[addfeatures] will compile glyph with negative advance width

[frankrolf]

I’ve been testing addfeatures, which is the replacement for makeotfexe.
Today I noticed that a glyph deliberately set to a negative width will make it through addfeatures without complaints.

It seems that the advance with in the resulting UFO is just subtracted from 2 ** 16 – these are examples with -1 and -100 units advance width.

[frankrolf]

Hmm. The behavior in makeotfexe seems to be the same.

    makeotf.lib version: 2.6.0
    OTF Library Version: 65793

Anyway, probably the font shouldn’t compile, and the user should know which glyphs have negative advance widths.