Re: [csswg-drafts] [css-display-4] Initial value of `reading-flow` (#11396)

To hopefully close the loop on this issue:

* We (Chrome) are cool with keeping the initial value as `normal` (instead of `none`).
* We're cool with adding a `source-order` value, and making it work for Flex, Grid, *and Block* (it's the only value that works for Block, currently).
* We're also okay with *not* opting dense grids into `reading-flow` by default. (As I said in my previous comment, this was added in an attempt to address feedback from Apple, but if Apple impls don't want it either, we're happy to go back to <em>not</em> doing it. ^_^)
* We're **not** okay with `reading-order` on a child automatically opting a `reading-flow: normal` parent into `reading-flow: source-order`. As I explained last week when discussing [#11208 (see minutes)](https://github.com/w3c/csswg-drafts/issues/11208#issuecomment-2701683923), this has both perf and author-surprise implications (due to the side-effects of `reading-flow`), and can trigger side-effects unpredictably due to a single child being present/absent across different instances of the same markup or due to the single child being hidden/shown dynamically. It also has forward-compat issues for any layout types that don't *currently* respect the `source-order` value, like Table.

    It's not a big request for authors using `reading-order` to set the container to `reading-flow: source-order`, as that's the property they'll be using to do *anything else* related to the reading order. This ensures the side-effects of `reading-flow` occur stably and predictably, and avoid any possible perf implications.

So, if the WG approves, we'd like the following resolutions:
* Leave the the initial value of `reading-flow` named `normal` (rather than changing it to `none`).
* Add the value `source-order` to `reading-flow`, which solely triggers "reading flow container" side-effects (including allowing `reading-order` on the element's children), and works on Flex/Grid/Block containers.
* Do not add any default `reading-flow` behavior for dense grids. (Authors have to manually set `reading-flow` to the non-initial value they want.)
* Do not add any default `reading-flow` behavior for elements that have `reading-order` children. (Authors have to manually set `reading-flow` to a non-initial value for `reading-order` to work on children.)

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Received on Tuesday, 11 March 2025 22:50:08 UTC