Math font recommendations sometimes include non-math fonts

[Enivex]

Description

If I write #set math.equation: set text(font: ) then recommendations correctly show only math fonts

However, if I input "" (which is natural if I want to input a font name, then the list suddenly includes all fonts

This is problematic, because non-math fonts simply don't function properly in math. This has come up several times on the Discord.

Reproduction URL

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OS

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[IgKh]

Funnily enough, this has nothing to do with the quotes - the way the code currently detects that it should limit suggested fonts to math fonts only is by checking if the 25 characters before the cursor contain the word "equation"... the opening quote is just enough to get the "e" out of that window. Can be also seen by having the set rule start with anything other than font, e.g.:

#show math.equation: set text(size: 10pt, font: |)

(where | the cursor location when asking for completions) will also suggest all fonts, no quotes involved.

Just increasing the character lookback window seems kinda silly, there surely should be a better way to recognize this situation. Furthermore, selection of math fonts is done by checking if the string "Math" is in the family name which also doesn't seem like the most reliable way to go about it.

[Enivex]

The selection should ideally check for the presence of a math table instead of by name

[laurmaedje]

Checking for a math table necessitates downloading/loading the font, which is too expensive.

Detecting the situation in a more robust way is surely possible, the person who wrote this (I think it was me), just didn't bother enough.

[Enivex]

Checking for a math table necessitates downloading/loading the font, which is too expensive.

In the web app this information could be cached server side could it not?

[laurmaedje]

Yes, I forgot to add that part. The web app has a font index for these kinds of things, but math information is not currently part of it. Changing the font index while keeping compatibility with old compilers is generally a bit tricky, but in this case would actually be pretty easy. Whether it's a math font could be added to the font flags:

typst/crates/typst-library/src/text/font/book.rs

Line 192 in df89a0e

pub struct FontFlags: u32 {