fractional scaling not working when setting on individual monitors

[astromatt42]

I am using a docking station connected to two external displays with a HiDPI laptop screen. Getting fractional scaling to work was a bit of hit and miss in LM 20, however it has now broken again in 21.
The setting should be 100% for the two external monitors and 200% for the laptop screen. When I do this, the layout seems to be correct, see screenshot one, however it forces the external monitors to overflow badly, i.e. I am only shown the top left quadrant blown up by a factor of 2 on each external monitor, while the laptop screen scales correctly.
If I set everything to 100% (Screenshot 2), the external monitors are set correctly, however the laptop screen is now unscaled so too small (as expected).
I have tried this with the Nvidia and the nouveau open source drivers, the behaviour is the same.

Cinnamon 5.4.12
xsession-errors.txt

[astromatt42]

A workaround for this is to manually force a lower resolution on the HiDPI monitor when connected to the docking station, however the fractional scaling should still work.

[ridiche34]

Same problem, pls fix.
@astromatt42, can you please elaborate, I don't understand.

[astromatt42]

Hi, I'm closing this as it has been resolved since with updates. It was a problem of not being able to independently scale screens.

[ridiche34]

I am still experiencing this exact issue on the edge variant of 21.3 Cinnamon.

Upon scaling any monitor by a fractional value ("Enable fractional scaling controls (experimental)"), my second monitor only shows the top right corner of what it's supposed to show (my laptop monitor works perfectly fine).

[astromatt42]

Ok, I leave it open if you're still having issues. I don't remember when it resolved itself and am currently in the field so don't have an opportunity to test it with my setup for at least another few weeks.