On 7/16/2018 3:51 PM, Shai Berger via Unicode wrote:
And I should add, in response to the other points raised in this
thread, from the same page in the core standard: "If the same plain text
sequence is given to disparate rendering processes, there is no
expectation that rendered text in each instance should have the same
appearance. Instead, the disparate rendering processes are simply
required to make the text legible according to the intended reading."
That paragraph ends with the following summary, emphasized in the
source:

        Plain text must contain enough information to permit the text
        to be rendered legibly, and nothing more.

The last answer inhttp://www.unicode.org/faq/bidi.html  violates this
dictum, as I have showed here with different examples. As long as it
stands, the Unicode standard fails its own criteria.

I've been trying to following your reasoning in this long thread, but am still not finding much to convince that there is anything wrong in the #bidi8 FAQ entry
that you keep claiming is wrong.

First, for your "Hello, world!" example, in a rendering that imposes a RTL directional
context, the correct, conformant display of that string is:

!Hello, world

as you cited in your earlier example. To do otherwise, would represent a *non*-conformant
implementation of the UBA.

So your complaint seems to boil down to the claim that if you transmit "Hello, world!" to a process which then renders it conformantly according to the Unicode Standard (including UBA), then that process must somehow know *and honor* your intent that it display in a LTR directional context. That information, however, is explicitly *not* contained in the plain text string there, and has to be conveyed by means of a higher-level protocol.
(E.g. HTML markup as dir="ltr", etc.)

If the receiving process, by whatever means, has raised its hand and says, effectively, "I assume a RTL context for all text display", that is its right. You can't complain if it displays your "Hello, world!" as shown above. Well, you *can* complain, but you wouldn't be correct. Basically, you and the receiving process do not share the same assumptions about the higher-level protocol involved which specifies paragraph
direction.

So as I see it, you are either wanting the plain text to somehow contain and enforce upon the renderer your assumption about the directional context that it should be displayed in, OR, you are just unhappy about the bidirectional rendering conundrums of some edge cases for the UBA. In either case, the remedy is the application of LTR characters to provide context (or directional isolate controls, or explicit
higher-level markup).

--Ken

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