It's not useful advice. One does not simply add complex script support to some simplistic text drawing codebase. You have to take on dependencies to codebases at least an order of magnitude larger than GuiLite itself (wc harfbuzz/src/*.{h,hh,cc} is 86kloc and doesn't include the Unicode functions). Thus, it's a major architectural decision to support complex scripts at all, and to figure out how to do it.