After the delivery of plasma 5.11.3 via the kubuntu backports ppa (ppa:kubuntu-ppa/backports) on my Kubuntu artful systems, firefox is completely unusable. Seen on two different machines, one with intel graphics (haswell) and one with nvidia quadro FX570 using the nouveau driver. Firefox cannot be used unless compositing is turned off in kwin, so I suspect an issue in the latter. Specifically, all firefox buttons that are expected to open a window (e.g., the main menu button, the bookmark button, most of the extensions button) do not, making the browser limited to mere browsing (no bookmarks, no advanced actions driven via the menu, no extensions). The two machines where I see the issue have in common the use of mesa as the opengl provider (latest mesa in fact). I do not have the option to try with proprietary graphics drivers.
Marked as major since breaking the platform main browser is a big issue. Also note that the browser does not complain. Simply, the buttons stop working. This makes one think at first that the issue is from the browser, which may cause mozilla or linux distros to receive many wrong bug reports.
There are no changes in 5.11.3 which could indicate such a problem. From the window manager perspective there are no differences between a Firefox and any other window. Either it's broken for all or for none. An issue which is only visible in one application normally means it's a problem caused in this application and that we cannot do anything about it. Normally I would just close this bug. I'm keeping it open as an exception for two weeks in case further users report it.
Thanks for keeping the bug open for some time. At this point, I do not know if other applications are affected. In case I find some, I'll report on it. Firefox may be a bit special in what it does, since the buttons are meant to cause some graphical overlays to open right below them. My seeing kwin as a suspect comes from these considerations: - Disabling compositing makes firefox behave correctly. With compositing, all the overlay windows/dialogs stop opening (you just see the button appearing as pressed for operations that involve buttons). Also dialogs such as confirmation actions (e.g. for installing extensions) stop appearing. - It is not something related to the firefox profile. Resetting the profile makes no difference. - It is not something related to the specific graphics card. Two machines, one with Intel and the other with NVIDIA seem affected. - It is not something related to the specific firefox version. Tried both 56 and 57 beta and both have the issue. Furthermore, the issue started appearing after I had used FF 56 successfully. - It is not something related to some obscure configuration from the user. I have created a new user on the machine and the issue is also present. - It is not something related to the ubuntu build of firefox. The issue is also present with the generic firefox binary for linux from mozilla. - The issue is also present running firefox with LIBGL_ALWAYS_SOFTWARE=1 Is there anything that you can suggest for confirming or excluding relation with kwin?
Done more testing. Noticed that I also had a mesa update at about the same time as the plasma one. Managed downgrading mesa and the issue seems gone. Sorry for the noise.
Setting to mesa bug.