@Override
		public BigInteger getIndexBefore(BigInteger index) {
			if (index.compareTo(BigInteger.ZERO) <= 0) {
				return null;
			}
			return index.subtract(BigInteger.ONE);
		}
Simple layoutModel to be used for the preview panel.
Ghidra/Features/Base/src/main/java/ghidra/app/util/viewer/options/OptionsGui.java