1219583 - Glitch of scroll position while changing body to position:fixed

Status: RESOLVED INCOMPLETE

(Firefox for Android Graveyard :: Toolbar, defect)

Description

[Bryan Failing]

Attachment: ffTest2.html

User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:41.0) Gecko/20100101 Firefox/41.0
Build ID: 20151014143721

Steps to reproduce:

This issue occurs when rendering the attached file in Firefox Mobile 41.0.2 on my AT&T Samsung S5.  

Steps to reproduce the issue(s):
1. Scroll down the page until the red bar is out of view
2. Click the checkbox at the top of the page to activate the "blocker" (adds the following inline styles to the body tag: position: fixed; overflow: hidden; and top: -XXXpx, where "XXX" is the current scroll position/offset determined using window.pageYOffset after checking the checkbox)
3. Click the checkbox at the top of the page to deactivate the "blocker" (removes all inline styles added to the body tag)


Actual results:

After completing step 2, the page scrolls to the top (showing the red bar) for a brief period, then flashes a white screen (hard to tell, but it seems like it is the entire screen), then displays the text content as expected (blocker overlaying the text content with the maintained previous scroll position).

After completing step 3, the header disappears and the blocker is partially displayed in the top portion of the screen (with the text content below in a different scroll position) above a white portion (the height of the white portion varies with scroll position).  After a brief period, the header and text content display as expected (with the maintained previous scroll position).


Expected results:

The scroll position of the text content should be maintained when activating and deactivating the blocker without any flashing (e.g., of the white screen), moving of content (e.g., the blocker upward to reveal the white portion below), or hiding/revealing of content (e.g., the header).  The expected behavior is observed in the following browsers on the same device: Chrome, Opera, and the stock Android browser.

Comment 1

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

I tested this with the C++ APZ code and it looks to be fixed by that, so marking dependent on apz-fennec.

Comment 2

[BMO Automation]

We have completed our launch of our new Firefox on Android. The development of the new versions use GitHub for issue tracking. If the bug report still reproduces in a current version of [Firefox on Android nightly](https://play.google.com/store/apps/details?id=org.mozilla.fenix) an issue can be reported at the [Fenix GitHub project](https://github.com/mozilla-mobile/fenix/). If you want to discuss your report please use [Mozilla's chat](https://wiki.mozilla.org/Matrix#Connect_to_Matrix) server https://chat.mozilla.org and join the [#fenix](https://chat.mozilla.org/#/room/#fenix:mozilla.org) channel.