200 lines
7.8 KiB
Plaintext
200 lines
7.8 KiB
Plaintext
-- $XFree86: xc/programs/xterm/README.i18n,v 1.1 2003/11/13 01:16:37 dickey Exp $
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Using xterm in your language
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============================
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Since XFree86 version 4.0, the internationalization (i18n) feature of
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xterm is gradually improved. Xterm is being improved even now. You
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need only set the standard locale environment variables such as
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LC_CTYPE, LC_ALL, LC_CTYPE, or LANG. Once the locale is set up you can
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use xterm in your favorite character encoding.
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This document explains how the i18n feature is realized and how to
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configure xterm for your character encoding.
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Refer to locale(7) for details of the locale mechanism.
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Basic i18n-related settings and resources
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=========================================
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These settings apply to XFree86 xterm patch #181, and the program luit
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which is distributed with XFree86 4.4
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1. Usage of "locale mode"
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On startup, xterm must be in "locale mode" to make it follow the
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current locale. You can invoke xterm in locale mode in these ways:
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a. Set "vt100.locale" resource "true". This resource was
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introduced since XFree86 4.3. The default value of the "locale"
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resource is "medium", which means xterm follows the locale only
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in Chinese, Japanese, Korean, or Thai locales. For example,
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XTerm*locale: true
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in your ~/.Xresources file.
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or
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b. Invoke xterm with the "-lc" option.
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2. Converter program "luit"
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The "luit" must be available in the standard XFree86 binary
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directory. It is usually available because it is part of the
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XFree86 distribution. The standard binary directory may differ from
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system to system. /usr/X11R6/bin/luit is an example.
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"luit" is used to convert between Unicode and the character encoding
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for your locale. When built for XFree86, xterm includes logic for
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invoking luit.
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3. Locale setting
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Finally, you will need to configure your locale. We expect that you
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have already configured your locale for other software. For example,
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LANG=de_DE@euro
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export LANG
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in your ~/.xsession file. There are many ways to configure locale.
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For example, your display manager may have a mechanism to invoke a
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window manager in your favorite locale, or you may have system-wide
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locale setting in /etc/environment. You may also have set the
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LC_ALL variable instead of the LANG variable.
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How to use xterm in different locale temporarily
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================================================
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You may sometimes need to invoke xterm in a different character encoding
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than your current locale. For example, use xterm to login remote systems
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in different locale.
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Do this by invoking xterm in the target locale. For example,
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$ LANG=ru_RU.KOI8-R xterm &
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Previously, font setting has been used in such cases.
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$ xterm -fn -misc-fixed-medium-r-normal--10-*-*-*-*-*-koi8-r &
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This does not work well in conjunction with the "locale" resource,
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because luit and xterm combined rely upon Unicode fonts.
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How to set fonts for UTF-8/locale modes
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=======================================
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Since xterm patch #181, xterm can automatically use Unicode fonts in
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UTF-8 mode and locale mode. Few of you will need to modify the default
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setting to display your language. In particular, Unicode fonts in
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combination with locale mode will satisfy the needs of not only
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ISO-8859-1 users but also East Asian and other non-ISO-8859-1 users.
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If you want to set your favorite Unicode font for UTF-8 and locale
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modes, you should add a line such as the following in your ~/.Xresources
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file:
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XTerm*VT100.utf8Fonts.font: \
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-misc-fixed-medium-r-semicondensed--13-120-75-75-c-60-iso10646-1
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The leading "XTerm*" pattern is more specific than the system's
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app-defaults file, therefore it overrides the corresponding line
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beginning with
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*VT100.utf8Fonts.font:
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Here is an additional note. If you want to display East Asian
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doublewidth characters (CJK Ideogram, Hiragana, Katakana, Hangul,
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and so on), we recommend using
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-misc-fixed-medium-r-semicondensed--13-*-*-*-*-*-iso10646-1
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or
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-misc-fixed-medium-r-normal--18-*-*-*-*-*-iso10646-1
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because these two fonts have corresponding doublewidth fonts. These
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fonts are used as default font and default "Large" font, respectively.
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The internals of xterm i18n
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===========================
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You do not need to read this section if you only want to configure your
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xterm. Here we describe how xterm is implemented to support i18n.
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The original version of xterm does not support locale or character
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encoding. Its I/O stream is interpreted as a mere 8-bit index for a
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font.
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Beginning with XFree86 4.0, xterm supported UTF-8. It was implemented
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as a separate UTF-8 mode from the conventional 8-bit mode. Character
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encodings had no effect on the 8-bit mode. The UTF-8 mode has been
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extended to support doublewidth characters (for East Asian characters)
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and combining characters (such as accents for Latin alphabets and Thai
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vowels/tone marks).
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Doublewidth characters are characters that occupy two continuing
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columns on the terminal. Xterm uses separate fonts for normal
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(singlewidth) characters and doublewidth characters. Though xterm has
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configuration items for specifying doublewidth fonts, it will
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automatically search for a font with exactly twice as wide and the same
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name as the specified normal font.
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The default behavior of xterm was modified to use this UTF-8 mode in
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UTF-8 locales. A command line option of "-u8" and a resource of "utf8"
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were introduced to choose UTF-8 mode.
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"luit" was introduced to XFree86 at version 4.2. It converts between
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UTF-8 and other encodings. When luit is invoked in a UTF-8 terminal,
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the terminal acts as if it is really running in the other encoding.
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Since XFree86 version 4.3, xterm provides a new mode to invoke luit
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automatically to support various encodings. The mode where xterm
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invokes luit is called "locale mode". It is the third mode following
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conventional 8-bit mode and UTF-8 mode. In the locale mode, xterm is
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aware of the current locale and character encoding. Since locale mode
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uses luit, it is based on the UTF-8 mode. That is, xterm works in UTF-8
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mode and luit works as a converter between UTF-8 and the character
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encoding for your locale. This is why the locale mode always needs
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Unicode fonts. The default behavior of xterm is modified so that the
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"locale mode" will be adopted in Chinese (Big5 and GB2312), Japanese
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(EUC-JP), Korean (EUC-KR), and Thai (ISO-8859-11, as known as TIS-620)
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locales. Locale mode is chosen for these character encodings because
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these encodings are not supported by conventional 8-bit mode even by
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changing fonts (ISO-8859-11 needs combining characters and others need
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doublewidth characters).
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To control the locale mode, command line options of "-lc" and "-en" and
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a resource of "locale" were introduced. The command line option of
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"-u8" and a resource of "utf8" were made obsolete by them, though
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retained for compatibility.
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Since XFree86 version 4.4, xterm can have two sets of default fonts,
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one for conventional 8-bit mode and another for UTF-8 and locale modes,
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by introducing the "utf8Fonts" subresource.
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Future TODO Items
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=================
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We anticipate that xterm's locale mode will be used increasingly in the
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future. Since the UTF-8 and locale modes use more resources than
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conventional 8-bit mode (because it needs larger fonts and another
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process "luit"), faster hardware may be needed to gain complete
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acceptance by users. However, the locale mechanism allows users
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to manipulate data in a standard form. Its usefulness compensates
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in part for reduced performance.
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Xterm supports antialiased fonts ("-fa" and "-fs" command line options).
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Currently UTF-8 nor locale modes do not work with antialiased fonts.
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Xterm does not support bi-directional or RTL languages such as Hebrew
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and Arab. A simple standard how terminal should behave for these
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languages is needed.
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Xterm does not support Unicode characters above U+10000.
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