W3C home > Mailing lists > Public > public-html@w3.org > July 2007

handling fallback content for still images

From: Robert Burns <rob@robburns.com>
Date: Sun, 1 Jul 2007 16:55:55 -0500
Message-Id: <5E43E679-9888-485C-B549-FE6F350120C6@robburns.com>
To: HTMLWG WG <public-html@w3.org>

I imagine there's already a a Wiki page on this, but I thought I'd  
post this here first. Late, I'll add this to the appropriate page or  
perhaps this warrants a new page.

Problem: There's no simple and unified mechanism to display still  
images in HTML with optional rich fallback content.

Solutions:

1) <picture>fallback</picture>

<picture
	src="picture.png"
	width="100%"
	height="500"
	alt="abbreviated fallback content"
 >
Some lengthy <em>or</em> semantically rich fallback content
</picture>

pro: as simple to use as <img> and if widely implemented would likely  
be widely adopted by authors
pro: requires no special CSS or scripting
con: not yet implemented in any UA (as far as I know)

<object

	type="image/png"
	data="picture.png"
	width="100%"
	height="500"
 >
	<param
		name="src"
		value="picture.png" /
	>
Fallback content
</object>

pro: already works in existing UAs
con: difficult for authors to use
con: makes adding fallback content seem difficult to do since the  
difficulty with dealing with <object> and <param> and MIME Types, etc  
are all associated by authors with simply adding some fallback content

<img
	src=picture.png
	width="100%"
	height="500"
	alt="Fallback content"
 >

pros: works in existing UAs
con: no semantically rich or media rich fallback is facilitated
con: @alt is typically expected to be a short fallback, so lengthy  
fallback is not facilitated
con: its not unified in the sense that images with fallback must be  
embedded in a different manner than images without fallback and that  
fallback for some embedded content (like <object>) is handled in a  
simplified way while <img> requires more complicated tacked-on methods.

for for lengthy or semantically rich fallback content
<img
	src=picture.png
	width="100%"
	height="500"
	alt="abbreviated fallback content"
	longdesc="#pictureLongDesc"
 >
<p
	id="pictureLongDesc"
	style="visibility: hidden;"
 >
Some lengthy <em>or</em> semantically rich fallback content
</p>

pros: works in existing UAs
con: requires special CSS or scripting (or loads a separate page for  
fallback if the @longdesc points to another page)
con: its not unified in the sense that images with fallback must be  
embedded in a different manner than images without fallback and that  
fallback for some embedded content (like <object>) is handled in a  
simplified way while <img> requires more complicated tacked-on methods.

Again, adding picture adds complexity to the language. But we're  
already adding elements with much less need (as far as I can tell)  
like <canvas>, <video>, and <audio> that can all be handled with  
<object> without much added difficulty (especially when compared to  
moving from <img> or <picture> to <object>).
Received on Sunday, 1 July 2007 21:56:02 UTC

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