Reset history states when (re)starting state machine

State saved in QHistoryState should not be persistent between
state machine starts/stops.

Task-number: QTBUG-8842
Reviewed-by: Eskil Abrahamsen Blomfeldt

3 files changed, 72 insertions, 0 deletions

diff --git a/src/corelib/statemachine/qstatemachine.cpp b/src/corelib/statemachine/qstatemachine.cpp
index bd7e626..9d5c49f 100644
--- a/src/corelib/statemachine/qstatemachine.cpp
+++ b/src/corelib/statemachine/qstatemachine.cpp
@@ -1175,6 +1175,16 @@ void QStateMachinePrivate::removeStartState()
     _startState = 0;
 }
 
+void QStateMachinePrivate::clearHistory()
+{
+    Q_Q(QStateMachine);
+    QList<QHistoryState*> historyStates = qFindChildren<QHistoryState*>(q);
+    for (int i = 0; i < historyStates.size(); ++i) {
+        QHistoryState *h = historyStates.at(i);
+        QHistoryStatePrivate::get(h)->configuration.clear();
+    }
+}
+
 void QStateMachinePrivate::_q_start()
 {
     Q_Q(QStateMachine);
@@ -1186,6 +1196,7 @@ void QStateMachinePrivate::_q_start()
     internalEventQueue.clear();
     qDeleteAll(externalEventQueue);
     externalEventQueue.clear();
+    clearHistory();
 
 #ifdef QSTATEMACHINE_DEBUG
     qDebug() << q << ": starting";
diff --git a/src/corelib/statemachine/qstatemachine_p.h b/src/corelib/statemachine/qstatemachine_p.h
index 0fead5d..5e1015f 100644
--- a/src/corelib/statemachine/qstatemachine_p.h
+++ b/src/corelib/statemachine/qstatemachine_p.h
@@ -126,6 +126,8 @@ public:
     QState *startState();
     void removeStartState();
 
+    void clearHistory();
+
     void microstep(QEvent *event, const QList<QAbstractTransition*> &transitionList);
     bool isPreempted(const QAbstractState *s, const QSet<QAbstractTransition*> &transitions) const;
     QSet<QAbstractTransition*> selectTransitions(QEvent *event) const;
diff --git a/tests/auto/qstatemachine/tst_qstatemachine.cpp b/tests/auto/qstatemachine/tst_qstatemachine.cpp
index 90b5a22..2bf76e7 100644
--- a/tests/auto/qstatemachine/tst_qstatemachine.cpp
+++ b/tests/auto/qstatemachine/tst_qstatemachine.cpp
@@ -155,6 +155,7 @@ private slots:
     void clearError();
     void historyStateHasNowhereToGo();
     void historyStateAsInitialState();
+    void historyStateAfterRestart();
     void brokenStateIsNeverEntered();
     void customErrorStateNotInGraph();
     void transitionToStateNotInGraph();
@@ -906,6 +907,64 @@ void tst_QStateMachine::historyStateHasNowhereToGo()
     QCOMPARE(machine.errorString(), QString::fromLatin1("Missing default state in history state 'historyState'"));
 }
 
+void tst_QStateMachine::historyStateAfterRestart()
+{
+    // QTBUG-8842
+    QStateMachine machine;
+
+    QState *s1 = new QState(&machine);
+    machine.setInitialState(s1);
+    QState *s2 = new QState(&machine);
+    QState *s21 = new QState(s2);
+    QState *s22 = new QState(s2);
+    QHistoryState *s2h = new QHistoryState(s2);
+    s2h->setDefaultState(s21);
+    s1->addTransition(new EventTransition(QEvent::User, s2h));
+    s21->addTransition(new EventTransition(QEvent::User, s22));
+    s2->addTransition(new EventTransition(QEvent::User, s1));
+
+    for (int x = 0; x < 2; ++x) {
+        QSignalSpy startedSpy(&machine, SIGNAL(started()));
+        machine.start();
+        QTRY_COMPARE(startedSpy.count(), 1);
+        QCOMPARE(machine.configuration().count(), 1);
+        QVERIFY(machine.configuration().contains(s1));
+
+        // s1 -> s2h -> s21 (default state)
+        machine.postEvent(new QEvent(QEvent::User));
+        QCoreApplication::processEvents();
+        QCOMPARE(machine.configuration().count(), 2);
+        QVERIFY(machine.configuration().contains(s2));
+        // This used to fail on the 2nd run because the
+        // history had not been cleared.
+        QVERIFY(machine.configuration().contains(s21));
+
+        // s21 -> s22
+        machine.postEvent(new QEvent(QEvent::User));
+        QCoreApplication::processEvents();
+        QCOMPARE(machine.configuration().count(), 2);
+        QVERIFY(machine.configuration().contains(s2));
+        QVERIFY(machine.configuration().contains(s22));
+
+        // s2 -> s1 (s22 saved in s2h)
+        machine.postEvent(new QEvent(QEvent::User));
+        QCoreApplication::processEvents();
+        QCOMPARE(machine.configuration().count(), 1);
+        QVERIFY(machine.configuration().contains(s1));
+
+        // s1 -> s2h -> s22 (saved state)
+        machine.postEvent(new QEvent(QEvent::User));
+        QCoreApplication::processEvents();
+        QCOMPARE(machine.configuration().count(), 2);
+        QVERIFY(machine.configuration().contains(s2));
+        QVERIFY(machine.configuration().contains(s22));
+
+        QSignalSpy stoppedSpy(&machine, SIGNAL(stopped()));
+        machine.stop();
+        QTRY_COMPARE(stoppedSpy.count(), 1);
+    }
+}
+
 void tst_QStateMachine::brokenStateIsNeverEntered()
 {
     QStateMachine machine;