handling fonts. If your window
511 manager does not use Xft for fonts, you can still use the FontSpec mentioned in
512 the previous section as a Unicode font.
513 </p>
515 <p>
516 Terminal emulators that use Xft and support Unicode are harder to come by.
517 Aside from Konsole and gnome-terminal, the best options in Portage are
518 <c>x11-terms/rxvt-unicode</c>, <c>xfce-extra/terminal</c>,
519 <c>gnustep-apps/terminal</c>, <c>x11-terms/mlterm</c>, <c>x11-terms/mrxvt</c> or
520 plain <c>x11-terms/xterm</c> when built with the <c>unicode</c> USE flag and
521 invoked as <c>uxterm</c>. <c>app-misc/screen</c> supports UTF-8 too, when
522 invoked as <c>screen -u</c> or the following is put into the
523 <path>~/.screenrc</path>:
524 </p>
526 <pre caption="~/.screenrc for UTF-8">
527 defutf8 on
528 </pre>
530 </body>
531 </section>
532 <section>
533 <title>Vim, Emacs, Xemacs and Nano</title>
534 <body>
536 <p>
537 Vim, Emacs and Xemacs provide full UTF-8 support, and also have builtin
538 detection of UTF-8 files. For further information in Vim, use <c>:help
539 mbyte.txt</c>.
540 </p>
542 <p>
543 Nano currently does not provide support for UTF-8, although it has been planned
544 for a long time. With luck, this will change in future. At the time of writing,
545 UTF-8 support is in Nano's CVS, and should be included in the next release.
546 </p>
548 </body>
549 </section>
550 <section>
551 <title>Shells</title>
552 <body>
554 <p>
555 Currently, <c>bash</c> provides full Unicode support through the GNU readline
556 library. Z Shell users are in a somewhat worse position -- no parts of the
557 shell have Unicode support, although there is a concerted effort to add
558 multibyte character set support underway at the moment.
559 </p>
561 <p>
562 The C shell, <c>tcsh</c> and <c>ksh</c> do not provide UTF-8 support at all.
563 </p>
565 </body>
566 </section>
567 <section>
568 <title>Irssi</title>
569 <body>
571 <p>
572 Since 0.8.10, Irssi has complete UTF-8 support, although it does require a user
573 to set an option.
574 </p>
576 <pre caption="Enabling UTF-8 in Irssi">
577 /set term_charset UTF-8
578 </pre>
580 <p>
581 For channels where non-ASCII characters are often exchanged in non-UTF-8
582 charsets, the <c>/recode</c> command may be used to convert the characters.
583 Type <c>/help recode</c> for more information.
584 </p>
586 </body>
587 </section>
588 <section>
589 <title>Mutt</title>
590 <body>
592 <p>
593 The Mutt mail user agent has very good Unicode support. To use UTF-8 with Mutt,
594 put the following in your <path>~/.muttrc</path>:
595 </p>
597 <pre caption="~/.muttrc for UTF-8">
598 set send_charset="utf8" <comment>(outgoing character set)</comment>
599 set charset="utf8" <comment>(display character set)</comment>
600 </pre>
602 <note>
603 You may still see '?' in mail you read with Mutt. This is a result of people
604 using a mail client which does not indicate the used charset. You can't do much
605 about this than to ask them to configure their client correctly.
606 </note>
608 <p>
609 Further information is available from the <uri
610 link="http://wiki.mutt.org/index.cgi?MuttFaq/Charset"> Mutt WikiWiki</uri>.
611 </p>
613 </body>
614 </section>
615 <section>
616 <title>Less</title>
617 <body>
619 <p>
620 We all use a lot of <c>more</c> or <c>less</c> along with the <c>|</c> to be
621 able to correctly see the output of a command, like for example
622 <c>dmesg | less</c>. While <c>more</c> only needs the shell to be UTF-8 aware,
623 <c>less</c> needs an environment variable set, <c>LESSCHARSET</c> to ensure
624 that unicode characters are rendered correctly. This can be set in
625 <path>/etc/profile</path> or <path>~/.bash_profile</path>. Fire up the editor
626 of your choice and the add the following line to one of the files mentioned
627 above.
628 </p>
630 <pre caption="Setting up the Environment variable for less">
632 </pre>
634 </body>
635 </section>
636 <section>
637 <title>Man</title>
638 <body>
640 <p>
641 Man pages are an integral part of any Linux machine. To ensure that any
642 unicode in your man pages render correctly, edit <path>/etc/man.conf</path>
643 and replace a line as shown below.
644 </p>
646 <pre caption="man.conf changes for Unicode support">
647 <comment>(This is the old line)</comment>
648 NROFF /usr/bin/nroff -Tascii -c -mandoc
649 <comment>(Replace the one above with this)</comment>
650 NROFF /usr/bin/nroff -mandoc -c
651 </pre>
653 </body>
654 </section>
655 <section>
656 <title>elinks and links</title>
657 <body>
659 <p>
660 These are commonly used text-based browsers, and we shall see how we can enable
661 UTF-8 support on them. On <c>elinks</c> and <c>links</c>, there are two ways to
662 go about this, one using the Setup option from within the browser or editing the
663 config file. To set the option through the browser, open a site with
664 <c>elinks</c> or <c>links</c> and then <c>Alt+S</c> to enter the Setup Menu then
665 select Terminal options, or press <c>T</c>. Scroll down and select the last
666 option <c>UTF-8 I/O</c> by pressing Enter. Then Save and exit the menu. On
667 <c>links</c> you may have to do a repeat <c>Alt+S</c> and then press <c>S</c> to
668 save. The config file option, is shown below.
669 </p>
671 <pre caption="Enabling UTF-8 for elinks/links">
672 <comment>(For elinks, edit /etc/elinks/elinks.conf or ~/.elinks/elinks.conf and
673 add the following line)</comment>
674 set terminal.linux.utf_8_io = 1
676 <comment>(For links, edit ~/.links/links.cfg and add the following
677 line)</comment>
678 terminal "xterm" 0 1 0 us-ascii utf-8
679 </pre>
681 </body>
682 </section>
683 <section>
684 <title>Testing it all out</title>
685 <body>
687 <p>
688 There are numerous UTF-8 test websites around. <c>net-www/w3m</c>,
689 <c>net-www/links</c>, <c>net-www/elinks</c>, <c>net-www/lynx</c> and all
690 Mozilla based browsers (including Firefox) support UTF-8. Konqueror and Opera
691 have full UTF-8 support too.
692 </p>
694 <p>
695 When using one of the text-only web browsers, make absolutely sure you are
696 using a Unicode-aware terminal.
697 </p>
699 <p>
700 If you see certain characters displayed as boxes with letters or numbers
701 inside, this means that your font does not have a character for the symbol or
702 glyph that the UTF-8 wants. Instead, it displays a box with the hex code of the
703 UTF-8 symbol.
704 </p>
706 <ul>
707 <li>
708 <uri link="http://www.w3.org/2001/06/utf-8-test/UTF-8-demo.html">A W3C
709 UTF-8 Test Page</uri>
710 </li>
711 <li>
712 <uri link="http://titus.uni-frankfurt.de/indexe.htm?/unicode/unitest.htm">
713 A UTF-8 test page provided by the University of Frankfurt</uri>
714 </li>
715 </ul>
717 </body>
718 </section>
719 <section>
720 <title>Input Methods</title>
721 <body>
723 <p>
724 <e>Dead keys</e> may be used to input characters in X that are not included on
725 your keyboard. These work by pressing your right Alt key (or in some countries,
726 AltGr) and an optional key from the non-alphabetical section of the keyboard to
727 the left of the return key at once, releasing them, and then pressing a letter.
728 The dead key should modify it. Input can be further modified by using the Shift
729 key at the same time as pressing the AltGr and modifier.
730 </p>
732 <p>
733 To enable dead keys in X, you need a layout that supports it. Most European
734 layouts already have dead keys with the default variant. However, this is not
735 true of North American layouts. Although there is a degree of inconsistency
736 between layouts, the easiest solution seems to be to use a layout in the form
737 "en_US" rather than "us", for example. The layout is set in
738 <path>/etc/X11/xorg.conf</path> like so:
739 </p>
741 <pre caption="/etc/X11/xorg.conf snippet">
742 Section "InputDevice"
743 Identifier "Keyboard0"
744 Driver "kbd"
745 Option "XkbLayout" "en_US" <comment># Rather than just "us"</comment>
746 <comment>(Other Xkb options here)</comment>
747 EndSection
748 </pre>
750 <note>
751 The preceding change only needs to be applied if you are using a North American
752 layout, or another layout where dead keys do not seem to be working. European
753 users should have working dead keys as is.
754 </note>
756 <p>
757 This change will come into effect when your X server is restarted. To apply the
758 change now, use the <c>setxkbmap</c> tool, for example, <c>setxkbmap en_US</c>.
759 </p>
761 <p>
762 It is probably easiest to describe dead keys with examples. Although the
763 results are locale dependent, the concepts should remain the same regardless of
764 locale. The examples contain UTF-8, so to view them you need to either tell
765 your browser to view the page as UTF-8, or have a UTF-8 locale already
766 configured.
767 </p>
769 <p>
770 When I press AltGr and [ at once, release them, and then press a, 'ä' is
771 produced. When I press AltGr and [ at once, and then press e, 'ë' is produced.
772 When I press AltGr and ; at once, 'á' is produced, and when I press AltGr and ;
773 at once, release them, and then press e, 'é' is produced.
774 </p>
776 <p>
777 By pressing AltGr, Shift and [ at once, releasing them, and then pressing a, a
778 Scandinavian 'å' is produced. Similarly, when I press AltGr, Shift and [ at
779 once, release <e>only</e> the [, and then press it again, '˚' is produced.
780 Although it looks like one, this (U+02DA) is not the same as a degree symbol
781 (U+00B0). This works for other accents produced by dead keys — AltGr and [,
782 releasing only the [, then pressing it again makes '¨'.
783 </p>
785 <p>
786 AltGr can be used with alphabetical keys alone. For example, AltGr and m, a
787 Greek lower-case letter mu is produced: 'µ'. AltGr and s produce a
788 scharfes s or esszet: 'ß'. As many European users would expect (because
789 it is marked on their keyboard), AltGr and 4 produces a Euro sign, '€'.
790 </p>
792 </body>
793 </section>
794 <section>
795 <title>Resources</title>
796 <body>
798 <ul>
799 <li>
800 <uri link="http://www.wikipedia.com/wiki/Unicode">The Wikipedia entry for
801 Unicode</uri>
802 </li>
803 <li>
804 <uri link="http://www.wikipedia.com/wiki/UTF-8">The Wikipedia entry for
805 UTF-8</uri>
806 </li>
807 <li><uri link="http://www.unicode.org">Unicode.org</uri></li>
808 <li><uri link="http://www.utf-8.com">UTF-8.com</uri></li>
809 <li><uri link="http://www.ietf.org/rfc/rfc3629.txt">RFC 3629</uri></li>
810 <li><uri link="http://www.ietf.org/rfc/rfc2277.txt">RFC 2277</uri></li>
811 <li>
812 <uri
813 link="http://www.tbray.org/ongoing/When/200x/2003/04/26/UTF">Characters vs.
814 Bytes</uri>
815 </li>
816 </ul>
818 </body>
819 </section>
820 </chapter>
821 </guide>

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