User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:75.0) Gecko/20100101 Firefox/75.0

Steps to reproduce:

Enabled webrender and go to Help > About mozilla

Actual results:

Window sometimes is transparent, black or normal.

Expected results:

Correct rendering.

Black window

Bugbug thinks this bug should belong to this component, but please revert this change in case of error.

Transparent, it's over a white background.

Can you attach the contents of about:support as a text file please?

I should note that I'm using the flatpak version of firefox and I think this problem has to do with it, I will see if this problem happens on the native firefox once the update to 75 comes.

Keep us posted on what you find.

Ok, it also happens on the native firefox 75 so this isn't a flatpak problem, I just upgraded from firefox 74 from the fedora repos to the flatpak 75 version and thought it was culprit as I don't remember seeing this before.

I have tested firefox 76.0b2 and 77.0a1 with the same profile and can't reproduce, maybe it is 75 specific.

Thanks! Can you reproduce this problem with the Library (Ctrl+Shift+O), too? Can this bug be caused by maximizing and unmaximizing it?

Doesn't happen with the library nor does with maximizing and unmaximizing.
If I click on the windows key while the about firefox is misbehaving and select the firefox window and then switching again to the about firefox it will render normally.

I have come across the same bug on the main firefox window, basically it became all transparent during a youtube video, I could only see the firefox tittle bar that has the button to close the window and the youtube video progress bar.

About Firefox was transparent at 2 times. It was transparent only the first time I open it in both cases.
I don't remember if the background was white or from the window behind it.

I enabled gfx.webrender.all and layers.acceleration.force-enabled.
Firefox was launched with the Intel GPU at least the second time.

CPU: Intel Core I5.
GPU: AMD Radeon HD 7670M.

bug 1611372 might have helped a bit. If you can fix it by maximizing and unmaximizing, it's bug 1502519.

I confirm that just maximizing the about firefox window makes it render correctly.

(In reply to Jan Andre Ikenmeyer [:darkspirit] from comment #12)

bug 1611372 might have helped a bit. If you can fix it by maximizing and unmaximizing, it's bug 1502519.

Oh, sorry, I meant "if a bug like this can be caused by maximizing, it's bug 1502519".

(In reply to monterro from comment #13)

I confirm that just maximizing the about firefox window makes it render correctly.

If I click on the windows key while the about firefox is misbehaving and select the firefox window and then switching again to the about firefox it will render normally.

If it's fixed with the next Nightly (build 20200418094905), we can close this as duplicate of bug 1611372.

(In reply to monterro from comment #10)

I have come across the same bug on the main firefox window, basically it became all transparent during a youtube video, I could only see the firefox tittle bar that has the button to close the window and the youtube video progress bar.

That sounds like a different problem. If you see it again, please make a screenshot of it and try to open about:support, click on "copy text to clipboard", paste it into a text file and attach both files to a new bug report.

On comment 7 I wrote I couldn't reproduce the bug on Firefox 76.0b2 and 77.0a1, maybe wait for Firefox 76 stable to rollout to confirm the fix and close the bug.

It happened the first time I opened About Firefox. It was transparent and I could see what was behind it. I don't know if it'll remain transparent if I moved it or not.

Firefox was installed from FlatHub.
OS: Fedora 31 with Gnome.

It is still present on Firefox 76 from flathub, maybe this is a flatpak specific bug.

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.)

The bug has been fixed for me with firefox 77 and now 78, can close the bug.