[Feature Request] Math bold greek

[Firestar-Reimu]

% this cannot display Math bold greek
\usepackage[math=+ss08]{libertinus}
\usepackage{bm}
\renewcommand\mathbf\bm

% this can display Math bold greek
% \usepackage[no-math]{fontspec}
% \setmainfont{Libertinus Serif}
% \setsansfont{Libertinus Sans}
% \usepackage[bold-style=ISO,sans-style=italic]{unicode-math}
% \setmathfont{Libertinus Math}[RawFeature={+ss08}]

test: \[ \mathbf{\Phi} \]

[hvoss49]

This works (lualatex):

\documentclass[a4paper]{article}
\usepackage[bold-style=ISO,sans-style=italic]{unicode-math}
\usepackage{libertinus}
\begin{document}

test: \[ \Phi \symbf{\Phi} \]

\end{document}

[Firestar-Reimu]

I use xelatex

I know that unicode-math can display math bold greek, but libertine-otf + bm cannot. Does that mean math bold greek is not part of the math font?

[hvoss49]

The math font has only a regular version. \mathbf uses by default text font whereas \symbf uses the math font. The bold math version is internally faked by using the embolden keyword. The text font has no bold uppercase greek

[Firestar-Reimu]

so unicode-math use fake-bold too?

[hvoss49]

It depends to the font. There are only a handful math fonts with an own bold face. And nearly all are commercial ones. All other fonts needs the "AutoFakeBold" of unicode-math; they have only the regular series.

[Firestar-Reimu]

so do you have the plan of making a bold-italic math font?

[hvoss49]

Why? AutoFakeBold does it all ...