I now have migrated LuaTex 1.10 and also 1.18 (with HarfBuzz) to my BUSY build system assuming that at least with the latter I could get rid of any TexLive dependency (especially the luaotfloader). I even implemented my own OTF loader in C (with Lua bindings for additional HarfBuzz functions) and added it to the LuaHBTex executable. The font loading works, and also the layout in principle, but the result is ugly. So I came to the conclusion that there is still a lot of Lua and TeX code required to get the famous LuaTeX typographic quality, and there is little chance to get it with only the LuaHBTeX engine itself.
What is your experience? Have you managed to use the LuaTeX engine stand-alone with decent results, or do you use additional TeX and Lua scripts?
Why such an old version? The latest version is 1.24.0, which should have lots of new features and fixes relative to v1.10. And if you're starting from scratch and not planning on using any of the TeX stuff, I'd really recommend using LuaMetaTeX since it cleans lots of stuff up, and doesn't use autotools at all.
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 idea was to use the version which was officially declared as "complete" and also the last before the development of the HB integration started.
HB is implemented as just another library, and it's pretty easy to exclude with the build script (ConTeXt does this).
> The problem seems rather to be, that luatex-fonts-merged.lua is not really usable outside of the ConTeXt or TexLive tree
So option 1 is to base things off of `luatex-plain` [0], which I believe is fully self-contained, but mostly undocumented. Option 2 is to base things off of luaotfload, which only depends on lualibs and luatexbase.
> There was e.g. the assumption that the global utf variable pointed to unicode.utf8 (at least that's what I assume).
It needs to be in the environment where you load the file, but that doesn't necessarily need to be the global environment. This is the fourth argument of the Lua "load" function.
> First the two words were apart half a page
I would randomly guess that your issue is that \parfillskip is initialized to 0pt from iniTeX, so the problem might go away if you typeset the text in an \hbox or node.hpack, or if you set \parfillskip/tex.parfillskip to "0pt plus 1fil".
> I like that it is still in C99 and C++ <= 11
I think that the latest versions of LuaTeX still only use C99 features, but they're also C23 compatible. The only thing that should use newer versions of C++ is HB I think.
> I also had an intense look at LuaMetaTeX but don't like the architectural decision to do even more stuff in Lua.
Fair enough :). The main thing that was moved from C to Lua was the PDF backend, because it's seriously unfun to write a PDF parser/writer in C.
Just wanted to say that I skipped LuaTex 1.10 because not even a bare Hello World worked. So I switched to LuaTex 1.18 including the HarfBuzz library. I even implemented my own OTF loader in C (with Lua bindings for additional required HarfBuzz functions) and added it to the LuaHBTex executable. The font loading works, and also the layout in principle, but the result is ugly. So I came to the conclusion that there is still a lot of Lua and TeX code required to get the famous LuaTeX typographic quality, and there is little chance to get it with only the LuaHBTeX engine itself.
For that reason I now left LuaTeX altogether and re-start with my own implementation of the Knuth algorithms based on HarfBuzz, FreeType, MicroTeX and Cairo. For the time being I limit the typesetting to western languages (LTR-only), which I hope allows me to get a working MVP version in a few months.
I have that on the radar indeed, but as far as I understand it still depends on plain.tex which again depends on tons of 1986 stuff (like old fonts) which I want to avoid. But due to my present experiments with the 40kLOC Lua machinery I'm scared of integrating this thing and would rather opt for avoiding it.
> that \parfillskip is initialized to 0pt from iniTeX
I did a lot of instrumented runs where values were printed and looked "unsuspicious". My best guess at the moment is that the Lua based machinery has an issue with the space in DejaVuSans.ttf, but that's just an assumption. I already stopped this path due to its apparent fragility and my reluctance of the architectural approach (I initially thought that everything required to do high-quality typesetting was already part of the luatex executable, but only realized this fragile dependency when doing larger test cases on my downsized engine version).
The dependencies might have a minimum C++ version, but I'd be pretty surprised if the core LuaTeX files couldn't be compiled with C99/C11. The recent C23 commits are just about adding support for compiling in C23 mode, so the main change is no longer using the implicit "everything is an int" function prototypes.
Thanks. The HB C++17 dependency is already a show-stopper for me. I want to be able to build everything on GCC 4.8, or even better 4.7. I also did some research what actually changed since 1.18.0 and didn't find features my project would depend on.
The downloadable ZIP is ready to run and does not need any additional libraries. (That said, I include some helpers, for example for https access. )