How do I add a custom math font / MLModern

Edoardo_Fiocchi · July 2, 2025, 9:44am

Hello, everyone.

I like a lot the New Computer Modern/Latin Modern variant called MLModern, that was available in LaTeX under the package mlmodern. It has thicker glyphs to enhance readability and comprises the whole set of math symbols.

What I have done so far

The original package from CTAN has various files, but the relevant ones are *.pfb files, i.e. type1 files. Since typst supports .ttf/.otf files, I’ve converted all the type1 files to .ttf using the script from this Reddit post. When I upload the converted .ttf files to typst, I am able to use the fonts in text using

#set text(font: "MLMRoman10")

but (A) I am not sure it is using correctly also the bold and italic variants, and (B) the same does not work for the math variants:

#show math.equation: set text(font: "MLMMathSymbols10")

the compiler gives an error when I try to use math:

This markup in “main.typ”…
$x^2$
…caused this problem:
Current font does not support math.

Type1 files

There are files for different styles and sizes (ranging from 5pt to 17pt depending on the style). Stripping the mlm prefix and <size>.pfb suffix, these are the font filenames: b, bx, csc, duno, mib, ro, ssbx, sso, tcso, tl, tlo, tto, vtko, vtt, bo, bxi, csco, ex, r, ss, ssdc, sy, tk, tlc, tt, u, vtl, vtto, bsy, bxo, dunh, mi, ri, ssbo, ssdo, tcsc, tko, tlco, tti, vtk, vtlo.

I don’t know what math fonts typst supports and which font files should be merged together (if a single file is needed) nor do I know how to do that preserving math properties. I suspect that, in the conversion from type1 to truetype, the MATH table has not been converted properly. Please help me find some leads.

Thank you all

nleanba · July 2, 2025, 10:26am

For math font choice,
```
#show math.equation: set text(font: "MLMMathSymbols10")
```
is correct.

However, Typst only accepts fonts with OTF Math support, so you probably need to figure out a way to create the relevant OTF tables in your conversion.
Combining files: for the math font, I think it should be one file, as the e.g. bold math letters are different unicode and OTF math variants, and not a bold variant of the font.

For the regular font, typst can handle fonts being split across multiple files, but it doesn’t always piece them together correctly. Especially for fonts with many variants, it sometimes does’t “merge” them all. You can find out more in the web-app by hovering over the font name in the set-rule, it will show you how many variants and weights it found.

It might help to use more standard font names (-Bold.ttf, -BoldItalic.ttf, -SemiBold.ttf,…), but honestly I’m not sure how it determines that multiple files belong to one font.

(Interestingly, this is not the same always in the web app vs locally, I have fonts where the web app has the condensed version as its own font-family (“[name] Condensed”), but locally its one font family with different stretch…)

nleanba · July 2, 2025, 10:40am

The following might be useful in figuring out the MATH tables:

github.com/notofonts/math

documentation/building-math-fonts/index.md

main

# Building OpenType math fonts
Math typesetting is different to regular text typesetting, for two main reasons: first, because math formulas are arranged in two dimensions, and second, because there is an interaction between symbols of different styles and sizes. Because of this, math fonts have always been a special kind of fonts. One of the most famous, if not the most famous, math typesetting engines is TeX, and its mathematical typesetting requires a complex setup involving a variety of fonts (for upright, italic, regular, bold, symbols, etc),  special metrics, and font parameters. TeX predates both TrueType and OpenType. When OpenType started supporting math typesetting, it built on the experience gained on TeX, but upgraded to support the newer technologies of Unicode and OpenType.

In OpenType math typesetting, instead of multiple fonts, all symbols are contained in a single font; the various “font styles” use dedicated Unicode math alphanumerics codepoints; and all the additional glyphs required (for example, superscripts and subscripts and variant sized versions of glyphs) are included in the same font. OpenType also introduced a new `MATH` table that stores various special parameters for typesetting math (*math constants*) and math-specific metrics, as well as a few registered feature tags to enable math-specific glyph substitutions. We will discuss more about both of these aspects below.

## Understanding math layout
Probably the the most detailed resource about math layout is Knuth’s *The TeXbook*, and particularly its “Appendix G: Generating Boxes from Formulas”. Appendix G is a heavy text that can be hard to follow at times without visual aide, so Bogusław Jackowski wrote [Appendix G Illuminated](https://tug.org/TUGboat/tb27-1/tb86jackowski.pdf) which provides a collection of illustrations to accompany Appendix G.

Appendix G documents algorithms using TeX fonts and metrics, which is very close to OpenType `MATH` table, but does not always map to it one-to-one, so Ulrik Vieth wrote [OpenType Math Illuminated](https://www.tug.org/~vieth/papers/bachotex2009/ot-math-paper.pdf), which illustrates the similarities and differences
between TeX math fonts and OpenType math fonts.

The OpenType spec documents the [`MATH` table](https://learn.microsoft.com/en-us/typography/opentype/spec/math), but the documentation mostly focusses on the data structure; it is light on the details of the algorithms involved in math layout and assumes prior familiarity with TeX math layout model, but it sometimes goes into details when discussing novel concepts which do not exist in TeX.

There is also the [MathML Core](https://www.w3.org/TR/mathml-core/) specification, which discusses math layout using MathML and OpenType math fonts. This is still a working draft (at the time of writing) and documents only a subset of math layout; it also uses a language that is probably only more penetrable to people familiar with W3C specifications.

## Character set
Math fonts require a large number of glyphs; the number can range from about 1000 to 6000 glyphs, depending on what character set is supported by the font. There is no single, well-defined character set for math fonts. Unicode includes thousands of math related characters, so each project defines its own character set based on its own requirements.

The [symbols defined](https://texdoc.org/serve/unimath-symbols.pdf/0) by the `unicode-math` LaTeX package is a good resource, and the subset of these symbols that are defined by Plain TeX, LaTeX, and `amssymb` (indicated in the document) should be a good start for new math fonts.

This file has been truncated. show original

(Worst case, how to build it by hand, but also how to find the relevant data in font-editing software, so you could check if the tables have been converted or not in the first place)

quachpas · July 2, 2025, 12:44pm

Hey,
I would say that the previous poster is on the right track. I can only advise to try and fix the font for export using fontforge directly instead of automatically converting from a script. The GUI will help you fix some issues for ttf/otf export.

Edoardo_Fiocchi · July 2, 2025, 9:25pm

Thanks everyone for your responses.

Unfortunately, for me it’s not worth the effort and I doubt that anyone will do it from the time being.