1658842 - Image strobing, alternating between image proper and alt tag

Status: RESOLVED WORKSFORME

(Core :: CSS Transitions and Animations, defect)

Description

[MarjaE]

Attachment: (Strobe warning!) screen recording

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:79.0) Gecko/20100101 Firefox/79.0

Steps to reproduce:

I visited https://www.americanheritage.com/political-machine-i-rise-and-fall-age-bosses (strobe warning).

Note that I am using accessibility and safety fixes, mainly to try to stop strobing and stop other animation. I don't know a good way to list them all, and can't safely test the page with or without these fixes.

Actual results:

An image started strobing. It seems to alternate between the image proper and the alt tag.

Expected results:

Nothing should ever strobe. ever.

Comment 1

[Sean Voisen (:svoisen)]

This doesn't appear to be alternating between the image and the alt tag. Rather, the image in question has a cross-fade animation on it that is interacting poorly with the popup that is placed on top. Specifically, they are animating the z-index between -100 and 9000, and the opacity between 0 and 1. The popup has a z-index of 1001. Hence the animation "through" the popup. This feels like a site issue we probably can't do much about.

Without any accessibility and safety fixes, the cross-fade animates smoothly (albeit probably should not be on top of the popup) — perhaps with the reporter's modifications the animation is broken, causing the strobe effect.

Comment 2

[Sean Voisen (:svoisen)]

Reporter: Can you provide any insight into the modifications you've made at all, even generally?

Comment 3

[MarjaE]

I've used a mix of preferences, user css, and add-ons to block strobing and as many other igraine triggers as possible.

One of the add-ons is No Transition. Using it to block or allow animation respectively seems to trigger or stop this strobing/animation, respectively. Other add-ons don't seem to affect this. So it looks like an add-on bug rather than Firefox core.

Comment 4

[Sean Voisen (:svoisen)]

I tried the site with just the No Transition add-on installed, and it prevented the animation correctly, without any strobing. So I suspect it's one of the other mitigations at fault.

Unfortunately, I don't think this is anything we can address in Firefox directly.

Comment 5

[MarjaE]

Another affected site, with screenshot:

https://www.theroot.com/im-not-saying-donald-trump-is-planning-a-coup-but-hes-1845802898

Comment 6

[MarjaE]

Attachment: (Strobe warning!) Screen Recording with Inspector, about 50 Hertz

Comment 7

[MarjaE]

No Transition does not work on that site.