private void armSelection(Navigatable navigatable) {
		markedNavigatable = navigatable;
		markedLocation = navigatable.getLocation();
		if (markedLocation == null) {
			markedNavigatable = null;
		}
	}
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