Sets the hint style for font outlines for the font options object.
This controls whether to fit font outlines to the pixel grid,
and if so, whether to optimize for fidelity or contrast.
The following constants can be passed in the hint_style argument:
#CAIRO_HINT_STYLE_DEFAULT-
Use the default hint style for font backend and target device.
#CAIRO_HINT_STYLE_NONE-
Do not hint outlines.
#CAIRO_HINT_STYLE_SLIGHT-
Hint outlines slightly to improve contrast while retaining good fidelity to the original shapes.
#CAIRO_HINT_STYLE_MEDIUM-
Hint outlines with medium strength giving a compromise between fidelity to the original shapes and contrast.
#CAIRO_HINT_STYLE_FULL-
Hint outlines to maximize contrast.