merge method
Returns a new icon theme that matches this icon theme but with some values replaced by the non-null parameters of the given icon theme. If the given icon theme is null, simply returns this icon theme.
Implementation
IconThemeData merge(IconThemeData other) {
if (other == null)
return this;
return copyWith(
color: other.color,
opacity: other.opacity,
size: other.size,
);
}