[css-content] computed value for 'content' property is unclear

[dbaron]

The definition of the content property says "Computed value: As specified below.".

But it doesn't seem to specify below.

And there are actually some interesting questions to answer, such as what the computed value is for elements when the specified value is one of the value types that apply only to pseudo-elements and not elements (since it says "Applies to: ::before, ::after, ::marker, and page margin boxes. Image and url values can apply to all elements.").

[dbaron]

Other related questions that the spec should answer but doesn't seem to: does the url() value for content only load images, or does it also load other sorts of resources like videos and iframes? If it's loading SVG images, is it loading them as full-fledged documents (like iframes) or in the somewhat reduced way that the <img> element loads them?

Apparently Blink implements this, and lack of that implementation in other engines leads to compatibility problems, so it would be good to get these questions answered in the interests of interop.

We have a Gecko bug on implementing this feature, but there's really very little actual spec to go on here.

[dauwhe]

[reminder to put example of using media query for aural generated content]

[atanassov]

[csswg f2f Seattle] - RESOLVED: url() in 'content' only applies to images and nothing else in visual canvas, and to audio files in aural canvas