Re: Proposal: position:fixed elements should form new stacking contexts

On Mon, May 14, 2012 at 2:31 PM, James Robinson <> wrote:

> It would be at least in theory possible to detangle this situation, but
> the complexity is daunting and as far as I know nobody has attempted this
> yet.

We have. In Gecko, scrolling of pages with fixed-position elements is
accelerated, even if the fixed-pos element has to be split into different
layers. In general, arbitrary interleaving of moving and non-moving content
is handled. This is true for scrolling in the viewport and in arbitrary
elements, and it works the same for desktop and mobile. (We also accelerate
scrolling in the presence of background-attachment:fixed root element
backgrounds in the same way.)

On mobile, asynchronous scrolling of pages with fixed-pos elements is not
fully done yet, which may be why you see jank there currently. We do have
the limitation that asynchronous scrolling doesn't work for scrolled
elements that have been split into multiple layers. As you note, that is
pretty rare.

So, Mozilla has no need for this proposed spec change.

“You have heard that it was said, ‘Love your neighbor and hate your enemy.’
But I tell you, love your enemies and pray for those who persecute you,
that you may be children of your Father in heaven. ... If you love those
who love you, what reward will you get? Are not even the tax collectors
doing that? And if you greet only your own people, what are you doing more
than others?" [Matthew 5:43-47]

Received on Thursday, 17 May 2012 06:34:58 UTC