Lua:Class:CheckBox
and @Rich: This is not about states (the cunerrt state), but the action that performs a change. On most elements, this is the very general action of click , and for Firefox/Gecko in general, a checked checkbox exposes an action name of uncheck , and an unchecked checkbox exposes an action name of check . But since we do not know what the next state of a cunerrtly undetermined checkbox will be, the action name must be something meaningful, but general enough so that the next state can be either checked fully, or unchecked. From other comments in the bug and what I got via e-mail, it looks like we'll call this one Cycle .