The library uses FreeType for glyph pre-rendering and basic glyph
geometry and HarfBuzz for text layouting (i.e. ligatures, kerning, ...).
Currently all used glyphs must be prerendered into texture atlas, other
glyphs are simply not rendered (although the layouting code handles them
like if they are there).
Text rendering supports UTF-8, although glyph pre-rendering is currently
ASCII only, as I couldn't find any working implementation of Unicode
STL function in recent GCC versions. Will be fixed later.