Intrigued by “Add “Axis Mappings” custom parameter to support avar table” in the changelog for 1261. Any guidance for how this can be used?
I’m not sure myself, yet.
But the idea is to be able to match instance instances with the proper weigh class. So if you have a light at 300 and a Bold at 800. You picked an instance position for the Regular to have the right weight bit the interpolated weight class will not match. So you can add 300 > 300, 567 > 500 and 900 > 900 as mapping values. (or 500 > 567 that is the part where I’m not sure, yet.)
I wonder if I could I use this to fix a non-rectangular designspace that isn’t building with fontmake…
I’m experimenting with this today, maybe it can help with this issue: https://github.com/lettersoup/Sofia-Sans/issues/6
None rectangular design spaces are not supported. avar can only change the behavior of one axis at a time inside the designspace (AFAIK).
Thanks! It looks like a really nice feature anyway. 
I hope it will support mapping along other axes too–right now I have a project that could use mapped opsz.
That is already possible. It should show the axis in the left list. Select it and add a bunch of mappings to it.
Ah ok, if anyone else is also confused by this, this is a custom parameter option that shows up on the Font tab of Font Info (I’d been trying to add it on the Instances tab).