Glyph: get Vecs out of Options?

[madig]

Currently, contours, components, anchors, codepoints and guidelines are Vecs hidden behind an Option, which seems to be because they allow for non-existence of attributes in a glif file. This leads to code like

fn move_glyph(glyph: &mut Glyph, delta: f32) {
    let Some(outline) = &mut glyph.outline {
        // ...
    }
}

which I don't find especially, uh, ergonomic? Same goes for anchors, etc. I'd rather have a

pub struct Glyph {
    pub name: GlyphName,
    pub format: GlifVersion,
    pub advance: Option<Advance>,
    pub codepoints: Vec<char>,
    pub note: Option<String>,
    pub guidelines: Vec<Guideline>,
    pub anchors: Vec<Anchor>,
    pub contours: Vec<Contour>,
    pub components: Vec<Component>,
    pub image: Option<Image>,
    pub lib: Option<Plist>,
}

Since empty Vecs can just not be serialized (and don't alloc until they have one member), I don't think making them optional holds semantic value? Same for lib maybe?

Related to #27.

[cmyr]

Yes, it's gross. my intention was to losslessly adhere to the UFO spec, and represent all fields that were optional as Option<_> on the rust code. I'm not sure if this matters nor not? The way that it might matter is for round-tripping, if we wanted to preserve empty collections or something.

I defer to you, here; if you think it makes sense to use an empty vec to represent a missing field, and not serialize empty vecs, that sounds good to me.

[madig]

• codepoints: defined by a full element, so can't be an empty collection
• guidelines: same
• anchors: same
• components: same
• contours: can have empty collection, but see Meaning of empty contour? unified-font-object/ufo-spec#150

FWIW, ufoLib2 and defcon use empty lists for the above.

[cmyr]

Happy to see this change, it will be a nice ergonomics improvement.

[madig]

I just noticed: in the same vein, advance width and height are kept behind Option. The spec says https://unifiedfontobject.org/versions/ufo3/glyphs/glif/#advance, i.e. both could be regular fields defaulting to 0. There has been some thinking about changing 0 though: unified-font-object/ufo-spec#95 -- but @anthrotype decided to not go ahead with it?

[cmyr]

this also sounds good, the only reason these various things are awkward is because i did not feel knowledgeable enough to take any liberties.

[madig]

Good thing you now have extreme prejudice on your team.