add private goToState() function to state machine

Needed for Declarative UI integration.

3 files changed, 138 insertions, 7 deletions

diff --git a/src/corelib/statemachine/qstatemachine.cpp b/src/corelib/statemachine/qstatemachine.cpp
index d89ad98..5aa5917 100644
--- a/src/corelib/statemachine/qstatemachine.cpp
+++ b/src/corelib/statemachine/qstatemachine.cpp
@@ -205,6 +205,7 @@ This is
 QStateMachinePrivate::QStateMachinePrivate()
 {
     state = NotRunning;
+    _startState = 0;
     processing = false;
     processingScheduled = false;
     stop = false;
@@ -1146,6 +1147,20 @@ protected:
 
 } // namespace
 
+QState *QStateMachinePrivate::startState()
+{
+    Q_Q(QStateMachine);
+    if (_startState == 0)
+        _startState = new StartState(q);
+    return _startState;
+}
+
+void QStateMachinePrivate::removeStartState()
+{
+    delete _startState;
+    _startState = 0;
+}
+
 void QStateMachinePrivate::_q_start()
 {
     Q_Q(QStateMachine);
@@ -1165,11 +1180,19 @@ void QStateMachinePrivate::_q_start()
     processingScheduled = true; // we call _q_process() below
     emit q->started();
 
-    StartState *start = new StartState(rootState());
-    QAbstractTransition *initialTransition = new InitialTransition(initial);
-    start->addTransition(initialTransition);
-    QList<QAbstractTransition*> transitions;
-    transitions.append(initialTransition);
+    QState *start = startState();
+    Q_ASSERT(start != 0);
+
+    QList<QAbstractTransition*> transitions = QStatePrivate::get(start)->transitions();
+
+    // If a transition has already been added, then we skip this step, as the
+    // initial transition in that case has been overridden.
+    if (transitions.isEmpty()) {
+        QAbstractTransition *initialTransition = new InitialTransition(initial);
+        start->addTransition(initialTransition);
+        transitions.append(initialTransition);
+    }
+
     QEvent nullEvent(QEvent::None);
     executeTransitionContent(&nullEvent, transitions);
     QList<QAbstractState*> enteredStates = enterStates(&nullEvent, transitions);
@@ -1177,7 +1200,7 @@ void QStateMachinePrivate::_q_start()
     applyProperties(transitions, QList<QAbstractState*>() << start,
                     enteredStates);
 #endif
-    delete start;
+    removeStartState();
 
 #ifdef QSTATEMACHINE_DEBUG
     qDebug() << q << ": initial configuration:" << configuration;
@@ -1277,6 +1300,67 @@ void QStateMachinePrivate::scheduleProcess()
     QMetaObject::invokeMethod(q_func(), "_q_process", Qt::QueuedConnection);
 }
 
+namespace {
+
+class GoToStateTransition : public QAbstractTransition
+{
+public:
+    GoToStateTransition(QAbstractState *target)
+        : QAbstractTransition(QList<QAbstractState*>() << target) {}
+protected:
+    void onTransition(QEvent *) { deleteLater(); }
+    bool eventTest(QEvent *) { return true; }
+};
+
+} // namespace
+
+/*!
+  \internal
+
+  Causes this state machine to unconditionally transition to the given
+  \a targetState.
+
+  Provides a backdoor for using the state machine "imperatively"; i.e.  rather
+  than defining explicit transitions, you drive the machine's execution by
+  calling this function. It breaks the whole integrity of the
+  transition-driven model, but is provided for pragmatic reasons.
+*/
+void QStateMachinePrivate::goToState(QAbstractState *targetState)
+{
+    if (!targetState) {
+        qWarning("QStateMachine::goToState(): cannot go to null state");
+        return;
+    }
+
+    if (configuration.contains(targetState))
+        return;
+
+    QState *sourceState = 0;
+    if (state == Running) {
+        QSet<QAbstractState*>::const_iterator it;
+        for (it = configuration.constBegin(); it != configuration.constEnd(); ++it) {
+            sourceState = qobject_cast<QState*>(*it);
+            if (sourceState != 0)
+                break;
+        }
+    } else {
+        sourceState = startState();
+    }    
+
+    Q_ASSERT(sourceState != 0);
+    // Reuse previous GoToStateTransition in case of several calls to
+    // goToState() in a row.
+    GoToStateTransition *trans = qFindChild<GoToStateTransition*>(sourceState);
+    if (!trans) {
+        trans = new GoToStateTransition(targetState);
+        sourceState->addTransition(trans);
+    } else {
+        trans->setTargetState(targetState);
+    }
+
+    scheduleProcess();
+}
+
 void QStateMachinePrivate::registerTransitions(QAbstractState *state)
 {
     QState *group = qobject_cast<QState*>(state);
diff --git a/src/corelib/statemachine/qstatemachine_p.h b/src/corelib/statemachine/qstatemachine_p.h
index 590cffe..714a40b 100644
--- a/src/corelib/statemachine/qstatemachine_p.h
+++ b/src/corelib/statemachine/qstatemachine_p.h
@@ -79,7 +79,7 @@ class QAbstractAnimation;
 #endif
 
 class QStateMachine;
-class QStateMachinePrivate : public QStatePrivate
+class Q_AUTOTEST_EXPORT QStateMachinePrivate : public QStatePrivate
 {
     Q_DECLARE_PUBLIC(QStateMachine)
 public:
@@ -116,6 +116,9 @@ public:
 
     QState *rootState() const;
 
+    QState *startState();
+    void removeStartState();
+
     void microstep(QEvent *event, const QList<QAbstractTransition*> &transitionList);
     bool isPreempted(const QAbstractState *s, const QSet<QAbstractTransition*> &transitions) const;
     QSet<QAbstractTransition*> selectTransitions(QEvent *event) const;
@@ -138,6 +141,8 @@ public:
     static bool isDescendantOf(const QAbstractState *s, const QAbstractState *other);
     static QList<QState*> properAncestors(const QAbstractState *s, const QState *upperBound);
 
+    void goToState(QAbstractState *targetState);
+
     void registerTransitions(QAbstractState *state);
     void registerSignalTransition(QSignalTransition *transition);
     void unregisterSignalTransition(QSignalTransition *transition);
@@ -162,6 +167,7 @@ public:
 #endif
 
     State state;
+    QState *_startState;
     bool processing;
     bool processingScheduled;
     bool stop;
diff --git a/tests/auto/qstatemachine/tst_qstatemachine.cpp b/tests/auto/qstatemachine/tst_qstatemachine.cpp
index 7f4d9f5..32812e2 100644
--- a/tests/auto/qstatemachine/tst_qstatemachine.cpp
+++ b/tests/auto/qstatemachine/tst_qstatemachine.cpp
@@ -192,6 +192,7 @@ private slots:
 //    void overrideDefaultTargetAnimationWithSource();
 
     void nestedStateMachines();
+    void goToState();
 };
 
 tst_QStateMachine::tst_QStateMachine()
@@ -3900,5 +3901,45 @@ void tst_QStateMachine::nestedStateMachines()
     QTRY_COMPARE(finishedSpy.count(), 1);
 }
 
+void tst_QStateMachine::goToState()
+{
+    QStateMachine machine;
+    QState *s1 = new QState(&machine);
+    QState *s2 = new QState(&machine);
+    machine.setInitialState(s1);
+    QSignalSpy startedSpy(&machine, SIGNAL(started()));
+    machine.start();
+    QTRY_COMPARE(startedSpy.count(), 1);
+
+    QStateMachinePrivate::get(&machine)->goToState(s2);
+    QCoreApplication::processEvents();
+    QCOMPARE(machine.configuration().size(), 1);
+    QVERIFY(machine.configuration().contains(s2));
+
+    QStateMachinePrivate::get(&machine)->goToState(s2);
+    QCoreApplication::processEvents();
+    QCOMPARE(machine.configuration().size(), 1);
+    QVERIFY(machine.configuration().contains(s2));
+
+    QStateMachinePrivate::get(&machine)->goToState(s1);
+    QStateMachinePrivate::get(&machine)->goToState(s2);
+    QStateMachinePrivate::get(&machine)->goToState(s1);
+    QCOMPARE(machine.configuration().size(), 1);
+    QVERIFY(machine.configuration().contains(s2));
+
+    QCoreApplication::processEvents();
+    QCOMPARE(machine.configuration().size(), 1);
+    QVERIFY(machine.configuration().contains(s1));
+
+    // go to state in group
+    QState *s2_1 = new QState(s2);
+    s2->setInitialState(s2_1);
+    QStateMachinePrivate::get(&machine)->goToState(s2_1);
+    QCoreApplication::processEvents();
+    QCOMPARE(machine.configuration().size(), 2);
+    QVERIFY(machine.configuration().contains(s2));
+    QVERIFY(machine.configuration().contains(s2_1));
+}
+
 QTEST_MAIN(tst_QStateMachine)
 #include "tst_qstatemachine.moc"