[whatwg] <link rel=icon width="" height="">

Maciej Stachowiak mjs at apple.com
Wed Apr 30 01:34:22 PDT 2008

On Apr 30, 2008, at 12:41 AM, Charles Iliya Krempeaux wrote:

> Hello,
> On Wed, Apr 30, 2008 at 12:19 AM, Maciej Stachowiak <mjs at apple.com>  
> wrote:
> On Apr 29, 2008, at 11:54 PM, Charles Iliya Krempeaux wrote:
> [...]
> In practice, these things usually do not matter when using an icon  
> in the user interface. But the sizes available do matter. I would  
> not want to download a 512x512 icon for use as an iPhone homescreen  
> icon (it's not anywhere near the right size) but it is irrelevant  
> whether the compression is lossy or how colors are represented. I  
> would prefer a multisize icon with a wide size range for Mac OS X or  
> Windows Vista but not for Windows XP or most mobile platforms.
> True... for an iPhone that might be the case.  Or even Mac OS X or  
> Windows Vista.  But it might become important in usages of this  
> metadata beyond just icons.
> For example, consider a photo blogging example...
> <link rel="enclosure" type="image/png" width="64" height="48"   
> compressioning="lossless" coloring="paletted" href="A.png">
> <link rel="enclosure" type="image/png" width="640" height="480"   
> compressioning="lossless" coloring="truecolor" href="B.png">
> <link rel="enclosure" type="image/png" width="640" height="480"   
> compressioning="lossless" coloring="grayscale" href="C.png">
> <link rel="enclosure" type="image/jpeg" width="2560" height="1920"  
> compressioning="lossy" coloring="truecolor" href="D.jpg">
> (The bottom <link> if the original image.  The 2 640x480 onews are  
> scaled version... one color and one grayscale.  And the top one is a  
> thumbnail.)

Has anyone actually asked for this kind of functionality or is this a  
hypothetical use case? I don't think we should tie solving a real  
problem (the need to specify icons at different sizes and let the UA  
know these sizes) to an open-ended metadata annotation mechanism.

> If we have this new attribute(s) available on the <link> element,  
> then it is very likely going to be used for other things besides  
> just icons.
> You could use width and height for videos too.  What if video wants  
> to be able to "declare" that the video has "closed captioning"  
> embedded or not?!  Or what language the video file has audio for?!   
> ("hreflang" would almost work for that... if it let you specify more  
> than one language.)  Or`what "ratings" that version of the video is?!
> What I was getting at with this suggestion is that if we start  
> adding the ability to specify all sorts of metadata about what's  
> being linked to and go along the path of #1, then we likely need to  
> create a kind of complex language to describe this.  (Something  
> approaching the complexity of CSS.)  And perhaps that's complicating  
> the <link> element too much.
> Maybe it's simpler to (do #2 and) just create a <link> for each thing.
> I'm not sure I understand this. Your proposal amounts to adding two  
> new attributes to the <link> element, "width" and "height" (and  
> possibly specifying a link of the same type to the same item  
> multiple times). My proposal involves a single new attribute on  
> <link>, with essentially the same information conveyed in a more  
> compact way. Why does my proposal lead to a CSS-like general-purpose  
> metadata language, but yours does not?
> It leads to a CSS-like language only if we start adding more  
> metadata in there besides just the width and height.
> For example, this...
> <link rel="enclosure" type="image/xxx" width="640" height="480"  
> compressioning="lossy" coloring="truecolor" href="A.xxx">
> <link rel="enclosure" type="image/xxx" width="1280" height="960"  
> compressioning="lossy" coloring="truecolor" href="A.xxx">
> <link rel="enclosure" type="image/xxx" width="2560" height="1920"  
> compressioning="lossy" coloring="truecolor" href="A.xxx">
> ... could become...
> <link rel="enclosure" type="image/xxx" metadata="size:640x480,  
> 1280x960, 2560x1920; compressioning:lossy; coloring:truecolor;"  
> href="A.xxx">
> The "metadata" attribute is where you start to get a CSS-like  
> language.  (Which seems to complicate the <link> element.)

I'm not in favor of a CSS-like metadata language or a metadata  
attribute. I don't think your suggested extra attributes are very  
useful either so I am not sure how it is relevant to discuss different  
syntax alternatives for them. That being said, this:

<link rel="enclosure" type="image/xxx" sizes="640x480 1280x960  
2560x1920" compressioning="lossy" coloring="truecolor" href="A.xxx">

Does not introduce a CSS-like metadata language any more than your  
first alternative. So I still do not see your point.


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