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, 3 insertions, 3 deletions

diff --git a/examples/statemachine/tankgame/mainwindow.cpp b/examples/statemachine/tankgame/mainwindow.cpp
index 68a8d68..596cdfe 100644
--- a/examples/statemachine/tankgame/mainwindow.cpp
+++ b/examples/statemachine/tankgame/mainwindow.cpp
@@ -160,7 +160,7 @@ void MainWindow::init()
     connect(quitAction, SIGNAL(triggered()), this, SLOT(close()));
 
     m_machine = new QStateMachine(this);
-    QState *stoppedState = new QState(m_machine->rootState());
+    QState *stoppedState = new QState(m_machine);
     stoppedState->setObjectName("stoppedState");
     stoppedState->assignProperty(runGameAction, "enabled", true);
     stoppedState->assignProperty(stopGameAction, "enabled", false);
@@ -188,14 +188,14 @@ void MainWindow::init()
     stoppedState->setInitialState(hs);
 
 //! [0]
-    m_runningState = new QState(QState::ParallelStates, m_machine->rootState());
+    m_runningState = new QState(QState::ParallelStates, m_machine);
 //! [0]
     m_runningState->setObjectName("runningState");
     m_runningState->assignProperty(addTankAction, "enabled", false);
     m_runningState->assignProperty(runGameAction, "enabled", false);
     m_runningState->assignProperty(stopGameAction, "enabled", true);
 
-    QState *gameOverState = new QState(m_machine->rootState());
+    QState *gameOverState = new QState(m_machine);
     gameOverState->setObjectName("gameOverState");
     gameOverState->assignProperty(stopGameAction, "enabled", false);
     connect(gameOverState, SIGNAL(entered()), this, SLOT(gameOver()));