Make sure QStateMachine stops when it's told to

If QStateMachine::stop() was called by an event test or while
transitioning to another state, the state machine could end up
in an inconsistent internal state (stop==true, but the stopped()
signal was not emitted). This also caused the machine to behave
incorrectly if it was then restarted (it would immediately stop
upon receiving the first event).

Solution: Move the stop-handling after the event processing loop,
so that it always takes precedence over other possible reasons
for exiting the loop (event queues exhausted, final state
entered).

Task-number: QTBUG-16463
Reviewed-by: Eskil Abrahamsen Blomfeldt

2 files changed, 73 insertions, 2 deletions

diff --git a/src/corelib/statemachine/qstatemachine.cpp b/src/corelib/statemachine/qstatemachine.cpp
index 392c45d..b2af5ca 100644
--- a/src/corelib/statemachine/qstatemachine.cpp
+++ b/src/corelib/statemachine/qstatemachine.cpp
@@ -1245,9 +1245,7 @@ void QStateMachinePrivate::_q_process()
 #endif
     while (processing) {
         if (stop) {
-            stop = false;
             processing = false;
-            stopProcessingReason = Stopped;
             break;
         }
         QSet<QAbstractTransition*> enabledTransitions;
@@ -1299,6 +1297,11 @@ void QStateMachinePrivate::_q_process()
 #ifdef QSTATEMACHINE_DEBUG
     qDebug() << q << ": finished the event processing loop";
 #endif
+    if (stop) {
+        stop = false;
+        stopProcessingReason = Stopped;
+    }
+
     switch (stopProcessingReason) {
     case EventQueueEmpty:
         break;
diff --git a/tests/auto/qstatemachine/tst_qstatemachine.cpp b/tests/auto/qstatemachine/tst_qstatemachine.cpp
index a03657f..231cab0 100644
--- a/tests/auto/qstatemachine/tst_qstatemachine.cpp
+++ b/tests/auto/qstatemachine/tst_qstatemachine.cpp
@@ -211,6 +211,9 @@ private slots:
     void postEventFromOtherThread();
     void eventFilterForApplication();
     void eventClassesExported();
+    void stopInTransitionToFinalState();
+    void stopInEventTest_data();
+    void stopInEventTest();
 };
 
 tst_QStateMachine::tst_QStateMachine()
@@ -4374,5 +4377,70 @@ void tst_QStateMachine::eventClassesExported()
     QStateMachine::SignalEvent *signalEvent = new QStateMachine::SignalEvent(0, 0, QList<QVariant>());
 }
 
+void tst_QStateMachine::stopInTransitionToFinalState()
+{
+    QStateMachine machine;
+    QState *s1 = new QState(&machine);
+    QFinalState *s2 = new QFinalState(&machine);
+    QAbstractTransition *t1 = s1->addTransition(s2);
+    machine.setInitialState(s1);
+
+    QObject::connect(t1, SIGNAL(triggered()), &machine, SLOT(stop()));
+    QSignalSpy stoppedSpy(&machine, SIGNAL(stopped()));
+    QSignalSpy finishedSpy(&machine, SIGNAL(finished()));
+    QSignalSpy s2EnteredSpy(s2, SIGNAL(entered()));
+    machine.start();
+
+    // Stopping should take precedence over finished.
+    QTRY_COMPARE(stoppedSpy.count(), 1);
+    QCOMPARE(finishedSpy.count(), 0);
+    QCOMPARE(s2EnteredSpy.count(), 1);
+    QCOMPARE(machine.configuration().size(), 1);
+    QVERIFY(machine.configuration().contains(s2));
+}
+
+class StopInEventTestTransition : public QAbstractTransition
+{
+public:
+    bool eventTest(QEvent *e)
+    {
+        if (e->type() == QEvent::User)
+            machine()->stop();
+        return false;
+    }
+    void onTransition(QEvent *)
+    { }
+};
+
+void tst_QStateMachine::stopInEventTest_data()
+{
+    QTest::addColumn<int>("eventPriority");
+    QTest::newRow("NormalPriority") << int(QStateMachine::NormalPriority);
+    QTest::newRow("HighPriority") << int(QStateMachine::HighPriority);
+}
+
+void tst_QStateMachine::stopInEventTest()
+{
+    QFETCH(int, eventPriority);
+
+    QStateMachine machine;
+    QState *s1 = new QState(&machine);
+    s1->addTransition(new StopInEventTestTransition());
+    machine.setInitialState(s1);
+
+    QSignalSpy startedSpy(&machine, SIGNAL(started()));
+    machine.start();
+    QTRY_COMPARE(startedSpy.count(), 1);
+
+    QSignalSpy stoppedSpy(&machine, SIGNAL(stopped()));
+    QSignalSpy finishedSpy(&machine, SIGNAL(finished()));
+    machine.postEvent(new QEvent(QEvent::User), QStateMachine::EventPriority(eventPriority));
+
+    QTRY_COMPARE(stoppedSpy.count(), 1);
+    QCOMPARE(finishedSpy.count(), 0);
+    QCOMPARE(machine.configuration().size(), 1);
+    QVERIFY(machine.configuration().contains(s1));
+}
+
 QTEST_MAIN(tst_QStateMachine)
 #include "tst_qstatemachine.moc"