The paint drawn as a foreground for the text.
The value should ideally be cached and reused each time if multiple text styles are created with the same paint settings. Otherwise, each time it will appear like the style changed, which will result in unnecessary updates all the way through the framework.
If color is specified, this value must be null. The color property
is shorthand for
Paint()..color = color.
In merge, apply, and lerp, conflicts between color and foreground specification are resolved in foreground's favor - i.e. if foreground is specified in one place, it will dominate color in another.
final Paint? foreground;