After upgrading from KDE 5.14.5 to 5.17.5, and it's still observed on 5.19.5, I noticed that my window title font has become bigger. I discovered that it is now controlled by the "General" font setting instead of "Window title" which does not affect anything now.

Demonstration follows. Look at the window title and the General and Window title font settings.

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Is it a known bug? Are my settings wrong?

p.s. a related question: does anyone know if/how it's possible to decrease the height of the title bar to get rid of this ridiculously spacious padding? I have a proper desktop computer, this is not a tablet or something like that, I want rational use of my screen real estate, especially its height. There's no need to waste half of the title bar's height.

Don't know why your window title font isn't being used...
but as to your ps. question, have you looked at the button size options in the window decorations of the Breeze theme?
(or simply use the Plastik theme)

I managed to solve it. After an upgrade to KDE 5.20 did not help, I started to lurk around, and found that I had a "QT_QPA_PLATFORMTHEME=qt5ct" environment variable being set in /etc/X11/Xsession.d/99qt5ct.

Why it was still being set despite the following condition:

Code: Select all

if [ -z "$QT_QPA_PLATFORMTHEME" ] && [ "$XDG_CURRENT_DESKTOP" != "KDE" ]

is beyond my understanding (or rather I don't want to spend time looking why $XDG_CURRENT_DESKTOP isn't set to KDE at the time of evaluation of this condition). It is set properly in a running KDE session.

So I went ahead and simply commented it out, after which the problem got solved. It also solved the problem of KDE apps (konsole etc) icons missing in the task bar, in the systemsettings menu entries, in the kicker (or whatever it is called these days) menu, etc. They were missing after logging in and until I switched to a different icon theme, then back to the original (no matter which) one. This made them reappear, but only until the next logout and login.

The only issue that I still can see is that the qBittorrent system tray icon is missing, and it reappears in the same way after switching the icon theme, after which it persists until the application restarts. I can live with that, I guess. It can be considered a negligible loss after such a thing as an upgrade of the KDE version :).

Regarding the second question, decreasing the window title buttons doesn't make the title bar height smaller. Only decreasing the font size does, but still it could be decreased even further be it not for that ridiculous padding. As far as the Plastik theme goes, its window title bar isn't any smaller than the Breeze's. However, I am almost fine with it as it is.

Hopefully this thread will help someone searching for the same symptoms that I observed.

Since I couldn't reproduce this here at all with neither 5.17.5 nor 5.19.5 on Kubuntu, how about reporting this to your distribution?