Error: In feature 'mkmk' lookup 'mkmk_latn_top' mark to base positioning rules cause an offset overflow

Glyphs
1

I’ve suddenly started seeing this error message when exporting:

In feature 'mkmk' lookup 'mkmk_latn_top' mark to base positioning rules cause an offset overflow (0x10218) to a lookup subtable

Could anyone explain what this means, what the 0x10218 here is, and what I should be looking for to fix it? I don’t know which glyph has a problem, and I don’t think 0x10218 is a valid Unicode number…

(Using Glyphs 2 (Version 2.6.6 (1352)))

2

That number doesn’t mean anything useful. It says that it is 537 bytes over the limit.

3

Ok, thanks… . :slight_smile: Any idea what could cause the error?

4

That error mean that there is too much GPOS. That is kerning and mark positioning. Mostly it is the kerning and the mark feature is just tipping the scale.

Check if you can reduce the kerning. Or add a Use Extension Kerning custom parameter to the font settings.