Total Kerning Pairs in Glyphs vs Exported Font

There often appears to be a small to sizeable difference in the total number of kerning pairs present within a source Glyphs file vs an exported OTF re-opened in Glyphs. In a typical Glyphs file the Kerning Window shows total kern pairs hitting around 4000–5000 pairs. If we open an OTF in Glyphs this number tends to increase by anything from 100 – 800 pairs.

I’m assuming that there is some de-compossing/re-writing of the kern table info upon Export. Or that the Kern Table is interpreted differently on OTF Import. I’m just curious if there was any more info on this?

If you have any kerning between a glyph and a class – most likely all you exceptions. This will result in a kerning pair for each member of class to the glyph. OpenType can only handle kerning between glyphs and between classes so all other pairs need to be decomposed.

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