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alerque / libertinus

The Libertinus font family
SIL Open Font License 1.1
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Request: Slashed zero as alternate form of U+2205 Empty Set #491

Open jcrippen opened 2 years ago

jcrippen commented 2 years ago

Many authors in mathematics and linguistics use a ‘slashed zero’ form for the empty set symbol, in contrast with the ‘slashed circle’ form that is the form currently used in the Libertinus fonts. A detailed discussion in a Unicode proposal from 2015 suggests that the slashed zero variant was popularized by Donald Knuth. There is also a short mention of this in the Wikipedia article ‘Empty set’ as well as some StackExchange discussions (math, TeX).

It would be nice if Libertinus could offer a slashed zero variant of ∅ U+2205 Empty Set. Three slashed zero glyphs are already available in v7.040 – namely glyph 2388, glyph 2573, and glyph 2574 – so adding a variant should presumably require only some OpenType magic.

According to Unicode 13 ch. 22, the slashed zero form of Empty Set should also be selectable with a variation selector: U+2205 U+FE00. I tried this in a text editor and nothing happened, but that could be the editor or text renderer rather than the font.

jcrippen commented 2 years ago

FontForge says the three slashed zero glyphs are “zero.slash.fitted”, “zero.slash.cap”, and “zero.slash.cap.fitted” if that helps.