qstatemachine: add methods detect when a machine has processed an event

currently when adding an event it is not possible to know when processing
it has finished.
In particular if the event is ignored no method is called.
Adding virtual methods to the private implementation (binary compatibility).
These methods allow for extended automatic testing of the state machines.

(cherry picked from commit e7feb95628)

Change-Id: Iaa48fb9d7f6a6cde1a8a7a2bece7b4df55c147e8
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@theqtcompany.com>

src/corelib/statemachine/qstatemachine.cpp

@@ -1878,9 +1878,11 @@ void QStateMachinePrivate::_q_process()
     Q_ASSERT(!processing);
     processing = true;
     processingScheduled = false;
+    beginMacrostep();
 #ifdef QSTATEMACHINE_DEBUG
     qDebug() << q << ": starting the event processing loop";
 #endif
+    bool didChange = false;
     while (processing) {
         if (stop) {
             processing = false;
@@ -1923,15 +1925,17 @@ void QStateMachinePrivate::_q_process()
             }
         }
         if (!enabledTransitions.isEmpty()) {
+            didChange = true;
             q->beginMicrostep(e);
             microstep(e, enabledTransitions, &calculationCache);
             q->endMicrostep(e);
         }
-#ifdef QSTATEMACHINE_DEBUG
         else {
+            noMicrostep();
+#ifdef QSTATEMACHINE_DEBUG
             qDebug() << q << ": no transitions enabled";
-        }
 #endif
+        }
         delete e;
     }
 #ifdef QSTATEMACHINE_DEBUG
@@ -1944,6 +1948,7 @@ void QStateMachinePrivate::_q_process()
 
     switch (stopProcessingReason) {
     case EventQueueEmpty:
+        processedPendingEvents(didChange);
         break;
     case Finished:
         state = NotRunning;
@@ -1960,6 +1965,7 @@ void QStateMachinePrivate::_q_process()
         emit q->runningChanged(false);
         break;
     }
+    endMacrostep(didChange);
 }
 
 void QStateMachinePrivate::_q_startDelayedEventTimer(int id, int delay)
@@ -2081,6 +2087,46 @@ void QStateMachinePrivate::emitStateFinished(QState *forState, QFinalState *guil
     QStatePrivate::get(forState)->emitFinished();
 }
 
+/*
+  This function is called when the state machine is performing no
+  microstep because no transition is enabled (i.e. an event is ignored).
+
+  The default implementation does nothing.
+*/
+void QStateMachinePrivate::noMicrostep()
+{ }
+
+/*
+  This function is called when the state machine has reached a stable
+  state (no pending events), and has not finished yet.
+  For each event the state machine receives it is guaranteed that
+  1) beginMacrostep is called
+  2) selectTransition is called at least once
+  3) begin/endMicrostep is called at least once or noMicrostep is called
+     at least once (possibly both, but at least one)
+  4) the state machine either enters an infinite loop, or stops (runningChanged(false),
+     and either finished or stopped are emitted), or processedPendingEvents() is called.
+  5) if the machine is not in an infinite loop endMacrostep is called
+
+  didChange is set to true if at least one microstep was performed, it is possible
+  that the machine returned to exactly the same state as before, but some transitions
+  were triggered.
+
+  The default implementation does nothing.
+*/
+void QStateMachinePrivate::processedPendingEvents(bool didChange)
+{
+    Q_UNUSED(didChange);
+}
+
+void QStateMachinePrivate::beginMacrostep()
+{ }
+
+void QStateMachinePrivate::endMacrostep(bool didChange)
+{
+    Q_UNUSED(didChange);
+}
+
 namespace _QStateMachine_Internal{
 
 class GoToStateTransition : public QAbstractTransition

src/corelib/statemachine/qstatemachine_p.h

@@ -128,6 +128,10 @@ public:
     void removeConflictingTransitions(QList<QAbstractTransition*> &enabledTransitions, CalculationCache *cache);
     void microstep(QEvent *event, const QList<QAbstractTransition*> &transitionList, CalculationCache *cache);
     QList<QAbstractTransition *> selectTransitions(QEvent *event, CalculationCache *cache);
+    virtual void noMicrostep();
+    virtual void processedPendingEvents(bool didChange);
+    virtual void beginMacrostep();
+    virtual void endMacrostep(bool didChange);
     void exitStates(QEvent *event, const QList<QAbstractState *> &statesToExit_sorted,
                     const QHash<QAbstractState*, QList<QPropertyAssignment> > &assignmentsForEnteredStates);
     QList<QAbstractState*> computeExitSet(const QList<QAbstractTransition*> &enabledTransitions, CalculationCache *cache);