Re: [csswg-drafts] [css-grid-3][masonry] Handling negative margins and dense packing for baseline calculation in the masonry axis (#13165)

Thanks for all the responses. It makes sense to me to rely on the placement rules/track order. Here're my thoughts in determining the first/last baseline candidate within a track:

In normal cases:
When an item arrives, if the related tracks do not yet have a first baseline, we use this item’s baseline as the first baseline. If a first baseline is already set, we skip this item because we know another item was placed earlier.
For the last baseline, we simply override the last baseline value in the related tracks. At the end, this gives us the logically last placed item as the last baseline candidate.
 
For dense packing:
Based on the spec stating that the running position of a track never decreases, we can rely on the running position to decide whether a densely-placed item should be treated as a first or last baseline candidate.
If the running position of this densely-placed item is equal to or greater than that of the current first/last baseline candidate, then the densely-placed item is considered later in placement order.

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Received on Wednesday, 10 December 2025 23:11:21 UTC