While creating the font’s weights, errors between regular and bold are indicated by the red color above each glyph, but version 2865 does not indicate these errors.
This has now been moved to the Validation wizard, as it was too time-consuming.
We try to balance between performance and convenience, and they are sometime conflicting, especially with large and/or complex fonts.
Maybe someone can come up with a smarter way to do this all, but right now we notice FontCreator becomes less responsive with larger and complex fonts.
That said, we are thinking about putting back this feature, but then other features might need to be addressed. For example updating/calculating side-bearing expressions takes a lot of time, so maybe that should only be done if requested.
We think this discussion can be worthwhile, but only if a serous group of users is able to discuss this together with us.
Putting it in as an option which can be switched on or off might be good. There could be a note next to the option or a tool tip to say that this may slow down the program for large fonts. Then it is down to the user if they want it or not.
Recent updates show incompatibility issues with a red filled header, but any interpolation issues will be found through the validation wizard as that is more time-consuming.
Interpolation issues are sometimes false positives, as for example FontCreator can’t always tell if a start point for a contour is equally set in two masters. Also sometimes a composite glyph has two equal glyph members that are swapped. See:
Sometimes masters have the same contour, but with an opposite direction, as shown here:
In most cases the detected issues are a flaw by the font designer, but it can also be done deliberately, so it is best to manually inspect the specific outlines issues.
A variable font can’t interpolate a specific glyph if it has incompatible layers, but it can still interpolate with interpolation issues.