I have to draw unicode vector fonts in Linux. I mean, using XLib or any other relatively low level library, not Qt, FLTK or GTK or other high level widget toolkit.
Any suggestions?

AFAIK there are some libraries that can to do it, but I never ever used them. Take a look at freetype.org, for example.

Why do you have to do that?

Because of FreshLib. It needs some portable text output libraries. I know how Windows works with fonts, but for Linux I know only how XLib works with fonts and there is no scalable fonts at all. So, if I want to make similar features for Windows and Linux, I have to look for better way to draw text.

is cairo enough low level for you? or xft?

Or do you mean XloadFont, XCreateGC, XDrawText, XFreeFont?

Well, XLib is ok for me. But XLoadFont and other X functions use only bitmap fonts. Or I am wrong? Is it possible to make XLib (actually X server) to use vector fonts...
Now I am reading FreeType documentation. It probably will do the job, but the implementation is really weird - you need to render the string char by char on bitmaps and then to draw the bitmaps to the screen.

Not weird, is the thing that every other library needed to do, just that the implementation is hidden in a more high level DrawString function...

XftFontOpenName -> XftTextExtents16 -> XftDrawCreate -> XftDrawString16

Yea, Xft is probably exactly what I need.
About FreeType you are right of course - it is only rendering engine. Not a library for application programming.