in src/font.rs [68:78]
fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
self.weight.hash(state);
self.italic.hash(state);
self.stretch.hash(state);
self.family.hash(state);
self.variations
.iter()
.map(|(s, v)| (s, OrderedFloat(*v)))
.collect::<Vec<_>>()
.hash(state);
}