[csswg-drafts] [css-inline-3] inline boxes and line-fit-edge vs text-box-trim/edge (#10834)

fantasai has just created a new issue for https://github.com/w3c/csswg-drafts:

== [css-inline-3] inline boxes and line-fit-edge vs text-box-trim/edge ==
Now that we've split `line-fit-edge` (inherited) and `text-box-edge` (non-inherited), there's an interesting question of how these two features interact when applied to inline boxes, particularly if they have conflicting "opinions".

Inline boxes currently have two sizes:
- the size used to calculate their "fit" within the line box
- the sized used to draw backgrounds and borders

In the existing line height model, these two are not the same: block-axis margin/padding/borders are ignored completely for sizing, in favor of `line-height`.

In the newer line-height model, as part of making inline layout more controllable, we want to use the margin box for sizing. That means `line-fit-edge` has to trim down the content box, not an imaginary other box, otherwise it's confusing (to size by applying margin/padding to one set of edges, but draw by applying it to a different set of edges). Thus by default, we need to apply trimming to inline boxes.

The initial value of `text-box-trim` is `none`. Should we:
- Make `text-box-edge` ignored by inline boxes and always trim to the `line-fit-edge`?
    - This means authors can only ever use `line-fit-edge` to control the sizing of an inline box; but `line-fit-edge` inherits and might not be appropriate if they want to change the value on one item in order to draw its border differently.
- Make `text-box-edge` apply to inline boxes regardless of `text-box-trim`? (Its initial value already defers to `line-fit-edge`.)?
- Make `text-box-edge` apply to the sides indicated by `text-box-trim` only, using `line-fit-edge` otherwise?
- Something else?

What would be useful and understandable?

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/10834 using your GitHub account


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Received on Wednesday, 4 September 2024 17:41:26 UTC