FontFeature constructor Null safety

const FontFeature(
  1. String feature,
  2. [int value = 1]
)

Creates a FontFeature object, which can be added to a TextStyle to change how the engine selects glyphs when rendering text.

feature is the four-character tag that identifies the feature. These tags are specified by font formats such as OpenType.

value is the value that the feature will be set to. The behavior of the value depends on the specific feature. Many features are flags whose value can be 1 (when enabled) or 0 (when disabled).

See docs.microsoft.com/en-us/typography/opentype/spec/featuretags

Implementation

const FontFeature(
  this.feature,
  [ this.value = 1 ]
) : assert(feature != null),
    assert(feature.length == 4, 'Feature tag must be exactly four characters long.'),
    assert(value != null),
    assert(value >= 0, 'Feature value must be zero or a positive integer.');