How can I get more granular control of Unity scaling factor?

Question

In the Displays section of the settings, Unity has an option to set "Scale for menu and title bars". This option is presented as a slider with notches every .125. However, I find that the optimal scaling factor for my display would be between two of these notches. How can I change it to something like 2.06 or 1.85?

Answer 1

Short answer: Not possible. This is just not supported. Maybe a future version of Ubuntu will offer more fine-grained control, but for now at least you will have to do with the values that are there.

Long answer: I very recently answered a similar question here: How do I get the value of Display -> "Scale for menu and title bars:" from the command line?

Essentially, the scaling factor is stored as a dconf setting. Run

dconf read /com/ubuntu/user-interface/scale-factor

to see what the current scaling factor is. For me this gives

{'LVDS1': 8, 'HDMI3': 8}

...where LVDS1 is my laptop display and HDMI3 is my monitor connected via the docking station (you can set different scaling factors in setups with multiple displays).

The value displayed as the Scale for menu and title bars in System Settings -> Displays is 1/8 of the dconf value of the corresponding display. So the above output means that the scaling factors for both of my displays are 1.

You could change this dconf value manually (using dconf write, see my other answer), however it must be an integer, and any integer lower than 4 or higher than 16 will confuse the system. Therefore you can only set it to values 4, 5, 6, ..., 16, which corresponds to scaling factors 4/8=.5, 5/8=.625, 6/8=.75, ..., 16/8=2. Those are the .125 steps you were seeing.