About special elements propagation #13435
Description
The CSS Backgrounds specification explicitly describes about the special elements [1]. I think web-devs will expect this property to be propagated (applied) to an animated background image for the root element.
For documents whose root element is an HTML HTML element or an XHTML html element [HTML]: if the computed value of background-image on the root element is none and its background-color is transparent, user agents must instead propagate the computed values of the background properties from that element’s first HTML BODY or XHTML body child element.
Since the specification points specific css properties, we should consider adding this property to this section or the appropriate section explicitly.
Aside, due to [2], we may need to think about this should be inherited property or not.
[1] https://drafts.csswg.org/css-backgrounds-3/#special-backgrounds
[2] https://www.w3.org/TR/design-principles/#example-58897411
Originally posted by @DevSDK in webplatformco/project-image-animation#4