User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:74.0) Gecko/20100101 Firefox/74.0

Steps to reproduce:

I am designing custom web app. I am using materialize css framework. I placed preloader into the parent form, which does have border-radius and to avoid preloader overflow, I set parent form overflow property to hidden.

Actual results:

Apparently, for the first ~5 seconds overflow hidden causes some visual glitches as shown in video. Overflow hidden property tries to hide overflown part of the preloader. As o f my understanding browser engine tries to hide overflown part, child elements css animation still overcomes hidding. seems that overflow hidden activates when it figures out that some part was overflown, but it is late since the animation already have been shown.

Expected results:

Overflow hidden must hide overflown parts properly all the time. It must monitor all the time to prevent possible glitches before they appear

Forgot to mention. Please take a look at the top right corner of the form to see the visual glitches

Hi,

@bekatd@gmail.com Unfortunately I cannot validate this issue since we don't have any access or copy of your wep app. Could you please provide us any clear steps to reproduce this issue on other environment or give us access to the correspond/copy of web app?

Thanks.

Ok. I tried to extract only the part that is shown on the video and apparently there's no issue anymore (so not even I can validate the "issue"), but on actual form still the same happens, even though other browsers render page perfectly fine. Anyway here is the html file if you wish.

attachment

Hi,

Unfortunately I'm not able to reproduce this issue. Anyway I'm setting component to COre - Graphics for someone to take a look at this.

Meanwhile @bekatd@gmail.com could you please try on our latest nightly build? You can download it from here: https://nightly.mozilla.org/.

Thanks

I just tested it on a nightly build and unfortunately the problem is still there.

I am attaching a new file. Now you can reproduce the issue :)

PS: Don't steal my design :)

To reproduce this issue, press the sign-in button and watch the top right corner of the form.

Issue reproduces with webrender disabled.
Issue does not reproduce with Webrender enabled.

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.)