Pango is a C API for Unicode-based text layout and rendering.
Pango allows advanced layout of text using C, C++, Perl, and a number of other languages. It is primarily used with cairo (pangocairo), although it can be used with other backends, such as Win32 API, Xft, and others.
The website is http://pango.org.
Documentation can be found at https://developer.gnome.org/pango/unstable/.