The QGraphicsEffect class is the base class for all graphics effects. More...

#include <qgraphicseffect.h>

Inheritance diagram for QGraphicsEffect:

Public Types
enum	ChangeFlag { SourceAttached = 0x1, SourceDetached = 0x2, SourceBoundingRectChanged = 0x4, SourceInvalidated = 0x8 }
	This enum describes what has changed in QGraphicsEffectSource. More...

enum	PixmapPadMode { NoPad, PadToTransparentBorder, PadToEffectiveBoundingRect }
	This enum describes how the pixmap returned from sourcePixmap should be padded. More...

Public Slots
void	setEnabled (bool enable)

void	update ()
	Schedules a redraw of the effect. More...

Public Slots inherited from QObject
void	deleteLater ()
	Schedules this object for deletion. More...

Signals
void	enabledChanged (bool enabled)
	This signal is emitted whenever the effect is enabled or disabled. More...

Signals inherited from QObject
void	destroyed (QObject *=0)
	This signal is emitted immediately before the object obj is destroyed, and can not be blocked. More...

Public Functions
QRectF	boundingRect () const
	Returns the effective bounding rectangle for this effect, i.e., the bounding rectangle of the source in device coordinates, adjusted by any margins applied by the effect itself. More...

virtual QRectF	boundingRectFor (const QRectF &sourceRect) const
	Returns the effective bounding rectangle for this effect, given the provided rect in the device coordinates. More...

bool	isEnabled () const

	QGraphicsEffect (QObject *parent=0)
	Constructs a new QGraphicsEffect instance having the specified parent. More...

QGraphicsEffectSource *	source () const
	Returns a pointer to the source, which provides extra context information that can be useful for the effect. More...

virtual	~QGraphicsEffect ()
	Removes the effect from the source, and destroys the graphics effect. More...

Public Functions inherited from QObject
bool	blockSignals (bool b)
	If block is true, signals emitted by this object are blocked (i.e., emitting a signal will not invoke anything connected to it). More...

const QObjectList &	children () const
	Returns a list of child objects. More...

bool	connect (const QObject sender, const char signal, const char *member, Qt::ConnectionType type=Qt::AutoConnection) const

bool	disconnect (const char signal=0, const QObject receiver=0, const char *member=0)

bool	disconnect (const QObject receiver, const char member=0)

void	dumpObjectInfo ()
	Dumps information about signal connections, etc. More...

void	dumpObjectTree ()
	Dumps a tree of children to the debug output. More...

QList< QByteArray >	dynamicPropertyNames () const
	Returns the names of all properties that were dynamically added to the object using setProperty(). More...

virtual bool	event (QEvent *)
	This virtual function receives events to an object and should return true if the event e was recognized and processed. More...

virtual bool	eventFilter (QObject , QEvent )
	Filters events if this object has been installed as an event filter for the watched object. More...

template<typename T >
T	findChild (const QString &aName=QString()) const
	Returns the child of this object that can be cast into type T and that is called name, or 0 if there is no such object. More...

template<typename T >
QList< T >	findChildren (const QString &aName=QString()) const
	Returns all children of this object with the given name that can be cast to type T, or an empty list if there are no such objects. More...

template<typename T >
QList< T >	findChildren (const QRegExp &re) const

bool	inherits (const char *classname) const
	Returns true if this object is an instance of a class that inherits className or a QObject subclass that inherits className; otherwise returns false. More...

void	installEventFilter (QObject *)
	Installs an event filter filterObj on this object. More...

bool	isWidgetType () const
	Returns true if the object is a widget; otherwise returns false. More...

void	killTimer (int id)
	Kills the timer with timer identifier, id. More...

virtual const QMetaObject *	metaObject () const
	Returns a pointer to the meta-object of this object. More...

void	moveToThread (QThread *thread)
	Changes the thread affinity for this object and its children. More...

QString	objectName () const

QObject *	parent () const
	Returns a pointer to the parent object. More...

QVariant	property (const char *name) const
	Returns the value of the object's name property. More...

Q_INVOKABLE	QObject (QObject *parent=0)
	Constructs an object with parent object parent. More...

void	removeEventFilter (QObject *)
	Removes an event filter object obj from this object. More...

void	setObjectName (const QString &name)

void	setParent (QObject *)
	Makes the object a child of parent. More...

bool	setProperty (const char *name, const QVariant &value)
	Sets the value of the object's name property to value. More...

void	setUserData (uint id, QObjectUserData *data)

bool	signalsBlocked () const
	Returns true if signals are blocked; otherwise returns false. More...

int	startTimer (int interval)
	Starts a timer and returns a timer identifier, or returns zero if it could not start a timer. More...

QThread *	thread () const
	Returns the thread in which the object lives. More...

QObjectUserData *	userData (uint id) const

virtual	~QObject ()
	Destroys the object, deleting all its child objects. More...

Protected Functions
virtual void	draw (QPainter *painter)=0
	This pure virtual function draws the effect and is called whenever the source needs to be drawn. More...

void	drawSource (QPainter *painter)
	Draws the source directly using the given painter. More...

	QGraphicsEffect (QGraphicsEffectPrivate &d, QObject *parent=0)

QRectF	sourceBoundingRect (Qt::CoordinateSystem system=Qt::LogicalCoordinates) const
	Returns the bounding rectangle of the source mapped to the given system. More...

virtual void	sourceChanged (ChangeFlags flags)
	This virtual function is called by QGraphicsEffect to notify the effect that the source has changed. More...

bool	sourceIsPixmap () const
	Returns true if the source effectively is a pixmap, e.g., a QGraphicsPixmapItem. More...

QPixmap	sourcePixmap (Qt::CoordinateSystem system=Qt::LogicalCoordinates, QPoint *offset=0, PixmapPadMode mode=PadToEffectiveBoundingRect) const
	Returns a pixmap with the source painted into it. More...

void	updateBoundingRect ()
	This function notifies the effect framework when the effect's bounding rectangle has changed. More...

Protected Functions inherited from QObject
virtual void	childEvent (QChildEvent *)
	This event handler can be reimplemented in a subclass to receive child events. More...

virtual void	connectNotify (const char *signal)
	This virtual function is called when something has been connected to signal in this object. More...

virtual void	customEvent (QEvent *)
	This event handler can be reimplemented in a subclass to receive custom events. More...

virtual void	disconnectNotify (const char *signal)
	This virtual function is called when something has been disconnected from signal in this object. More...

	QObject (QObjectPrivate &dd, QObject *parent=0)

int	receivers (const char *signal) const
	Returns the number of receivers connected to the signal. More...

QObject *	sender () const
	Returns a pointer to the object that sent the signal, if called in a slot activated by a signal; otherwise it returns 0. More...

int	senderSignalIndex () const

virtual void	timerEvent (QTimerEvent *)
	This event handler can be reimplemented in a subclass to receive timer events for the object. More...

Properties
bool	enabled
	whether the effect is enabled or not. More...

Friends
class	QGraphicsItem

class	QGraphicsItemPrivate

class	QGraphicsScenePrivate

class	QWidget

class	QWidgetPrivate

Additional Inherited Members
Static Public Functions inherited from QObject
static bool	connect (const QObject sender, const char signal, const QObject receiver, const char member, Qt::ConnectionType=Qt::AutoConnection)
	Creates a connection of the given type from the signal in the sender object to the method in the receiver object. More...

static bool	connect (const QObject sender, const QMetaMethod &signal, const QObject receiver, const QMetaMethod &method, Qt::ConnectionType type=Qt::AutoConnection)

static bool	disconnect (const QObject sender, const char signal, const QObject receiver, const char member)
	Disconnects signal in object sender from method in object receiver. More...

static bool	disconnect (const QObject sender, const QMetaMethod &signal, const QObject receiver, const QMetaMethod &member)

static uint	registerUserData ()

static QString	tr (const char sourceText, const char comment=0, int n=-1)

static QString	trUtf8 (const char sourceText, const char comment=0, int n=-1)

Static Public Variables inherited from QObject
static const QMetaObject	staticMetaObject
	This variable stores the meta-object for the class. More...

Protected Variables inherited from QObject
QScopedPointer< QObjectData >	d_ptr

Static Protected Variables inherited from QObject
static const QMetaObject	staticQtMetaObject

Related Functions inherited from QObject
T	qFindChildqFindChildren (const QObject *obj, const QString &name)()

QList< T >	qFindChildrenqFindChildren (const QObject *obj, const QString &name)()

QList< T >	qFindChildrenqFindChildren (const QObject *obj, const QRegExp &regExp)()

T *	qobject_cast (QObject *object)

	QObjectList

void *	qt_find_obj_child (QObject parent, const char type, const QString &name)
	Returns a pointer to the object named name that inherits type and with a given parent. More...

Detailed Description

The QGraphicsEffect class is the base class for all graphics effects.

Since: 4.6

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:

QGraphicsBlurEffect - blurs the item by a given radius
QGraphicsDropShadowEffect - renders a dropshadow behind the item
QGraphicsColorizeEffect - renders the item in shades of any given color
QGraphicsOpacityEffect - renders the item with an opacity

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 takes the painter with which to draw as an argument. For more information, refer to the documenation for draw(). In the draw() function you can call sourcePixmap() to get a pixmap of the graphics effect source which you can then process.

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 sourceChanged() function is called to notify the effects that the source has changed in some way - e.g., if the source is a QGraphicsRectItem and its rectangle parameters have changed.

See also: QGraphicsItem::setGraphicsEffect(), QWidget::setGraphicsEffect()

Definition at line 66 of file qgraphicseffect.h.

Enumerations

◆ ChangeFlag

enum QGraphicsEffect::ChangeFlag

This enum describes what has changed in QGraphicsEffectSource.

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

Enumerator
SourceAttached
SourceDetached
SourceBoundingRectChanged
SourceInvalidated

Definition at line 72 of file qgraphicseffect.h.

                     {
         SourceAttached = 0x1,
         SourceDetached = 0x2,
         SourceBoundingRectChanged = 0x4,
         SourceInvalidated = 0x8
     };

◆ PixmapPadMode

enum QGraphicsEffect::PixmapPadMode

This enum describes how the pixmap returned from sourcePixmap should be padded.

NoPad The pixmap should not receive any additional padding.
PadToTransparentBorder The pixmap should be padded to ensure it has a completely transparent border.
PadToEffectiveBoundingRect The pixmap should be padded to match the effective bounding rectangle of the effect.

Enumerator
NoPad
PadToTransparentBorder
PadToEffectiveBoundingRect

Definition at line 80 of file qgraphicseffect.h.

                        {
         NoPad,
         PadToTransparentBorder,
         PadToEffectiveBoundingRect
     };

Constructors and Destructors

◆ QGraphicsEffect() [1/2]

QGraphicsEffect::QGraphicsEffect ( QObject * parent = 0 )

Constructs a new QGraphicsEffect instance having the specified parent.

Definition at line 403 of file qgraphicseffect.cpp.

     : QObject(*new QGraphicsEffectPrivate, parent)
 {
 }

◆ ~QGraphicsEffect()

QGraphicsEffect::~QGraphicsEffect ( )

virtual

Removes the effect from the source, and destroys the graphics effect.

Definition at line 419 of file qgraphicseffect.cpp.

 {
     Q_D(QGraphicsEffect);
     d->setGraphicsEffectSource(0);
 }

◆ QGraphicsEffect() [2/2]

QGraphicsEffect::QGraphicsEffect	(	QGraphicsEffectPrivate &	dd,
		QObject *	parent = `0`
	)

protected

Warning: This function is not part of the public interface.

Definition at line 411 of file qgraphicseffect.cpp.

     : QObject(dd, parent)
 {
 }

Functions

◆ boundingRect()

QRectF QGraphicsEffect::boundingRect ( ) const

Returns the effective bounding rectangle for this effect, i.e., the bounding rectangle of the source in device coordinates, adjusted by any margins applied by the effect itself.

See also: boundingRectFor(), updateBoundingRect()

Definition at line 432 of file qgraphicseffect.cpp.

 {
     Q_D(const QGraphicsEffect);
     if (d->source)
         return boundingRectFor(d->source->boundingRect());
     return QRectF();
 }

◆ boundingRectFor()

QRectF QGraphicsEffect::boundingRectFor ( const QRectF & rect ) const

virtual

Returns the effective bounding rectangle for this effect, given the provided rect in the device coordinates.

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.

See also: sourceBoundingRect()

Reimplemented in QGraphicsDropShadowEffect, and QGraphicsBlurEffect.

Definition at line 449 of file qgraphicseffect.cpp.

Referenced by boundingRect(), and QGraphicsItemPrivate::effectiveBoundingRect().

 {
     return rect;
 }

◆ draw()

void QGraphicsEffect::draw ( QPainter * painter )

protectedpure virtual

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 painter.

For example:

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

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

Implemented in QGraphicsOpacityEffect, QGraphicsDropShadowEffect, QGraphicsBlurEffect, QGraphicsColorizeEffect, QGraphicsShaderEffect, and ShaderEffect.

Referenced by QGraphicsScenePrivate::drawSubtreeRecursive(), QWidgetPrivate::drawWidget(), and QGraphicsDropShadowEffect::setYOffset().

◆ drawSource()

void QGraphicsEffect::drawSource ( QPainter * painter )

protected

Draws the source directly using the given painter.

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

For example:

MyGraphicsOpacityEffect::draw(QPainter *painter)
{
    // Fully opaque; draw directly without going through a pixmap.
    if (qFuzzyCompare(m_opacity, 1)) {
        drawSource(painter);
        return;
    }
    ...
}

See also: QGraphicsEffect::draw()

Definition at line 255 of file qgraphicseffect.cpp.

Referenced by ShaderEffect::draw(), QGraphicsShaderEffect::draw(), QGraphicsColorizeEffect::draw(), QGraphicsBlurEffect::draw(), QGraphicsDropShadowEffect::draw(), QGraphicsOpacityEffect::draw(), and ShaderEffect::updateRenderTargets().

 {
     Q_D(const QGraphicsEffect);
     if (d->source)
         d->source->draw(painter);
 }

◆ enabledChanged

void QGraphicsEffect::enabledChanged ( bool enabled )

signal

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

The enabled parameter holds the effects's new enabled state.

See also: isEnabled()

Referenced by setEnabled().

◆ isEnabled()

bool QGraphicsEffect::isEnabled ( ) const

Definition at line 470 of file qgraphicseffect.cpp.

Referenced by QGraphicsScenePrivate::drawSubtreeRecursive(), QWidgetPrivate::drawWidget(), QGraphicsItemPrivate::effectiveBoundingRect(), and QGraphicsItemPrivate::markParentDirty().

 {
     Q_D(const QGraphicsEffect);
     return d->isEnabled;
 }

◆ setEnabled

void QGraphicsEffect::setEnabled ( bool enable )

slot

Definition at line 476 of file qgraphicseffect.cpp.

 {
     Q_D(QGraphicsEffect);
     if (d->isEnabled == enable)
         return;
 
     d->isEnabled = enable;
     if (d->source) {
         d->source->d_func()->effectBoundingRectChanged();
         d->source->d_func()->invalidateCache();
     }
     emit enabledChanged(enable);
 }

◆ source()

QGraphicsEffectSource * QGraphicsEffect::source ( ) const

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

Warning: This function is not part of the public interface.

See also: draw()

Definition at line 526 of file qgraphicseffect.cpp.

Referenced by QGraphicsScenePrivate::drawSubtreeRecursive(), QWidgetPrivate::drawWidget(), QGraphicsItemPrivate::invalidateChildGraphicsEffectsRecursively(), QWidgetPrivate::invalidateGraphicsEffectsRecursively(), QGraphicsItemPrivate::invalidateParentGraphicsEffectsRecursively(), and QGraphicsItemPrivate::markParentDirty().

 {
     Q_D(const QGraphicsEffect);
     return d->source;
 }

◆ sourceBoundingRect()

QRectF QGraphicsEffect::sourceBoundingRect ( Qt::CoordinateSystem system = Qt::LogicalCoordinates ) const

protected

Returns the bounding rectangle of the source mapped to the given system.

Calling this function with Qt::DeviceCoordinates outside of QGraphicsEffect::draw() will give undefined results, as there is no device context available.

See also: draw()

Definition at line 175 of file qgraphicseffect.cpp.

Referenced by QGraphicsOpacityEffect::draw().

 {
     Q_D(const QGraphicsEffect);
     if (d->source)
         return d->source->boundingRect(system);
     return QRectF();
 }

◆ sourceChanged()

void QGraphicsEffect::sourceChanged ( ChangeFlags flags )

protectedvirtual

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 flags describes what has changed.

Reimplemented in ShaderEffect.

Definition at line 607 of file qgraphicseffect.cpp.

Referenced by QGraphicsScenePrivate::resetDirtyItem().

 {
     Q_UNUSED(flags);
 }

◆ sourceIsPixmap()

bool QGraphicsEffect::sourceIsPixmap ( ) const

protected

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.

Definition at line 295 of file qgraphicseffect.cpp.

Referenced by QGraphicsShaderEffect::draw(), QGraphicsColorizeEffect::draw(), and QGraphicsOpacityEffect::draw().

 {
     return source() ? source()->isPixmap() : false;
 }

◆ sourcePixmap()

QPixmap QGraphicsEffect::sourcePixmap	(	Qt::CoordinateSystem	system = `Qt::LogicalCoordinates`,
		QPoint *	offset = `0`,
		QGraphicsEffect::PixmapPadMode	mode = `PadToEffectiveBoundingRect`
	)		const

protected

Returns a pixmap with the source painted into it.

The system specifies which coordinate system to be used for the source. The optional offset parameter returns the offset where the pixmap should be painted at using the current painter. For control on how the pixmap is padded use the mode parameter.

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

Calling this function with Qt::DeviceCoordinates outside of QGraphicsEffect::draw() will give undefined results, as there is no device context available.

See also: draw(), boundingRect()

Definition at line 370 of file qgraphicseffect.cpp.

Referenced by QGraphicsShaderEffect::draw(), QGraphicsColorizeEffect::draw(), QGraphicsBlurEffect::draw(), QGraphicsDropShadowEffect::draw(), and QGraphicsOpacityEffect::draw().

 {
     Q_D(const QGraphicsEffect);
     if (d->source)
         return d->source->pixmap(system, offset, mode);
     return QPixmap();
 }

◆ update

void QGraphicsEffect::update ( )

slot

Schedules a redraw of the effect.

Call this function whenever the effect needs to be redrawn. This function does not trigger a redraw of the source.

See also: updateBoundingRect()

Definition at line 508 of file qgraphicseffect.cpp.

Referenced by QGraphicsColorizeEffect::setColor(), QGraphicsDropShadowEffect::setColor(), QGraphicsOpacityEffect::setOpacity(), QGraphicsOpacityEffect::setOpacityMask(), and QGraphicsColorizeEffect::setStrength().

 {
     Q_D(QGraphicsEffect);
     if (d->source)
         d->source->update();
 }

◆ updateBoundingRect()

void QGraphicsEffect::updateBoundingRect ( )

protected

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.

This function will call update() if this is necessary.

See also: boundingRectFor(), boundingRect(), sourceBoundingRect()

Definition at line 542 of file qgraphicseffect.cpp.

Referenced by QGraphicsBlurEffect::setBlurRadius(), QGraphicsDropShadowEffect::setBlurRadius(), and QGraphicsDropShadowEffect::setOffset().

 {
     Q_D(QGraphicsEffect);
     if (d->source) {
         d->source->d_func()->effectBoundingRectChanged();
         d->source->d_func()->invalidateCache(QGraphicsEffectSourcePrivate::EffectRectChanged);
     }
 }

Friends and Related Functions

◆ QGraphicsItem

friend class QGraphicsItem

friend

Definition at line 117 of file qgraphicseffect.h.

◆ QGraphicsItemPrivate

friend class QGraphicsItemPrivate

friend

Definition at line 118 of file qgraphicseffect.h.

◆ QGraphicsScenePrivate

friend class QGraphicsScenePrivate

friend

Definition at line 119 of file qgraphicseffect.h.

◆ QWidget

friend class QWidget

friend

Definition at line 120 of file qgraphicseffect.h.

◆ QWidgetPrivate

friend class QWidgetPrivate

friend

Definition at line 121 of file qgraphicseffect.h.

Properties

◆ enabled

QGraphicsEffect::enabled

private

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.

Definition at line 70 of file qgraphicseffect.h.

The documentation for this class was generated from the following files:

/src/gui/effects/qgraphicseffect.h
/src/gui/effects/qgraphicseffect.cpp

Public Types

Public Slots

Signals

Public Functions

Protected Functions

Properties

Friends

Additional Inherited Members

Detailed Description

Enumerations

◆ ChangeFlag

◆ PixmapPadMode

Constructors and Destructors

◆ QGraphicsEffect() [1/2]

◆ ~QGraphicsEffect()

◆ QGraphicsEffect() [2/2]

Functions

◆ boundingRect()

◆ boundingRectFor()

◆ draw()

◆ drawSource()

◆ enabledChanged

◆ isEnabled()

◆ setEnabled

◆ source()

◆ sourceBoundingRect()

◆ sourceChanged()

◆ sourceIsPixmap()

◆ sourcePixmap()

◆ update

◆ updateBoundingRect()

Friends and Related Functions

◆ QGraphicsItem

◆ QGraphicsItemPrivate

◆ QGraphicsScenePrivate

◆ QWidget

◆ QWidgetPrivate

Properties

◆ enabled