Dealing with Unencodeable Characters

[Philippe Verdy]

2016-10-06 21:03 GMT+02:00 Doug Ewell <doug at ewellic.org>:

> > * "Wingdings", "Wingdings 2", are here again maaping various forms of
> > arrows and arrow heads, plus some emojis or enclosed characters, or
> > decorative characters. "Wingdings" also includes another Windows logo
> > at position 0xFF; these fonts are not mapped to Unicode but to 8-bit
> > code positions 0x21..0xFF.
> > * "Wingdings 3" uses a mix of non-Unicode mappings in 0x21..0xFF and
> > some characters and other regular Unicode positions (in 0x2000..
> > 0X9FFF) multiple times (every block of 0x100 code positions, i.e. each
> > glyph is mapped 128 or 129 times in that font). None of these
> > characters have a Unicode mapping.
>
> It's true that the Wingdings and Webdings fonts themselves, which date
> back to the 1990s, are "symbol fonts" with glyphs mapped to the ASCII
> range. However, to clear up any possible confusion, all glyphs in these
> fonts have had actual Unicode mappings since version 7.0 (June 2014).
>
These mappings exist theoretically but not in these fonts themselves
(notably not when there are multiple variants of the same encoded
characters, notably for many arrows and arrow heads).

The 3 glyphs for the Earth globe (centered on Americas, or Europe+Africa or
South/East Asia+Australia) are not distinguished at all in Unicode (I've
not seen any sequence with variants selectors to help distinguishinhg them,
and there are some fonts showing the Earth globe centered on the
Antarctic). Unicode seems to also allow the character to show a flat
Mercator map centered on these positions, or other projections, as the
encoded character just means "Earth".

So no, the mappings are theoretical and allow wide variations, that these
fonts purposely want to distinguish. They are used without directly without
using any Unicode mapping, for internal implementation reasons, or specific
meanings in specific applications, or because this makes a coherent
graphical design for an UI (fonts are used for this prupose, but many
applications do not need fonts for this usage, they just use collections of
icons, frequently packed in a ZIP/JAR archive, or using CSS selectors in
SVG files, or hidden in their graphic source code by directly using drawing
APIs, in which they can add custom visual effects such as animations,
glowing, transparency, custom superpositions and compositions custom
layouts and interaction with user events or application events and states).
Using the Unicode mappings in these fonts would not allow selecting the
appropriate dinctiguished glyphs, the UI would become confusive or no
longer usable or would create a ugly patchwork.
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