Demystifying “symbol” fonts

Hi all,

I’m looking into bug 103944, which is mainly about handling so-called
symbol fonts.

The bullets in the bug document use the “Symbol” font from Windows,
which has “symbol” cmap subtable that maps characters from Private Use
Area to its own glyphs. Because the document uses PUA symbols, without
this font installed or another font that has the exact same glyphs for
PUA characters we can get anything from boxes to totally unrelated
glyphs.

Now, AFAIK, all glyphs in “Symbol” font have proper characters in
Unicode (and the font itself supports them as well, in its non-symbol
cmap subtable), so my question is what is the expected behaviour here,
map the PUA to proper Unicode characters? Expect the font or a
compatible one to be installed and usable? Bundle a compatible font?

Regards,
Khaled

1. https://bugs.documentfoundation.org/show_bug.cgi?id=103944