On Thursday, February 26, 2015 at 1:06:15 PM UTC-5, Paul Rouget wrote:
> I need a pretty picture to explain my problem:
> http://people.mozilla.org/~prouget/scrollIssue.png
Thanks for the pretty picture! It makes it much easier to visualize the problem
:)
> I tried to scroll the parent and
> the child process in opposite directions. It works, but it's choppy
> and not at all seamless.
This is pretty much what I would suggest, short of inventing some new API to do
this.
> Any idea how I could achieve this effect in a efficient way? I was
> thinking about changing (and animating) the scroll position of the
> content from the main process. Maybe finding a way to make
> `scrollBy{behavior: 'smooth'}` for content and parent to be synced... I
> don't know. Does that make sense? If so, how to build that? If not,
> any alternative way to show this toolbar?
Were you able to successfully get both things to scroll with behaviour:smooth?
Was that still choppy? If so, were you able to tell why? Was it just that one
animation started slightly before the other and so it resulted in a jittery
effect? Or did the animations actually jank while in progress?
I think if you trigger both scrolls inside a RAF and have both APZ-driven
smooth scrolling and vsync-triggered refresh driver it should be possible to
get this working, because then it will be the same layers transaction that
carries over both animations to the compositor, and they should proceed in
sync. I could be wrong though - CC'ing mason also who can provide more
information about vsync-triggered refresh driver and whether it might help in
this scenario.
kats
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