Enum FontHinting 

pub enum FontHinting {
    Smooth = 0,
    Normal = 1,
    Monochrome = 2,
}

The font hinting algorithm.

Variants

Smooth = 0

Lighter hinting algorithm– glyphs are slightly fuzzier but better resemble their original shape. This is achieved by snapping glyphs to the pixel grid only vertically which better preserves inter-glyph spacing.

Normal = 1

Default hinting algorithm– offers a good balance between sharpness and shape at smaller font sizes.

Monochrome = 2

Strongest hinting algorithm– outputs only black/white glyphs. The result is usually unpleasant if the underlying TTF does not contain hints for this type of rendering.