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Input method

From Wikipedia:Input method:

An input method (or input method editor, commonly abbreviated as IME) is an operating system component or program that enables users to generate characters not natively available on their input devices by using sequences of characters (or mouse operations) that are natively available on their input devices. Using an input method is usually necessary for languages that have more graphemes than there are keys on the keyboard.

In very simplified terms, an IME is an application that takes Latin characters that you type on your keyboard and outputs them on your screen as non-Latin characters. The IME does this through a process called romanization, which is the transliteration of non-Latin language sounds into the Latin equivalents that most closely resemble them.

ヒント: If parts of the following text show on your screen as gibberish, please make sure you have installed a Japanese font on your system. See Localization/Japanese#Fonts for a non-exhaustive list of available fonts.

As an example, the Japanese written word for sake is 酒, also written as さけ, and romanized as "sake". The IME's role is to act as a middleman between the keyboard and the screen, so that when we type "sake" it will intercept the keyboard's input, replace "sake" with 酒 or さけ (as chosen by us) and put the native characters on the screen instead of what we actually typed.

ノート: For the sake of simplicity only the keyboard has been mentioned in the example, but an IME can actually produce native characters via a number of ways and input devices, like e.g. drawing characters by hand using a mouse or a Wacom tablet.

Input method framework

Most IMEs work as part of an input method framework (commonly abbreviated as IMF), which is an application that allows the user to easily switch between different IMEs. In fact, this is the exact same application that many of us unknowingly use everyday to switch between the different Latin keyboard layouts (e.g. English, Spanish, German, etc).

The most common, most diverse and most well supported input method frameworks are Fcitx (mostly used in KDE and other Qt-based environments) and IBus (mostly used in GNOME and other GTK-based environments). Less common ones include Uim, Scim, Hime, Gcin and Nimf. Additionally, Emacs is a very popular text editor that contains its own internal IMF.

See also Wikipedia:List of input methods for Unix platforms.

List of available input method editors

The following table shows the IMEs for the various languages currently available in the Arch repositories and the AUR.

ノート: In some cases, multiple AUR packages exist for the same IME. A good example of this is Mozc: as the currently most popular Japanese IME, multiple packagers have attempted over the years to create the "perfect" Mozc package. In the table below, a single Mozc package has been included for each IMF; but this does not imply that these are the only Mozc packages a user should ever consider to install.

ヒント: Fcitx5 is the successor of Fcitx. It is still fairly new, so some IMEs lack support for it for the time being (though this is something that should be quickly rectified in the coming weeks or months); still, if it covers your needs then you should probably prefer it over the previous version.

	Fcitx	Fcitx5	IBus	Uim	Emacs	Scim	Hime	Gcin	Nimf
Chinese
Rime	fcitx-rime	fcitx5-rime	ibus-rime	—	—	—	—	—	built-in
Sogou	fcitx-sogoupinyinAUR	—	—	—	—	—	—	—	—
Baidu	fcitx-baidupinyinAUR	—	—	—	—	—	—	—
Chewing	fcitx-chewing	fcitx5-chewing	ibus-chewing	—	—	scim-chewing	—	—	built-in
Wubixing	built-in	built-in	ibus-table	built-in	—	scim-tablesAUR	—	—	—
Libpinyin	fcitx-libpinyin	—	ibus-libpinyin	—	—	—	—	—	—
Google Pinyin	fcitx-googlepinyin	—	ibus-googlepinyinAUR	—	—	—	—	—	—
SunPinyin	fcitx-sunpinyin	—	ibus-sunpinyin	—	—	—	—	—	—
Japanese
Mozc	fcitx-mozc-utAUR	fcitx5-mozc	ibus-mozc-utAUR	uim-mozc-ut2AUR	emacs-mozc-utAUR	—	—	—	—
Anthy	fcitx-anthy	fcitx5-anthy	ibus-anthy	built-in	—	—	built-in	built-in	built-in
SKK	fcitx-skk	fcitx5-skk	ibus-skk	built-in	—	—	—	—	—
KKC	fcitx-kkc	fcitx5-kkc	ibus-kkc	—	—	—	—	—	—
Korean
Libhangul	fcitx-hangul	fcitx5-hangul	ibus-hangul	built-in	—	scim-hangulAUR	—	—	built-in
Vietnamese
UniKey	fcitx-unikey	fcitx5-unikey	ibus-unikey	—	—	—	—	—	—
Bamboo	—	—	ibus-bambooAUR	—	—	—	—	—	—
Indic
m17n	fcitx-m17n	fcitx5-m17n	ibus-m17n	—	—	scim-m17nAUR	—	—	—
Varnam	—	—	libvarnam-ibus-gitAUR	—	—	—	—	—	—
Helakuru	—	—	ibus-helakuruAUR	—	—	—	—	—	—

Configuration

In order for your desktop environment to properly register an installed input method framework as available and assign it to handle user input, a set of environment variables must be configured accordingly. A good place to do so is /etc/environment.

ノート: If these variables are not set, both GTK and Qt will attempt to read the system's locale settings to determine which IMF they should use, but this process relies on guesswork and can be very error-prone. For a properly working system, you should always opt to explicitly set these variables yourself.

ヒント: If for some reason you wish to completely disable your desktop environment from handling input via an IMF (NOT recommended in GNOME due to tight integration with IBus), then you may either leave these variables unset or, in the case of GTK and Qt, you can replace their values with: GTK_IM_MODULE=gtk-im-context-simple and QT_IM_MODULE=simple.

Fcitx

See also Fcitx for more information.

GTK_IM_MODULE=fcitx
QT_IM_MODULE=fcitx
XMODIFIERS=@im=fcitx

IBus

See also IBus for more information.

GTK_IM_MODULE=ibus
QT_IM_MODULE=ibus
XMODIFIERS=@im=ibus

Uim

See also Uim for more information.

GTK_IM_MODULE=uim
QT_IM_MODULE=uim
XMODIFIERS=@im=uim

Emacs

According to this Fcitx wiki entry, "in some case, including emacs and java. Emacs has a historical bug, that under en_US.UTF-8 or similar locale, it will never use XIM (Though emacs is a gtk app, it use XIM). The only way to walkaround this is to use LC_CTYPE to fix this."

Scim

See also Scim for more information.

GTK_IM_MODULE=scim
QT_IM_MODULE=scim
XMODIFIERS=@im=scim

See also

• Fedora:I18N/InputMethods
• Gentoo:Input methods
• Wikipedia:Input method