Clumsy horizontal scroll when menu is open on mobile

[promz]

Steps to reproduce:

1. Open WP Admin in mobile
2. Click on the burger menu icon, this will open the menu
3. Try to horizontally scroll to bottom-left

Result: The screen should scroll to left as shown in the attached GIF.

Tested on: Chrome on Mac and Chrome on Android (Honor Play)

[promz]

Horizontal scroll problem

[promz]

I realized that changing the position of#adminmenuback from Absolute to Fixed fixes the problem.

.auto-fold #adminmenuback {
	position: fixed;
}

[man4toman]

Hi @promz
I check it on latest version of Firefox and Opera with Windows OS, I can't reproduce the problem.

[promz]

@man4toman you should probably check on a real device. Here are the screencasts:

Android: ​https://drive.google.com/file/d/16VNImnh2g9Ncg7cXU8XvwabGcKJEtzDS/view?usp=sharing

iPhone (horizontal scroll problem is not there but there is another scrolling problem):
​https://drive.google.com/file/d/1NOlWNZmzTgnB2vXzlfnetT1ExpYQLmbM/view?usp=sharing

The problem is with the older WordPress versions too.

[promz]

This fixes the problem and doesn't caused any problems as far as I have tested.

[SergeyBiryukov]

Hi @promz, welcome to WordPress Trac! Thanks for the report.

I'm removing the trunk version, as this doesn't seem to be a regression in 5.2.

[antpb]

Hi @SergeyBiryukov ! This patch looks good in my testing and still applies clean. It is also in line with the focus of 5.3 on UI improvements.

If you're good with it, I can commit. :)

[kirasong]

We chatted about this ticket in today's triage.

@antpb I think that unless @SergeyBiryukov has any hesitations here, your +1 along with previous testing seems good to me.

[antpb]

In 46460:

Administration: Prevents horizontal scroll jumping around while admin menu is open.

This sets the #adminmenuback position CSS property to fixed.

Props promz, man4toman.
Fixes #47010.