The way to configure HiDPI font and icon scaling in KDE has changed
least a couple of times: (Note: Some programs, such as Chromium and Java,
ignore all these settings and have to be configured independently.)
1. In the original implementation of HiDPI support for KDE, as documented
in blog posts by KDE developer David Edmundson, it was necessary to set
both "force font DPI" - for fonts - and "scale display" - for
2. In January when I first installed Fedora 23, setting both "force font
DPI" and "scale display" produced unexpected results - I eventually
figured out that in fact, it worked much better if I just set "scale
display" to 2.
3. I've since changed jobs and installed Fedora 23 on a new laptop, and
with all the updates installed, it's again necessary to set both "force
font DPI" and "scale display" for everything to be legible without
squinting. But this it's undesirable to set both, because now with both
set, most KDE applications have huge fonts. Non-KDE applications like
Thunderbird look OK though.
Some possible clues as to why this has changed again:
Clue 1: If I leave "force font DPI" unset, it's actually set to 0 in a
config file, and the fonts are really tiny, suggesting that 0 is being
interpreted as "very small".
Clue 2: I now get these messages when I run a KDE application from a
Warning: QT_DEVICE_PIXEL_RATIO is deprecated. Instead use:
QT_AUTO_SCREEN_SCALE_FACTOR to enable platform plugin controlled
per-screen factors. QT_SCREEN_SCALE_FACTORS to set per-screen factors.
QT_SCALE_FACTOR to set the application global scale factor.
So I'm guessing that Qt has been upgraded to a newer version, but KDE
hasn't been updated to take account of the changes mentioned above.
Since they are environment variables, it looks like I can set them myself
without needing to wait for KDE to be fixed. So how should I set them?
where/how are you setting these variables?