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authorKent Hansen <khansen@trolltech.com>2009-09-28 17:08:00 (GMT)
committerKent Hansen <khansen@trolltech.com>2009-09-29 10:02:09 (GMT)
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doc: Describe the semantics of targetless state machine transitions
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For parallel state groups, the QState::finished() signal is emitted when \e
all the child states have entered final states.
+ \section1 Targetless Transitions
+
+ A transition need not have a target state. A transition without a target can
+ be triggered the same way as any other transition; the difference is that
+ when a targetless transition is triggered, it doesn't cause any state
+ changes. This allows you to react to a signal or event when your machine is
+ in a certain state, without having to leave that state. Example:
+
+ \code
+ QStateMachine machine;
+ QState *s1 = new QState(&machine);
+
+ QPushButton button;
+ QSignalTransition *trans = new QSignalTransition(&button, SIGNAL(clicked()));
+ s1->addTransition(trans);
+
+ QMessageBox msgBox;
+ msgBox.setText("The button was clicked; carry on.");
+ QObject::connect(trans, SIGNAL(triggered()), &msgBox, SLOT(exec()));
+
+ machine.setInitialState(s1);
+ \endcode
+
+ The message box will be displayed each time the button is clicked, but the
+ state machine will remain in its current state (s1). If the target state
+ were explicitly set to s1, however, s1 would be exited and re-entered each
+ time (e.g. the QAbstractState::entered() and QAbstractState::exited()
+ signals would be emitted).
+
\section1 Events, Transitions and Guards
A QStateMachine runs its own event loop. For signal transitions