[whatwg] Responsive images using http headers
bzbarsky at MIT.EDU
Mon Jun 25 11:10:24 PDT 2012
On 6/25/12 1:34 PM, Oscar Otero wrote:
> For example, for an image 100% width in a div of 400px, the browser
> would send a header indicating it need a 400px width image.
The problem is that the browser typically does not know the following
pieces of information when it sends the image request:
1) The styles of the image.
2) The parent of the image (or even whether the parent is unique;
image loads are coalesced if the same URL appears in the page
It could have that information available if it waited a lot longer to
request images , but right now browsers try to kick off requests as
soon as they can. For example in this example:
<link rel="stylesheet" href="something.css">
browsers will currently start loading the image before the stylesheet is
done loading. With your proposal they would have to stop doing that, right?
 Though in cases like this:
<img src="img1" style="width: 100%">
<img src="img2" style="width: 100%">
the actual layout width of either image can't be determined until the
intrinsic size of both images is known. There are lots of other cases
like this involving flexbox, floats, etc, etc.
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