[css-contain] Does inline-size containment remove the natural aspect ratio?

[Loirooriol]

From https://drafts.csswg.org/css-contain-2/#containment-size, with full size containment,

Replaced elements must be treated as having an natural width and height of 0 and no natural aspect ratio.

From https://drafts.csswg.org/css-contain-3/#containment-inline-size,

Giving an element inline-size containment applies size containment to the inline-axis sizing of its principal box. This means the inline-axis intrinsic sizes of the principal box are determined as if the element had no content. However, content continues to impact the box’s block-axis intrinsic sizes as usual, and the box is allowed to fragment normally in the block axis.

I guess this means that only the natural inline-size is treated as 0, the natural block-size is preserved.

But what about the aspect ratio? Blink keeps it, Firefox removes it like in full size containment.

<img src="image" style="contain: inline-size; border: solid; height: 100px">

[mirisuzanne]

If it's possible to keep the aspect-ratio, that seems ideal - the less invasive the better. But I'm not sure about the implications of that, or how Blink manages it while maintaining containment. Maybe someone from Blink (@lilles or @bfgeek?) can speak to that more?

[lilles]

Adding @mstensho who implemented inline-size containment in Blink.

[mstensho]

Maybe Blink's behavior violates the philosophy behind size containment? I don't know.

<div id="container" style="height:100px;">
  <img src="http://mstensho.org/bilen.jpg" style="contain:inline-size; border:solid; height:100%;">
</div>
<script>
  onclick = function() {
    container.style.height = "200px";
  }
</script>

[tabatkins]

aspect-ratio should still work, I think. It doesn't violate anything philosophically - if your inline axis is auto while your block axis is definite, using the aspect-ratio to resolve the width is perfectly compatible with "pretend the box is empty" since you'll get the same behavior if the box really is empty.

[Loirooriol]

Does full size containment need to clear the natural width, natural height, and natural aspect ratio?

[bfgeek]

IMO inline-size containment should drop the aspect-ratio (and we have quite a few WPT tests asserting this indirectly).

Basically aspect-ratio is derived from the natural-width, and natural-height. If you say "ignore the natural-width" we can't really get the aspect-ratio.

Note that mostly this doesn't matter if people add the width/height attributes to their images, as this will set the aspect-ratio via. the presentational-hint style.