Re: aspect ratio as an attribute

I'm curious if it was to be defined in an HTML attribute how you would target it with a @media query, or with pseudo-classes like :hover? If it needs to be present in an HTML attribute, can you use it with a pseudo-element like :before or :after?

The way I can see this working would be as a CSS property:

#demo-1 {
  aspect-ratio: 16/9;
}

#demo-2 {
  width: 200px;
  aspect-ratio: 16/9;
}

#demo-3 {
  height: 200px;
  aspect-ratio: 16/9;
}

#demo-4 {
  width: 200px;
  height: 200px;
  aspect-ratio: 16/9;
}

#demo-5 {
  width: 200px;
  height: 200px;
  aspect-ratio: 16/9 !important;
}

With a demo here <https://tomhodgins.github.io/aspect-ratio-spec/demo.html> of what these should do

> On Dec 14, 2016, at 4:21 PM, Yoav Weiss <yoav@yoav.ws> wrote:
> 
> Can you clarify your use-case? Maybe provide a link for a page that demonstrates it?
> 
> I'm not clear on which parts should be defined (from your perspective) in HTML and which in CSS. (e.g. where is width defined? where is height defined? Are the images constrained by their container? etc)
> 
> On Wed, Dec 14, 2016 at 10:02 PM Adam van den Hoven <adam@littlefyr.com <mailto:adam@littlefyr.com>> wrote:
> The problem with CSS arises with what you are trying to say. If you are saying that the image should be laid our with a certain aspect ratio, then the value belongs in the CSS. If, however, you are saying that the image resource has a specific aspect ratio then it should come from the resource. The HTML is closest to the resource (in a cms, for example) so it should be able to declare the aspect ratio. 
> 
> If we're talking logos or anything that is constant through the life of a site (relatively speaking) the CSS is fine. But for content, and content is the prime use case I would think, you can't know at "design time" what the aspect ratio of all your resources are because content creators either don't listen or they forget or they just get it wrong (scaling gave them 640 x 479 for some reason). 
> 
> Allowing the aspect ratio to come from HTML, means your CMS, which may already know the aspect ratio, can set it dynamically. Dynamically generating CSS is really difficult on a page by page basis (you end up rendering the page twice so it's slow). 
> 
> To be clear. I'm ignoring the idea of inline CSS on the assumption that if the dominant use case is inline CSS, then you've just chosen awkward syntax for declaring it in HTML. There might be other reasons to do it in CSS I just don't think the arguments against doing it in HTML in this thread are sufficiently argued. 
> 
> Is also possible that I'm missing some piece of information
> 
> 
> On Dec 14, 2016 2:46 AM, "Yoav Weiss" <yoav@yoav.ws <mailto:yoav@yoav.ws>> wrote:
> I'd like to +1 Greg's concerns regarding adding this to HTML. There's no real technical reason to do that (i.e. there are no performance benefits to doing so) and the aspect-ratio is required for display of all elements, so it makes sense for it to be part of CSS.
> 
> On Fri, Dec 2, 2016 at 2:34 PM Simon Pieters <simonp@opera.com <mailto:simonp@opera.com>> wrote:
> On Tue, 29 Nov 2016 17:03:07 +0100, <alex@bellandwhistle.net <mailto:alex@bellandwhistle.net>> wrote:
> 
> > Hi,
> >
> > I’ve been lurking here and just wanted to put two cents in about
> > aspect-ratio.
> >
> > Like most devs here I’ve often dreamed of a way to hint the browser
> > about image proportions during page load, but without fixing either
> > dimension.  I often use padding-boxes for above-the-fold images, to
> > limit layout jumps during load. It works, but it’s a pretty miserable,
> > time-consuming pattern. It seems to me that this is the really urgent
> > use case. Speaking as a user, when I accidentally tap on the wrong link
> > because an image just above my finger has suddenly loaded, the
> > irritation factor is really high.
> >
> > Putting together lots of what’s been said, it seems that solution needs
> > to be:
> >
> > 1) Attribute-based. The CSS aspect-ratio proposals solve different, more
> > complicated problems. They are harder to understand, harder to
> > implement, harder to polyfill. I don’t want to wait five years. Since
> > the ratio is a property of the asset, it should be marked up with the
> > image/video.
> >
> > 2) Only a hint during load. Once the asset (metadata) is loaded
> > successfully, the actual aspect-ratio of the asset takes over. If the
> > image fails to load, the image’s box retains the hint. This fails
> > gracefully, in cases of sloppy authoring. It also allows conventional
> > stretching via CSS, as Tommy Hodgins has requested. Basically, it should
> > do its job and then get out of the way.
> >
> > 3) Distinct from sizes attribute. I don’t see a way to add onto the
> > existing sizes syntax without backwards-incompatible changes. zcorpan,
> > correct me if I’m wrong here? Even if there were a way to do it, I’m
> > worried it would be hard to read.
> 
> We can add new things to sizes="" in a backwards-compatible way; the sizes
> parsing algorithm was specifically designed to make this possible. In
> particular, items in the list that fail to parse get dropped, so the
> subsequent items can be used as fallback. For example:
> 
> <img
>     sizes="(min-width: 40em) something new, (min-width: 60em) something
> new, something new,
>            (min-width: 40em) 60vw         , (min-width: 60em)
> 80vw,          100vw"
>     srcset="examples/images/medium.jpg 375w,
>             examples/images/large.jpg 480w,
>             examples/images/extralarge.jpg 768w"
>     alt="…">
> 
> 
> > I suggest a syntax that closely parallels sizes, e.g.:
> >
> > <img
> >    sizes="(min-width: 40em) 60vw, (min-width: 60em) 80vw, 100vw"
> >    aspect-ratio=“(min-width: 40em) 3:2, (min-width: 60em) 16:9, 4:3”
> >    srcset="examples/images/medium.jpg 375w,
> >            examples/images/large.jpg 480w,
> >            examples/images/extralarge.jpg 768w"
> >    alt="…">
> >
> >
> > This has the advantage of being familiar, and handles the the
> > “art-direction” use case easily.
> 
> If you have different aspect ratios for different breakpoints, then you
> are probably doing art direction, and should be using <picture><source
> media>, not srcset+sizes. I think it makes more sense to have a single
> aspect ratio apply to all assets in `srcset`.
> 
> --
> Simon Pieters
> Opera Software
>