Arch Linux

Gnome has built-in support for input methods with ibus, these input methods needed for entering characters in asian languages as Mandarin.
To be able to take advantage of this feature one need to install ibus and the wanted input method engine (e.g. ibus-libpinyin, ibus-googlepinyin).

The input method engines depends on ibus package so no need to add ibus to optional depends.

Currently the available ibus input engines at the official repositories (no counting AUR):

ibus-anthy Japanese input method Anthy IMEngine for IBus Framework
ibus-chewing Chinese Chewing Engine for IBus Framework
ibus-googlepinyin IBus Wrapper for libgooglepinyin
ibus-hangul Korean input engine for IBus
ibus-kkc libkkc (Japanese Kana Kanji input method) engine for ibus
ibus-libpinyin Intelligent Pinyin engine based on libpinyin for IBus
ibus-m17n M17N engine for IBus
ibus-pinyin Pinyin (Chinese) input method for the IBus framework
ibus-qt IBus qt library and IBus qt input method plugin
ibus-rime Rime input method engine for ibus
ibus-skk Japanese input method SKK engine for IBus
ibus-sunpinyin IBus Wrapper for sunpinyin
ibus-table IM Engine framework for table-based input methods, such as ZhengMa, WuBi, ErBi, CangJie and so on
ibus-table-chinese Some table-based input method of tables engines for IBus
ibus-table-extraphrase The extra phrases of tables engines for IBus
ibus-unikey IBus module for Vietnamese Keyboard

I only tried ibus-libpinyin and ibus-googlepinyin which works great.

It's a long list, maybe better just to add ibus as optional depends with the description "ibus: for input method engines for Asian languages" and separately I will ask for the ibus package maintainer to add the input engines list above as optdepends.