[css-flexbox] Use flex-order first or document-order first item's baseline?

[fantasai]

In #197, it was noted that there's an inconsistency between Grid and Flexbox in whether the baseline is taken from the first item in document order or visual order. Grid clearly defines using the visual (grid) order; flexbox should probably account for 'order' and 'flex-direction' as well.

[SelenIT]

Using visually first flex item definitely makes more sense. As my quick test suggests, browsers also seem to consistently use the visually first item's baseline as a flex container baseline.

[astearns]

Would this be visually first or flex-order first? Given a dom-order 1-2-3 that's flex-ordered 2-1-3 then displayed in a reverse flex container so that it appears on the page as 3-1-2, which item is 'first'?

[fantasai]

That's a good question, and I think it should be visually first. The goal of first-baseline alignment is to align the visually first line of text; last-baseline alignment the visually last. Aligning a random line of text somewhere in the middle of the box isn't helpful.

[astearns]

RESOLVED: take the visually first line when considering baseline alignment in flexboxes

[tabatkins]

Fixed in 620eb8c.