Created attachment 129796 [details] good/bad antialiasing SUMMARY bad scaling on external monitor, almost impossible to read at normal size, if QT_SCREEN_SCALE_FACTORS is set. STEPS TO REPRODUCE 1. have a Hi-DPI laptop (here 3200x1800) 2. connect an external normal-dpi monitor (1920x1200) to extend the desktop 3. open a PDF document and move the window onto the external screen OBSERVED RESULT the PDF is scaled with very bad antialiasing. EXPECTED RESULT nice antialiasing SOFTWARE/OS VERSIONS Linux/KDE Plasma: Neon User KDE Plasma Version: 5.19.2 KDE Frameworks Version: 5.71.0 Qt Version: 5.14.2 ADDITIONAL INFORMATION Workaround: export QT_SCREEN_SCALE_FACTORS='' before using okular, then it works
I experienced something similar, as described in https://bugs.kde.org/show_bug.cgi?id=421634 Can you please check whether that is related?
@Oliver, I'm not sure but I don't think so, since in my case the problem is due to different scalings on the monitors.
That's possible. What do you set QT_SCREEN_SCALE_FACTORS to?
Yes, mixed values of QT_SCREEN_SCALE_FACTORS are not supported on X11 for this and many other reasons. There is a proposal to begin supporting this; see https://phabricator.kde.org/D12405. However a lot of work will be required to get there. In the meantime, the Wayland session already supports this feature so I would recommend giving that a try.
my QT_SCREEN_SCALE_FACTORS is eDP-1=2;DP-1=1;HDMI-1=1;DP-2=1;HDMI-2=1; (notice the "2" for the laptop screen eDP-1)
@Nate, unfortunately I use displaylink driver for my external screen, and it won't work with Wayland. (not detected)
Yeah, I'm afraid mixed DPI on X11 is not supported for precisely this reason. It's a can of worms. We *might* be able to implement it eventually, but it will be very challenging. So at the moment, if you use it anyway, you're on your own. :) Can you file a bug for the Wayland issue?