1625999 - Websites' resolution change when activating Touch Simulation in RDM mode

Status: RESOLVED DUPLICATE of bug 1888242

(DevTools :: Responsive Design Mode, defect, P3)

Description

[Clara Guerrero ( Need Info Brindusa Tot Please)]

Attachment: resolutin.MOV

[Affected versions]
Release 74.0 (64-bit)
Beta 75.0b11 (64-bit)
Firefox Nightly 76.0a1 (2020-03-31) (64-bit)

[Affected platforms]
All

[Steps to reproduce]

1- visit youtube or facebook
2- Make sure "reload when touch simulation is toggled" is checked.
3- Click on touch simulation button to activate and deactivate.

[Expected result]
Website should be displayed properly.

[Actual result]
Resolution changes

Comment 1

[Clara Guerrero ( Need Info Brindusa Tot Please)]

Attachment: resolution.MOV

Comment 2

[Clara Guerrero ( Need Info Brindusa Tot Please)]

Attachment: resolution2.MOV

Comment 3

[Brad Werth [:bradwerth]]

I can't reproduce this exactly, but I can reproduce a case that seems related. On facebook.com, with touch simulation ON, toggling RDM on and off (repeatedly) will sometimes display the RDM off case with a clipped viewport. This reminds me of Bug 1569626. I'll try to debug this behavior, then check in with Clara to see if it solves the original issue.

Comment 4

[Firefox Bug Husbandry Bot]

Because this bug's Severity has not been changed from the default since it was filed, and it's Priority is P3 (Backlog,) indicating it has been triaged, the bug's Severity is being updated to S3 (normal.)

Comment 5

[Micah [:mtigley] (she/her)]

Attachment: fb_class_toggle.gif

Interestingly, with the Facebook example, I can see a class being toggled on the document's HTML tag when touch simulation is enabled/disabled. See attached gif.

Comment 6

[Brad Werth [:bradwerth]]

I'm getting pulled onto other things. I'm taking myself off this bug. My best guess is that the class change noted in comment 5 is happening in the middle of the RDM teardown, and depending on when that script runs, we get different results. So possible fixes would include:

1. Preventing script from running during RDM teardown. Probably hard to do.
2. Running reflow/repaint one more time after at the end of RDM teardown. This would add to the already jarring pop-in that we get from RDM transitions.