merge method
Implementation
FocusThemeData merge(FocusThemeData? other) {
if (other == null) return this;
return FocusThemeData(
primaryBorder: other.primaryBorder ?? primaryBorder,
secondaryBorder: other.secondaryBorder ?? secondaryBorder,
borderRadius: other.borderRadius ?? borderRadius,
glowFactor: other.glowFactor ?? glowFactor,
glowColor: other.glowColor ?? glowColor,
renderOutside: other.renderOutside ?? renderOutside,
);
}