path: root/src/corelib/statemachine/qstate.cpp

/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** Contact: Qt Software Information (qt-info@nokia.com)
**
** This file is part of the QtCore module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** No Commercial Usage
** This file contains pre-release code and may not be distributed.
** You may use this file in accordance with the terms and conditions
** contained in the either Technology Preview License Agreement or the
** Beta Release License Agreement.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Nokia gives you certain
** additional rights. These rights are described in the Nokia Qt LGPL
** Exception version 1.0, included in the file LGPL_EXCEPTION.txt in this
** package.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3.0 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU General Public License version 3.0 requirements will be
** met: http://www.gnu.org/copyleft/gpl.html.
**
** If you are unsure which license is appropriate for your use, please
** contact the sales department at qt-sales@nokia.com.
** $QT_END_LICENSE$
**
****************************************************************************/

#include "qstate.h"
#include "qstate_p.h"
#include "qhistorystate.h"
#include "qhistorystate_p.h"
#include "qabstracttransition.h"
#include "qabstracttransition_p.h"
#include "qsignaltransition.h"
#include "qstatefinishedtransition.h"
#include "qstatemachine.h"
#include "qstatemachine_p.h"

QT_BEGIN_NAMESPACE

/*!
  \class QState

  \brief The QState class provides a general-purpose state for QStateMachine.

  \since 4.6
  \ingroup statemachine

  QState objects can have child states, and can have transitions to other
  states. QState is part of \l{The State Machine Framework}.

  The addTransition() function adds a transition. The removeTransition()
  function removes a transition.

  \section1 States with Child States

  For non-parallel state groups, the setInitialState() function must be called
  to set the initial state. The child states are mutually exclusive states,
  and the state machine needs to know which child state to enter when the
  parent state is the target of a transition.

  The addHistoryState() function adds a history state.

  The addFinishedTransition() function creates and adds a transition that's
  triggered when a final child state is entered.

  The setErrorState() sets the state's error state. The error state is the
  state that the state machine will transition to if an error is detected when
  attempting to enter the state (e.g. because no initial state has been set).
*/

/*!
  \enum QState::Type

  This enum specifies the type of a state.

  \value Normal A normal state. If the state has no child states, it is an
  atomic state; otherwise, the child states are mutually exclusive and an
  initial state must be set by calling QState::setInitialState().

  \value ParallelGroup The state is a parallel group state. When a parallel
  group state is entered, all its child states are entered in parallel.
*/

/*!
  \enum QState::HistoryType

  This enum specifies the type of history that a QHistoryState records.

  \value ShallowHistory Only the immediate child states of the parent state
  are recorded. In this case a transition with the history state as its
  target will end up in the immediate child state that the parent was in the
  last time it was exited. This is the default.

  \value DeepHistory Nested states are recorded. In this case a transition
  with the history state as its target will end up in the most deeply nested
  descendant state the parent was in the last time it was exited.
*/

QStatePrivate::QStatePrivate()
    : errorState(0), isParallelGroup(false), initialState(0)
{
}

QStatePrivate::~QStatePrivate()
{
}

QStatePrivate *QStatePrivate::get(QState *q)
{
    if (!q)
        return 0;
    return q->d_func();
}

const QStatePrivate *QStatePrivate::get(const QState *q)
{
    if (!q)
        return 0;
    return q->d_func();
}

/*!
  Constructs a new state with the given \a parent state.
*/
QState::QState(QState *parent)
    : QActionState(*new QStatePrivate, parent)
{
}

/*!
  Constructs a new state of the given \a type with the given \a parent state.
*/
QState::QState(Type type, QState *parent)
    : QActionState(*new QStatePrivate, parent)
{
    Q_D(QState);
    d->isParallelGroup = (type == ParallelGroup);
}

/*!
  \internal
*/
QState::QState(QStatePrivate &dd, QState *parent)
    : QActionState(dd, parent)
{
}

/*!
  Destroys this state.
*/
QState::~QState()
{
}

QList<QAbstractState*> QStatePrivate::childStates() const
{
    QList<QAbstractState*> result;
    QList<QObject*>::const_iterator it;
#ifdef QT_STATEMACHINE_SOLUTION
    const QObjectList &children = q_func()->children();
#endif
    for (it = children.constBegin(); it != children.constEnd(); ++it) {
        QAbstractState *s = qobject_cast<QAbstractState*>(*it);
        if (!s || qobject_cast<QHistoryState*>(s))
            continue;
        result.append(s);
    }
    return result;
}

QList<QHistoryState*> QStatePrivate::historyStates() const
{
    QList<QHistoryState*> result;
    QList<QObject*>::const_iterator it;
#ifdef QT_STATEMACHINE_SOLUTION
    const QObjectList &children = q_func()->children();
#endif
    for (it = children.constBegin(); it != children.constEnd(); ++it) {
        QHistoryState *h = qobject_cast<QHistoryState*>(*it);
        if (h)
            result.append(h);
    }
    return result;
}

QList<QAbstractTransition*> QStatePrivate::transitions() const
{
    QList<QAbstractTransition*> result;
    QList<QObject*>::const_iterator it;
#ifdef QT_STATEMACHINE_SOLUTION
    const QObjectList &children = q_func()->children();
#endif
    for (it = children.constBegin(); it != children.constEnd(); ++it) {
        QAbstractTransition *t = qobject_cast<QAbstractTransition*>(*it);
        if (t)
            result.append(t);
    }
    return result;
}

/*!
  Returns this state group's error state. 

  \sa QStateMachine::errorState(), QStateMachine::setErrorState()
*/
QAbstractState *QState::errorState() const
{
    Q_D(const QState);
    return d->errorState;
}

/*!
  Sets this state's error state to be the given \a state. If the error state
  is not set, or if it is set to 0, the state will inherit its parent's error
  state recursively.

  \sa QStateMachine::setErrorState(), QStateMachine::errorState()
*/
void QState::setErrorState(QAbstractState *state)
{
    Q_D(QState);
    if (state != 0 && QAbstractStatePrivate::get(state)->machine() != d->machine()) {
        qWarning("QState::setErrorState: error state cannot belong "
                 "to a different state machine");
        return;
    }

    d->errorState = state;
}

/*!
  Adds the given \a transition. The transition has this state as the source.
  This state takes ownership of the transition.
*/
void QState::addTransition(QAbstractTransition *transition)
{
    Q_D(QState);
    if (!transition) {
        qWarning("QState::addTransition: cannot add null transition");
        return;
    }
    const QList<QAbstractState*> &targets = QAbstractTransitionPrivate::get(transition)->targetStates;
    for (int i = 0; i < targets.size(); ++i) {
        QAbstractState *t = targets.at(i);
        if (!t) {
            qWarning("QState::addTransition: cannot add transition to null state");
            return;
        }
        if ((QAbstractStatePrivate::get(t)->machine() != d->machine())
            && QAbstractStatePrivate::get(t)->machine() && d->machine()) {
            qWarning("QState::addTransition: cannot add transition "
                     "to a state in a different state machine");
            return;
        }
    }
    transition->setParent(this);
}

/*!
  Adds a transition associated with the given \a signal of the given \a sender
  object, and returns the new QSignalTransition object. The transition has
  this state as the source, and the given \a target as the target state.
*/
QSignalTransition *QState::addTransition(QObject *sender, const char *signal,
                                         QAbstractState *target)
{
    if (!sender) {
        qWarning("QState::addTransition: sender cannot be null");
        return 0;
    }
    if (!signal) {
        qWarning("QState::addTransition: signal cannot be null");
        return 0;
    }
    QSignalTransition *trans = new QSignalTransition(sender, signal, QList<QAbstractState*>() << target);
    addTransition(trans);
    return trans;
}

/*!
  Adds a transition that's triggered by the finished event of this state, and
  returns the new QStateFinishedTransition object. The transition has the
  given \a target state.

  \sa QStateFinishedEvent
*/
QStateFinishedTransition *QState::addFinishedTransition(QAbstractState *target)
{
    QStateFinishedTransition *trans = new QStateFinishedTransition(this, QList<QAbstractState*>() << target);
    addTransition(trans);
    return trans;
}

namespace {

// ### Make public?
class UnconditionalTransition : public QAbstractTransition
{
public:
    UnconditionalTransition(QAbstractState *target)
        : QAbstractTransition(QList<QAbstractState*>() << target) {}
protected:
    void onTransition() {}
    bool eventTest(QEvent *) const { return true; }
};

} // namespace

/*!
  Adds an unconditional transition from this state to the given \a target
  state, and returns then new transition object.
*/
QAbstractTransition *QState::addTransition(QAbstractState *target)
{
    UnconditionalTransition *trans = new UnconditionalTransition(target);
    addTransition(trans);
    return trans;
}

/*!
  Removes the given \a transition from this state.  The state releases
  ownership of the transition.

  \sa addTransition()
*/
void QState::removeTransition(QAbstractTransition *transition)
{
    Q_D(QState);
    if (!transition) {
        qWarning("QState::removeTransition: cannot remove null transition");
        return;
    }
    if (transition->sourceState() != this) {
        qWarning("QState::removeTransition: transition %p's source state (%p)"
                 " is different from this state (%p)",
                 transition, transition->sourceState(), this);
        return;
    }
    QStateMachinePrivate *mach = QStateMachinePrivate::get(d->machine());
    if (mach)
        mach->unregisterTransition(transition);
    transition->setParent(0);
}

/*!
  Returns the list of transitions from this state, or an empty list if there
  are no transitions from this state.

  \sa addTransition(), removeTransition()
*/
QList<QAbstractTransition*> QState::transitions() const
{
    Q_D(const QState);
    return d->transitions();
}

/*!
  Creates a history state of the given \a type for this state and returns the
  new state.  The history state becomes a child of this state.
*/
QHistoryState *QState::addHistoryState(HistoryType type)
{
    return QHistoryStatePrivate::create(type, this);
}

/*!
  \reimp
*/
void QState::onEntry()
{
    QActionState::onEntry();
}

/*!
  \reimp
*/
void QState::onExit()
{
    QActionState::onExit();
}

/*!
  Returns this state's initial state, or 0 if the state has no initial state.
*/
QAbstractState *QState::initialState() const
{
    Q_D(const QState);
    return d->initialState;
}

/*!
  Sets this state's initial state to be the given \a state.
  \a state has to be a child of this state.
*/
void QState::setInitialState(QAbstractState *state)
{
    Q_D(QState);
    if (d->isParallelGroup) {
        qWarning("QState::setInitialState: ignoring attempt to set initial state "
                 "of parallel state group %p", this);
        return;
    }
    if (state && (state->parentState() != this)) {
        qWarning("QState::setInitialState: state %p is not a child of this state (%p)",
                 state, this);
        return;
    }
    d->initialState = state;
}

/*!
  \reimp
*/
bool QState::event(QEvent *e)
{
    return QActionState::event(e);
}

QT_END_NAMESPACE