W3C home > Mailing lists > Public > public-respimg@w3.org > December 2016

RE: aspect ratio as an attribute

From: Greg Whitworth <gwhit@microsoft.com>
Date: Thu, 15 Dec 2016 17:14:55 +0000
To: Adam van den Hoven <adam@littlefyr.com>, Tommy Hodgins <tomhodgins@gmail.com>
CC: Yoav Weiss <yoav@yoav.ws>, "Hall, Charles (DET-MRM)" <Charles.Hall@mrm-mccann.com>, "public-respimg@w3.org" <public-respimg@w3.org>, Jason Grigsby <jason@cloudfour.com>, Paul Deschamps <pdescham49@gmail.com>, Simon Pieters <simonp@opera.com>, "alex@bellandwhistle.net" <alex@bellandwhistle.net>, Jonathan Kingston <jonathan@jooped.co.uk>, "steve@steveclaflin.com" <steve@steveclaflin.com>
Message-ID: <SN2PR03MB2158B9FBF694C210F227BF2DA49D0@SN2PR03MB2158.namprd03.prod.outlook.com>
Maybe I’m missing something, but why is this the case?

> Your CSS solution cannot give the browser enough information…


From: Adam van den Hoven [mailto:adam@littlefyr.com]
Sent: Wednesday, December 14, 2016 3:27 PM
To: Tommy Hodgins <tomhodgins@gmail.com>
Cc: Yoav Weiss <yoav@yoav.ws>; Hall, Charles (DET-MRM) <Charles.Hall@mrm-mccann.com>; Greg Whitworth <gwhit@microsoft.com>; public-respimg@w3.org; Jason Grigsby <jason@cloudfour.com>; Paul Deschamps <pdescham49@gmail.com>; Simon Pieters <simonp@opera.com>; alex@bellandwhistle.net; Jonathan Kingston <jonathan@jooped.co.uk>; steve@steveclaflin.com
Subject: Re: aspect ratio as an attribute

sorry I just changed a few things to be somewhat clearer in that HTML example.

On Wed, Dec 14, 2016 at 3:21 PM, Adam van den Hoven <adam@littlefyr.com<mailto:adam@littlefyr.com>> wrote:
I'm not saying that you don't need a more reliable way than JS or padding top on a pseudo element to say that this thing should have an aspect ratio of 4/3 or 9/16 or 4/4 or whatever. I'm saying that for the use case whereby you want to give the browser enough information to correctly layout a page before loading all the resources, signalling the aspect ratio (or the true dimensions) of those resources in the HTML is the best and only solution (maybe a manifest file that maps resources URLs to a specific size but that may be tricky to do efficiently).

Your problem, "I want visual element to have a fixed aspect ratio," is an important problem to solve (particularly if you know the height, not the width), but its a generalized CSS problem. Aspect ratio of resources (images and video) is a different problem that also needs solving. That's the problem the alex, I think, is grappling with.

Imagine the following HTML: https://jsfiddle.net/littlefyr/173xmov9/

Simple (naive, I know bear with me) layout. Now imagine that for various reasons those images take noticeable time to load.

Your CSS solution cannot give the browser enough information to avoid reflow once the images load (which for a non-trivial layout may be hugely problematic). The value is different for each individual image (notwithstanding that I'm using two images twice, pretend I'm not lazy) and you cannot reliably put in your external CSS. You'd have to do it for all your images on the site (imagine flickr) and it would be painful.

Your only solution (if the only available approach is CSS) is to inline the aspect ratio on the element. The fact that you have to do this tells you that its a CONTENT issue not a design issue. I take it for granted that we should try to solve content issues with HTML and design issues with CSS.

Now it may be that a CSS aspect-ratio may be a pragmatic solution if it only requires ONE set of changes, not two. That's a bit of different question, however (how todo something, not what to do).

On Wed, Dec 14, 2016 at 2:42 PM, Tommy Hodgins <tomhodgins@gmail.com<mailto:tomhodgins@gmail.com>> wrote:
I'm envisioning this being useful for a lot more than just photographs and pixel-based images or video!

It would be a huge benefit to CSS for all sorts of use cases to be able to define a desired aspect ratio for any element in a way that's easy to override with other CSS, able to be set or changed with @media queries, and works with the normal states the browser and CSS are aware of for styling, like hover.

The HTML attribute doesn't really help me with my responsive design, it seems like I'd still have to do all those hacks and JavaScript juggling for layout stuff, wishing there was an aspect-ratio property in CSS 😟

On Dec 14, 2016, at 5:34 PM, Adam van den Hoven <adam@littlefyr.com<mailto:adam@littlefyr.com>> wrote:


What happens when the image that is given that CSS is this one: https://marketplace.canva.com/MAB1YTyBMXY/1/0/thumbnail_large/canva-butterfly-timeline-infographic-MAB1YTyBMXY.jpg (which picked at random from a google search). You're trying to say it is something it is not. Or what if #demo-5 has text in it?

CSS should not be concerned with what something is only with how the DOM element should appear. Using aspect-ratio in this context makes as much sense as having a file-size attribute to allow the browser to prioritize things.

But your demo only shortcutting a difficult calculation. Except for the first case, there is no reason not to specify the height and width in both. its always the same fixed number. Its only when you have relative dimension (100% as in demo1) that this has any utility. And I agree that this syntax is better than the padding tricks we do now for that problem.

But this is the use case I mean, which I realize is a better answer to Yoav:

Given an image of arbitrary aspect ratio, how can I give the browser enough information to lay out the page correctly before loading the image resource if that image is created AFTER I publish the CSS.

On Wed, Dec 14, 2016 at 1:28 PM, Tommy Hodgins <tomhodgins@gmail.com<mailto:tomhodgins@gmail.com>> wrote:
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<mailto: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:

    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"

> 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

Received on Thursday, 15 December 2016 17:15:32 UTC

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