what is 'fcitx XFT版'?

[uzycx]

Hi,
what is 'fcitx XFT版'?
if
./configure –prefix=<安装目录> --disable-xft
what'll be the differences?

[uzycx]

Xft, the X FreeType interface library, is a free computer program library written by Keith Packard. As of version 2.1, it is licensed under a quasi-BSD license.

It is designed to allow the FreeType rasterizer to be used with the X Rendering Extension; it is generally employed to use FreeType's antialiased fonts with the X Window System. Xft also depends on fontconfig for access to the system fonts.

Do ubuntu9.10 have that library?How can I know that?