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

#include <qgraphicseffect.h>

Inheritance diagram for QGraphicsEffect:

Collaboration 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.

Public Slots inherited from QObject
void	deleteLater ()
	\threadsafe

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

Signals inherited from QObject
void	destroyed (QObject *=nullptr)
	This signal is emitted immediately before the object obj is destroyed, after any instances of QPointer have been notified, and cannot be blocked.

void	objectNameChanged (const QString &objectName, QPrivateSignal)
	This signal is emitted after the object's name has been changed.

Public Member Functions
	QGraphicsEffect (QObject *parent=nullptr)
	Constructs a new QGraphicsEffect instance having the specified parent.

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

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

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.

bool	isEnabled () const

QGraphicsEffectSource *	source () const

Public Member Functions inherited from QObject
Q_INVOKABLE	QObject (QObject *parent=nullptr)
	Constructs an object with parent object parent.

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

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

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

QString	objectName () const

Q_WEAK_OVERLOAD void	setObjectName (const QString &name)
	Sets the object's name to name.

void	setObjectName (QAnyStringView name)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

QBindable< QString >	bindableObjectName ()

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

bool	isWindowType () const
	Returns `true` if the object is a window; otherwise returns `false`.

bool	isQuickItemType () const
	Returns `true` if the object is a QQuickItem; otherwise returns `false`.

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

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

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

bool	moveToThread (QThread *thread QT6_DECL_NEW_OVERLOAD_TAIL)
	Changes the thread affinity for this object and its children and returns `true` on success.

int	startTimer (int interval, Qt::TimerType timerType=Qt::CoarseTimer)
	This is an overloaded function that will start a timer of type timerType and a timeout of interval milliseconds.

int	startTimer (std::chrono::nanoseconds time, Qt::TimerType timerType=Qt::CoarseTimer)

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

void	killTimer (Qt::TimerId id)

template<typename T >
T	findChild (QAnyStringView aName, Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
	Returns the child of this object that can be cast into type T and that is called name, or \nullptr if there is no such object.

template<typename T >
QList< T >	findChildren (QAnyStringView aName, Qt::FindChildOptions options=Qt::FindChildrenRecursively) 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.

template<typename T >
T	findChild (Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

template<typename T >
QList< T >	findChildren (Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

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

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

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

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

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

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

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

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

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

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

bool	setProperty (const char *name, QVariant &&value)

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

QList< QByteArray >	dynamicPropertyNames () const

QBindingStorage *	bindingStorage ()

const QBindingStorage *	bindingStorage () const

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

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`.

Protected Member Functions
	QGraphicsEffect (QGraphicsEffectPrivate &d, QObject *parent=nullptr)

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

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

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

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

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

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

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

Protected Member Functions inherited from QObject
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 \nullptr.

int	senderSignalIndex () const

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

bool	isSignalConnected (const QMetaMethod &signal) const

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

virtual void	childEvent (QChildEvent *event)
	This event handler can be reimplemented in a subclass to receive child events.

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

virtual void	connectNotify (const QMetaMethod &signal)

virtual void	disconnectNotify (const QMetaMethod &signal)

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

Properties
bool	enabled
	whether the effect is enabled or not.

Properties inherited from QObject
QString	objectName
	the name of this object

Friends
class	QGraphicsItem

class	QGraphicsItemPrivate

class	QGraphicsScenePrivate

class	QWidget

class	QWidgetPrivate

Additional Inherited Members
Static Public Member Functions inherited from QObject
static QMetaObject::Connection	connect (const QObject sender, const char signal, const QObject receiver, const char member, Qt::ConnectionType=Qt::AutoConnection)
	\threadsafe

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

template<typename Func1 , typename Func2 >
static QMetaObject::Connection	connect (const typename QtPrivate::FunctionPointer< Func1 >::Object sender, Func1 signal, const typename QtPrivate::ContextTypeForFunctor< Func2 >::ContextType context, Func2 &&slot, Qt::ConnectionType type=Qt::AutoConnection)

template<typename Func1 , typename Func2 >
static QMetaObject::Connection	connect (const typename QtPrivate::FunctionPointer< Func1 >::Object *sender, Func1 signal, Func2 &&slot)

static bool	disconnect (const QObject sender, const char signal, const QObject receiver, const char member)
	\threadsafe

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

static bool	disconnect (const QMetaObject::Connection &)
	Disconnect a connection.

template<typename Func1 , typename Func2 >
static bool	disconnect (const typename QtPrivate::FunctionPointer< Func1 >::Object sender, Func1 signal, const typename QtPrivate::FunctionPointer< Func2 >::Object receiver, Func2 slot)

template<typename Func1 >
static bool	disconnect (const typename QtPrivate::FunctionPointer< Func1 >::Object sender, Func1 signal, const QObject receiver, void **zero)

Protected Attributes inherited from QObject
QScopedPointer< QObjectData >	d_ptr

Related Symbols inherited from QObject
template< class T > T	qobject_cast (const QObject *object)
	Returns the given object cast to type T if the object is of type T (or of a subclass); otherwise returns \nullptr.

template< typename T > T	qFindChildqFindChildren (const QObject *obj, const QString &name)()

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

	QObjectList
	\macro Q_CLASSINFO(Name, Value)

Detailed Description

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

Since: 4.6

\inmodule QtWidgets

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

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 \endlist

\table \row

{2,1} \row
\row
\endtable

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 documentation 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 26 of file qgraphicseffect.h.

Member Enumeration Documentation

◆ ChangeFlag

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.

Enumerator
SourceAttached
SourceDetached
SourceBoundingRectChanged
SourceInvalidated

Definition at line 31 of file qgraphicseffect.h.

◆ PixmapPadMode

enum QGraphicsEffect::PixmapPadMode

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

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

Enumerator
NoPad
PadToTransparentBorder
PadToEffectiveBoundingRect

Definition at line 40 of file qgraphicseffect.h.

Constructor & Destructor Documentation

◆ QGraphicsEffect() [1/2]

QGraphicsEffect::QGraphicsEffect ( QObject * parent = nullptr )

Constructs a new QGraphicsEffect instance having the specified parent.

Definition at line 363 of file qgraphicseffect.cpp.

◆ ~QGraphicsEffect()

QGraphicsEffect::~QGraphicsEffect ( )

virtual

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

Definition at line 379 of file qgraphicseffect.cpp.

◆ QGraphicsEffect() [2/2]

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

protected

Definition at line 371 of file qgraphicseffect.cpp.

Member Function Documentation

◆ 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 392 of file qgraphicseffect.cpp.

◆ 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 QGraphicsBlurEffect, and QGraphicsDropShadowEffect.

Definition at line 409 of file qgraphicseffect.cpp.

◆ draw()

virtual 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 QGraphicsBlurEffect, QGraphicsColorizeEffect, QGraphicsDropShadowEffect, and QGraphicsOpacityEffect.

◆ 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 215 of file qgraphicseffect.cpp.

◆ 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()

◆ isEnabled()

bool QGraphicsEffect::isEnabled ( ) const

Definition at line 427 of file qgraphicseffect.cpp.

◆ setEnabled

void QGraphicsEffect::setEnabled ( bool enable )

slot

Definition at line 433 of file qgraphicseffect.cpp.

◆ source()

QGraphicsEffectSource * QGraphicsEffect::source ( ) const

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

See also: draw()

Definition at line 477 of file qgraphicseffect.cpp.

◆ 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 135 of file qgraphicseffect.cpp.

◆ 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.

Definition at line 552 of file qgraphicseffect.cpp.

◆ 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 255 of file qgraphicseffect.cpp.

◆ sourcePixmap()

QPixmap QGraphicsEffect::sourcePixmap	(	Qt::CoordinateSystem	system = Qt::LogicalCoordinates,
		QPoint *	offset = nullptr,
		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 330 of file qgraphicseffect.cpp.

◆ 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 462 of file qgraphicseffect.cpp.

◆ 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 493 of file qgraphicseffect.cpp.

Friends And Related Symbol Documentation

◆ QGraphicsItem

friend class QGraphicsItem

friend

Definition at line 77 of file qgraphicseffect.h.

◆ QGraphicsItemPrivate

friend class QGraphicsItemPrivate

friend

Definition at line 78 of file qgraphicseffect.h.

◆ QGraphicsScenePrivate

friend class QGraphicsScenePrivate

friend

Definition at line 79 of file qgraphicseffect.h.

◆ QWidget

friend class QWidget

friend

Definition at line 80 of file qgraphicseffect.h.

◆ QWidgetPrivate

friend class QWidgetPrivate

friend

Definition at line 81 of file qgraphicseffect.h.

Property Documentation

◆ enabled

bool QGraphicsEffect::enabled

readwrite

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 29 of file qgraphicseffect.h.

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

qtbase/src/widgets/effects/qgraphicseffect.h (05fc3aef53348fb58be6308076e000825b704e58)
qtbase/src/widgets/effects/qgraphicseffect.cpp (05fc3aef53348fb58be6308076e000825b704e58)

Public Types

Public Slots

Signals

Public Member Functions

Protected Member Functions

Properties

Friends

Additional Inherited Members

Detailed Description

Member Enumeration Documentation

◆ ChangeFlag

◆ PixmapPadMode

Constructor & Destructor Documentation

◆ QGraphicsEffect() [1/2]

◆ ~QGraphicsEffect()

◆ QGraphicsEffect() [2/2]

Member Function Documentation

◆ boundingRect()

◆ boundingRectFor()

◆ draw()

◆ drawSource()

◆ enabledChanged

◆ isEnabled()

◆ setEnabled

◆ source()

◆ sourceBoundingRect()

◆ sourceChanged()

◆ sourceIsPixmap()

◆ sourcePixmap()

◆ update

◆ updateBoundingRect()

Friends And Related Symbol Documentation

◆ QGraphicsItem

◆ QGraphicsItemPrivate

◆ QGraphicsScenePrivate

◆ QWidget

◆ QWidgetPrivate

Property Documentation

◆ enabled