Two layers of button on Firefox

[Rafi Hasan]

I'm getting tow layers of minimize, maximize and exit buttons on Firefox.
And I don't think it's because of my themes, as default themes has the same issues.

[Sai Vinoba (saivinob)]

Which UM and Firefox versions are you using? Any info as when did it start or how one can reproduce the fault?

[Rafi Hasan (rafihasan0178)]

Version -72.0.1 (64-bit)
I don't know what UM is, but everything is default, I didn't change any think.
It starts if you go to customize in firefox and disable the title bar.

[Sai Vinoba (saivinob)]

Hi Rafi, sorry, by UM I mean UbuntuMATE. Thank you for mentioning how to reproduce the issue. I confirm the bug. See my screenshot.

If we disable title bar (from 'Customize' option) and then 'un-maximize' the firefox window, we see two layers of windows. If we take screenshot, both the layers are captured (see attached). I confirm this issue on Ubuntu MATE-20.04 and 18.04.

However, when I checked on Ubuntu (default) where Firefox has titlebar disabled by default, no such issues when we un-maximize. Enabled and disabled titlebar, still no issue. I also checked in Debian MATE. Firefox behavior with or without titlebar is normal.

[Sai Vinoba (saivinob)]

It looks like Ubuntu font is causing the issue. I was fiddling with system font settings and changed to Cantarell from Ubuntu and by chance noticed there was no double layered windows anymore when un-maximized. Changed back to Ubuntu fonts and the issue came back. I checked on both 20.04 and 18.04.

I made a screencast but not sure if I can upload video as attachment. If not possible to upload here, will upload to youtube and share link.

[Sai Vinoba (saivinob)]

Nevermind. After a system reboot, I see the double-layer again when un-maximizing Firefox :( However, it does go away and function normal for sometime.

[Rafi Hasan (rafihasan0178)]

I'm using Ubuntu Mate 19.10
It causes no issue if I keep the title bar. But keeping the title bar enabled is a bit annoying as I lose some screen and I don't have a large monitor. But I'm getting used to it, it's not a big thing, just wanted to report a bug for the first time 😅

[Sai Vinoba (saivinob)]

This seems not issue with Firefox alone but all GTK3 windows which do not use title bar. There is a bug #1854383 already for similar issue called window decorations. I could reproduce the issue consistently with steps given there.

There is a discussion thread at Ubuntu MATE community (https://ubuntu-mate.community/t/will-this-window-decoration-bug-ever-be-addressed/20924/3).