- From: Marcos Caceres <marcos@marcosc.com>
- Date: Tue, 1 Oct 2013 19:30:14 +0100
- To: "matmarquis.com" <mat@matmarquis.com>
- Cc: Scott Jehl <scottjehl@gmail.com>, "Tab Atkins Jr." <jackalmage@gmail.com>, "public-respimg@w3.org" <public-respimg@w3.org>, Robin Berjon <robin@w3.org>
On Friday, September 27, 2013 at 6:15 PM, matmarquis.com wrote: > [ snip ] > > > > > > > > > > 3. In non-supporting browsers, the src image always will be http > > > > prefetched,meaning a polyfill for this syntax may not be able to avoid > > > > wasteful overhead. Element based approaches like picture can avoid overhead > > > > through use of noscript wrappers on fallback content. Could srcN be > > > > polyfilled without waste? > > > > > > > > > To an extent. If you avoid use of src entirely and polyfill with > > > script in downlevel browsers, you'll get good behavior in new > > > browsers, okay (script-gated) behavior in older browsers running > > > script, and failure in older browsers without JS. > > > > > > Alternately, a similar strategy to what you described can be used: > > > > > > <img src1="..." src2="..."> > > > <noscript><img src="..."></noscript> > > > > > > This is then similar to the behavior of your proposal - it's good in > > > up-level browsers running script and down-level browsers not running > > > script, okay in down-level browsers running script, and bad in > > > up-level browsers not running script (as both images will be shown). > > > This last problem could probably be worked around by adding a > > > src1="0x0_image.png" to the fallback, so the image still shows up in > > > the page, but doesn't display. > > > > > > ~TJ > > > > > > I can dig it up to confirm, but I thought there were existing (popular) browsers that will make a wasteful HTTP request on <img> even if a src attr is omitted? Perhaps someone else can chime in. > > It looks as it if isn’t entirely uncommon, based on http://www.nczonline.net/blog/2010/07/13/empty-string-urls-browser-update/ > > I wrote up some of my initial thoughts on potential polyfill patterns at https://etherpad.mozilla.org/polyfilling-srcN — I’d love to get more eyes on it. Some more discussions going on here: https://gist.github.com/bjankord/6781503
Received on Tuesday, 1 October 2013 18:30:46 UTC