gio:property-action-invert-boolean (object)

object -- a g:property-action object
invert -- a boolean whether the state of the action will be the negation

The accessor for the invert-boolean slot of the g:property-action class returns whether the state of the action will be the negation of the property value. If true, the state of the action will be the negation of the property value, provided the property is boolean.