main.cpp Example File

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 #include <QtWidgets>

 class Window : public QWidget
 {
 public:
     Window(QWidget *parent = 0)
         : QWidget(parent)
     {
         QPushButton *button = new QPushButton(this);
         button->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);

         QVBoxLayout *layout = new QVBoxLayout;
         layout->addWidget(button);
         layout->setContentsMargins(80, 80, 80, 80);
         setLayout(layout);

         QStateMachine *machine = new QStateMachine(this);

         QState *s1 = new QState();
         s1->assignProperty(button, "text", "Outside");

         QState *s2 = new QState();
         s2->assignProperty(button, "text", "Inside");

         QEventTransition *enterTransition = new QEventTransition(button, QEvent::Enter);
         enterTransition->setTargetState(s2);
         s1->addTransition(enterTransition);

         QEventTransition *leaveTransition = new QEventTransition(button, QEvent::Leave);
         leaveTransition->setTargetState(s1);
         s2->addTransition(leaveTransition);

         QState *s3 = new QState();
         s3->assignProperty(button, "text", "Pressing...");

         QEventTransition *pressTransition = new QEventTransition(button, QEvent::MouseButtonPress);
         pressTransition->setTargetState(s3);
         s2->addTransition(pressTransition);

         QEventTransition *releaseTransition = new QEventTransition(button, QEvent::MouseButtonRelease);
         releaseTransition->setTargetState(s2);
         s3->addTransition(releaseTransition);

         machine->addState(s1);
         machine->addState(s2);
         machine->addState(s3);

         machine->setInitialState(s1);
         machine->start();
     }
 };

 int main(int argc, char **argv)
 {
     QApplication app(argc, argv);
     Window window;
     window.resize(300, 300);
     window.show();

     return app.exec();
 }