QStateMachine: fix history state restoration.

When a history state is entered that has an actual saved history (so not
the initial state), the entry set was calculated wrongly in some cases.
See the bug report for the specific case.

The fix is to fully implement the standard, so method names in the
private class are updated to reflect the names as used in the standard.

Note that, as mentioned in the bug report, the algorithm as described in
http://www.w3.org/TR/2014/WD-scxml-20140529/ has a bug. What is
implemented is the fixed algorithm as described in the current working
draft as of Friday March 13, 2015. This draft can be found at:
http://www.w3.org/Voice/2013/scxml-irp/SCXML.htm

[ChangeLog][QtCore] Fixed an issue where a history state restore would
activate too many states, possibly putting the state machine in an
invalid state.

Change-Id: Ibb5491b2fdcf3a167c223fa8c9c4aad302dbb795
Task-number: QTBUG-44963
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@theqtcompany.com>

1 files changed, 10 insertions, 4 deletions

diff --git a/src/corelib/statemachine/qstatemachine_p.h b/src/corelib/statemachine/qstatemachine_p.h
index d0cc56bc2a..a8f0745730 100644
--- a/src/corelib/statemachine/qstatemachine_p.h
+++ b/src/corelib/statemachine/qstatemachine_p.h
@@ -100,7 +100,8 @@ public:
 
     static QStateMachinePrivate *get(QStateMachine *q);
 
-    QState *findLCA(const QList<QAbstractState*> &states) const;
+    QState *findLCA(const QList<QAbstractState*> &states, bool onlyCompound = false) const;
+    QState *findLCCA(const QList<QAbstractState*> &states) const;
 
     static bool stateEntryLessThan(QAbstractState *s1, QAbstractState *s2);
     static bool stateExitLessThan(QAbstractState *s1, QAbstractState *s2);
@@ -137,12 +138,17 @@ public:
                      , const QList<QAbstractAnimation*> &selectedAnimations
 #endif
                      );
-    QList<QAbstractState*> computeStatesToEnter(const QList<QAbstractTransition*> &enabledTransitions,
-                                                QSet<QAbstractState*> &statesForDefaultEntry);
+    QList<QAbstractState*> computeEntrySet(const QList<QAbstractTransition*> &enabledTransitions,
+                                           QSet<QAbstractState*> &statesForDefaultEntry);
+    QAbstractState *getTransitionDomain(QAbstractTransition *t,
+                                        const QList<QAbstractState *> &effectiveTargetStates);
+    void addDescendantStatesToEnter(QAbstractState *state,
+                                    QSet<QAbstractState*> &statesToEnter,
+                                    QSet<QAbstractState*> &statesForDefaultEntry);
     void addStatesToEnter(QAbstractState *s, QState *root,
                           QSet<QAbstractState*> &statesToEnter,
                           QSet<QAbstractState*> &statesForDefaultEntry);
-    void addAncestorStatesToEnter(QAbstractState *s, QState *root,
+    void addAncestorStatesToEnter(QAbstractState *s, QAbstractState *ancestor,
                                   QSet<QAbstractState*> &statesToEnter,
                                   QSet<QAbstractState*> &statesForDefaultEntry);