User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:90.0) Gecko/20100101 Firefox/90.0

Steps to reproduce:

1. If you prefer, go to about:profiles and create a brand new profile to test the next steps.
2. Open a standard webpage (i.e. not "about:…" nor AMO), https://bugzilla.mozilla.org/home will do.
3. Open the protections panel (shield icon), then click one of its "Allowed" or "Blocked" sub-panels

Actual results:

The opening animation is janky, namely the sub-panel opens in two visible steps (half opened, then full opened). Closing the sub-panel by clicking the top-left arrow does the same.

This is happening probably since the beginning of Proton UI. This is a 64-bit Windows 10 laptop with only built-in Intel graphics (WebRender is functional).

Expected results:

Both the opening and closing animation for these sub-panels should be smooth like every other sub-panel.

The Bugbug bot thinks this bug should belong to the 'Firefox::Protections UI' component, and is moving the bug to that component. Please revert this change in case you think the bot is wrong.

Hey Mauro,
I tried reproducing this on the latest versions of Firefox Nightly 90.0a1 (2021-05-24), beta 89.0b15 and release 88.0.1 but the animation feels and acts normal.

Can you test the issue while in Safe Mode? You can find helpful info here : https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode .
Also a fresh new profile could help. You can find more about creating a new profile here : https://support.mozilla.org/en-US/kb/troubleshoot-and-diagnose-firefox-problems#w_6-create-a-new-firefox-profile .
If possible, you can test this issue on the nightly build as well. Download the build from : https://www.mozilla.org/en-US/firefox/nightly/all/ .

Hi Andrei; as you requested:

• Tested in Troubleshoot Mode (aka Safe Mode) I cannot reproduce the issue, alas…
• … testing a new profile (as pointed in my STR) does reproduce the issue; I guess this discards 3rd party extension interference.
• And I am already in the Nightly build (the user agent in the OP is legit); this was tested in today's build (90.0a1, 20210524084213).

I would like to post an animation of the issue but don't know an easy way to do it (the XBOX Game Bar in my system says something like it hasn't enough resources to do a video screen capture).

After a little experimenting found that:

• Troubleshoot Mode/Safe Mode sets "Compositing" to "Basic" and this issue is gone.
• Setting gfx.webrender.force-disable to true sets "Compositing" to "Direct3D 11" and this issue is gone as well.

So it seems to be a WebRender kink.

You can add any video (even one captured with your phone) if you would like; it would help us I'm sure. Upload it to a google drive it it's too large and just leave a link.
Since the issue already has a component set it the devs will be aware of it.

Created a GIF animation @30 fps hopefully showing the issue. The first part shows the Tracking Protection sub-panels (in this case "Blocked/Third-Party Cookies" and "Blocked/Tracking Content") where the opening/closing animations are janky; then the second part shows the Site Information sub-panel (in this case "Connection secure") where the same animations are smooth.

With today's update this issue is gone; checking the bug list for today's update it turns out this was solved in Bug 1708446 so marking this one as duplicate; thanks.