Blend2D
2D Vector Graphics Engine
Associates a font feature tag with a value. Tag describes the feature (as provided by the font) and value
describes its value. Some features only allow boolean values 0 and 1 and some allow values up to 65535. Values above 65535 are invalid, however, only BL_FONT_FEATURE_INVALID_VALUE should be used as invalid value in general.
Registered OpenType features:
Feature value.