sCapHeight and sxHeight Consistency across a Font Family

ClintGoss
ClintGoss Posts: 66
in Font Technology
SIL's Font Development Best Practices recommends consistency of ascender and descender line metrics across fonts in a (R, B, I, BI) family.

Should the same hold true for OS/2.sCapHeight and .sxHeight? Maybe there are apps that use these values for something significant?
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  • Thomas Phinney
    Thomas Phinney Posts: 3,058
    ClintGoss wrote:
    SIL's Font Development Best Practices recommends consistency of ascender and descender line metrics across fonts in a (R, B, I, BI) family.

    Should the same hold true for OS/2.sCapHeight and .sxHeight? Maybe there are apps that use these values for something significant?
    These latter are normally typographically accurate measurements for the particular font, so whether they vary depends on whether the family actually varies.

    Most type designers keep cap height constant across most/all family members, and tend to vary x-height. Bolder styles tend to get a larger x-height. How much larger varies quite a bit.
  • ClintGoss
    ClintGoss Posts: 66
    edited May 2019
    Thomas Phinney said:
    .sCapHeight and .sxHeight ... are normally typographically accurate measurements for the particular font,
    Thanks for that ... and ... here are other metrics that I can imagine are actively used by applications:

    post.underlineThickness and its shadow OS/2.yStrikeoutSize as well as post.underlinePosition are supposed to be based on the metrics of "_". However, if the thickness of "_" changes between Regular and Bold (which sounds likely) an underscore painted by an app based on the declared post metrics will change and maybe look odd.

    Should I set post.underlineThickness, post.underlinePosition, OS/2.yStrikeoutSize, and OS/2.yStrikeoutPosition the same across a font family?
  • Thomas Phinney
    Thomas Phinney Posts: 3,058
    I make these things font-specific, if I care about them at all. It is reasonable to vary them depending on the thickness of the underline character and have both vary depending on the weight of the font. Thin underlines look really silly in ultrabold fonts!

    And yes, typographically savvy users avoid underlining if they can. However, they may be forced to by other circumstances. And one might want one's font to still look as good as possible, even when set by less savvy users.

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