Negative-width glyphs

Hello, I am working on a file with fractions that have a specific design that requires the fraction glyph to have very negative sidebearings – so negative, in fact, that the glyph width needs to be negative. Sadly, this doesn’t appear to be possible in Glyphs, as the smallest width is 0. Is this intentional, and if so, why? This use case makes perfect sense to me. Or is it a technical limitation? I sincerely hope I don’t have to solve this with kerning.

Thank you for any ideas!

Edit: Workaround in case anybody else runs into this issue:

for m in Font.masters:
	kerning = Font.glyphs["fraction"].layers[].LSB - Font.glyphs["fraction"].layers[].RSB
	for num in ["one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "zero"]:
		Font.setKerningForPair(, "fraction", num + ".dnom", kerning)

The ‘fraction’ glyph can have negative side bearings so the glyph will fit over adjoining figures.

I am talking about the fraction glyph having so much of a negative sidebearing that the actual width of fraction becomes negative (Note how, in your screenshot, the width is still positive 116). This does not appear to be possible.

No, a glyph cannot have a negative width. This is not possible with OpenType.

What would this accomplish? There has to be some anchoring point to push against.

You can’t have negative width. But you can add kerning between the numbers and the fraction.