[webkit-dev] Lazy loading

[Scott Little]

> Are there plans to better specify CSS background images lazy loading?

There aren't currently any plans to add lazy CSS background images to a
spec, or at least no plans that I know of right now.

Right now in Chromium, the default lazy loading behavior is essentially
based on whether or not the user has opted into Lite Mode (aka Data Saver),
so we've mostly been treating CSS background image lazy loading as kind of
an extra intervention or optimization to help these Lite Mode users save
more data.

Chromium code currently decides whether or not to lazily load CSS
background images according to the default lazy loading behavior, but if in
the future Chromium ever turns on automatic lazy loading as the default
behavior for non-Lite Mode users, we'd first either want lazy CSS
background images to be part of the spec, or we'd separate out lazy CSS
background images to be restricted to Lite Mode.

Cheers,
- Scott

On Mon, Oct 28, 2019 at 8:08 PM Rob Buis <rbuis at igalia.com> wrote:

> > Regarding lazily loading CSS background images, Chromium determines whether
> > or not to lazily load CSS background images according to the default lazy
> > loading behavior, and isn't directly controlled by the "loading" attribute.
> > There are some heuristics involved, e.g. background images inside an iframe
> > that was itself lazily loaded are loaded eagerly for performance reasons,
> > but those heuristics are just part of the default lazy loading behavior.
>
> Scott, thanks for the clarification! Are there plans to better specify CSS
> background images lazy loading?
>
> Regards,
>
> Rob.
>
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