[csswg-drafts] [css-writing-modes] body propagation of writing-mode/direction/text-orientation and computed vs used styles (#12586)

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

== [css-writing-modes] body propagation of writing-mode/direction/text-orientation and computed vs used styles ==
The current Writing Mode spec defines writing mode propagation [like this](https://www.w3.org/TR/css-writing-modes-4/#principal-flow):

> As a special case for handling HTML documents, if the root element has a body child element [HTML], the used value of the of writing-mode and direction properties on root element are taken from the computed writing-mode and direction of the first such child element instead of from the root element’s own values. The UA may also propagate the value of text-orientation in this manner. Note that this does not affect the computed values of writing-mode, direction, or text-orientation of the root element itself.

IIRC the reason we made this only affect the used style on `<body>` was because it created difficulties in implementations to affect the computed style, not because it's better. (AFAICT, it's actually better for authors if it _does_ affect the computed style.) However WebKit has the opposite problem: it's much more difficult to _not_ affect the computed style.

Checking the computed style here is pretty weird edge case, so my question here is: do we need interoperability on exactly how the `<body>` style gets propagated here, or can we allow both options?

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/12586 using your GitHub account


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Received on Friday, 8 August 2025 16:32:52 UTC