On 2/13/12 9:29 AM, Bjartur Thorlacius wrote:
On Mon, 13 Feb 2012 14:17:28 -0000, Boris Zbarsky <[email protected]> wrote:
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.
Well, UAs would fetch the images to be displayed first first, and then
prefetch images until they have more than a screenful of undisplayed
content loaded.
What does "screenful of undisplayed content" mean for some slide-deck
site that just moves images in and out of view via script?
But yes, fast scrolling would break this. Not even
knowing the rough size of images before fetching them makes them hard to
lay out until they have been downloaded.
Not knowing the size makes it _impossible_ to do layout correctly.
Again, UAs would only be able to skip getting images that have explicit
height and width attributes.
And even then, things could be troublesome if the pseudo-clases for
detecting loading state are added, since those could affect layout...
-Boris
