Handle relation TODO:

[schriftgestalt]

• [ ] Calculate and display the intra-curve coefficients. For shallow curves, this may be non-trivial.
• [ ] Refine the definition of “close enough”.
• [ ] How about intermediate special layers?
• [ ] Look at the interpolated exports and ignore masters that are not used in interpolations (to be precise, there may even be independent groups of masters that are only interpolated among themselves).
• [ ] Detect if all masters have the same (or similar enough) angle. What if some masters have the same angle, and some have the same relative handle lengths? Need to think about that carefully, and respect the interpolated exports.

[schriftgestalt]

How about intermediate special layers?

    otherLayers = [layr for layr in layer.parent.layers if not layr is layer]

This should cover this already. But I would check for layer.isMasterLayer and layer.isBraceLayer.

Look at the interpolated exports and ignore masters that are not used in interpolations (to be precise, there may even be independent groups of masters that are only interpolated among themselves).

instead of this:

otherLayers = [layr for layr in layer.parent.layers if not layr is layer]

use something like this:

glyph = layer.parent
layerGroups = glyph.layerGroups()

That returned a list of lists of layers. This will respect bracket layers and such.