Which one should I use, pango or xft or core x font?

[Huang Ying <hying_debian sina com cn>]

Now, I am writing a gtk+ frontend for lyx. I need something to render
text in lyx. Because the lyx project begins earlier than pango project,
they do i18n things, such as RTL rendering, themselves, and need a very
low level rendering system that simply render a string with given text
and font or fontset. But I just see a very high level rendering api in
pango.
The question is: for project like lyx that does all the i18n work and
line breaks, word breaks things themselves, Which rendering system
should be used? Pango, xft or core x font system?