Demystifying “symbol” fonts

[Khaled Hosny]

On Thu, Nov 17, 2016 at 02:07:34PM +0100, Stephan Bergmann wrote:
> On 11/17/2016 01:00 PM, Khaled Hosny wrote:
> > 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?
> 
> Another interesting question would be whether LO makes it too easy to create
> a document with PUA instead of "proper" characters (by deceivingly offering
> PUA characters in "Insert - Special Character...", say), but looking at
> <https://bugs.documentfoundation.org/show_bug.cgi?id=103944> that bug .doc
> at least is presumably created with something else?

I’m mostly concerned about “standardized” PUA like bullets and other
stuff generated by other office suits, not user input. If I user is
entering PUA directly, then it is not a bug when the original font is
missing and he gets garbage, he (or the document author) brought it on
himself.

Regards,
Khaled