[Dev-luatex] Re: question about \vcenter

On Friday, February 6th, 2026 at 9:55 PM, luigi scarso wrote:

On Fri, 6 Feb 2026 at 12:28, Udi Fogiel wrote:

...

The fact that \vcenter does not accept a (b)dir and attr keywords does make sense, but what more bother me is if the side effects of that, i.e. setting the vlist direction as \bodydirection rather than \mathdirection (which I find it odd for math typesetting), and not setting \textdirection, \pardirection and \bodydirection inside the group (which is a bit inconsistent), are desired.

I guess this isn't a new idea, but you can ask some free AI chat something like "In luatex, why doesn't \vcenter have the (b)dir attribute like \vbox?" and, once in context, "A Lua script that "monkey-patches" \vcenter to take a dir argument." At least you can have some fun coding.

Sure, but that still won't answer my question. Why the direction of a \vcenter is \bodydirection and not \mathdirection, and why aren't \textdirection, \bodydirection and \pardirection are not set inside its group, regardless of the (b)dir attribute. At least I'll have some fun :) Udi