[webkit-dev] ProgressEvents for Images

Dean Jackson dino at apple.com
Mon Jan 23 14:55:13 PST 2012

On 17/01/2012, at 10:41 AM, Bear Travis wrote:

> A group of us at Adobe has been looking into adding support for ProgressEvents 
> to images.  The overall goal is to simplify image download progress reporting 
> by supporting roughly the same progress events as XHR and the File API for 
> image elements.   For example one could connect an image to a progress element 
> like this:
> <img id="image" src="sample.jpg"
>     onloadstart="showProgressBar()"
>     onprogress="updateProgressBar(event)"
>     onloadend="hideProgressBar()"/>
> Developers have taken various tacks to enable progress reporting, for example 
> in some cases XHR can be used to download image files.  Max Vujovic just 
> published a blog about the practicalities of doing so: 
> http://blogs.adobe.com/openweb/2012/01/13/html5-image-progress-events/.  We 
> think it would be preferable to provide support for image progress events 
> directly.

I think this would be extremely useful. It would require a proposal to
W3C or WHATWG though.


> We're working on a prototype implementation for WebKit and have filed a bug 
> that explains what we're up to in a little more detail: 
> https://bugs.webkit.org/show_bug.cgi?id=76102
> It's probably worth pointing out that the beforeload event, which is currently 
> under discussion, addresses a different use case.  Our proposal is intended to 
> enable applications to give the user feedback about image download progress, 
> it's not intended to enable security or efficiency by preemptively blocking or 
> transforming image downloads.
> We'd appreciate feedback on this proposal.
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