Components could have a baseLayer attribute to allow components from other layers

[klaavo]

This would make working with components and layers more flexible and powerful.
The ufo3 spec states that "Components must only reference glyphs within the same layer that the component belongs to." This is good mainly for multiple master kind of approach in mind, but we'll hopefully have a better format in the future for font-to-font interpolation.
Many tools also currently use the primary layer as the default component source on all layers.

[madig]

Any opinions on this?

[LettError]

Which many tools do this?

[madig]

Glyphs for one.

[LettError]

I gathered. Any others?

[madig]

If I could figure out how to work Fontlab 6, I could test it there. @twardoch?

[belluzj]

As a comment for the meeting, we're still interested in having this, if only for the sake of allowing better roundtrip with glyphsLib when concerned with background layers.

In case there is a concern that this is a big feature to add, the spec could allow this and then there would be serveral levels of conformance with this among UFO tools:

1. make sure to read this data and write it back (allows good round-trip with Glyphs.app)
2. actually take into account in the editors' UI (allows to use this in background layers to have the foreground as a reference while designing; what Glyphs.app allows)
3. actually take into account when compiling the UFO (allows "more flexible and powerful" work with components, as requested by the OP).

Nikolaus and me asking for this is on behalf of Dalton Maag is because we're interested in 1. so far, not much more yet.

[justvanrossum]

One concern is pens. The pen protocols are hard to change.

[schriftgestalt]

On top of the background components if would be interesting to have components referencing different masters. Several users asked for it. But I don’t have a format for that, yet.