Okular and other Qt applications do not create any visible windows

[soundofthunder]

@johnfoot

alas removing this package

As mentioned, it was likely part of the solution. Also, one presumes that the theme wasn’t in use at the time, and a reboot was subsequently performed. You might have better luck finding the thread than I did. Cheers.

[johnfoot]

Ah I see. I looked for kvantum-related threads, but essentially found that people had to also install kvantum-qt5 following the recent stable updates, which was already installed on my machine.

I tried removing the kvantum-theme-matcha, rebooting, removing all kvantum config I could find (inside ~/.config/Kvantum, there was nothing inside /etc/xdg/), but nothing changed…

What bugs me is that I can see from top that the apps seem to be running fine, I just can’t see anything

[johnfoot]

Hi again,

Here’s the output of telegram-desktop (5.1.1 static build and from manjaro extra package):

QPainter::begin: Paint device returned engine == 0, type: 2
QWidget::render: Cannot render with an inactive painter
QXcbSystemTrayBackingStore: Failed to create Picture with format 1e2 for window 340000c, error code 9
QRhiGles2: Failed to make context current. Expect bad things to happen.
Failed to create QRhi for QBackingStoreRhiSupport
QOpenGLFramebufferObject: Framebuffer incomplete attachment.
QOpenGLFramebufferObject: Framebuffer incomplete attachment.
QOpenGLFramebufferObject: Framebuffer incomplete attachment.
QOpenGLFramebufferObject: Framebuffer incomplete attachment.
QOpenGLFramebufferObject: Framebuffer incomplete, missing attachment.

I’m not very familiar with Qt objects, but maybe this gives more hints about what is going on ?

[johnfoot]

I found the culprit ! In my case, defining QT_SCALE_FACTOR broke the qt6 applications.

I had a complex set of qt environment variables defined through trial and error so as to get correct scaling inside all apps with a HiDPI.

Here is a set that currently works for me and scales both qt5 and qt6 apps well:

export QT_AUTO_SCREEN_SCALE_FACTOR=0
export QT_ENABLE_HIGHDPI_SCALING=0
export QT_SCALE_FACTOR="" # do not define this one !
export QT_SCREEN_SCALE_FACTORS=1.5
export QT_FONT_DPI=144
export QT_QPA_PLATFORMTHEME=qt5ct:qt6ct

Thanks to everyone who helped me looking into the problem.