Re: [csswg-drafts] [css-overflow] Line-clamp and approaches to ellipsis insertion (#10844)

The proposal in my comment of 12 September (which was discussed in the 17 September I18N+CSS call) was based on breaking in logical order and I'm glad to see that conclusion.

The directionality of the ellipsis isolate refers to the _interior_ of the isolate, right? That direction could be strongly LTR or RTL, although `auto` recommends itself. 

Any isolate is treated by UAX#9 as if it were a single neutral character (the entire isolate is skipped!) in P2/P3. Isolating the block overflow ellipsis makes it behave like U+2026, even if the character sequence it contains has strongly directional characters inside it.
_(When I say "ellipsis" from here in this comment, I mean the isolated block overflow ellipsis sequence)_ The neutral still "needs" to know where the elided text would have rendered--either extending the current run or adding/removing an embedding level. 

Another way to say this would be: the ellipsis acts as if you had inserted it into the string, done embedding level computation on the resulting string, and then removed ("forget to draw") the text after the ellipsis. The result makes logical sense because, if one made the line a little bit longer, the next character(s) to appear would be where the ellipsis was and it would correspond to paragraph embedding levels as you describe.

If there are other proposals, we should detail what they are. At a guess, they would be to ignore the elided text and let the ellipsis draw wherever UAX9 puts the isolate/neutral.

---

Here are some test cases in which I have included RLM/LRM in the ellipsized lines depending on the "next strong" elided character. I included a couple of screen shots for convenience. To compare performance to the same string without the strong mark: copy the text into our [bidi demo page](https://w3c.github.io/i18n-discuss/explainers/bidi-html-demo.html) and then use the "remove controls" button.

```
البحرين مصر الكويت!
البحرين مصر…‏
البحرين مصر Kuwait!
البحرين مصر…‎
البحرين Egypt الكويت!
البحرين Egypt…‏
البحرين Egypt Kuwait!
البحرين Egypt…‎
```

![image](https://github.com/user-attachments/assets/abb1b2cf-61e4-49c7-894c-cbf70586d1d1)
![image](https://github.com/user-attachments/assets/b9e180a6-48da-49fe-8a61-03c1fbe7cc88)



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Received on Thursday, 5 December 2024 18:15:42 UTC