post

com.google.fonts/check/family/underline_thickness

Fonts have consistent underline thickness?

Rationale:

Dave C Lemon (Adobe Type Team) recommends setting the underline thickness to be consistent across the family.

If thicknesses are not family consistent, words set on the same line which have different styles look strange.

Legacy check originally simply called ‘check/008’. We used to lack richer metadata back in 2015. We’re open to further improvements to this description.

com.google.fonts/check/italic_angle

Checking post.italicAngle value.

Rationale:

The ‘post’ table italicAngle property should be a reasonable amount, likely not more than 30°. Note that in the OpenType specification, the value is negative for a rightward lean.

https://docs.microsoft.com/en-us/typography/opentype/spec/post

Legacy check originally simply called ‘check/130’. We used to lack richer metadata back in 2015. We’re open to further improvements to this description.

com.google.fonts/check/post_table_version

Font has correct post table version?

Rationale:

Format 2.5 of the ‘post’ table was deprecated in OpenType 1.3 and should not be used.

According to Thomas Phinney, the possible problem with post format 3 is that under the right combination of circumstances, one can generate PDF from a font with a post format 3 table, and not have accurate backing store for any text that has non-default glyphs for a given codepoint.

It will look fine but not be searchable. This can affect Latin text with high-end typography, and some complex script writing systems, especially with higher-quality fonts. Those circumstances generally involve creating a PDF by first printing a PostScript stream to disk, and then creating a PDF from that stream without reference to the original source document. There are some workflows where this applies,but these are not common use cases.

Apple recommends against use of post format version 4 as “no longer necessary and should be avoided”. Please see the Apple TrueType reference documentation for additional details.

https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6post.html

Acceptable post format versions are 2 and 3 for TTF and OTF CFF2 builds, and post format 3 for CFF builds.

Legacy check originally simply called ‘check/015’. We used to lack richer metadata back in 2015. We’re open to further improvements to this description. - Some additional changes were proposed at https://github.com/google/fonts/issues/215 / https://github.com/fonttools/fontbakery/issues/2638 / https://github.com/fonttools/fontbakery/issues/3635