Support variable features when building static instances #945
Description
Currently, a variable font may be built containing variable features through use of: a) the nascent variable feature syntax, or b) having otherwise identical feature files in different sources with different scalar values.
These are not supported when building static instances, however. (a) will fail to compile, while (b) will compile correctly for instances that match exact source positions, but will incorrectly take on the values at the default designspace position for any instances that must be interpolated.
Suggested resolution
- Instantiate variable feature files into static feature files during UFO instance generation
- Warn or reject designspaces with non-identical feature files when building static instances