Re: image width & height, summary

On Wed, Jun 3, 2009 at 1:50 PM, Larry Masinter <masinter@adobe.com> wrote:

> I'm not sure where the support for this requirement comes
> from, though. How do we know what JavaScript programmers
> assume, and why this requirement is necessary? Are there
> well-known JavaScript DOM texts which include this
> assumption?  Common JavaScript libraries that would fail?
> Isn't this just one of many things that might break in a
> typical script? Was this requirement in any previous
> specification?


I don't know about this particular requirement, but we generally discover
script assumptions by accidentally or intentionally varying behaviour across
browsers and browser versions and observing bug reports about real Web
pages/apps failing. Sometimes this information is easily documented by
referring to a bug in a public bug tracking system, but sometimes it isn't.
I don't think it's feasible to reference such documentation in the spec.

Why is something that can't actually be promised -- that all
> images on a page MUST be cached once they have been loaded
> -- a requirement at all?


Because sites depend on it. (For example, I happen to know that
ebay.comscripts have quite strong requirements on images remaining in
cache.)

A user agent can't "promise" anything in the face of resource limits, user
cancellation, or physical attacks on the machine --- it's inevitable that in
such circumstances UAs will fail to satisfy the spec. The most we can say is
that if the UA behaves according to the spec, Web sites will work as
intended, but if the UA does not follow the spec for whatever reason, sites
probably won't work.

Rob
-- 
"He was pierced for our transgressions, he was crushed for our iniquities;
the punishment that brought us peace was upon him, and by his wounds we are
healed. We all, like sheep, have gone astray, each of us has turned to his
own way; and the LORD has laid on him the iniquity of us all." [Isaiah
53:5-6]