[whatwg] Image cache behaviour
ian at hixie.ch
Mon Jun 11 14:48:18 PDT 2012
On Wed, 21 Mar 2012, Andrew Oakley wrote:
> I've noticed that some browsers (Firefox, Opera, IE) cache images
> without following the HTTP expiry rules. This does not appear to be
> permitted by the HTML5 specification.
> I've got a test case for this (with explanation) here:
> Boris Zbarsky believes this behaviour is required for compatibility so I
> think it is worth adding to HTML5. This was discussed on the Mozilla
> bug tracker here: https://bugzilla.mozilla.org/show_bug.cgi?id=295942
> How do other browsers handle this? It seems to be possible to get Opera
> and IE to throw the image away by changing the src attribute on the img.
> Are there similar caches for any other type of object or is this just
For images in <img> elements I've now explicitly added spec-level support
for such a cache. Not my favourite part of the spec, but if it's what
implementors do interoperably...
The spec is a bit vague, let me know if there's anything I can do to
tighten it up while still being compatible with what UAs will implement.
On Wed, 21 Mar 2012, Boris Zbarsky wrote:
> Gecko has a similar (different in mechanism, but not too different in
> effect) cache for stylesheets. I seem to recall that there was explicit
> text about this as well, but I can't find it now. The closest I can
> locate at the moment is the first paragraph at
> If the resource is identified by an absolute URL, and the resource
> is to be obtained using an idempotent action (such as an HTTP GET
> or equivalent), and it is already being downloaded for other reasons
> (e.g. another invocation of this algorithm), and this request would
> be identical to the previous one (e.g. same Accept and Origin
> headers), and the user agent is configured such that it is to reuse
> the data from the existing download instead of initiating a new one,
> then use the results of the existing download instead of starting a
> new one.
Right now I haven't specced anything like this. Ideally I'd like to move
all the CSS logic out of the HTML spec, since e.g.I assume that any
caching for <link rel=styleseet> would also need to happen for @import.
Ian Hickson U+1047E )\._.,--....,'``. fL
http://ln.hixie.ch/ U+263A /, _.. \ _\ ;`._ ,.
Things that are impossible just take longer. `._.-(,_..'--(,_..'`-.;.'
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