@Override
	public FieldLocation getFieldLocation(ListingField bf, BigInteger index, int fieldNum,
			ProgramLocation loc) {
		if (loc instanceof FunctionPurgeFieldLocation) {
			FunctionPurgeFieldLocation functionPurgeLoc = (FunctionPurgeFieldLocation) loc;
			return new FieldLocation(index, fieldNum, 0, functionPurgeLoc.getCharOffset());
		}
		return null;
	}
@see ghidra.app.util.viewer.field.FieldFactory#getFieldLocation(ghidra.app.util.viewer.field.ListingField, BigInteger, int, ghidra.program.util.ProgramLocation)
Ghidra/Features/Base/src/main/java/ghidra/app/util/viewer/field/FunctionPurgeFieldFactory.java