@Override
	public ProgramLocation getProgramLocation(int row, int col, ListingField bf) {
		ProxyObj<?> proxy = bf.getProxy();
		Object obj = bf.getProxy().getObject();
		if (obj instanceof CodeUnit) {
			ListingModel layoutModel = proxy.getListingLayoutModel();
			Program program = layoutModel.getProgram();
			return new EntropyFieldLocation(program, ((CodeUnit) obj).getAddress(), col);
		}
		return null;
	}
@see ghidra.app.util.viewer.field.FieldFactory#getProgramLocation(int, int, ghidra.app.util.viewer.field.ListingField)
Ghidra/Extensions/sample/src/main/java/ghidra/examples/EntropyFieldFactory.java