Private Use areas (was: Re: Thoughts on working with the Emoji Subcommittee (was ...))

[via Unicode]

On 2018-08-21 08:04, Mark E. Shoulson via Unicode wrote:
> On 08/20/2018 03:12 PM, Mark Davis ☕️ via Unicode wrote:
> 
>>> ... some people who would call a PUA solution either batty > or
>> crazy.
>> 
>> I don't think it is either batty or crazy. People can certainly use
>> the PUA to interchange text (assuming that they have downloaded
>> fonts and keyboards or some other input method beforehand), and
>> it  can definitely serve as a proof of concept
>> . Plain symbols — with no interactions between them (like changing
>> shape with complex scripts), no combining/non-spacing marks, no case
>> mappings, and so on — are the best possible case for PUA.
> 
> It is kind of a bummer, though, that you can't experiment (easily?  or
> at all?) in the PUA with scripts that have complex behavior, or even
> not-so-complex behavior like accents & combining marks, or RTL
> direction (here, also, am I speaking true?  Is there a block of RTL
> PUA also?  I guess there's always RLO, but meh.)  Still, maybe it
> doesn't really matter much: your special-purpose font can treat any
> codepoint any way it likes, right?
> 

Not all properties come from the font. For example a Zhuang character 
PUA font, which supplements CJK ideographs, does not rotate characters 
90 degrees, when change from RTL to vertical display of text.

John Knightley

> ~mark