On Thu, May 22, 2014 at 1:50 PM, Kip Gilbert <[email protected]> wrote: > Link to standard: > > http://dev.w3.org/csswg/cssom-view/#smooth-scrolling:-the-%27scroll-behavior%27-property
How will "scroll-behavior: instant" work on platforms that use APZ? I worry about authors expect it to enable them to do a bunch of DOM mutations and then set the scroll position and allow them to be sure that rendering can't happen of the new DOM but at the old scroll position (or the old DOM but at the new scroll position). Can we promise that when using APZ? One use case that has come up for us in FirefoxOS is the ability to add a few elements to the top of a page, shifting down the contents of the page, but then make that transparent to the user by adjusting the scroll position accordingly. That isn't possible with APZ since the user might be actively scrolling and so if we just do something like div.scrollTop += hightOfNewContent; then the newly set scroll position will be based off of an old value which has already changed on the compositing thread. Basically we need an API like div.addToScrollPosition(hightOfNewContent); This would allow the browser to send this delta to the compositing thread along with the newly updated painting of the DOM. I wonder if we need something similar for smooth-scrolling. So rather than a CSS property, have something like something like: div.smoothScrollTo(pos, n); // does a smooth scroll over n ms. div.setScrollPosition(pos); // ensures that the next time we paint, we paint at scroll position pos div.immediatelyScrollTo(pos); // sends a signal immediately to the composition thread to jump to pos, possibly before any painting has happened. I'm not sure if this one has use cases. / Jonas _______________________________________________ dev-platform mailing list [email protected] https://lists.mozilla.org/listinfo/dev-platform
