@Override
	public FieldLocation getFieldLocation(ListingField bf, BigInteger index, int fieldNum,
			ProgramLocation loc) {
		Object obj = bf.getProxy().getObject();
		if ((obj instanceof Function) && loc.getClass() == RegisterFieldLocation.class) {
			RegisterFieldLocation regLoc = (RegisterFieldLocation) loc;
			return new FieldLocation(index, fieldNum, regLoc.getRow(), regLoc.getCharOffset());
		}
		return null;
	}
Field to show register values at the function entry point.
Ghidra/Features/Base/src/main/java/ghidra/app/util/viewer/field/RegisterFieldFactory.java