1236593 - Frequent artifacting when scrolling medium.com articles w/ APZ enabled

Status: RESOLVED DUPLICATE of bug 1251894

(Core :: Panning and Zooming, defect)

Description

[Ryan VanderMeulen [:RyanVM]]

Feel free to dupe this to another bug as-needed. It's hard to get a sense of which specific issues overlap across different websites going through the deps of bug 1013364. See also bug 1188532 which might be related.

On the page linked from the URL field (and other medium.com articles), I frequently see text duplication/overlaying and images flashing in and out when scrolling with the mousewheel. No issues with APZ disabled or when using the arrow keys to scroll.

Reproduced on Win10. It's reproducible on Linux as well, but I find it more difficult as scrolling seems hella-laggy in general. In case it matters, this is on a HiDPI laptop (4K screen).

Comment 1

[Kartikaya Gupta (email:[e-mail])]

I can't repro on my piddly non-4k screens. That being said this might be a dupe of bug 1201996; that's the closest one I can think of.

Comment 2

[Ben Kelly [:bkelly, not reviewing]]

See the text tearing/blurring in this video I took on win10 e10s today:

  https://www.dropbox.com/s/dxbkwvaau4tiyu1/VID_20160108_123523.mp4?dl=0

Comment 3

[Kartikaya Gupta (email:[e-mail])]

Attachment: Frame from bkelly's video

I screenshotted a frame from bkelly's video which shows the issue (I think).

Comment 4

[Ben Kelly [:bkelly, not reviewing]]

Another screenshot directly from my windows machine:

  https://www.dropbox.com/s/svu099arlffyotw/Screenshot%202016-01-08%2012.45.54.png?dl=0

Comment 5

[Kartikaya Gupta (email:[e-mail])]

Based on the investigation in bug 1201996, medium.com uses a canvas that they draw into on scroll events, or something like that. So it's quite possible that this duplicate-drawing stuff is a stale canvas element being combined with content scrolling on top.

Comment 6

[Ben Kelly [:bkelly, not reviewing]]

That would also explain why the artifacting only happens on the first scroll-through of the page.  The canvas is complete after that.

Comment 7

[Andrew McCreight [:mccr8]]

I've also seen some blurring on the first scrollthrough on Medium, though not nearly as severe as the screen shot. I don't have a 4k monitor.

Comment 8

[Ben Kelly [:bkelly, not reviewing]]

I don't have a 4k monitor either.  Note, the screenshot looks worse than what I see since its very transient.

Comment 10

[Ryan VanderMeulen [:RyanVM]]

Another good example:
https://medium.com/female-founders/my-startup-failed-and-this-is-what-it-feels-like-c5d64b3ae96b#.n1e7qq1ji

Comment 12

[Kelsey Gilbert [:jgilbert]]

Bug 1252317 has another example:
https://medium.com/@elliot_f/my-journey-into-web-speed-optimization-part-2-52fc48c3b106#.4q071ow7r

Comment 13

[Patrick Brosset <:pbro>]

Attachment: scrolling-on-medium.gif

I also reproduce this on dev edition (FF46) on windows 10.
Here's a gif recording while scrolling with the mouse wheel.

Comment 14

[Markus Stange [:mstange]]

I'm pretty sure this was fixed bug 1251894, which has already landed on Nightly.