QStateMachine: add internal transitions.

The behavior of "external" and "internal" transitions is identical,
except in the case of a transition whose source state is a compound
state and whose target(s) is a descendant of the source. In such a case,
an internal transition will not exit and re-enter its source state,
while an external one will.

[ChangeLog][State machine] Added support for internal transitions.

Change-Id: I9efb1e7368ee52aa2544eb84709a00ae3d5350d3
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@theqtcompany.com>

4 files changed, 69 insertions, 13 deletions

diff --git a/src/corelib/statemachine/qabstracttransition.cpp b/src/corelib/statemachine/qabstracttransition.cpp
index f128acd54e..81b38ea4c4 100644
--- a/src/corelib/statemachine/qabstracttransition.cpp
+++ b/src/corelib/statemachine/qabstracttransition.cpp
@@ -101,7 +101,35 @@ QT_BEGIN_NAMESPACE
     parallel group state.
 */
 
+/*!
+    \property QAbstractTransition::transitionType
+
+    \brief indicates whether this transition is an internal transition, or an external transition.
+
+    Internal and external transitions behave the same, except for the case of a transition whose
+    source state is a compound state and whose target(s) is a descendant of the source. In such a
+    case, an internal transition will not exit and re-enter its source state, while an external one
+    will.
+
+    By default, the type is an external transition.
+*/
+
+/*!
+  \enum QAbstractTransition::TransitionType
+
+  This enum specifies the kind of transition. By default, the type is an external transition.
+
+  \value ExternalTransition Any state that is the source state of a transition (which is not a
+                            target-less transition) is left, and re-entered when necessary.
+  \value InternalTransition If the target state of a transition is a sub-state of a compound state,
+                            and that compound state is the source state, an internal transition will
+                            not leave the source state.
+
+  \sa QAbstractTransition::transitionType
+*/
+
 QAbstractTransitionPrivate::QAbstractTransitionPrivate()
+    : transitionType(QAbstractTransition::ExternalTransition)
 {
 }
 
@@ -249,6 +277,24 @@ void QAbstractTransition::setTargetStates(const QList<QAbstractState*> &targets)
 }
 
 /*!
+  Returns the type of the transition.
+*/
+QAbstractTransition::TransitionType QAbstractTransition::transitionType() const
+{
+    Q_D(const QAbstractTransition);
+    return d->transitionType;
+}
+
+/*!
+  Sets the type of the transition to \a type.
+*/
+void QAbstractTransition::setTransitionType(TransitionType type)
+{
+    Q_D(QAbstractTransition);
+    d->transitionType = type;
+}
+
+/*!
   Returns the state machine that this transition is part of, or 0 if the
   transition is not part of a state machine.
 */
diff --git a/src/corelib/statemachine/qabstracttransition.h b/src/corelib/statemachine/qabstracttransition.h
index 768a364a4b..bf32b3e825 100644
--- a/src/corelib/statemachine/qabstracttransition.h
+++ b/src/corelib/statemachine/qabstracttransition.h
@@ -59,7 +59,14 @@ class Q_CORE_EXPORT QAbstractTransition : public QObject
     Q_PROPERTY(QState* sourceState READ sourceState)
     Q_PROPERTY(QAbstractState* targetState READ targetState WRITE setTargetState NOTIFY targetStateChanged)
     Q_PROPERTY(QList<QAbstractState*> targetStates READ targetStates WRITE setTargetStates NOTIFY targetStatesChanged)
+    Q_PROPERTY(TransitionType transitionType READ transitionType WRITE setTransitionType)
 public:
+    enum TransitionType {
+        ExternalTransition,
+        InternalTransition
+    };
+    Q_ENUM(TransitionType)
+
     QAbstractTransition(QState *sourceState = 0);
     virtual ~QAbstractTransition();
 
@@ -69,6 +76,9 @@ public:
     QList<QAbstractState*> targetStates() const;
     void setTargetStates(const QList<QAbstractState*> &targets);
 
+    TransitionType transitionType() const;
+    void setTransitionType(TransitionType type);
+
     QStateMachine *machine() const;
 
 #ifndef QT_NO_ANIMATION
diff --git a/src/corelib/statemachine/qabstracttransition_p.h b/src/corelib/statemachine/qabstracttransition_p.h
index d89d057497..4b0644acd9 100644
--- a/src/corelib/statemachine/qabstracttransition_p.h
+++ b/src/corelib/statemachine/qabstracttransition_p.h
@@ -73,6 +73,7 @@ public:
     void emitTriggered();
 
     QList<QPointer<QAbstractState> > targetStates;
+    QAbstractTransition::TransitionType transitionType;
 
 #ifndef QT_NO_ANIMATION
     QList<QAbstractAnimation*> animations;
diff --git a/src/corelib/statemachine/qstatemachine.cpp b/src/corelib/statemachine/qstatemachine.cpp
index d91b4ba14a..6e36f93c40 100644
--- a/src/corelib/statemachine/qstatemachine.cpp
+++ b/src/corelib/statemachine/qstatemachine.cpp
@@ -889,23 +889,22 @@ QAbstractState *QStateMachinePrivate::getTransitionDomain(QAbstractTransition *t
     if (cache->transitionDomain(t, &domain))
         return domain;
 
-#if 0
-    // Qt only has external transitions, so skip the special case for the internal transitions
-    if (QState *tSource = t->sourceState()) {
-        if (isCompound(tSource)) {
-            bool allDescendants = true;
-            foreach (QAbstractState *s, effectiveTargetStates) {
-                if (!isDescendant(s, tSource)) {
-                    allDescendants = false;
-                    break;
+    if (t->transitionType() == QAbstractTransition::InternalTransition) {
+        if (QState *tSource = t->sourceState()) {
+            if (isCompound(tSource)) {
+                bool allDescendants = true;
+                foreach (QAbstractState *s, effectiveTargetStates) {
+                    if (!isDescendant(s, tSource)) {
+                        allDescendants = false;
+                        break;
+                    }
                 }
-            }
 
-            if (allDescendants)
-                return tSource;
+                if (allDescendants)
+                    return tSource;
+            }
         }
     }
-#endif
 
     QList<QAbstractState *> states(effectiveTargetStates);
     if (QAbstractState *src = t->sourceState())