[whatwg] Deferring image load

[Charles McCathieNevile]

On Mon, 13 Feb 2012 12:00:52 +0100, Kang-Hao (Kenny) Lu  
<kennyluck at csail.mit.edu> wrote:

> (12/02/13 18:33), Bjartur Thorlacius wrote:
>> On 2/13/12, Gray Zhang <otakustay at gmail.com> wrote:

>>>    2. On an album page where hundreds of pictures are expected to be  
>>> shown,
>>>    it is often required that pictures currently in a user's screen  
>>> should
>>>    appear as fast as possible. Loading of a picture outside the screen  
>>> can
>>> be
>>>    deferred to the time that the picture enters or is about to enter  
>>> the
>>>    screen, for the purpose of optimization user experience.
>> This seems like something interactive user agents should implement.
>
> But it is currently not reliable to the extent that Web authors can rely
> on it. The current spec for <img>[1] says
>
>   # User agents may obtain images immediately or on demand.
>
> Is there actually an existing user agent that obtain images on demand?

Opera.

cheers

>>>    3. a global switch as a http header or an attribute on html to  
>>> switch
>>>    UAs image loading from "obtain images immediately" to "obtain on  
>>> demand"
>>> or
>>>    vice versa.
>> Would this not depend equally on factors such as whether the user
>> agent would download the images over a metered connection?
>
> Could you elaborate a little more on this? What is a metered connection?

One where you pay for the amount of data you use. The common global model  
for data connections.

And to answer the previous question, Yes, that is one factor. It also  
depends on the speed of your connection. In Madrid, and Melbourne, since  
the start of this year, I regularly have actual throughput in single-digit  
kb. Being able to selectively get the images I want becomes key to working  
usefully...

cheers

Chaals

-- 
Charles 'chaals' McCathieNevile  Opera Software, Standards Group
     je parle français -- hablo español -- jeg kan litt norsk
http://my.opera.com/chaals       Try Opera: http://www.opera.com