copyWith method

Creates a copy of this object with the given fields replaced with the new values.

For nullable fields, passing null leaves the field unchanged (standard Dart copyWith behavior). To explicitly reset a nullable field to null, pass a domain-invalid sentinel value:

• String? fields: pass an empty string (isEmpty) to reset to null.
• List? / Set? fields: pass an empty collection (isEmpty) to reset to null.
• double?/int? fields (positive-only, e.g. height/width/angle): pass a negative value (isNegative) to reset to null.

These sentinel values are never valid for the respective fields (enforced by constructor assertions), making the intent unambiguous.

• mainColor: The primary color of the element.
• shape: The shape of the element.
• offset: The offset position of the element.
• heightFactor: The height factor of the element.
• widthFactor: The width factor of the element. Pass a negative value to reset to null.
• angle: The rotation angle of the element in degrees. Pass a negative value to reset to null.
• child: A potential child element.