On Tue, 11 Nov 2025 02:14:11 +0800, Ihor Radchenko wrote: > > Huang Jing <[email protected]> writes: > > >> How does it play with babel and polyglossia? > > > > It's not mentioned in the documents of xeCJK and luatex-ja, however I > > believe they do work together. From my limited testing, when loaded as > > packages, xeCJK and luatex-ja does no localization, thus relying on > > babel. However they will override the font settings by babel, which is > > totally acceptable. > > That actually depends. If the user of Org mode customizes fonts, it may > be a surprise when xeCJK/luatex-ja override the fonts. So, we might only > load these packages conditionally, when no font of explicitly selected. > Or maybe we simply put font settings _after_ xeCJK/luatex-ja is loaded.
We don't need to configure fonts for babel, and it only provides localization. xeCJK provides the \setCJK...font control sequence while luatex-ja provides \set...jfont, so we can use them for font configuration. > > 1. Under XeTeX and LuaTeX, xeCJK and luatex-ja will setup font support > > according to the platform (operating system) detected, and activate > > font, kinsoku, line-breaking support. They will not change the > > \baselineskip. > > > > 2. When ctex is being used, it will also configure correct > > \baselineskip (from the default 12pt to 16pt). It will also try to > > support pdfTeX. > > > > 3. Localization support provided by babel. > > > > So it's actually necessary to load babel when not using the document > > classes provided. It's safer to load babel first though. > > Note that babel also provides rules for typography. So, > xeCJK/lualatex-ja do step onto babel a bit. But, as you said, they > basically add missing typographical rules, so it might be reasonable. > > > Neither xeCJK nor luatex-ja is necessary for font configuration when > > babel is being used. Since babel only support Chinese and Japanese on > > LuaTeX and XeTeX with OTF support, the CJK font can be loaded the same > > way as latin fonts. See > > https://latex3.github.io/babel/guides/locale-chinese.html. > > > However babel is hardly ever used in Chinese or Japanese community, > > since their support is so, primitive. For example it does not add > > xkanjiskip between latin and CJK characters. Here's a relevant > > discussion on relying on babel for localization in the ctex community: > > https://github.com/CTeX-org/ctex-kit/issues/626#issuecomment-1147428749. > > My understanding from this is that we (1) always want to load xeCJK for > Chinese documents (what about luatex?); (2) always want to load > luatex-ja for Japanese (what about xetex?). We can configure luatex-ja for Chinese documents on LuaTeX, by changing the \parindent to 2\zw, change the default font (HaranoAji) to FandolSong, and change the JFM (Japanese font metric). Vice versa. > >> > For the \setCJK...font declaration, I can provide a wrapper in LaTeX > >> > if needed, compatible with XeTeX, LuaTeX and probabily other > >> > engines. You will need xeCJK for this control sequence while other > >> > engines will not compile because it is provided by the xeCJK package. > >> > Under other engines, there are different control sequences used for > >> > font configuration (i.e., under LuaTeX thus luatex-ja, you use > >> > \set...jfont). > > Could you expand on "other engines will not compile"? How does it fit to > "compatible with XeTeX, LuaTeX, and probably other engines"? > (Note that inclusion or not inclusion of xeCJK can be controlled by us - > we know which compiler is used for export during export and can > conditionally include it on Elisp level) What I mean by ``other engines will not compile'' is when directly using \setCJK...font in the exported document, even though ctex works across different TeX engines, since it's xeCJK providing these commands, it will not compile under, i.e., LuaTeX. But as we don't use ctex now, we just need to call \setCJK...font for XeTeX after loading xeCJK, and \set...jfont for luatex-ja under LuaTeX. Since we can access the target engine through org-latex-compilers. > >> Could you provide more details about these commands? > > > > Equivalents to \setCJK...font provided by luatex-ja are documented in > > English here: > > https://mirrors.ctan.org/macros/luatex/generic/luatexja/doc/luatexja-en.pdf > > Search for ``Tabel 1: Commands of luatexja-fontspec'' in that > > PDF. They are provided by luatexja-fontspec, which autoloads luatexja > > and fontspec. > > Ok. \setmainjfont, \setsansjfont, and \setmonojfont seems to be of > interest. They are direct equivalents of \setCJKmainfont, > \setCJKsansfont, and \setCJKmonofont. This is probably only relevant > when using bare bones fontspec or polyglossia to set fonts. When using > babel, it probably makes sense to keep using \babelfont[chinese]{rm}{...} I think we should configure fonts through xeCJK or luatex-ja provided interface, since they will override the babel font. Babel will not complain about no font specified. > > luatexja also patches LaTeX2e's NFSS2, adding CJK font > > support. However unless there's a specific reason we shouldn't use > > that in Org export results. > > That sounds concerning. What are the potential consequences? I think no observable consequences for Org export. It will not interfere with any existing functionality. What is does is extending existing framework, providing NFSS2 like interfaces for document classes, handling CJK font scaling, vertical typesetting, etc features. However I was thinking to not use luatexja-fontspec, that is we no longer have \set...jfont control sequences. Since luatexja-fontspec should be loaded after fontspec as it patches fontspec. As a replacement, we can use (ref. luatexja document section 8.3) \ltj@stdmcfont -> The default Japanese font for the mincho family (serif) \ltj@stdgtfont -> The default Japanese font for the gothic family (sans serif and monospace) \ltj@stdyokojfm -> The default JFM for horizontal direction \ltj@stdtatejfm -> The default JFM for vertical direction > > I'm currently having my mid-term exams, so I'll be able to work on > > this after Tuesday. > > No problem. I think Pedro wanted the whole thing to be in mergeable > state (not necessary final) before EmacsConf, but we are generally not > very pushy - we are all volunteers after all. > > >> Org mode only supports exporting via pdflatex, xelatex, and lualatex. > > > > Then my idea is to drop ctex, and use xeCJK or luatex-ja with babel. > > These two packages support both Chinese and Japanese, while xeCJK > > comes with out-of-the-box Chinese support and luatex-ja comes with > > out-of-the-box Japanese support. > > Good. > > > pdfTeX support is also feasible, through the CJK package, which is > > used by ctex as well. > > Note that pdfTeX is something we are not certain about. I wish we could > do it, but it seems tricky. We will need to work out how we want to > design the pdftex support. Tentatively, we may add a field to > `org-latex-language-alist' where standard per-language config will be > stored and loaded according to #+LANAGUAGE settings (note that there > might be multiple languages in one document). CJK support on pdfTeX would require appropriate tfm, then we should be able to use \pdfmapline to setup CJK font. It is tricky somehow. > -- > Ihor Radchenko // yantar92, > Org mode maintainer, > Learn more about Org mode at <https://orgmode.org/>. > Support Org development at <https://liberapay.com/org-mode>, > or support my work at <https://liberapay.com/yantar92>
