The idea was to use the version which was officially declared as "complete" and also the last before the development of the HB integration started. My focus is on stability. The idea was to go with a minimal system and even integrate luatex-fonts-merged.lua as part of the binary, so there are no external dependencies.
The problem seems rather to be, that luatex-fonts-merged.lua is not really usable outside of the ConTeXt or TexLive tree, because it makes a lot of assumptions which are not met in my environment, and finding such dependencies in ~40kLOC of a dynamic language is nearly impossible. There was e.g. the assumption that the global utf variable pointed to unicode.utf8 (at least that's what I assume). So I had to set that before loading luatex-fonts-merged.lua. I assume there are many more such "tricks". After two days of experimenting, not even a "Hello World" is properly typeset. First the two words were apart half a page, and now they are set on two lines and I don't find out why.
These experiments brought me to the conclusion, that implementing so fundamental and complex logic in Lua is a very bad idea. So I'm currently evaluating LuaHBTex in the stable version 1.18.0. I like that it is still in C99 and C++ <= 11 (at least that's what I understood so far). I also had an intense look at LuaMetaTeX but don't like the architectural decision to do even more stuff in Lua. I'm using and integrating this language since 25 years and think it is good for a bit of glue code (max. 1-2 kLOC), but larger code bases pass the limit of practicability of a dynamic language. I even implemented a few statically typed languages which generate Lua source and bytecode to reuse the technology without this disadvantage.
The problem seems rather to be, that luatex-fonts-merged.lua is not really usable outside of the ConTeXt or TexLive tree, because it makes a lot of assumptions which are not met in my environment, and finding such dependencies in ~40kLOC of a dynamic language is nearly impossible. There was e.g. the assumption that the global utf variable pointed to unicode.utf8 (at least that's what I assume). So I had to set that before loading luatex-fonts-merged.lua. I assume there are many more such "tricks". After two days of experimenting, not even a "Hello World" is properly typeset. First the two words were apart half a page, and now they are set on two lines and I don't find out why.
These experiments brought me to the conclusion, that implementing so fundamental and complex logic in Lua is a very bad idea. So I'm currently evaluating LuaHBTex in the stable version 1.18.0. I like that it is still in C99 and C++ <= 11 (at least that's what I understood so far). I also had an intense look at LuaMetaTeX but don't like the architectural decision to do even more stuff in Lua. I'm using and integrating this language since 25 years and think it is good for a bit of glue code (max. 1-2 kLOC), but larger code bases pass the limit of practicability of a dynamic language. I even implemented a few statically typed languages which generate Lua source and bytecode to reuse the technology without this disadvantage.