The QOpenGLVertexArrayObject class wraps an OpenGL Vertex Array Object. More...

#include <qopenglvertexarrayobject.h>

Inheritance diagram for QOpenGLVertexArrayObject:

Collaboration diagram for QOpenGLVertexArrayObject:

Classes
class	Binder
	The QOpenGLVertexArrayObject::Binder class is a convenience class to help with the binding and releasing of OpenGL Vertex Array Objects. More...

Public Member Functions
	QOpenGLVertexArrayObject (QObject *parent=nullptr)
	Creates a QOpenGLVertexArrayObject with the given parent.

	~QOpenGLVertexArrayObject ()
	Destroys the QOpenGLVertexArrayObject and the underlying OpenGL resource.

bool	create ()
	Creates the underlying OpenGL vertex array object.

void	destroy ()
	Destroys the underlying OpenGL vertex array object.

bool	isCreated () const
	Returns `true` is the underlying OpenGL vertex array object has been created.

GLuint	objectId () const
	Returns the id of the underlying OpenGL vertex array object.

void	bind ()
	Binds this vertex array object to the OpenGL binding point.

void	release ()
	Unbinds this vertex array object by binding the default vertex array object (id = 0).

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`.

Additional Inherited Members
Public Slots inherited from QObject
void	deleteLater ()
	\threadsafe

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.

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 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)

Protected Attributes inherited from QObject
QScopedPointer< QObjectData >	d_ptr

Properties inherited from QObject
QString	objectName
	the name of this object

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 QOpenGLVertexArrayObject class wraps an OpenGL Vertex Array Object.

\inmodule QtOpenGL

Since: 5.1

A Vertex Array Object (VAO) is an OpenGL container object that encapsulates the state needed to specify per-vertex attribute data to the OpenGL pipeline. To put it another way, a VAO remembers the states of buffer objects (see QOpenGLBuffer) and their associated state (e.g. vertex attribute divisors). This allows a very easy and efficient method of switching between OpenGL buffer states for rendering different "objects" in a scene. The QOpenGLVertexArrayObject class is a thin wrapper around an OpenGL VAO.

For the desktop, VAOs are supported as a core feature in OpenGL 3.0 or newer and by the GL_ARB_vertex_array_object for older versions. On OpenGL ES 2, VAOs are provided by the optional GL_OES_vertex_array_object extension. You can check the version of OpenGL with QOpenGLContext::surfaceFormat() and check for the presence of extensions with QOpenGLContext::hasExtension().

As with the other Qt OpenGL classes, QOpenGLVertexArrayObject has a create() function to create the underlying OpenGL object. This is to allow the developer to ensure that there is a valid current OpenGL context at the time.

Once you have successfully created a VAO the typical usage pattern is:

\list

In scene initialization function, for each visual object: \list
Bind the VAO
Set vertex data state for this visual object (vertices, normals, texture coordinates etc.)
Unbind (release()) the VAO \endlist
In render function, for each visual object: \list
Bind the VAO (and shader program if needed)
Call a glDraw*() function
Unbind (release()) the VAO \endlist \endlist

The act of binding the VAO in the render function has the effect of restoring all of the vertex data state setup in the initialization phase. In this way we can set a great deal of state when setting up a VAO and efficiently switch between state sets of objects to be rendered. Using VAOs also allows the OpenGL driver to amortise the validation checks of the vertex data.

Note: Vertex Array Objects, like all other OpenGL container objects, are specific to the context for which they were created and cannot be shared amongst a context group.

See also: QOpenGLVertexArrayObject::Binder, QOpenGLBuffer

Definition at line 18 of file qopenglvertexarrayobject.h.

Constructor & Destructor Documentation

◆ QOpenGLVertexArrayObject()

QOpenGLVertexArrayObject::QOpenGLVertexArrayObject ( QObject * parent = nullptr )

explicit

Creates a QOpenGLVertexArrayObject with the given parent.

You must call create() with a valid OpenGL context before using.

Definition at line 360 of file qopenglvertexarrayobject.cpp.

◆ ~QOpenGLVertexArrayObject()

QOpenGLVertexArrayObject::~QOpenGLVertexArrayObject ( )

Destroys the QOpenGLVertexArrayObject and the underlying OpenGL resource.

Definition at line 376 of file qopenglvertexarrayobject.cpp.

References destroy().

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Member Function Documentation

◆ bind()

void QOpenGLVertexArrayObject::bind ( )

Binds this vertex array object to the OpenGL binding point.

From this point on and until release() is called or another vertex array object is bound, any modifications made to vertex data state are stored inside this vertex array object.

If another vertex array object is then bound you can later restore the set of state associated with this object by calling bind() on this object once again. This allows efficient changes between vertex data states in rendering functions.

Definition at line 442 of file qopenglvertexarrayobject.cpp.

References d.

Referenced by QOpenGLTextureGlyphCache::resizeTextureData().

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◆ create()

bool QOpenGLVertexArrayObject::create ( )

Creates the underlying OpenGL vertex array object.

There must be a valid OpenGL context that supports vertex array objects current for this function to succeed.

Returns true if the OpenGL vertex array object was successfully created.

When the return value is false, vertex array object support is not available. This is not an error: on systems with OpenGL 2.x or OpenGL ES 2.0 vertex array objects may not be supported. The application is free to continue execution in this case, but it then has to be prepared to operate in a VAO-less manner too. This means that instead of merely calling bind(), the value of isCreated() must be checked and the vertex arrays has to be initialized in the traditional way when there is no vertex array object present.