[whatwg] Deferring image load

[Boris Zbarsky]

On 2/13/12 5:33 AM, Bjartur Thorlacius 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.

This is a difficult optimization to make.  You can only do it for images 
that have a height and width specified in the markup, and worse yet it 
leads to pretty bad flicker as the user scrolls (because network 
roundtrip times are measured in hundreds of milliseconds to seconds). 
So doing this by default is not likely to happen.  Having a page opt 
into it is a different story, though.

-Boris