Cargo Features

harfbuzz-sys = { version = "0.5.0", default-features = false, features = ["build-native-harfbuzz", "build-native-freetype"] }
default = build-native-freetype, build-native-harfbuzz

These default features are set whenever harfbuzz-sys is added without default-features = false somewhere in the dependency tree.

build-native-harfbuzz default = cc, pkg-config
build-native-freetype default

Enables freetype-sys of freetype

Features from optional dependencies

In crates that don't use the dep: syntax, optional dependencies automatically become Cargo features.

pkg-config build build-native-harfbuzz
cc build build-native-harfbuzz