1407932 - ydonation.org hero image jumps or flashes when scrolling starts

Status: RESOLVED INCOMPLETE

(Core :: Graphics, defect, P3)

Description

[Chris Peterson [:cpeterson]]

STR:
1. Load https://www.ydonation.org/
2. After the page loads, slowly scroll down the page while watching the "hero image" of the children.

RESULT:
The hero image will jump or flicker when scrolling starts, briefly showing a superimposed copy of the hero image.

I can reproduce the flicker in:

* Firefox 52-58 on Windows 10 and macOS 10.13
* Edge and IE11 on Windows 10

I can't reproduce the flicker in:

* Chrome on macOS 10.13 and Windows 10
* Safari on macOS 10.13

Comment 1

[Milan Sreckovic [:milan] (needinfo for best results)]

Botond, is this the initial async scroll, or the way content is set up?

Comment 2

[Chris Peterson [:cpeterson]]

I can only reproduce the image flash after force-reloading the page with Alt+Shift+R but not Alt+R. Perhaps this is a cache timing issue? However, I see the flash even if I wait 5+ seconds for page to finish loading after Alt+Shift+R.

I sent Botond a screen capture video demonstrating the image flash, but he says he can now reproduce the problem if the browser window width is below a certain threshold.

Comment 3

[Botond Ballo [:botond]]

(In reply to Milan Sreckovic [:milan] from comment #1)
> Botond, is this the initial async scroll

Assuming you mean something related to the initial layerization of a scroll frame - no, it doesn't look like it.

> , or the way content is set up?

The page is using a scroll-linked effect to implement its parallax, but the jump in this bug is definitely worse than just an artifact of the scroll-linked effect. It may well be a bug on our side; worth investigating further.

Comment 4

[Botond Ballo [:botond]]

(In reply to Chris Peterson [:cpeterson] from comment #2)
> I can only reproduce the image flash after force-reloading the page with
> Alt+Shift+R but not Alt+R. Perhaps this is a cache timing issue? However, I
> see the flash even if I wait 5+ seconds for page to finish loading after
> Alt+Shift+R.
> 
> I sent Botond a screen capture video demonstrating the image flash, but he
> says he can now reproduce the problem if the browser window width is below a
> certain threshold.

In fact, just resizing the browser width back and forth triggers the bug intermittently. I think that probably rules out a cache timing issue; more likely something on the layout side.

Comment 5

[Botond Ballo [:botond]]

Markus had an idea that the bug here may be the same as the underlying issue in bug 1406183, but after some investigation it doesn't look like that's the case.

I think at this point we should get a regression window and see what it turns up.

Comment 6

[Botond Ballo [:botond]]

I tried to get a regression window (using the resizing STR mentioned in comment 4, which is easier to repro), and found that the issue goes back at least as far as Firefox 30. Firefox 29 and earlier do not render this page at all, so I couldn't get a specific window.

Comment 7

[Firefox Bug Husbandry Bot]

https://wiki.mozilla.org/Bug_Triage/Projects/Bug_Handling/Bug_Husbandry#Move_fix-optionals

Comment 8

[Chris Peterson [:cpeterson]]

Closing this bug because the ydonation.org website no longer exists.