path: root/src/gui/widgets/qcheckbox.cpp

/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** All rights reserved.
** Contact: Nokia Corporation (qt-info@nokia.com)
**
** This file is part of the QtGui 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 Technology Preview License Agreement accompanying
** this package.
**
** 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 1.1, included in the file LGPL_EXCEPTION.txt in this package.
**
** If you have questions regarding the use of this file, please contact
** Nokia at qt-info@nokia.com.
**
**
**
**
**
**
**
**
** $QT_END_LICENSE$
**
****************************************************************************/

#include "qcheckbox.h"
#include "qapplication.h"
#include "qbitmap.h"
#include "qicon.h"
#include "qstylepainter.h"
#include "qstyle.h"
#include "qstyleoption.h"
#include "qevent.h"

#include "private/qabstractbutton_p.h"

QT_BEGIN_NAMESPACE

class QCheckBoxPrivate : public QAbstractButtonPrivate
{
    Q_DECLARE_PUBLIC(QCheckBox)
public:
    QCheckBoxPrivate()
        : QAbstractButtonPrivate(QSizePolicy::CheckBox), tristate(false), noChange(false),
          hovering(true), publishedState(Qt::Unchecked) {}

    uint tristate : 1;
    uint noChange : 1;
    uint hovering : 1;
    uint publishedState : 2;

    void init();
};

/*!
    \class QCheckBox
    \brief The QCheckBox widget provides a checkbox with a text label.

    \ingroup basicwidgets


    A QCheckBox is an option button that can be switched on (checked) or off
    (unchecked). Checkboxes are typically used to represent features in an
    application that can be enabled or disabled without affecting others, but
    different types of behavior can be implemented. For example, a
    QButtonGroup can be used to group check buttons logically, allowing
    exclusive checkboxes. However, QButtonGroup does not provide any visual
    representation.

    The image below further illustrates the differences between exclusive and
    non-exclusive checkboxes.

    \table
    \row \o \inlineimage checkboxes-exclusive.png
         \o \inlineimage checkboxes-non-exclusive.png
    \endtable

    Whenever a checkbox is checked or cleared it emits the signal
    stateChanged(). Connect to this signal if you want to trigger an action
    each time the checkbox changes state. You can use isChecked() to query
    whether or not a checkbox is checked.

    In addition to the usual checked and unchecked states, QCheckBox optionally
    provides a third state to indicate "no change". This is useful whenever you
    need to give the user the option of neither checking nor unchecking a
    checkbox. If you need this third state, enable it with setTristate(), and
    use checkState() to query the current toggle state.

    Just like QPushButton, a checkbox displays text, and optionally a small
    icon. The icon is set with setIcon(). The text can be set in the
    constructor or with setText(). A shortcut key can be specified by preceding
    the preferred character with an ampersand. For example:

    \snippet doc/src/snippets/code/src_gui_widgets_qcheckbox.cpp 0

    In this example the shortcut is \e{Alt+A}. See the \l{QShortcut#mnemonic}
    {QShortcut} documentation for details (to display an actual ampersand,
    use '&&').

    Important inherited functions: text(), setText(), text(), pixmap(),
    setPixmap(), accel(), setAccel(), isToggleButton(), setDown(), isDown(),
    isOn(), checkState(), autoRepeat(), isExclusiveToggle(), group(),
    setAutoRepeat(), toggle(), pressed(), released(), clicked(), toggled(),
    checkState(), and stateChanged().

    \table 100%
    \row
        \o \inlineimage macintosh-checkbox.png Screenshot of a Macintosh style checkbox
        \o A checkbox shown in the \l{Macintosh Style Widget Gallery}{Macintosh widget style}.
    \row
        \o \inlineimage windows-checkbox.png Screenshot of a Windows XP style checkbox
        \o A checkbox shown in the \l{Windows XP Style Widget Gallery}{Windows XP widget style}.
    \row
        \o \inlineimage plastique-checkbox.png Screenshot of a Plastique style checkbox
        \o A checkbox shown in the \l{Plastique Style Widget Gallery}{Plastique widget style}.
    \endtable

    \sa QAbstractButton, QRadioButton, {fowler}{GUI Design Handbook: Check Box}
*/

/*!
    \enum QCheckBox::ToggleState
    \compat

    \value Off  Use Qt::Unchecked instead.
    \value NoChange  Use Qt::PartiallyChecked instead.
    \value On  Use Qt::Checked instead.
*/

/*!
    \fn void QCheckBox::stateChanged(int state)

    This signal is emitted whenever the check box's state changes, i.e.
    whenever the user checks or unchecks it.

    \a state contains the check box's new Qt::CheckState.
*/

/*!
    \property QCheckBox::tristate
    \brief whether the checkbox is a tri-state checkbox

    The default is false; i.e. the checkbox has only two states.
*/

void QCheckBoxPrivate::init()
{
    Q_Q(QCheckBox);
    q->setCheckable(true);
    q->setMouseTracking(true);
    q->setForegroundRole(QPalette::WindowText);
    setLayoutItemMargins(QStyle::SE_CheckBoxLayoutItem);
}

/*!
    Initializes \a option with the values from this QCheckBox. This method is
    useful for subclasses that require a QStyleOptionButton, but do not want
    to fill in all the information themselves.

    \sa QStyleOption::initFrom()
*/
void QCheckBox::initStyleOption(QStyleOptionButton *option) const
{
    if (!option)
        return;
    Q_D(const QCheckBox);
    option->initFrom(this);
    if (d->down)
        option->state |= QStyle::State_Sunken;
    if (d->tristate && d->noChange)
        option->state |= QStyle::State_NoChange;
    else
        option->state |= d->checked ? QStyle::State_On : QStyle::State_Off;
    if (testAttribute(Qt::WA_Hover) && underMouse()) {
        if (d->hovering)
            option->state |= QStyle::State_MouseOver;
        else
            option->state &= ~QStyle::State_MouseOver;
    }
    option->text = d->text;
    option->icon = d->icon;
    option->iconSize = iconSize();
}

/*!
    Constructs a checkbox with the given \a parent, but with no text.

    \a parent is passed on to the QAbstractButton constructor.
*/

QCheckBox::QCheckBox(QWidget *parent)
    : QAbstractButton (*new QCheckBoxPrivate, parent)
{
    Q_D(QCheckBox);
    d->init();
}

/*!
    Constructs a checkbox with the given \a parent and \a text.

    \a parent is passed on to the QAbstractButton constructor.
*/

QCheckBox::QCheckBox(const QString &text, QWidget *parent)
    : QAbstractButton (*new QCheckBoxPrivate, parent)
{
    Q_D(QCheckBox);
    d->init();
    setText(text);
}

void QCheckBox::setTristate(bool y)
{
    Q_D(QCheckBox);
    d->tristate = y;
}

bool QCheckBox::isTristate() const
{
    Q_D(const QCheckBox);
    return d->tristate;
}


/*!
    Returns the check box's check state. If you do not need tristate support,
    you can also  use \l QAbstractButton::isChecked() which returns a boolean.

    \sa setCheckState() Qt::CheckState
*/
Qt::CheckState QCheckBox::checkState() const
{
    Q_D(const QCheckBox);
    if (d->tristate &&  d->noChange)
        return Qt::PartiallyChecked;
    return d->checked ? Qt::Checked : Qt::Unchecked;
}

/*!
    Sets the check box's check state to \a state. If you do not need tristate
    support, you can also use \l QAbstractButton::setChecked() which takes a
    boolean.

    \sa checkState() Qt::CheckState
*/
void QCheckBox::setCheckState(Qt::CheckState state)
{
    Q_D(QCheckBox);
    if (state == Qt::PartiallyChecked) {
        d->tristate = true;
        d->noChange = true;
    } else {
        d->noChange = false;
    }
    d->blockRefresh = true;
    setChecked(state != Qt::Unchecked);
    d->blockRefresh = false;
    d->refresh();
    if ((uint)state != d->publishedState) {
        d->publishedState = state;
        emit stateChanged(state);
    }
}


/*!
    \reimp
*/
QSize QCheckBox::sizeHint() const
{
    Q_D(const QCheckBox);
    if (d->sizeHint.isValid())
        return d->sizeHint;
    ensurePolished();
    QFontMetrics fm = fontMetrics();
    QStyleOptionButton opt;
    initStyleOption(&opt);
    QSize sz = style()->itemTextRect(fm, QRect(0, 0, 1, 1), Qt::TextShowMnemonic, false,
                                     text()).size();
    if (!opt.icon.isNull())
        sz = QSize(sz.width() + opt.iconSize.width() + 4, qMax(sz.height(), opt.iconSize.height()));
    d->sizeHint = (style()->sizeFromContents(QStyle::CT_CheckBox, &opt, sz, this)
                  .expandedTo(QApplication::globalStrut()));
    return d->sizeHint;
}

/*!
    \reimp
*/
void QCheckBox::paintEvent(QPaintEvent *)
{
    QStylePainter p(this);
    QStyleOptionButton opt;
    initStyleOption(&opt);
    p.drawControl(QStyle::CE_CheckBox, opt);
}

/*!
    \reimp
*/
void QCheckBox::mouseMoveEvent(QMouseEvent *e)
{
    Q_D(QCheckBox);
    if (testAttribute(Qt::WA_Hover)) {
        bool hit = false;
        if (underMouse())
            hit = hitButton(e->pos());

        if (hit != d->hovering) {
            update(rect());
            d->hovering = hit;
        }
    }

    QAbstractButton::mouseMoveEvent(e);
}


/*!
    \reimp
*/
bool QCheckBox::hitButton(const QPoint &pos) const
{
    QStyleOptionButton opt;
    initStyleOption(&opt);
    return style()->subElementRect(QStyle::SE_CheckBoxClickRect, &opt, this).contains(pos);
}

/*!
    \reimp
*/
void QCheckBox::checkStateSet()
{
    Q_D(QCheckBox);
    d->noChange = false;
    Qt::CheckState state = checkState();
    if ((uint)state != d->publishedState) {
        d->publishedState = state;
        emit stateChanged(state);
    }
}

/*!
    \reimp
*/
void QCheckBox::nextCheckState()
{
    Q_D(QCheckBox);
    if (d->tristate)
        setCheckState((Qt::CheckState)((checkState() + 1) % 3));
    else {
        QAbstractButton::nextCheckState();
        QCheckBox::checkStateSet();
    }
}

/*!
    \reimp
*/
bool QCheckBox::event(QEvent *e)
{
    Q_D(QCheckBox);
    if (e->type() == QEvent::StyleChange
#ifdef Q_WS_MAC
            || e->type() == QEvent::MacSizeChange
#endif
            )
        d->setLayoutItemMargins(QStyle::SE_CheckBoxLayoutItem);
    return QAbstractButton::event(e);
}

#ifdef QT3_SUPPORT
/*!
    Use one of the constructors that doesn't take the \a name
    argument and then use setObjectName() instead.
*/
QCheckBox::QCheckBox(QWidget *parent, const char* name)
    : QAbstractButton (*new QCheckBoxPrivate, parent)
{
    Q_D(QCheckBox);
    setObjectName(QString::fromAscii(name));
    d->init();
}

/*!
    Use one of the constructors that doesn't take the \a name
    argument and then use setObjectName() instead.
*/
QCheckBox::QCheckBox(const QString &text, QWidget *parent, const char* name)
    : QAbstractButton (*new QCheckBoxPrivate, parent)
{
    Q_D(QCheckBox);
    setObjectName(QString::fromAscii(name));
    d->init();
    setText(text);
}

#endif


/*!
    \fn void QCheckBox::setNoChange()
    \compat

    Use setCheckState() instead.
*/

/*!
    \fn void QCheckBox::setState(ToggleState state)
    \compat

    Use setCheckState() instead.
*/

/*!
    \fn QCheckBox::ToggleState QCheckBox::state() const
    \compat

    Use checkState() instead.
*/

QT_END_NAMESPACE