Make QStateMachine inherit QState

This removes the need for a "root state" in the machine; or rather,
the machine _is_ the root state.
User code can now pass in a QStateMachine directly to the QState
constructor, instead of machine->rootState().
This also means we could get rid of the "proxying" from the machine
to the root state for things like properties (initialState et al),
finished() signal and auto-reparenting of states (the ChildAdded
event hack).
A fun little side-effect of this change is that it's now possible
to embed state machines within state machines. We can't think of
a good use case yet where you would rather embed a stand-alone
state machine (with its own event processing etc.) rather than
having just a regular nested state, but it's neat and it works.

Reviewed-by: Eskil Abrahamsen Blomfeldt

1 files changed, 8 insertions, 16 deletions

diff --git a/src/corelib/statemachine/qstate.cpp b/src/corelib/statemachine/qstate.cpp
index 83dd869..f74edc3 100644
--- a/src/corelib/statemachine/qstate.cpp
+++ b/src/corelib/statemachine/qstate.cpp
@@ -71,7 +71,7 @@ QT_BEGIN_NAMESPACE
   The assignProperty() function is used for defining property assignments that
   should be performed when a state is entered.
 
-  Top-level states must be passed QStateMachine::rootState() as their parent
+  Top-level states must be passed a QStateMachine object as their parent
   state, or added to a state machine using QStateMachine::addState().
 
   \section1 States with Child States
@@ -242,7 +242,7 @@ void QState::assignProperty(QObject *object, const char *name,
 /*!
   Returns this state's error state. 
 
-  \sa QStateMachine::errorState(), QStateMachine::setErrorState()
+  \sa QStateMachine::error()
 */
 QAbstractState *QState::errorState() const
 {
@@ -256,19 +256,17 @@ QAbstractState *QState::errorState() const
   state recursively. If no error state is set for the state itself or any of 
   its ancestors, an error will cause the machine to stop executing and an error
   will be printed to the console.
-
-  \sa QStateMachine::setErrorState(), QStateMachine::errorState()
 */
 void QState::setErrorState(QAbstractState *state)
 {
     Q_D(QState);
-    if (state != 0 && state->machine() != machine()) {
-        qWarning("QState::setErrorState: error state cannot belong "
-                 "to a different state machine");
+    if (state != 0 && qobject_cast<QStateMachine*>(state)) {
+        qWarning("QStateMachine::setErrorState: root state cannot be error state");
         return;
     }
-    if (state != 0 && state->machine() != 0 && state->machine()->rootState() == state) {
-        qWarning("QStateMachine::setErrorState: root state cannot be error state");
+    if (state != 0 && (!state->machine() || ((state->machine() != machine()) && !qobject_cast<QStateMachine*>(this)))) {
+        qWarning("QState::setErrorState: error state cannot belong "
+                 "to a different state machine");
         return;
     }
 
@@ -288,12 +286,7 @@ QAbstractTransition *QState::addTransition(QAbstractTransition *transition)
         return 0;
     }
 
-    // machine() will always be non-null for root state
-    if (machine() != 0 && machine()->rootState() == this) {
-        qWarning("QState::addTransition: cannot add transition from root state");
-        return 0;
-    }
-
+    transition->setParent(this);
     const QList<QPointer<QAbstractState> > &targets = QAbstractTransitionPrivate::get(transition)->targetStates;
     for (int i = 0; i < targets.size(); ++i) {
         QAbstractState *t = targets.at(i);
@@ -308,7 +301,6 @@ QAbstractTransition *QState::addTransition(QAbstractTransition *transition)
             return 0;
         }
     }
-    transition->setParent(this);
     if (machine() != 0 && machine()->configuration().contains(this))
         QStateMachinePrivate::get(machine())->registerTransitions(this);
     return transition;