Is there a way to reuse a master in a variable font to extend an axis where only the sidebearings change?

[SCarewe (Sebastian Carewe)]

Have a look at this thread:

Side bearing deltas / intermediate sidebearings

Hi! Here’s an interesting problem with linear interpolation: narrow styles require letter spacing to be equal to the counter space, but only until some point, when a tighter spacing is preferred (wide, normal and slightly narrow styles). Thus, if you interpolate between ultra condensed and normal widths, everything in-between is spaced too tightly, as you can see on the example below. In static instances that can be solved with a filter, cool. Is there a solution for variable fonts? Perhaps, a …

Specifically, you want to add a virtual master. See further down:

Side bearing deltas / intermediate sidebearings

Hello, I am trying to achieve something similar. I have a project with only a weight and an italic axis. I would now like to add an opsz axis that controls only the spacing. Ideally, in my working file, I would like to add as little as possible in order to keep everything easily editable. My thought process is the following: I add an opsz axis and set the same value for all masters (20, let’s say) I add a “Virtual Master” custom parameter and set opsz to 8. I add variable GPOS code like in t…

Summary:

• add a “Virtual master” custom parameter in Font Info > Font. Set its opsz location to 100. Don’t change the other values.
• in Font Info > Features, add a feature “kern”, and write:

pos @All <0 0 0 0 (opsz:100) -20 0 -20 0>;

where -20 is the amount by which you want to change the spacing (or, technically, half).