private void updateAction() {
		String menuName = "Mark Selection Start";
		String description = "Mark current location for selection start";
		Icon icon = unarmedIcon;

		if (markedLocation != null) {
			Address address = markedLocation.getByteAddress();
			menuName = "Create Selection from " + address;
			description = "Create selection from marked location: " + address;
			icon = armedIcon;
		}

		MenuData menuBarData = getMenuBarData();
		menuBarData.setMenuItemName(menuName);
		setDescription(description);
		getToolBarData().setIcon(icon);

	}
Actions for creating a selection using two distinct steps. The first time the action is invoked,
it records the current location as the start of a selection. The second time the action is
invoked it creates a selection from the recorded location to the current location.
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/codebrowser/MarkAndSelectionAction.java