r12a

_The first comment in this issue contains text that will automatically appear in one or more gap-analysis documents as a subsection with the same title as this issue. Any edits...

By coincidence, i've been working on a new [test rig for text-decoration](https://w3c.github.io/i18n-tests/exploratory/text_decoration/int-text-decor.html). I created [4 tests that are relevant here](https://w3c.github.io/i18n-tests/results/int-text-decoration). I'll edit the comment above to reflect the results.

I rewrote this section to take into account pointers by @fantasai and @xfq.

Thanks @hober but this particular issue is focused on Arabic, and unfortunately, `text-underline-position: from-font` doesn't appear to work very well for Arabic. See [this test](https://w3c.github.io/i18n-tests/exploratory/text_decoration/int-text-decor.html?lang=ar&fontSize=36&fontFamily=noto%20naskh%20arabic&width=715&height=266&textDecorationLine=underline&textUnderlinePosition=from-font&textDecorationStyle=solid&textDecorationColor=red&textDecorationThickness=&textUnderlineOffset=&textDecorationSkipInk=auto&textDecorationSkipSpaces=start&textDecorationSkipInset=none&height=266&text=%3C%2Fp%3E%D9%84%D9%83%D9%84%20%D8%A3%D9%86%20%D9%84%D9%87%D9%85%20%D9%85%D9%85%D9%90%20%D9%81%D9%8A%D9%90%20%D9%81%D9%8A%20%D8%B9%D8%AD%20%D8%BA%20%D8%A5%D8%A3%D9%8E%D9%83%D9%8E%D9%91%3C%2Fp%3E%3Cp%3E%D9%84%D9%83%D9%84%20%D8%A3%D9%86%20%D9%84%D9%87%D9%85%20%D9%81%D9%8A%20%D8%B9%D8%AD%20%D8%BA%20%D8%A5%D8%A3%D9%8E%D9%83%D9%8E%D9%91%3Cp%3E) You can type various font...

Updated the results to include a test for `text-underline-position:from-font`, and noted that Blink now supports `text-underline-offset`.

I suspect that actually the Diacritics section is currently referring to all combining characters, be they tashkīl or other, since the first sentence talks in terms of code point positioning.

Btw, the glossary refers to the dots as [ijam](https://w3c.github.io/alreq/#def_ijam), though we don't appear to use that term in the body of the document. There is also a definition of [tashkil](https://w3c.github.io/alreq/#def_tashkil)....

To make sure i'm clear, is the issue about font vs typface related specifically to section 2.7.4 https://w3c.github.io/alreq/#h_fonts or more widespread in section 2.7? Also, presumably, there is no issue...

> Re. ijam – this opens a much wider question: should Arabic terms be used, or should English terms be used, or a combination thereof? Indeed. See a similar comment...

I would have expected that the bidi isolation that applies to an HTML `div` or `li` when it is a block element would remain unchanged around the content of the...