[Fontconfig-bugs] [Bug 58641] font "Wingdings" is displayed incorrectly and the bug in fontconfig crashes xfd

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=58641

--- Comment #18 from Diego Santa Cruz <Diego.SantaCruz at spinetix.com> ---
We are actually stumbling on the same problem with fontconfig 2.10.1 and pango
1.32.3 with the M$ Webdings font, but the issue boils down to the same thing I
think.

The coverage computed by fontconfig is empty as the Apple Roman cmap is no
longer read and the MS Symbol cmap is read but fontconfig only takes into
account entries 0x20-0xFE, but Webdings has entries 0xF020-0xF0FF.

Reading the OpenType spec it appears to me that Windows treats Symbol fonts
(i.e. having a cmap with platform ID 3 and encoding ID 0) specially, in that it
remaps its entries to Unicode code points starting at usFirstCharIndex from the
OS/2 table and can only map 234 characters at most. See the "Non-Standard
(Symbol) Fonts" paragraph at
http://www.microsoft.com/typography/otspec/recom.htm.

In our case, as fontconfig computes an empty coverage, pango never uses the
font and always tries a fallback, so it is impossible to render with it (or at
least we have not managed to do so in our application).

I do not know what would be the proper course of action:

- emulate Windows handling of symbol fonts as per the OpenType spec?

- emulate Mac by using the Apple Roman cmap (but only for fonts without a
unicode cmap)?

- Read the MS symbol cmap entries in the UPA range and mark them as covered in
fontconfig so that apps using such codepoints can render with these fonts? But
in this case the fonts would not behave as one would expect from Windows or Mac
experience, so I do not think it is very useful.

- other?

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