Adds the state of the specified type to the state set if it is not already present.
Note that because an StateSet is a read-only object, this method should be used to add a state to a newly-created set which will then be returned by ref_state_set . It should not be used to modify the existing state of an object. See also notify_state_change.
this |
an StateSet |
type |
an StateType |
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