1357464 - Slide down/up animation is really slow on long pages

Status: UNCONFIRMED

(Core :: Graphics, defect, P3)

Description

[Valentin]

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:54.0) Gecko/20100101 Firefox/54.0
Build ID: 20170415004005

Steps to reproduce:

1. Open a web page with a long list of items and a slide down/up animation on button click, e.g. https://forum2null.de/

2. Click on the menu button and look at the animation framerate of the slidedown event.

(3. Set display: none to some of the posts below and try again. It's smoot now.)


Actual results:

The open/close animation of the menu is not smooth in Firefox, but it is in other browsers like Chrome or Edge.


Expected results:

The animation should be smooth also on long pages.

Comment 1

[Brian Birtles (:birtles)]

This isn't DOM: Animation since it's not using declarative animation but rather JS animation. Looking at this with a profiler it seems to be nearly all in painting.

Comment 2

[Vincent Liu[:vliu]]

(In reply to Valentin from comment #0)
> User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:54.0)
> Gecko/20100101 Firefox/54.0
> Build ID: 20170415004005
> 
> Steps to reproduce:
> 
> 1. Open a web page with a long list of items and a slide down/up animation
> on button click, e.g. https://forum2null.de/
> 
> 2. Click on the menu button and look at the animation framerate of the
> slidedown event.
> 
  Do you have more explanation about how to operate 2. ? Really thanks.

Comment 3

[Valentin]

(In reply to Vincent Liu[:vliu] from comment #2)
> (In reply to Valentin from comment #0)
> > 2. Click on the menu button and look at the animation framerate of the
> > slidedown event.
> > 
>   Do you have more explanation about how to operate 2. ? Really thanks.

It can be observed really easily when doing this click first in Firefox and then in Chrome. The menu slides down but the animation is not smooth. In Chrome it is really smooth. Do you need any more explanations?