path: root/src/gui/effects/qgraphicseffect.cpp

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/*!
    \class QGraphicsEffect
    \brief The QGraphicsEffect class is the base class for all graphics
           effects.
    \since 4.6
    \ingroup multimedia
    \ingroup graphicsview-api

    Effects alter the appearance of elements by hooking into the rendering
    pipeline and operating between the source (e.g., a QGraphicsPixmapItem)
    and the destination device (e.g., QGraphicsView's viewport). Effects can be
    disabled by calling setEnabled(false). If effects are disabled, the source
    is rendered directly.

    To add a visual effect to a QGraphicsItem, for example, you can use one of
    the standard effects, or alternately, create your own effect by creating a
    subclass of QGraphicsEffect. The effect can then be installed on the item
    using QGraphicsItem::setGraphicsEffect().

    Qt provides the following standard effects:

    \list
    \o QGraphicsGrayScaleEffect - renders the item in shades of gray
    \o QGraphicsColorizeEffect - renders the item in shades of any given color
    \o QGraphicsPixelizeEffect - pixelizes the item with any pixel size
    \o QGraphicsBlurEffect - blurs the item by a given radius
    \o QGraphicsDropShadowEffect - renders a dropshadow behind the item
    \o QGraphicsOpacityEffect - renders the item with an opacity
    \o QGrahicsShaderEffect - renders the item with a pixel shader fragment
    \endlist


    For more information on how to use each effect, refer to the specific
    effect's documentation.

    To create your own custom effect, create a subclass of QGraphicsEffect (or
    any other existing effects) and reimplement the virtual function draw().
    This function is called whenever the effect needs to redraw. The draw()
    function accepts two arguments: the painter and a pointer to the source
    (QGraphicsEffectSource). The source provides extra context information,
    such as a pointer to the item that is rendering the effect, any cached
    pixmap data, or the device rectangle bounds. For more information, refer to
    the documenation for draw(). To obtain a pointer to the current source,
    simply call source().

    If your effect changes, use update() to request for a redraw. If your
    custom effect changes the bounding rectangle of the source, e.g., a radial
    glow effect may need to apply an extra margin, you can reimplement the
    virtual boundingRectFor() function, and call updateBoundingRect() to notify
    the framework whenever this rectangle changes. The virtual
    sourceBoundingRectChanged() function is called to notify the effects that
    the source's bounding rectangle has changed - e.g., if the source is a
    QGraphicsRectItem and its rectangle parameters have changed.

    \sa QGraphicsItem::setGraphicsEffect(), QWidget::setGraphicsEffect(),
    QGraphicsEffectSource
*/

#include "qgraphicseffect_p.h"

#include <QtGui/qimage.h>
#include <QtGui/qpainter.h>
#include <QtCore/qrect.h>
#include <QtCore/qdebug.h>

QT_BEGIN_NAMESPACE

/*!
    \class QGraphicsEffectSource
    \brief The QGraphicsEffectSource represents the source on which a
           QGraphicsEffect is installed on.
    \since 4.6

    When a QGraphicsEffect is installed on a QGraphicsItem, for example, this
    class will act as a wrapper around QGraphicsItem. Then, calling update() is
    effectively the same as calling QGraphicsItem::update().

    QGraphicsEffectSource also provides a pixmap() function which creates a
    pixmap with the source painted into it.

    \sa QGraphicsItem::setGraphicsEffect(), QWidget::setGraphicsEffect.
*/
QGraphicsEffectSource::QGraphicsEffectSource(QGraphicsEffectSourcePrivate &dd, QObject *parent)
    : QObject(dd, parent)
{}

QGraphicsEffectSource::~QGraphicsEffectSource()
{}

/*!
    Returns the bounds of the current painter's device.

    This function is useful when you want to draw something in device
    coordinates and ensure the size of the pixmap is not bigger than the size
    of the device.

    Calling QGraphicsEffectSource::pixmap(Qt::DeviceCoordinates) always returns
    a pixmap which is bound to the device's size.

    \sa pixmap()
*/
QRect QGraphicsEffectSource::deviceRect() const
{
    return d_func()->deviceRect();
}

/*!
    Returns the bounding rectangle of the source mapped to the given \a system.

    \sa draw()
*/
QRectF QGraphicsEffectSource::boundingRect(Qt::CoordinateSystem system) const
{
    return d_func()->boundingRect(system);
}

/*!
    Returns a pointer to the item if this source is a QGraphicsItem; otherwise
    returns 0.

    \sa widget()
*/
const QGraphicsItem *QGraphicsEffectSource::graphicsItem() const
{
    return d_func()->graphicsItem();
}

/*!
    Returns a pointer to the widget if this source is a QWidget; otherwis
     returns 0.

    \sa graphicsItem()
*/
const QWidget *QGraphicsEffectSource::widget() const
{
    return d_func()->widget();
}

/*!
    Returns a pointer to the style options (used when drawing the source) if
    available; otherwise returns 0.

    \sa graphicsItem(), widget()
*/
const QStyleOption *QGraphicsEffectSource::styleOption() const
{
    return d_func()->styleOption();
}

/*!
    Draws the source using the given \a painter.

    This function should only be called from QGraphicsEffect::draw().

    For example:

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

    \sa QGraphicsEffect::draw()
*/

void QGraphicsEffectSource::draw(QPainter *painter)
{
    d_func()->draw(painter);
}

/*!
    Schedules a redraw of the source. Call this function whenever the source
    needs to be redrawn.

    \sa QGraphicsEffect::updateBoundingRect(), QWidget::update(),
        QGraphicsItem::update(),
*/
void QGraphicsEffectSource::update()
{
    d_func()->update();
}

/*!
    Returns true if the source effectively is a pixmap, e.g., a
    QGraphicsPixmapItem.

    This function is useful for optimization purposes. For instance, there's no
    point in drawing the source in device coordinates to avoid pixmap scaling
    if this function returns true - the source pixmap will be scaled anyways.
*/
bool QGraphicsEffectSource::isPixmap() const
{
    return d_func()->isPixmap();
}

/*!
    Returns a pixmap with the source painted into it.

    The \a system specifies which coordinate system to be used for the source.
    The optional \a offset parameter returns the offset where the pixmap should
    be painted at using the current painter.

    The returned pixmap is bound to the current painter's device rectangle when
    \a system is Qt::DeviceCoordinates.

    \sa QGraphicsEffect::draw(), boundingRect(), deviceRect()
*/
QPixmap QGraphicsEffectSource::pixmap(Qt::CoordinateSystem system, QPoint *offset) const
{
    return d_func()->pixmap(system, offset);
}

/*!
    Constructs a new QGraphicsEffect instance.
*/
QGraphicsEffect::QGraphicsEffect(QObject *parent)
    : QObject(*new QGraphicsEffectPrivate, parent)
{
}

/*!
    \internal
*/
QGraphicsEffect::QGraphicsEffect(QGraphicsEffectPrivate &dd, QObject *parent)
    : QObject(dd, parent)
{
}

/*!
    Removes the effect from the source, and destroys the graphics effect.
*/
QGraphicsEffect::~QGraphicsEffect()
{
    Q_D(QGraphicsEffect);
    d->setGraphicsEffectSource(0);
}

/*!
    Returns the bounding rectangle for this effect, i.e., the bounding
    rectangle of the source, adjusted by any margins applied by the effect
    itself.

    \sa boundingRectFor(), updateBoundingRect()
*/
QRectF QGraphicsEffect::boundingRect() const
{
    Q_D(const QGraphicsEffect);
    if (d->source)
        return boundingRectFor(d->source->boundingRect());
    return QRectF();
}

/*!
    Returns the bounding rectangle for this effect, given the provided source
    \a rect. When writing you own custom effect, you must call
    updateBoundingRect() whenever any parameters are changed that may cause
    this this function to return a different value.

    \sa boundingRect()
*/
QRectF QGraphicsEffect::boundingRectFor(const QRectF &rect) const
{
    return rect;
}

/*!
    \property QGraphicsEffect::enabled
    \brief whether the effect is enabled or not.

    If an effect is disabled, the source will be rendered with as normal, with
    no interference from the effect. If the effect is enabled, the source will
    be rendered with the effect applied.

    This property is enabled by default.

    Using this property, you can disable certain effects on slow platforms, in
    order to ensure that the user interface is responsive.

    \sa enabledChanged()
*/
bool QGraphicsEffect::isEnabled() const
{
    Q_D(const QGraphicsEffect);
    return d->isEnabled;
}

void QGraphicsEffect::setEnabled(bool enable)
{
    Q_D(QGraphicsEffect);
    if (d->isEnabled == enable)
        return;

    d->isEnabled = enable;
    if (d->source)
        d->source->update();
    emit enabledChanged(enable);
}

/*!
    \fn void QGraphicsEffect::enabledChanged(bool enabled)

    This signal is emitted whenever the effect is enabled or disabled.

    \sa isEnabled()
*/

/*!
    Returns a pointer to the source, which provides extra context information
    that can be useful for the effect.

    \sa draw()
*/
QGraphicsEffectSource *QGraphicsEffect::source() const
{
    Q_D(const QGraphicsEffect);
    return d->source;
}

/*!
    This function notifies the effect framework when the effect's bounding
    rectangle has changed. As a custom effect author, you must call this
    function whenever you change any parameters that will cause the virtual
    boundingRectFor() function to return a different value.

    \sa boundingRectFor(), boundingRect()
*/
void QGraphicsEffect::updateBoundingRect()
{
    Q_D(QGraphicsEffect);
    if (d->source)
        d->source->update();
}

/*!
    \fn virtual void QGraphicsEffect::draw(QPainter *painter,
    QGraphicsEffectSource *source) = 0

    This pure virtual function draws the effect and is called whenever the
    source() needs to be drawn.

    Reimplement this function in a QGraphicsEffect subclass to provide the
    effect's drawing implementation, using \a painter. The \a source parameter
    is provided for convenience; its value is the same as source().

    For example:

    \snippet doc/src/snippets/code/src_gui_effects_qgraphicseffect.cpp 1

    This function should not be called explicitly by the user, since it is
    meant for reimplementation purposes only.

    \sa QGraphicsEffectSource
*/

/*!
    \enum QGraphicsEffect::ChangeFlag

    This enum describes what has changed in QGraphicsEffectSource.

    \value SourceAttached The effect is installed on a source.
    \value SourceDetached The effect is uninstalled on a source.
    \value SourceBoundingRectChanged The bounding rect of the source has
           changed.
    \value SourceInvalidated The visual appearance of the source has changed.
*/

/*!
    This virtual function is called by QGraphicsEffect to notify the effect
    that the source has changed. If the effect applies any cache, then this
    cache must be purged in order to reflect the new appearance of the source.

    The \a flags describes what has changed.
*/
void QGraphicsEffect::sourceChanged(ChangeFlags flags)
{
    Q_UNUSED(flags);
}

/*!
    \class QGraphicsGrayscaleEffect
    \brief The QGraphicsGrayscaleEffect class provides a grayscale effect.
    \since 4.6

    A grayscale effect renders the source in shades of gray.

    \sa QGraphicsDropShadowEffect, QGraphicsBlurEffect, QGraphicsPixelizeEffect,
        QGraphicsColorizeEffect, QGraphicsOpacityEffect
*/
QGraphicsGrayscaleEffect::QGraphicsGrayscaleEffect(QObject *parent)
    : QGraphicsEffect(*new QGraphicsGrayscaleEffectPrivate, parent)
{
}

QGraphicsGrayscaleEffect::~QGraphicsGrayscaleEffect()
{
}

void QGraphicsGrayscaleEffect::draw(QPainter *painter, QGraphicsEffectSource *source)
{
    Q_D(QGraphicsGrayscaleEffect);
    QPoint offset;
    if (source->isPixmap()) {
        // No point in drawing in device coordinates (pixmap will be scaled anyways).
        const QPixmap pixmap = source->pixmap(Qt::LogicalCoordinates, &offset);
        d->filter->draw(painter, offset, pixmap);
        return;
    }

    // Draw pixmap in device coordinates to avoid pixmap scaling;
    const QPixmap pixmap = source->pixmap(Qt::DeviceCoordinates, &offset);
    QTransform restoreTransform = painter->worldTransform();
    painter->setWorldTransform(QTransform());
    d->filter->draw(painter, offset, pixmap);
    painter->setWorldTransform(restoreTransform);

}

/*!
    \class QGraphicsColorizeEffect
    \brief The QGraphicsColorizeEffect provides a colorize effect.
    \since 4.6

    A colorize effect renders the source with a tint of its color(). The color
    can be modified using the setColor() function.

    By default, the color is light blue (QColor(0, 0, 192)).

    \sa QGraphicsDropShadowEffect, QGraphicsBlurEffect, QGraphicsPixelizeEffect,
        QGraphicsGrayscaleEffect, QGraphicsOpacityEffect
*/
QGraphicsColorizeEffect::QGraphicsColorizeEffect(QObject *parent)
    : QGraphicsEffect(*new QGraphicsColorizeEffectPrivate, parent)
{
}

QGraphicsColorizeEffect::~QGraphicsColorizeEffect()
{
}

/*!
    Returns the color.

    \sa setColor(), colorChanged()
*/
QColor QGraphicsColorizeEffect::color() const
{
    Q_D(const QGraphicsColorizeEffect);
    return d->filter->color();
}

/*!
    Sets the color to the given \a color.

    \sa color(), colorChanged()
*/
void QGraphicsColorizeEffect::setColor(const QColor &color)
{
    Q_D(QGraphicsColorizeEffect);
    if (d->filter->color() == color)
        return;

    d->filter->setColor(color);
    emit colorChanged(color);
}

/*!
    \fn void QGraphicsColorizeEffect::colorChanged(const QColor &color)

    This signal is emitted whenever the effect's color changes.
*/

void QGraphicsColorizeEffect::draw(QPainter *painter, QGraphicsEffectSource *source)
{
    Q_D(QGraphicsColorizeEffect);
    QPoint offset;
    if (source->isPixmap()) {
        // No point in drawing in device coordinates (pixmap will be scaled anyways).
        const QPixmap pixmap = source->pixmap(Qt::LogicalCoordinates, &offset);
        d->filter->draw(painter, offset, pixmap);
        return;
    }

    // Draw pixmap in deviceCoordinates to avoid pixmap scaling.
    const QPixmap pixmap = source->pixmap(Qt::DeviceCoordinates, &offset);
    QTransform restoreTransform = painter->worldTransform();
    painter->setWorldTransform(QTransform());
    d->filter->draw(painter, offset, pixmap);
    painter->setWorldTransform(restoreTransform);
}

/*!
    \class QGraphicsPixelizeEffect
    \brief The QGraphicsPixelizeEffect provides a pixelize effect.
    \since 4.6

    A pixelize effect renders the source in lower resolution. This effect is
    useful for reducing details, like censorship. The resolution can be
    modified using the setPixelSize() function.

    By default, the pixel size is 3.

    \sa QGraphicsDropShadowEffect, QGraphicsBlurEffect, QGraphicsGrayscaleEffect,
        QGraphicsColorizeEffect, QGraphicsOpacityEffect
*/
QGraphicsPixelizeEffect::QGraphicsPixelizeEffect(QObject *parent)
    : QGraphicsEffect(*new QGraphicsPixelizeEffectPrivate, parent)
{
}

QGraphicsPixelizeEffect::~QGraphicsPixelizeEffect()
{
}

/*!
    Returns the size of a pixel.

    \sa setPixelSize(), pixelSizeChanged()
*/
int QGraphicsPixelizeEffect::pixelSize() const
{
    Q_D(const QGraphicsPixelizeEffect);
    return d->pixelSize;
}

/*!
    Sets the size of a pixel to the given \a size.

    Setting \a size to 2 means two pixels in the source will be used to
    represent one pixel. Using a bigger size results in lower resolution.

    \sa pixelSize(), pixelSizeChanged()
*/
void QGraphicsPixelizeEffect::setPixelSize(int size)
{
    Q_D(QGraphicsPixelizeEffect);
    if (d->pixelSize == size)
        return;

    d->pixelSize = size;
    emit pixelSizeChanged(size);
}

/*!
    \fn void QGraphicsPixelizeEffect::pixelSizeChanged(int size)

    This signal is emitted whenever the effect's pixel size changes.
*/

static inline void pixelize(QImage *image, int pixelSize)
{
    Q_ASSERT(pixelSize > 0);
    Q_ASSERT(image);
    int width = image->width();
    int height = image->height();
    for (int y = 0; y < height; y += pixelSize) {
        int ys = qMin(height - 1, y + pixelSize / 2);
        QRgb *sbuf = reinterpret_cast<QRgb*>(image->scanLine(ys));
        for (int x = 0; x < width; x += pixelSize) {
            int xs = qMin(width - 1, x + pixelSize / 2);
            QRgb color = sbuf[xs];
            for (int yi = 0; yi < qMin(pixelSize, height - y); ++yi) {
                QRgb *buf = reinterpret_cast<QRgb*>(image->scanLine(y + yi));
                for (int xi = 0; xi < qMin(pixelSize, width - x); ++xi)
                    buf[x + xi] = color;
            }
        }
    }
}

void QGraphicsPixelizeEffect::draw(QPainter *painter, QGraphicsEffectSource *source)
{
    Q_D(QGraphicsPixelizeEffect);
    if (d->pixelSize <= 0) {
        source->draw(painter);
        return;
    }

    QPoint offset;
    if (source->isPixmap()) {
        const QPixmap pixmap = source->pixmap(Qt::LogicalCoordinates, &offset);
        QImage image = pixmap.toImage().convertToFormat(QImage::Format_ARGB32);
        pixelize(&image, d->pixelSize);
        painter->drawImage(offset, image);
        return;
    }

    // Draw pixmap in device coordinates to avoid pixmap scaling.
    const QPixmap pixmap = source->pixmap(Qt::DeviceCoordinates, &offset);

    // pixelize routine
    QImage image = pixmap.toImage().convertToFormat(QImage::Format_ARGB32);
    pixelize(&image, d->pixelSize);

    QTransform restoreTransform = painter->worldTransform();
    painter->setWorldTransform(QTransform());
    painter->drawImage(offset, image);
    painter->setWorldTransform(restoreTransform);
}

/*!
    \class QGraphicsBlurEffect
    \brief The QGraphicsBlurEffect provides a blur effect.
    \since 4.6

    A blur effect blurs the source. This effect is useful for reducing details,
    such as when the source loses focus and you want to draw attention to other
    elements. The level of detail can be modified using the setBlurRadius()
    function.

    By default, the blur radius is 5 pixels.

    \sa QGraphicsDropShadowEffect, QGraphicsPixelizeEffect, QGraphicsGrayscaleEffect,
        QGraphicsColorizeEffect, QGraphicsOpacityEffect
*/
QGraphicsBlurEffect::QGraphicsBlurEffect(QObject *parent)
    : QGraphicsEffect(*new QGraphicsBlurEffectPrivate, parent)
{
}

QGraphicsBlurEffect::~QGraphicsBlurEffect()
{
}

/*!
    Returns the blur radius.

    \sa setBlurRadius(), blurRadiusChanged()
*/
int QGraphicsBlurEffect::blurRadius() const
{
    Q_D(const QGraphicsBlurEffect);
    return d->filter->radius();
}

/*!
    Sets the blur radius to the given \a radius.

    Using a smaller radius results in a sharper appearance, whereas a bigger
    radius results in a more blurred appearance.

    \sa blurRadius(), blurRadiusChanged()
*/
void QGraphicsBlurEffect::setBlurRadius(int radius)
{
    Q_D(QGraphicsBlurEffect);
    if (d->filter->radius() == radius)
        return;

    d->filter->setRadius(radius);
    updateBoundingRect();
    emit blurRadiusChanged(radius);
}

/*!
    \fn void QGraphicsBlurEffect::blurRadiusChanged(int radius)

    This signal is emitted whenever the effect's blur radius changes.
*/

QRectF QGraphicsBlurEffect::boundingRectFor(const QRectF &rect) const
{
    Q_D(const QGraphicsBlurEffect);
    return d->filter->boundingRectFor(rect);
}

void QGraphicsBlurEffect::draw(QPainter *painter, QGraphicsEffectSource *source)
{
    Q_D(QGraphicsBlurEffect);
    if (d->filter->radius() <= 0) {
        source->draw(painter);
        return;
    }

    QPoint offset;
    if (source->isPixmap()) {
        // No point in drawing in device coordinates (pixmap will be scaled anyways).
        const QPixmap pixmap = source->pixmap(Qt::LogicalCoordinates, &offset);
        d->filter->draw(painter, offset, pixmap);
        return;
    }

    // Draw pixmap in device coordinates to avoid pixmap scaling.
    const QPixmap pixmap = source->pixmap(Qt::DeviceCoordinates, &offset);
    QTransform restoreTransform = painter->worldTransform();
    painter->setWorldTransform(QTransform());
    d->filter->draw(painter, offset, pixmap);
    painter->setWorldTransform(restoreTransform);
}

/*!
    \class QGraphicsDropShadowEffect
    \brief The QGraphicsDropShadowEffect class provides a drop shadow effect.
    \since 4.6

    A drop shadow effect renders the source with a drop shadow. The color of
    the drop shadow can be modified using the setColor() function. The drop
    shadow offset can be modified using the setOffset() function and the blur
    radius of the drop shadow can be changed with the setBlurRadius()
    function.

    By default, the drop shadow is a semi-transparent dark gray
    (QColor(63, 63, 63, 180)) shadow, blurred with a radius of 1 at an offset
    of 8 pixels towards the lower right.

    \sa QGraphicsBlurEffect, QGraphicsPixelizeEffect, QGraphicsGrayscaleEffect,
        QGraphicsColorizeEffect, QGraphicsOpacityEffect
*/
QGraphicsDropShadowEffect::QGraphicsDropShadowEffect(QObject *parent)
    : QGraphicsEffect(*new QGraphicsDropShadowEffectPrivate, parent)
{
}

QGraphicsDropShadowEffect::~QGraphicsDropShadowEffect()
{
}

/*!
    Returns the shadow offset in pixels.

    \sa setOffset(), blurRadius(), color(), offsetChanged()
*/
QPointF QGraphicsDropShadowEffect::offset() const
{
    Q_D(const QGraphicsDropShadowEffect);
    return d->filter->offset();
}

/*!
    Sets the shadow offset in pixels to the given \a offset.

    \sa offset(), setBlurRadius(), setColor(), offsetChanged()
*/
void QGraphicsDropShadowEffect::setOffset(const QPointF &offset)
{
    Q_D(QGraphicsDropShadowEffect);
    if (d->filter->offset() == offset)
        return;

    d->filter->setOffset(offset);
    updateBoundingRect();
    emit offsetChanged(offset);
}

/*!
    \fn void QGraphicsDropShadowEffect::offsetChanged(const QPointF &offset)

    This signal is emitted whenever the effect's shadow offset changes.
*/

/*!
    Returns the radius in pixels of the blur on the drop shadow.

    \sa setBlurRadius(), color(), offset(), blurRadiusChanged()
*/
int QGraphicsDropShadowEffect::blurRadius() const
{
    Q_D(const QGraphicsDropShadowEffect);
    return d->filter->blurRadius();
}

/*!
    Sets the radius in pixels of the blur on the drop shadow to the
    \a blurRadius specified.

    Using a smaller radius results in a sharper shadow, whereas using a bigger
    radius results in a more blurred shadow.

    \sa blurRadius(), setColor(), setOffset(), blurRadiusChanged()
*/
void QGraphicsDropShadowEffect::setBlurRadius(int blurRadius)
{
    Q_D(QGraphicsDropShadowEffect);
    if (d->filter->blurRadius() == blurRadius)
        return;

    d->filter->setBlurRadius(blurRadius);
    updateBoundingRect();
    emit blurRadiusChanged(blurRadius);
}

/*!
    \fn void QGraphicsDropShadowEffect::blurRadiusChanged(int blurRadius)

    This signal is emitted whenever the effect's blur radius changes.
*/

/*!
    Returns the color of the drop shadow.

    \sa setColor, offset(), blurRadius(), colorChanged()
*/
QColor QGraphicsDropShadowEffect::color() const
{
    Q_D(const QGraphicsDropShadowEffect);
    return d->filter->color();
}

/*!
    Sets the color of the drop shadow to the given \a color.

    \sa color(), setOffset(), setBlurRadius(), colorChanged()
*/
void QGraphicsDropShadowEffect::setColor(const QColor &color)
{
    Q_D(QGraphicsDropShadowEffect);
    if (d->filter->color() == color)
        return;

    d->filter->setColor(color);
    emit colorChanged(color);
}

/*!
    \fn void QGraphicsDropShadowEffect::colorChanged(const QColor &color)

    This signal is emitted whenever the effect's color changes.
*/

QRectF QGraphicsDropShadowEffect::boundingRectFor(const QRectF &rect) const
{
    Q_D(const QGraphicsDropShadowEffect);
    return d->filter->boundingRectFor(rect);
}

void QGraphicsDropShadowEffect::draw(QPainter *painter, QGraphicsEffectSource *source)
{
    Q_D(QGraphicsDropShadowEffect);
    if (d->filter->blurRadius() <= 0 && d->filter->offset().isNull()) {
        source->draw(painter);
        return;
    }

    QPoint offset;
    if (source->isPixmap()) {
        // No point in drawing in device coordinates (pixmap will be scaled anyways).
        const QPixmap pixmap = source->pixmap(Qt::LogicalCoordinates, &offset);
        d->filter->draw(painter, offset, pixmap);
        return;
    }

    // Draw pixmap in device coordinates to avoid pixmap scaling.
    const QPixmap pixmap = source->pixmap(Qt::DeviceCoordinates, &offset);
    QTransform restoreTransform = painter->worldTransform();
    painter->setWorldTransform(QTransform());
    d->filter->draw(painter, offset, pixmap);
    painter->setWorldTransform(restoreTransform);
}

/*!
    \class QGraphicsOpacityEffect
    \brief The QGraphicsOpacityEffect class provides an opacity effect.
    \since 4.6

    An opacity effect renders the source with an opacity. This effect is useful
    for making the source semi-transparent, similar to a fade-in/fade-out
    sequence. The opacity can be modified using the setOpacity() function.

    By default, the opacity is 0.7.

    \sa QGraphicsDropShadowEffect, QGraphicsBlurEffect, QGraphicsPixelizeEffect,
        QGraphicsGrayscaleEffect, QGraphicsColorizeEffect
*/
QGraphicsOpacityEffect::QGraphicsOpacityEffect(QObject *parent)
    : QGraphicsEffect(*new QGraphicsOpacityEffectPrivate, parent)
{
}

QGraphicsOpacityEffect::~QGraphicsOpacityEffect()
{
}

/*!
    Returns the opacity.

    \sa setOpacity(), opacityChanged()
*/
qreal QGraphicsOpacityEffect::opacity() const
{
    Q_D(const QGraphicsOpacityEffect);
    return d->opacity;
}

/*!
    Sets the opacity to the given \a opacity. The value should be in the range
    of 0.0 to 1.0, where 0.0 is fully transparent and 1.0 is fully opaque.

    \sa opacity(), opacityChanged()
*/
void QGraphicsOpacityEffect::setOpacity(qreal opacity)
{
    Q_D(QGraphicsOpacityEffect);
    opacity = qBound(qreal(0.0), opacity, qreal(1.0));

    if (qFuzzyCompare(d->opacity, opacity))
        return;

    d->opacity = opacity;
    emit opacityChanged(opacity);
}

/*!
    \fn void QGraphicsOpacityEffect::opacityChanged(qreal opacity)

    This signal is emitted whenever the effect's opacity changes.
*/

void QGraphicsOpacityEffect::draw(QPainter *painter, QGraphicsEffectSource *source)
{
    Q_D(QGraphicsOpacityEffect);

    // Transparent; nothing to draw.
    if (qFuzzyIsNull(d->opacity))
        return;

    // Opaque; draw directly without going through a pixmap.
    if (qFuzzyIsNull(d->opacity - 1)) {
        source->draw(painter);
        return;
    }

    painter->save();
    painter->setOpacity(d->opacity);

    QPoint offset;
    if (source->isPixmap()) {
        // No point in drawing in device coordinates (pixmap will be scaled anyways).
        const QPixmap pixmap = source->pixmap(Qt::LogicalCoordinates, &offset);
        painter->drawPixmap(offset, pixmap);
    } else {
        // Draw pixmap in device coordinates to avoid pixmap scaling;
        const QPixmap pixmap = source->pixmap(Qt::DeviceCoordinates, &offset);
        painter->setWorldTransform(QTransform());
        painter->drawPixmap(offset, pixmap);
    }

    painter->restore();
}

QT_END_NAMESPACE