>
> DP-3-1 connected primary 1920x1200+0+0 (normal left inverted right x axis y
> axis) 518mm x 324mm
>
> Not sure what you think is hiding it, sounds like KDE is just broken.
Well, no, that's not fair - X allows you to query the display size, and
it used to return whatever the display claimed was its physical size,
then it changed to returning a lie explicitly intended to cause things
that do a DPI calculation to calculate 96pdi. KDE uses that X
interface, and so when X changed its behaviour, it resulted in KDE
almost always rendering at 96dpi (which is basically the result the X
change wanted, but wasn't necessarily what the KDE developers wanted).
It's true that they *can* still query the actual EDID-reported display
size somehow, but it's not really fair to say that KDE is 'broken' when
X explicitly went and changed the interface KDE was using with the
intent of making KDE do something different to what it thought it was
doing.
They can use xrandr to get the screen size connected to the output, I'm
not sure what else they want.
The old DPI reporting was always broken for multimonitor, so was deprecated
in favour of reporting the sizes and letting the DE do whatever it wants,
the old API was also fixed in time as 96, you can override it on the X.org
command line if you want, but really to support multi-head properly, use
the new API.
Dave.