The QOpenGLTimeMonitor class wraps a sequence of OpenGL timer query objects. More...

#include <qopengltimerquery.h>

Inheritance diagram for QOpenGLTimeMonitor:

Collaboration diagram for QOpenGLTimeMonitor:

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

	~QOpenGLTimeMonitor ()
	Destroys the QOpenGLTimeMonitor and any underlying OpenGL resources.

void	setSampleCount (int sampleCount)
	Sets the number of sample points to sampleCount.

int	sampleCount () const
	Returns the number of sample points that have been requested with setSampleCount().

bool	create ()
	Instantiate sampleCount() OpenGL timer query objects that will be used to track the amount of time taken to execute OpenGL commands between successive calls to recordSample().

void	destroy ()
	Destroys any OpenGL timer query objects used within this instance.

bool	isCreated () const
	Returns `true` if the underlying OpenGL query objects have been created.

QList< GLuint >	objectIds () const
	Returns a QList containing the object Ids of the OpenGL timer query objects.

int	recordSample ()
	Issues an OpenGL timer query at this point in the OpenGL command queue.

bool	isResultAvailable () const
	Returns `true` if the OpenGL timer query results are available.

QList< GLuint64 >	waitForSamples () const
	Returns a QList containing the GPU timestamps taken with recordSample().

QList< GLuint64 >	waitForIntervals () const
	Returns a QList containing the time intervals delimited by the calls to recordSample().

void	reset ()
	Resets the time monitor ready for use in another frame of rendering.

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 QOpenGLTimeMonitor class wraps a sequence of OpenGL timer query objects.

\inmodule QtOpenGL

Since: 5.1

The QOpenGLTimeMonitor class is a convenience wrapper around a collection of OpenGL timer query objects used to measure intervals of time on the GPU to the level of granularity required by your rendering application.

The OpenGL timer queries objects are queried in sequence to record the GPU timestamps at positions of interest in your rendering code. Once the results for all issues timer queries become available, the results can be fetched and QOpenGLTimerMonitor will calculate the recorded time intervals for you.

The typical use case of this class is to either profile your application's rendering algorithms or to adjust those algorithms in real-time for dynamic performance/quality balancing.

Prior to using QOpenGLTimeMonitor in your rendering function you should set the required number of sample points that you wish to record by calling setSamples(). Note that measuring N sample points will produce N-1 time intervals. Once you have set the number of sample points, call the create() function with a valid current OpenGL context to create the necessary query timer objects. These steps are usually performed just once in an initialization function.

Use the recordSample() function to delimit blocks of code containing OpenGL commands that you wish to time. You can check availability of the resulting time samples and time intervals with isResultAvailable(). The calculated time intervals and the raw timestamp samples can be retrieved with the blocking waitForIntervals() and waitForSamples() functions respectively.

After retrieving the results and before starting a new round of taking samples (for example, in the next frame) be sure to call the reset() function which will clear the cached results and reset the timer index back to the first timer object.

See also: QOpenGLTimerQuery

Definition at line 46 of file qopengltimerquery.h.

Constructor & Destructor Documentation

◆ QOpenGLTimeMonitor()

QOpenGLTimeMonitor::QOpenGLTimeMonitor ( QObject * parent = nullptr )

explicit

Creates a QOpenGLTimeMonitor instance with the given parent.

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

See also: setSampleCount(), create()

Definition at line 655 of file qopengltimerquery.cpp.

◆ ~QOpenGLTimeMonitor()

QOpenGLTimeMonitor::~QOpenGLTimeMonitor ( )

Destroys the QOpenGLTimeMonitor and any underlying OpenGL resources.

Definition at line 663 of file qopengltimerquery.cpp.

Member Function Documentation

◆ create()

bool QOpenGLTimeMonitor::create ( )

Instantiate sampleCount() OpenGL timer query objects that will be used to track the amount of time taken to execute OpenGL commands between successive calls to recordSample().

Returns true if the OpenGL timer query objects could be created.

See also: destroy(), setSampleCount(), recordSample()

Definition at line 732 of file qopengltimerquery.cpp.

◆ destroy()

void QOpenGLTimeMonitor::destroy ( )

Destroys any OpenGL timer query objects used within this instance.

See also: create()

Definition at line 743 of file qopengltimerquery.cpp.

◆ isCreated()

bool QOpenGLTimeMonitor::isCreated ( ) const

Returns true if the underlying OpenGL query objects have been created.

If this returns true and the associated OpenGL context is current, then you are able to record time samples with this object.

Definition at line 754 of file qopengltimerquery.cpp.

◆ isResultAvailable()

bool QOpenGLTimeMonitor::isResultAvailable ( ) const

Returns true if the OpenGL timer query results are available.

See also: waitForSamples(), waitForIntervals()

Definition at line 789 of file qopengltimerquery.cpp.

◆ objectIds()

QList< GLuint > QOpenGLTimeMonitor::objectIds ( ) const

Returns a QList containing the object Ids of the OpenGL timer query objects.

Definition at line 763 of file qopengltimerquery.cpp.

◆ recordSample()

int QOpenGLTimeMonitor::recordSample ( )

Issues an OpenGL timer query at this point in the OpenGL command queue.

Calling this function in a sequence in your application's rendering function, will build up details of the GPU time taken to execute the OpenGL commands between successive calls to this function.

See also: setSampleCount(), isResultAvailable(), waitForSamples(), waitForIntervals()

Definition at line 777 of file qopengltimerquery.cpp.

◆ reset()

void QOpenGLTimeMonitor::reset ( )

Resets the time monitor ready for use in another frame of rendering.

Call this once you have obtained the previous results and before calling recordSample() for the first time on the next frame.

See also: recordSample()

Definition at line 838 of file qopengltimerquery.cpp.

◆ sampleCount()

int QOpenGLTimeMonitor::sampleCount ( ) const

Returns the number of sample points that have been requested with setSampleCount().

If create was successfully called following setSampleCount(), then the value returned will be the actual number of sample points that can be used.

The default value for sample count is 2, leading to the measurement of a single interval.

See also: setSampleCount()

Definition at line 717 of file qopengltimerquery.cpp.

◆ setSampleCount()

void QOpenGLTimeMonitor::setSampleCount ( int sampleCount )

Sets the number of sample points to sampleCount.

After setting the number of samples with this function, you must call create() to instantiate the underlying OpenGL timer query objects.

The new sampleCount must be at least 2.

See also: sampleCount(), create(), recordSample()

Definition at line 697 of file qopengltimerquery.cpp.

◆ waitForIntervals()

QList< GLuint64 > QOpenGLTimeMonitor::waitForIntervals ( ) const

Returns a QList containing the time intervals delimited by the calls to recordSample().

The resulting vector will contain one fewer element as this represents the intervening intervals rather than the actual timestamp samples.

This function will block until OpenGL indicates the results are available. It is recommended to check the availability of the result prior to calling this function with isResultAvailable().

See also: waitForSamples(), isResultAvailable()

Definition at line 825 of file qopengltimerquery.cpp.

◆ waitForSamples()

QList< GLuint64 > QOpenGLTimeMonitor::waitForSamples ( ) const

Returns a QList containing the GPU timestamps taken with recordSample().