Any way to automate brace layer metric interpolation?

Is there any way to automate the brace layer metric interpolation? May be a special formula in the metrics field?

This would actually be great. Setting (max. 2) of the metrics (LSB, RSB, width) to interpolated would be very useful. Can’t count the number of times I overlooked this…

You mean that the brace layer should have warn when the sidebearing are not what “Re-interpolate Metrics” would set? For a live setting this would be quite difficult as it would need to interpolate the outlines all the time. Maybe that could be a script that would check all brace layer and fixes them if needed.

What actually happens for Re-interpolate Metrics? What exactly is interpolated? LSB and width, or LSB and RSB? Or are the actual outlines interpolated and the sidebearings/width of the outlines applied?

In any case, you wouldn’t need to interpolate everything all the time, you only need to re-interpolate the values if the metrics change in one layer and check whether they match the current brace layer metrics values.

But to check if the values match, you actually need to interpolate the outlines for the spot where the brace layer is, measure the side bearings and compare them with the ones from the brace layer. And ‘if something has changed’ can be a lot (e.g. components and corners)

So it is not possible, to simply get LSB and RSB from the ambient layers and calculate it for the brace layer? Or is the problem caused by the external changes in components?
But there must be a point, where glyphs recalculates everything…(simply ignore, if my thoughts do not make any sense)

If not, it could be helpful for the forgetful designer, if a mark appears on changing metrics in a layer, that affects a brace layer. Or would this also be too complex because of the components and corners?

Finally, It would be sufficient, if the user gets a warning on exporting font files.

I had a look at the code again and there is a lot interpolation going on in there cases so it can’t be too bad do add another one.
To sync the metics of the brace layer, you can add ==glyphname metrics keys (where glyphname is the name of the glyphs itself. And the == mean that it is only applied to that layer not to the whole glyph.

Sounds good!