The QOffscreenSurface class represents an offscreen surface in the underlying platform. More...

Inheritance diagram for QOffscreenSurface:

Public Signals
void	screenChanged (QScreen *screen)

Public Signals inherited from QObject
void	destroyed (QObject *obj=nullptr)

void	objectNameChanged (const QString &objectName)

Public Methods
	QOffscreenSurface (QScreen *screen=nullptr)

virtual	~QOffscreenSurface ()

void	create ()

void	destroy ()

QSurfaceFormat	format () const override

bool	isValid () const

QSurfaceFormat	requestedFormat () const

QScreen *	screen () const

void	setFormat (const QSurfaceFormat &format)

void	setScreen (QScreen *screen)

QSize	size () const override

SurfaceType	surfaceType () const override

Public Methods inherited from QObject
	QObject (QObject *parent=nullptr)

	~QObject ()

bool	blockSignals (bool block)

const QList< QObject * > &	children () const

bool	connect (const QObject *sender, const QString &signalMethod, const QString &location, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)

bool	connect (const QObject *sender, const QString &signalMethod, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)

bool	disconnect (const QObject *receiver, const QString &slotMethod=QString ()) const

bool	disconnect (const QString &signalMethod, const QString &location, const QObject *receiver=nullptr, const QString &slotMethod=QString ()) const

bool	disconnect (const QString &signalMethod=QString (), const QObject *receiver=nullptr, const QString &slotMethod=QString ()) const

void	dumpObjectInfo ()

void	dumpObjectTree ()

QList< QString >	dynamicPropertyNames () const

virtual bool	event (QEvent *event)

virtual bool	eventFilter (QObject watched, QEvent event)

template<typename T >
T	findChild (const QString &childName=QString ()) const

template<class T >
QList< T >	findChildren (const QRegularExpression &regExp, Qt::FindChildOptions options=Qt::FindChildrenRecursively) const

template<class T >
QList< T >	findChildren (const QString &childName=QString (), Qt::FindChildOptions options=Qt::FindChildrenRecursively) const

bool	inherits (const QString &className) const

void	installEventFilter (QObject *filterObj)

bool	isWidgetType () const

bool	isWindowType () const

void	killTimer (int id)

const QMetaObject *	metaObject () const

void	moveToThread (QThread *targetThread)

QString	objectName () const

QObject *	parent () const

template<class T = QVariant>
T	property (const QString &name) const

void	removeEventFilter (QObject *obj)

void	setObjectName (const QString &name)

void	setParent (QObject *parent)

bool	setProperty (const QString &name, const QVariant &value)

bool	signalsBlocked () const

int	startTimer (int interval, Qt::TimerType timerType=Qt::CoarseTimer)

QThread *	thread () const

Public Methods inherited from QSurface
virtual	~QSurface ()

bool	supportsOpenGL () const

SurfaceClass	surfaceClass () const

Additional Inherited Members
Public Types inherited from QSurface
enum	SurfaceClass

enum	SurfaceType

Public Slots inherited from QObject
void	deleteLater ()

Static Public Methods inherited from QObject
static bool	connect (const QObject sender, const QMetaMethod &signalMethod, const QObject receiver, const QMetaMethod &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)

static bool	connect (const QObject sender, const QString &signalMethod, const QObject receiver, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection, const QString &location=QString ())

static bool	connect (const QObject sender, const QString &signalMethod, const QString &location, const QObject receiver, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)

template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class SlotClass , class... SlotArgs, class SlotReturn >
static bool	connect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver receiver, SlotReturn (SlotClass::slotMethod)(SlotArgs...), Qt::ConnectionType type=Qt::AutoConnection)

template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class T >
static bool	connect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver *receiver, T slotLambda, Qt::ConnectionType type=Qt::AutoConnection)

static bool	disconnect (const QObject sender, const QMetaMethod &signalMethod, const QObject receiver, const QMetaMethod &slotMethod)

static bool	disconnect (const QObject sender, const QString &signalMethod, const QObject receiver, const QString &slotMethod)

static bool	disconnect (const QObject sender, const QString &signalMethod, const QString &location, const QObject receiver, const QString &slotMethod)

static bool	disconnect (const QObject sender, std::nullptr_t, const QObject receiver, std::nullptr_t)

template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class SlotClass , class... SlotArgs, class SlotReturn >
static bool	disconnect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver receiver, SlotReturn (SlotClass::slotMethod)(SlotArgs...))

template<class Sender , class SignalClass , class... SignalArgs, class Receiver >
static bool	disconnect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver *receiver, std::nullptr_t slotMethod=nullptr)

template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class T >
static bool	disconnect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver *receiver, T slotMethod)

static QMetaObject &	staticMetaObject ()

static QString	tr (const char text, const char comment=nullptr, std::optional< int > numArg=std::optional< int >())

Protected Methods inherited from QObject
virtual void	childEvent (QChildEvent *event)

virtual void	connectNotify (const QMetaMethod &signalMethod) const

virtual void	customEvent (QEvent *event)

virtual void	disconnectNotify (const QMetaMethod &signalMethod) const

bool	isSignalConnected (const QMetaMethod &signalMethod) const

int	receivers (const QString &signal) const

QObject *	sender () const

int	senderSignalIndex () const

virtual void	timerEvent (QTimerEvent *event)

Protected Methods inherited from QSurface
	QSurface (SurfaceClass type)

Properties inherited from QObject
	objectName

Related Functions inherited from QObject
T	qobject_cast (QObject *object)

	QObjectList

Detailed Description

The QOffscreenSurface class represents an offscreen surface in the underlying platform.

QOffscreenSurface is intended to be used with QOpenGLContext to allow rendering with OpenGL in an arbitrary thread without the need to create a QWindow.

Even though the surface is typically renderable, the surface's pixels are not accessible. QOffscreenSurface should only be used to create OpenGL resources such as textures or framebuffer objects.

An application will typically use QOffscreenSurface to perform some time-consuming tasks in a separate thread in order to avoid stalling the main rendering thread. Resources created in the QOffscreenSurface's context can be shared with the main OpenGL context. Some common use cases are asynchronous texture uploads or rendering into a QOpenGLFramebufferObject.

How the offscreen surface is implemented depends on the underlying platform, but it will typically use a pixel buffer (pbuffer). If the platform does not implement or support offscreen surfaces, QOffscreenSurface will use an invisible QWindow internally.

Due to the fact that QOffscreenSurface is backed by a QWindow on some platforms, cross-platform applications must ensure that create() is only called on the main (GUI) thread. The QOffscreenSurface is then safe to be used with makeCurrent() on other threads, but the initialization and destruction must always happen on the main (GUI) thread.

In order to create an offscreen surface that is guaranteed to be compatible with a given context and window, make sure to set the format to the context's or the window's actual format, that is, the QSurfaceFormat returned from QOpenGLContext::format() or QWindow::format() after the context or window has been created. Passing the format returned from QWindow::requestedFormat() to setFormat() may result in an incompatible offscreen surface since the underlying windowing system interface may offer a different set of configurations for window and pbuffer surfaces.

Some platforms may utilize a surfaceless context extension (for example EGL_KHR_surfaceless_context) when available. In this case there will be no underlying native surface. For the use cases of QOffscreenSurface (rendering to FBOs, texture upload) this is not a problem.

Constructor & Destructor Documentation

QOffscreenSurface::QOffscreenSurface ( QScreen * screen = nullptr )

explicit

Creates an offscreen surface for the screen. The underlying platform surface is not created until create() is called.

See also: setScreen(), create()

QOffscreenSurface::~QOffscreenSurface ( )

virtual

Destroys the offscreen surface.

Method Documentation

void QOffscreenSurface::create ( )

Allocates the platform resources associated with the offscreen surface. It is at this point that the surface format set using setFormat() gets resolved into an actual native surface.

Call destroy() to free the platform resources if necessary.

Note: Some platforms require this function to be called on the main (GUI) thread.

See also: destroy()

void QOffscreenSurface::destroy ( )

Releases the native platform resources associated with this offscreen surface.

See also: create()

QSurfaceFormat QOffscreenSurface::format ( ) const

overridevirtual

Returns the actual format of this offscreen surface.

After the offscreen surface has been created, this function will return the actual surface format of the surface. It might differ from the requested format if the requested format could not be fulfilled by the platform.

See also: create(), requestedFormat()

Implements QSurface::format()

bool QOffscreenSurface::isValid ( ) const

Returns true if this offscreen surface is valid, otherwise returns false.

The offscreen surface is valid if the platform resources have been successfully allocated.

See also: create()

QSurfaceFormat QOffscreenSurface::requestedFormat ( ) const

Returns the requested surfaceformat of this offscreen surface. If the requested format was not supported by the platform implementation, the requestedFormat will differ from the actual offscreen surface format.

This is the value set with setFormat().

See also: setFormat(), format()

QScreen * QOffscreenSurface::screen ( ) const

Returns the screen to which the offscreen surface is connected.

See also: setScreen()

void QOffscreenSurface::screenChanged ( QScreen * screen )

signal

This signal is emitted when the screen for an offscreen surface changes. This can occur by explicitly calling setScreen() or happened automatically when the window's screen is removed.

void QOffscreenSurface::setFormat ( const QSurfaceFormat & format )

Sets the offscreen surface format.

The surface format will be resolved in the create() function. Calling this function after create() will not re-resolve the surface format of the native surface.

See also: create(), destroy()

void QOffscreenSurface::setScreen ( QScreen * screen )

Sets the screen to which the offscreen surface is connected. If the offscreen surface has been created, it will be recreated on the screen.

See also: screen()

QSize QOffscreenSurface::size ( ) const

overridevirtual

Returns the size of the offscreen surface.

Implements QSurface::size()

QOffscreenSurface::SurfaceType QOffscreenSurface::surfaceType ( ) const

overridevirtual

Returns the surface type of the offscreen surface. The surface type of an offscreen surface is always QSurface::OpenGLSurface.

Implements QSurface::surfaceType()

Public Signals

Public Methods

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

Method Documentation