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

Re: aspect ratio as an attribute

From: Simon Pieters <simonp@opera.com>
Date: Mon, 19 Dec 2016 12:16:54 +0100
To: "L. David Baron" <dbaron@dbaron.org>
Cc: "Adam van den Hoven" <adam@littlefyr.com>, "Greg Whitworth" <gwhit@microsoft.com>, "Tommy Hodgins" <tomhodgins@gmail.com>, "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>, "alex@bellandwhistle.net" <alex@bellandwhistle.net>, "Jonathan Kingston" <jonathan@jooped.co.uk>, "steve@steveclaflin.com" <steve@steveclaflin.com>
Message-ID: <op.ysptmgsridj3kv@simons-mbp>
On Mon, 19 Dec 2016 04:29:18 +0100, L. David Baron <dbaron@dbaron.org>  

> On Thursday 2016-12-15 22:32 +0100, Simon Pieters wrote:
>> On Thu, 15 Dec 2016 19:49:37 +0100, Greg Whitworth  
>> <gwhit@microsoft.com> wrote:
>> > > In his original post, Alex said: "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." (emphasis mine)
>> >
>> > This is a great point, that said there is nothing stopping us from
>> > making it so that the CSS property can accomplish this and we should
>> > ensure that the CSS property is able to do this. I would prefer to not
>> > have an HTML attribute that behaves differently than the CSS property.
>> It would not need to behave differently. If there are good reasons to  
>> have
>> an HTML attribute (I recall someone mentioning lint checkers being able  
>> to
>> check HTML attributes but not so much parse and apply CSS), we can  
>> define it
>> as a "presentational hint" attribute that just maps to the CSS  
>> property. A
>> lot of HTML presentational attributes do this.
> I don't think this is necessarily the desired approach here.
> I think it was a design mistake in the early days of HTML that the
> height and width attributes on img overrode the intrinsic sizes of
> the image, rather than just being hints for when the image was
> loading.  This has led to many unintentionally-scaled images, and
> a decent number of images that use way more bandwidth than needed.
> Had that mistake not been made, mapping the height and width
> attributes on img into the 'height' and 'width' CSS properties
> wouldn't have made sense.  They would have instead mapped to
> intrinsic dimensions (as defined in
> https://drafts.csswg.org/css-images/#sizing-terms ).
> Wanting a way to describe the intrinsic size of an external resource
> so that relayout doesn't happen when the resource loads is a useful
> goal.  Making the mechanism for that have effects after the resource
> has loaded, or interacting with the CSS model in any way other than
> providing intrinsic dimensions (as defined above, including
> intrinsic aspect ratio) prior to the resource being loaded,
> complicates the mechanism and causes it to have undesired effects
> for the simple (and important) use case of avoiding relayout.
> This seems like it might become more important as developers do more
> responsive things with images using some of the new mechanisms
> available in CSS (e.g., object-fit/object-position, flexbox, grid,
> and correct implementation of min/max-height/width).

Yeah, I think you are right. We also still have an opportunity to map to  
intrinsic dimensions for <source>.

Still, the behavior you describe could also be (new) CSS properties,  
possibly useful for generated content.

Simon Pieters
Opera Software
Received on Monday, 19 December 2016 11:17:38 UTC

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