Created attachment 137921 [details] adwaita and breeze-qt SUMMARY STEPS TO REPRODUCE 1. Open Firefox 2. Maximize the window OBSERVED RESULT The restore button is the same of the maximize button. EXPECTED RESULT SOFTWARE/OS VERSIONS Operating System: Kubuntu 21.04 KDE Plasma Version: 5.21.4 KDE Frameworks Version: 5.80.0 Qt Version: 5.15.2 ADDITIONAL INFORMATION This doesn't happen in other themes such as Adwaita.
Created attachment 137922 [details] breeze-qt restore button
Also, the minimize, maximize and restore buttons are more washed out than in Qt applications. It seems that the opacity is different.
I'm having a hard time understanding the problem. As far as I can see from your screenshots, everything looks fine. Can you clarify?
In Firefox (GTK app), the restore buttons shows as a ^ (is the same of the maximize button) instead of being diamond-shaped
Gotcha. Cannot reproduce. What apps are you able to reproduce this with? All? Some? Only one? Under which conditions?
Created attachment 137985 [details] gnome clocks Only Firefox so far. But the weird thing is: if I switch to Adwaita, the restore and maximize buttons becomes different. So I really don't know if this specific to Firefox. Other GTK apps such as GIMP, GNOME Clocks and GNOME Disk Utility doesn't have this problem.
Created attachment 137986 [details] bug happening in Firefox Here's a video.
Can reproduce with just Firefox. It's either an issue with out GTK theming that's specific to Firefox, or else a bug in Firefox itself.
It's really weird, because this happens with other themes such as Qogir, but not with Adwaita.
reported to Firefox devs: https://bugzilla.mozilla.org/show_bug.cgi?id=1574291 Chromium has the same bug, see bug 414591
I guess it's an upstream issue, then. Thanks.