Re: How to recognize keyboard insertion?

[Jason Rumney <jasonr@gnu.org>]

Eli Zaretskii wrote:
> But that is wrong: per the Unicode Bidirectional Algorithm
> (a.k.a. UAX#9), a `(' should only be mirrored if its resolved
> directionality is R:
>   

I don't think you can do that mirroring on input, as the directionality 
will change as the user types (Assume below letters represent an Arabic 
or Hebrew character):

User types: ABCD(
Displayed as: )DCBA

User types: ABCD(4
Displayed as: 4)DCBA or (4DCBA? I suspect the first, as the user might 
type something other than a number next

User types: ABCD(4+5)
Displayed as: (4+5)DCBA regardless of how directionality of parens is 
interpreted.

User types: ABCD(4+5)*9
Displayed as: (4+5)*9DCBA Parens here must be LTR

I guess this is why the mirroring happens at keyboard driver level and 
applications do not try to do it correctly, because in practice doing it 
correctly results in text jumping around, confusing the user more than 
it confuses them to manually fix the problems of a dumb implementation. 
And there are always going to be ambiguous cases, where leaving the user 
to manually DTRT will be the only option.