Handle overlaps when compiling static fonts

[rsheeter]

Overlaps produce cutouts when drawn with evenodd fill. Apparently older versions of macos and maybe some printers do this.

When compiling a static (non-variable) font do at least one of:

• At least set OVERLAP_SIMPLE (only if there are overlaps?), https://learn.microsoft.com/en-us/typography/opentype/spec/glyf
• Actually remove the overlaps.
  • No Rust implementation equivalent ot Skia pathops appears to exist, would likely have to call into pathops
  • @simoncozens https://github.com/simoncozens/rust-font-tools/blob/main/fonttools-cli/src/bin/ttf-remove-overlap.rs does this via https://docs.rs/crate/skia-safe/latest

The importance of actually removing the overlaps is a bit unclear to me. It used to be done for macos but now we have the overlap simple flag. Rumor has it that old printers might need actual removal but I don't have specific examples.

References:

• https://github.com/fonttools/fonttools/issues/2059 discusses FreeType and Microsoft handling
• https://github.com/google/fonts/issues/2602#issuecomment-679031978
• https://twardoch.github.io/test-fonts/varia/160413-EvenOddTT/

[rsheeter]

Courtesy of @simoncozens , "There are many experienced designers out there sharing their perspective on this topic why it’s not needed to outline your text anymore but it’s still the go-to method for most designers whenever they’re preparing their files for print. " (https://www.jukeboxprint.com/blog/is-it-still-necessary-to-outline-your-fonts)