Section on ZWNJ and ZWJ

[behnam]

Importing from ACTION-80 (https://www.w3.org/International/groups/arabic-layout/track/actions/80)

This will set the ground (specially, some definitions) for #91 .

[behnam]

I'm expanding section "2.4 Joining" to explain for use of ZWJ/ZWNJ. Doing this, I noticed this paragraph:

Almost all the non-alphabetical characters are non-joining. The few exceptions will be discussed in this document.

I'm not sure what exceptions this sentence is talking about. @mostafah, can you elaborate on this?

Also, we have this:

Please refer to The Unicode Standard Version 8.0, Section 9.2, for full explanation of Arabic cursive joining.

I assume we have many references to make, to various parts of the Unicode standard, as well as other resources. Should we put all these references in a standalone appendix and link to those entries? @r12a, what do you think?

[mostafah]

ZWJ and Tatweel are the exceptions, and I added that sentence for the sake of correctness, but we may want to omit the promise of discussing them later.

…

On Mar 21, 2017, at 19:09, Behnam Esfahbod ***@***.***> wrote: I'm expanding section "2.4 Joining" to explain for use of ZWJ/ZWNJ. Doing this, I noticed this paragraph: Almost all the non-alphabetical characters are non-joining. The few exceptions will be discussed in this document. I'm not sure what exceptions this sentence is talking about. @mostafah, can you elaborate on this? Also, we have this: Please refer to The Unicode Standard Version 8.0, Section 9.2, for full explanation of Arabic cursive joining. I assume we have many references to make, to various parts of the Unicode standard, as well as other resources. Should we put all these references in a standalone appendix and link to those entries? @r12a, what do you think? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub, or mute the thread.

[behnam]

ZWJ and Tatweel are the exceptions, and I added that sentence for the sake of correctness, but we may want to omit the promise of discussing them later.

Thanks, @mostafah. So, since I'm adding text here to explain ZWJ/ZWNJ usage here, I'll drop that line.

[behnam]

Regarding question about link to Unicode spec, see #103

[behnam]

Here's my draft for updating "2.4 Joining" to expand definitions for joining behavior, and add definition for ZWNJ and ZWJ:
https://docs.google.com/document/d/1AmQK5Nj37Fl0VJbPGRtlF9b4SKRSoCZWf61iGftEvZQ/edit (Open for suggest edits and comments)

[r12a]

I made some purely editorial suggestions in the google doc. Hopefully they will stick when i leave the page...

[behnam]

Regarding Joining Rule 3: from #91 (comment)

[behnam]

U+0640 TATWEEL used as Joining Enforcer in Persian abbreviation:

[behnam]

I created a new issue for "Section on Hyphenation" (#108) as a follow-up from the work here.

"Section on Abbreviation" (#91) would be another follow up.

[behnam]

TODO after #110:

• Add the missing images.
• Section on connection types and broken (dangling) connections.

Follow up work:

• More on joining segments and context-based joining in section on Line Break.
• More on elongation and joining segments.
• List counters: cover closed and open joining segments.

Misc from https://www.microsoft.com/typography/OpenTypeDev/arabic/intro.htm

• Contextual substitutions
• Dotted-Circle for invalid diacritic logic