How do you deal with different physical DPIs on monitors?

[Łukasz Maśko]

Hello.
I've recently bought a new 12.5" laptop with FullHD display, which gives a 
density about 176dpi. I'm also using an external 19" monitor with 1440x900 
resolution (connected to a docking station), which has density almost equal to 
90dpi. I have my KDE environment configured for the internal panel (dpi, font 
sizes and so on). It looks nice and allows for comfortable work.

The problem is, that when I attach the external screen, everything rendered on 
it gets extremally big. It is easy to explain - pixels are almost 2 times 
bigger (physically). But it makes things look... bad. And the screen surface 
is "wasted" in a way.

I tried to - in a way - emulate higher density with xrandr:

$ xrandr --fb 4800x1800 --output DP1-3 --scale-from 2880x1800 --output eDP1 --
pos 2880x0

And it - in a  way - does the job. Unfortunately, although sizes get adjusted, 
scaling does not always make things look acceptable, especially when text is 
considered.

Do you have any ways of dealing wiht a problem of concurrently connected 
monitors with different physical pixel densities? What would you propose? 
Apart from buying another monitor, for it probably would need to be of UltraHD 
density ;-)
-- 
Łukasz Maśko                                                            _o)
Lukasz.Masko(at)ipipan.waw.pl                                           /\\
Registered Linux User #61028                                           _\_V
Ubuntu: staroafrykańskie słowo oznaczające "Nie umiem zainstalować Debiana"