Math font covers are not effective

[gbchu]

$pi$

#show math.equation: set text(
  font: (
    (name: "TeX Gyre Termes Math", covers: regex("[^\u{03C0}]")),
  ),
)

$pi$

[bluss]

More information about this, if you want it to match, you need to find the correct unicode codepoint. I just found this by experiment.

The relevant codepoint for your example is U+1D70B MATHEMATICAL ITALIC SMALL PI; so we notice there are different codepoints for different mathematical styles and variants (wikipedia tables). I see that this also affects latin letters like A, [A-Z] won’t match italic As and so on.

$A pi upright(pi)$

#show math.equation: set text(
  font: (
    // U+1D70B MATHEMATICAL ITALIC SMALL PI
    (name: "TeX Gyre Termes Math", covers: regex("[^A^\u{1D70B}]")),
    (name: "New Computer Modern Math")
  ),
)

$A pi upright(pi)$

[gbchu]

thanks , it’s working perfectly!

[Y.D.X]

@bluss

found this by experiment

Tip: A simple method is copying the character from the exported PDF.