Hi, I have noticed something with the way ConTeXt is treating math kerns that I do not understand. Consider a prescript such as \startformula H^^^M \stopformula If the math.tl anchor on H is negative then the M is moved to the left (i.e away from the H). This is the opposite of what I would have expected, but perhaps I am confused. Also if the math.tl anchor on H is positive then ConTexT appears to be ignoring this kerning, and the position of the M is unchanged. Is this expected, or is this behaviour subject to some setting? The version of ConTeXt used is pasted below. Thanks! Julius context --version mtx-context | ConTeXt Process Management 1.06 mtx-context | mtx-context | main context file: /Users/juliusross/context/tex/texmf-context/tex/context/base/mkiv/context.mkiv mtx-context | current version: 2024.11.01 19:19 mtx-context | main context file: /Users/juliusross/context/tex/texmf-context/tex/context/base/mkxl/context.mkxl mtx-context | current version: 2024.11.01 19:19

Mikael, Thank you. Your reply is enough for me to understand that I am not doing anything (obviously) wrong! I am not sure I have the expertise enough to contribute. But having a negative kern value in a font move glyphs apart feels more like a sign-error/bug than a choice/convention. I never use (and rarely see) prescripts in mathematics, and I only learned of their existence in TeX from your "math in context" document :-) The opentype math spec certainly implies they were thinking of postscripts, and I just presumed symmetry. So.for a symmetric letter (e.g. V) I would expect the presubscript and postsubscript to be placed symmetrically as they would both be qualifying the variable V. That said, it seems that other fonts have not bothered taking care with this (e.g. STIX has bottom right corner kerns on V but not bottom left). So perhaps just not worrying too much about prescripts (for mathematics) is the way to go. Happy holidays to you all. Julius On Tue, Dec 24, 2024 at 10:45 AM Mikael Sundqvist wrote:

Hi,

On Mon, Dec 23, 2024 at 6:03 PM Julius Ross wrote:

...

Hi,

I have noticed something with the way ConTeXt is treating math kerns

that I do not understand.

...

Consider a prescript such as \startformula H^^^M \stopformula

If the math.tl anchor on H is negative then the M is moved to the left

(i.e away from the H). This is the opposite of what I would have expected, but perhaps I am confused. Also if the math.tl anchor on H is positive then ConTexT appears to be ignoring this kerning, and the position of the M is unchanged.

...

Is this expected, or is this behaviour subject to some setting? The

version of ConTeXt used is pasted below.

...

Thanks!

Julius

You can try to also set the leftbottom kern to a negative value. These were at some point made to align, because prescripts were mainly used for chemistry, and different alignment on top and bottom did look weird in the examples we looked at. I think that if the logic is about to change, real user examples are needed, with explanations on what one expects, where, and also why.

/Mikael

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