[Dev-luatex] \mathchar feature request

Linas Stonys lstonys at vtex.lt
Thu Mar 21 13:03:10 CET 2019

I was tracing \mathchar created nodes in text mode and they are just a 
simple glyph nodes with subtype 256.
The problem is that there is no how to control the output changing the 
text font. It's ok if engine throws messages about missing characters in 
font. But if current font has a different character in this slot that is 
a problem.

Documentation says that this command is allowed in text mode:

The commands \mathchar, and \Umathchar and control sequences that are 
the result of \math-
chardef or \Umathchardef are also acceptable in the horizontal and 
vertical modes. In those
cases, the \textfont from the requested math family is used.

but maybe could be any other subtype assigned to the glyph node that 
these characters could be traced down and one could write some control 
functions (for example error "\mathchar is not allowed in text mode")

What do you think?


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