Re: [csswg-drafts] [css-align-3][css-tables-3] Define last baseline for tables. (#7655)

The CSS Working Group just discussed `last baseline of tables`, and agreed to the following:

* `RESOLVED: Table baselines match grid, per details above.`
* `RESOLVED: Rowspanning cells particpate only in first baseline alignment of their first row, and last baseline alignment in the last row`

<details><summary>The full IRC log of that discussion</summary>
&lt;TabAtkins> Topic: last baseline of tables<br>
&lt;fantasai> github: https://github.com/w3c/csswg-drafts/issues/7655<br>
&lt;TabAtkins> iank_: Tables work by taking the first baseline from the first row in the larger table<br>
&lt;TabAtkins> iank_: Importantly, we skip captions, this is intentional<br>
&lt;TabAtkins> iank_: So how do we determine last baseline?<br>
&lt;TabAtkins> iank_: First relatively obvious bit is we probably want the last row<br>
&lt;TabAtkins> iank_: Given the reoslution we just had for flex and grid, we can probably do something similar<br>
&lt;TabAtkins> iank_: So if you've got a lot of baseline-aligned items, we'll take the first-baseline of those items and use it as the table's last baseline; toherwise we'll synthesize<br>
&lt;TabAtkins> fantasai: Alignment expands baseline alignment for tables, says align-content works on cells; "normal" looks at vertical-align, but you can use first/last baseline normally<br>
&lt;heycam> q+<br>
&lt;TabAtkins> fantasai: So probably just want to take literally the grid behavior and apply it here<br>
&lt;TabAtkins> iank_: Yeah, fine with that<br>
&lt;TabAtkins> iank_: Not implementing it yet, but seems fine<br>
&lt;TabAtkins> iank_: Important is to not consider captions<br>
&lt;TabAtkins> fantasai: agreed<br>
&lt;fremy> q+<br>
&lt;TabAtkins> iank_: (I'll show Firefox folks some cases for why caption should be ignored later)<br>
&lt;Rossen_> ack heycam<br>
&lt;TabAtkins> heycam: How do spanning cells impact this?<br>
&lt;TabAtkins> iank_: it gets a little complex<br>
&lt;TabAtkins> iank_: this wouldn't apply until impls support align-content; if something is spanning multiple rows, its first baseline currently only contributes to its first spanned row<br>
&lt;TabAtkins> iank_: And last-baseline, you can only get spanned cells affecting the last baseline if you support align-content:last-baseline<br>
&lt;TabAtkins> fantasai: So a spanned cell only affects first baseline alignment in its first row, and last baseline in its last row, and that's it<br>
&lt;Rossen_> ack fremy<br>
&lt;TabAtkins> fantasai: so it doesn't affect first-baseline alignmetn in its last row, etc<br>
&lt;TabAtkins> fremy: When you synthesize, do you include the table border?<br>
&lt;TabAtkins> iank_: TAbles always have a valid baseline - it's complicated - if there's a tbody, you ahve a baseline bc you synthesize it using the content edge of the first row<br>
&lt;TabAtkins> iank_: I think if you have captions but no body there's no exported baseline, so you'd synthesize from the table border<br>
&lt;TabAtkins> iank_: Need to do some investigation on our behavior<br>
&lt;TabAtkins> fantasai: proposed resolution: finding first/last baseline of a table cell works same as in grid<br>
&lt;TabAtkins> iank_: And last baseline of a table is taken from teh corret baseline-sharing group in the alst table row<br>
&lt;TabAtkins> Rossen_: objections?<br>
&lt;TabAtkins> RESOLVED: Table baselines match grid, per details above.<br>
&lt;fantasai> RESOLVED: Rowspanning cells particpate only in first baseline alignment of their first row, and last baseline alignment in the last row<br>
&lt;TabAtkins> fremy: Should I modify Tables?<br>
&lt;TabAtkins> fantasai: We might be able to do it generically in Align.<br>
&lt;TabAtkins> fantasai: If we can't we'll ping you.<br>
</details>


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Received on Thursday, 15 September 2022 19:36:11 UTC