[webkit-dev] beforeload & link (esp rel prefetch)

Alexey Proskuryakov ap at webkit.org
Thu Jan 13 09:48:14 PST 2011

13.01.2011, в 09:14, Julian Reschke написал(а):

>> I'm wondering what the use cases are. To me, adding a way for metadata to change document behavior sounds like a misfeature - it adds significant complexity to the system, while taking away existing functionality. As a specific example discussed in this thread, we'd break some browser extensions like Incognito if resource loading could bypass onbeforeload. As another example, we'd break<base> element.
> Well, there are document types where you *can't* inline the metadata.

Indeed, and I don't have anything against metadata as long as it doesn't directly modify actual data. For example, Last-Modified and Cache-Control are quite obvious example of what can be in HTTP headers. Despite the practical/historical difficulties that I mentioned with Content-Type, it's arguably a valid example of metadata, too.

Subresource references on the other hand are a part of a document, not of its metadata. Am I just missing a reason why one would want to prefetch subresources for a JPEG image?

> We should distinguish between the act of declaring the link, and the moment where a potential fetch actually happens (it doesn't always happen, after all).
> I agree that stuffing things just to get a fetch to happen "earlier" maybe a premature optimization.

Optimizing prefetch to start before actual document data arrives is highly controversial, but I believe that it's the primary reason why we're considering the Link header implementation.

- WBR, Alexey Proskuryakov

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