Certain non-text widgets can have a 'read only' state, such as cb4 on this test page . Because this state is not exposed to ATs, ATs have no way to present this condition to the user.
While this *could* be done via an object attribute (for instance), I personally think that the read-only state is, well, a state. ;) For this reason I opened the following ATK/AT-SPI bugs: . I also think that this condition/state is sufficiently rare that it would be worth waiting for the creation of the new ATK state rather than going the object-attribute (or similar) route.