opentype__unitsperem

Checking unitsPerEm value is reasonable.

opentype/unitsperem

• Applies to: TTF
• Fontspector can hotfix?: no
• Fontspector can fix sources?: no

Rationale

According to the OpenType spec:

The value of unitsPerEm at the head table must be a value between 16 and 16384. Any value in this range is valid.

In fonts that have TrueType outlines, a power of 2 is recommended as this allows performance optimizations in some rasterizers.

But 1000 is a commonly used value. And 2000 may become increasingly more common on Variable Fonts.

Proposal

• https://github.com/fonttools/fontbakery/issues/4829

Profiles

• opentype (in section 'Opentype Specification Checks')

• universal (in section 'Opentype Specification Checks')

• googlefonts (in section 'Opentype Specification Checks')