W3C home > Mailing lists > Public > public-respimg@w3.org > November 2014

Re: Informing the browser of the expected size of the image

From: <steve@steveclaflin.com>
Date: Mon, 17 Nov 2014 13:08:17 -0600
To: Simon Pieters <simonp@opera.com>
Cc: Attiks <attiks@gmail.com>, Nelson Menezes <nelson@fittopage.org>, Greg Whitworth <gwhit@microsoft.com>, Yoav Weiss <yoav@yoav.ws>, Fréd\"éric Kayser\" <f.kayser@free.fr>, public-respimg@w3.org, Simon Miles-Taylor <smilestaylor@gmail.com>, Ilya Grigorik <igrigorik@google.com>
Message-ID: <12381b25a7d6f7087f850b5a8001b25a@steveclaflin.com>
On 2014-11-11 15:11, Simon Pieters wrote:
> On Tue, 11 Nov 2014 16:15:46 +0100, <steve@steveclaflin.com> wrote:

>> Benefits would include:
>> 
>>    availability of clearer and more verbose descriptions for the  
>> individual images,
> 
> I don't understand what this means.

I don't consider the current syntax clear, due to it's terseness and 
lack of names for individual values.  It's like the condensed form of 
background in CSS, which is a lot clearer when it's spelled out with 
background-image, background-position, etc.  In CSS, at least the more 
verbose option is available.  As tag attributes, we're trying to cram 
all the information into a single string without identifying what the 
values stand for.  So, if that information was somewhere else, outside 
the img tag, like in a descriptor in the head section, it could be more 
descriptive.

Even though I see a strong analogy to @font-face, I can't come up with a 
good parallel syntax for images, because of the necessity for criteria, 
but something like the following is what I had in mind:

@srcset {
   name: scene1,
   {
     src: url(scene1.png),
   },
   {
     src: url(scene1-med.png),
     media: min-width: 600px;
   },
   {
     src: url(scene1-lg.png),
     media: min-width: 960px;
   }
}
(I realize that's kind of an ugly syntax, but there's no good array 
syntax in CSS.  I don't really like the comma-separated { }, but I can' 
see any use for giving each candidate image a separate name. Maybe the 
target query can be like a property name, and its property value the 
src.  Or maybe the properties could be srcN, where N is an integer - I 
didn't really like that suggestion for the img tag, but that's because 
it would mean variable attribute names; here it would just be an 
ignorable identifier.)

Or, instead of CSS, a tag form like:

<srcset id="scene1">
     <candidate-image src="scene1.png">
     <candidate-image src="scene1-med.png" media="min-width: 600px">
     <candidate-image src="scene1-lg.png" media="min-width: 960px">
</srcset>


And then in an img tag:

<img srcset="#scene1" src="scene1.png">

So, the more "verbose part" is specific named properties instead of a 
space-separated list of terms, and the clarity part ought to be obvious.

> 
>>    reusability of descriptors
> 
> Is it common to use the same image sets multiple times?

Usually not within the same page, although list or table where each item 
includes an icon from some limited set of choices, might be an example.

If I can have a descriptor in a separate place, particularly in CSS, 
then I can link the same file into multiple pages to get reusability 
across documents.

And, for temporal reusability, what if I want to do image rollovers?  
With the current syntax, I would assume that I need to set src AND those 
big long srcset strings any time I want to swap an image.  Under this 
approach, I'd still have to swap both src and srcset, but the srcset 
would just be the identifier.


> I think in general indirection increases cognitive load for Web
> developers  and increases complexity and causes bugs for implementors.
> c.f.  https://wiki.whatwg.org/wiki/Namespace_confusion

I think this is a far cry from namespaces - again, I see it as being 
closer to fonts.  For me at least, cryptic strings cause a lot more 
confusion and bugs than a little indirection.
Received on Monday, 17 November 2014 19:01:33 UTC

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