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The state machine framework in Qt provides classes for creating and executing state graphs. Qt's event system is used to drive the state machines, where transitions between states can be triggered by using signals, and then the slots on the other end will be invoked by the signals to perform an action, such as playing an animation.

Once you understand the basics of state machines, you can use them to do other things as well. The state graph in the state machine framework is hierarchical. Just like the animation group in the previous section, states can also be nested inside of other states: