Jeff Muizelaar [:jrmuizel] Reporter
	Description • 9 years ago

https://medium.com/@firstround/300-baud-modems-and-autonomous-vehicles-d15a983adb25

Chrome doesn't seem to APZ. Edge has a large amount of lag.

	Kartikaya Gupta (email:kats@mozilla.staktrace.com)
	Comment 1 • 9 years ago

I don't understand how this page is doing that background image. There seems to be a div which has it as the background image, but that's display:none. And there's a canvas involved somehow. I think they found some new and "interesting" way to implement parallax scrolling.

	Markus Stange [:mstange]
	Comment 2 • 9 years ago

Yes, they're moving the picture by drawImage'ing it to a position:fixed canvas. This is option 3 recommended by http://www.html5rocks.com/en/tutorials/speed/parallax/#toc-option3 . :(

	Kartikaya Gupta (email:kats@mozilla.staktrace.com)
	Comment 3 • 9 years ago

So as far as I can tell there isn't even a visually observable parallax effect for the top image on this page. Scrolling up and down with APZ disabled everything seems to be moving at the same speed, so if they were trying to implement parallax it doesn't seem to have worked. Perhaps the code is just built into their publishing platform or something. Regardless if they want a parallax effect they can now use the CSS perspective property as described at http://keithclark.co.uk/articles/pure-css-parallax-websites/ to get compositor-driven parallax effects.

	Mike Taylor [:miketaylr]
	Comment 5 • 8 years ago

I don't get any lag when flinging this around on a retina MBP. Jeff, can you still reproduce (and maybe make a screencast if so)?

	Karl Dubost💡 :karlcow
	Comment 6 • 8 years ago

No issue for me too. :/ or maybe \o/

	Michelle Funches - QA
	Comment 7 • 8 years ago

Name 	Firefox
Version 	47.0a1
Build ID 	20160201030241
User Agent 	Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:47.0) Gecko/20100101 Firefox/47.0

	Kartikaya Gupta (email:kats@mozilla.staktrace.com)
	Comment 8 • 8 years ago

I can still see this, although it's pretty hard to observe. The easiest way I think is to look at the gap between the top image and the start of the article text as you scroll around. The gap shrinks/widens a little bit. It's more observable on the URL https://medium.com/@samson_hu/building-analytics-at-500px-92e9a7005c83 (taken from the bug duped to this one) because on that page there's a caption just below the image, and so the gap changing size is more obvious.

	Kartikaya Gupta (email:kats@mozilla.staktrace.com)
	Comment 9 • 8 years ago

Here's a screencast, look closely at the gap just below the image and above the "Photo credit" text.

	Mike Taylor [:miketaylr]
	Comment 10 • 8 years ago

Ah, now I see it. (And now I'm kinda dizzy...)

	Mike Taylor [:miketaylr]
	Comment 11 • 8 years ago

https://medium.com/message/the-tech-diversity-story-thats-not-being-told-9a36fb40530f#.mlu27rx9i is another very visible URL.

	Botond Ballo [:botond]
	Comment 12 • 8 years ago

So Markus pointed out that newly published Medium posts don't seem to have a parallax effect any more. They seem to have realized that it doesn't work well and removed it.

Older articles, like the ones linked in this bug, still have the (broken) parallax behaviour. Possibly they are using an older snapshot of their JS code while newly published articles use newer code.

Given that, is there any point in reaching out to them? Presumably they have a reason for not updating their older articles to use their newer code.

	Botond Ballo [:botond]
	Comment 13 • 8 years ago

I'm going to close this as WONTFIX as per comment 12.

If someone feels strongly that we should reach out to Medium about their older posts, or take some other action, please feel free to reopen and make your case.