The QPlatformSharedGraphicsCache is an abstraction of a cross-process graphics cache. More...

#include <qplatformsharedgraphicscache.h>

Inheritance diagram for QPlatformSharedGraphicsCache:

Collaboration diagram for QPlatformSharedGraphicsCache:

Public Types
enum	PixelFormat { Alpha8 }
	Defines the pixel format of a cache. More...

enum	BufferType { OpenGLTexture }
	Defines how the type of buffer required to contain a cache. More...

Signals
void	itemsMissing (const QByteArray &cacheId, const QList< quint32 > &itemIds)
	This signal is emitted when requestItems() has been called for one or more items in the cache named cacheId which are not yet available in the cache.

void	itemsAvailable (const QByteArray &cacheId, void *bufferId, const QList< quint32 > &itemIds, const QList< QPoint > &positionsInBuffer)
	This signal can be emitted at any time when either requestItems() or insertItems() has been called by the application for one or more items in the cache named cacheId, as long as releaseItems() has not subsequently been called for the same items.

void	itemsInvalidated (const QByteArray &cacheId, const QList< quint32 > &itemIds)
	This signal is emitted when the items given by itemIds in the cache named cacheId have been removed from the cache and the previously reported information about them is considered invalid.

void	itemsUpdated (const QByteArray &cacheId, void *bufferId, const QList< quint32 > &itemIds, const QList< QPoint > &positionsInBuffer)
	This signal is similar in usage to the itemsAvailable() signal, but will be emitted when the location of a previously requested or inserted item has been updated.

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
	QPlatformSharedGraphicsCache (QObject *parent=nullptr)

virtual void	beginRequestBatch ()=0
	This is a hint to the cache that a burst of requests is pending.

virtual void	ensureCacheInitialized (const QByteArray &cacheId, BufferType bufferType, PixelFormat pixelFormat)=0
	Initializes a cache named cacheId if it has not yet been initialized.

virtual void	requestItems (const QByteArray &cacheId, const QList< quint32 > &itemIds)=0
	Requests all the items in itemIds from the cache with the name cacheId.

virtual void	insertItems (const QByteArray &cacheId, const QList< quint32 > &itemIds, const QList< QImage > &items)=0
	Inserts the items in itemIds into the cache named cacheId.

virtual void	releaseItems (const QByteArray &cacheId, const QList< quint32 > &itemIds)=0
	Releases the reference to the items in itemIds from the cache named cacheId.

virtual void	endRequestBatch ()=0
	Signals to the cache that the request sequence which has previously been commenced using beginRequestBatch() has now finished.

virtual bool	requestBatchStarted () const =0
	Returns `true` if a request batch has previously been started using beginRequestBatch() and not yet stopped using endRequestBatch().

virtual uint	textureIdForBuffer (void *bufferId)=0
	Returns an OpenGL texture ID corresponding to the buffer bufferId, which has previously been passed through signals itemsAvailable() or itemsUpdated().

virtual void	referenceBuffer (void *bufferId)=0
	Registers a reference to the buffer bufferId.

virtual bool	dereferenceBuffer (void *bufferId)=0
	Removed a previously registered reference to the buffer bufferId.

virtual QSize	sizeOfBuffer (void *bufferId)=0
	Returns the size of the buffer bufferId.

virtual void *	eglImageForBuffer (void *bufferId)=0
	Returns an EGLImageKHR image corresponding to the buffer bufferId.

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.

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

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::milliseconds time, Qt::TimerType timerType=Qt::CoarseTimer)

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

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

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 QPlatformSharedGraphicsCache is an abstraction of a cross-process graphics cache.

Since: 5.0

\preliminary

If supported, it is possible to retrieve a QPlatformSharedGraphicsCache object from the platform integration. This is typically used to store graphical items which should be shared between several processes.

Items are requested from the cache by calling requestItems(). If the cache contains the requested items in the requested cache, the itemsAvailable() signal is emitted with the ID of the graphical buffer and each item's coordinates inside the buffer. Before requesting items from a cache, the user must call ensureCacheInitialized() to set the correct parameters for the cache.

If the cache does not yet contain the requested items, it will emit a similar itemsMissing() signal. The client can then call updateItems() with rasterizations of the items and they will be entered into the shared cache. As the items are rendered into the cache, itemsAvailable() signals will be emitted for each of the items which have previously been requested and which have not yet been reported as ready.

Using beginRequestBatch() and endRequestBatch(), it's possible to batch glyph requests, which could improve performance in cases where you have a sequence of requests pending, and you do not need the results during this sequence.

Definition at line 22 of file qplatformsharedgraphicscache.h.

Member Enumeration Documentation

◆ BufferType

enum QPlatformSharedGraphicsCache::BufferType

Defines how the type of buffer required to contain a cache.

\value OpenGLTexture The buffer will be allocated in graphics memory, and an OpenGL texture for a buffer belonging to the cache can be requested using textureIdForBuffer().

Enumerator
OpenGLTexture

Definition at line 31 of file qplatformsharedgraphicscache.h.

◆ PixelFormat

enum QPlatformSharedGraphicsCache::PixelFormat

Defines the pixel format of a cache.

\value Alpha8 The cache will use 8 bits to represent the alpha value of each pixel. If an OpenGL texture is created for a buffer belong to the cache, it will have the pixel format GL_ALPHA.

Enumerator
Alpha8

Definition at line 26 of file qplatformsharedgraphicscache.h.

Constructor & Destructor Documentation

◆ QPlatformSharedGraphicsCache()

QPlatformSharedGraphicsCache::QPlatformSharedGraphicsCache ( QObject * parent = nullptr )

inlineexplicit

Definition at line 36 of file qplatformsharedgraphicscache.h.

Member Function Documentation

◆ beginRequestBatch()

void QPlatformSharedGraphicsCache::beginRequestBatch ( )

pure virtual

This is a hint to the cache that a burst of requests is pending.

In some implementations, this will improve performance, as the cache can focus on handling the requests and wait with the results until it is done. It should typically be called prior to a sequence of calls to requestItems() and releaseItems().

Any call to beginRequestBatch() must be followed at some point by a call to endRequestBatch(). Failing to do this may lead to the results of requests never being emitted.

Note: beginRequestBatch() and endRequestBatch() have no stacking logic. Calling beginRequestBatch() twice in a row has no effect, and the single existing batch will be ended by the earliest call to endRequestBatch().

See also: endRequestBatch(), requestBatchStarted()

◆ dereferenceBuffer()

bool QPlatformSharedGraphicsCache::dereferenceBuffer ( void * bufferId )

pure virtual

Removed a previously registered reference to the buffer bufferId.

Returns true if there are still more references to the buffer in question, or false if this was the last reference (in which case the buffer may have been deleted in the cache.)

See also: dereferenceBuffer()

◆ eglImageForBuffer()

void * QPlatformSharedGraphicsCache::eglImageForBuffer ( void * bufferId )

pure virtual

Returns an EGLImageKHR image corresponding to the buffer bufferId.

See also: textureIdForBuffer(), sizeOfBuffer()

◆ endRequestBatch()

void QPlatformSharedGraphicsCache::endRequestBatch ( )

pure virtual

Signals to the cache that the request sequence which has previously been commenced using beginRequestBatch() has now finished.

See also: beginRequestBatch(), requestBatchStarted()

◆ ensureCacheInitialized()

void QPlatformSharedGraphicsCache::ensureCacheInitialized	(	const QByteArray &	cacheId,
		BufferType	bufferType,
		PixelFormat	pixelFormat
	)

pure virtual

Initializes a cache named cacheId if it has not yet been initialized.

The bufferType and pixelFormat gives the format of the buffers that will be used to contain the items in the cache. If a cache with the same cacheId has previously been initialized, the call will be ignored. The cache will keep its previously set buffer type and pixel format.

◆ insertItems()

void QPlatformSharedGraphicsCache::insertItems	(	const QByteArray &	cacheId,
		const QList< quint32 > &	itemIds,
		const QList< QImage > &	items
	)

pure virtual

Inserts the items in itemIds into the cache named cacheId.

The appearance of each item is stored in items. The format of the QImage objects is expected to match the pixel format of the cache as it was initialized in ensureCacheInitialized().

When the items have been successfully entered into the cache, one or more itemsAvailable() signals will be emitted for the items.

If the cache already contains the items, the behavior is implementation-specific. The implementation may choose to ignore the items or it may overwrite the existing instances in the cache. Either way, itemsAvailable() signals corresponding to the inserted items will be emitted.

◆ itemsAvailable

void QPlatformSharedGraphicsCache::itemsAvailable	(	const QByteArray &	cacheId,
		void *	bufferId,
		const QList< quint32 > &	itemIds,
		const QList< QPoint > &	positionsInBuffer
	)

signal

This signal can be emitted at any time when either requestItems() or insertItems() has been called by the application for one or more items in the cache named cacheId, as long as releaseItems() has not subsequently been called for the same items.

It instructs the application on where to find the items that have been entered into the cache. When the application receives a buffer, it is expected to reference it using referenceBuffer() on it if it keeps a reference to the buffer.

The bufferId is an ID for the buffer that contains the items. The bufferId can be converted to a format usable by the application depending on which format it was given at initialization. If it is a OpenGLTexture, its texture ID can be requested using the textureIdForBuffer() function. The dimensions of the buffer are given by bufferSize.

The items provided by the cache are identified in the itemIds list. The positionsInBuffer list contains the locations inside the buffer of each item. Each entry in positionsInBuffer corresponds to an item in itemIds.

The buffer and the items' locations within the buffer can be considered valid until an itemsInvalidated() signal has been emitted for the items, or until releaseItems() is called for the items.

See also: itemsMissing(), requestItems(), bufferType()

◆ itemsInvalidated

void QPlatformSharedGraphicsCache::itemsInvalidated	(	const QByteArray &	cacheId,
		const QList< quint32 > &	itemIds
	)

signal

This signal is emitted when the items given by itemIds in the cache named cacheId have been removed from the cache and the previously reported information about them is considered invalid.

It will only be emitted for items for which a buffer has previously been identified through the itemsAvailable() signal (either as response to a requestItems() call or an insertItems() call.)

The application is expected to throw away information about the items in the itemIds array and drop any references it might have to the memory held by the buffer. If the items are still required by the application, it can re-commit them to the cache using the insertItems() function.

If the application no longer holds any references to previously referenced items in a given cache, it should call releaseItems() for these items, at which point it will no longer receive any itemsInvalidated() signal for these items.

◆ itemsMissing

void QPlatformSharedGraphicsCache::itemsMissing	(	const QByteArray &	cacheId,
		const QList< quint32 > &	itemIds
	)

signal

This signal is emitted when requestItems() has been called for one or more items in the cache named cacheId which are not yet available in the cache.

The user is then expected to call insertItems() to update the cache with the respective items, at which point they will become available to all clients of the shared cache.

The itemIds list contains the IDs of the items that need to be inserted into the cache.

See also: itemsAvailable(), insertItems(), requestItems()

◆ itemsUpdated

void QPlatformSharedGraphicsCache::itemsUpdated	(	const QByteArray &	cacheId,
		void *	bufferId,
		const QList< quint32 > &	itemIds,
		const QList< QPoint > &	positionsInBuffer
	)

signal

This signal is similar in usage to the itemsAvailable() signal, but will be emitted when the location of a previously requested or inserted item has been updated.

The application must update its data for the respective items and release any references to old buffers held by the items.

If the application no longer holds any references to previously referenced items in a given cache, it should call releaseItems() for these items, at which point it will no longer receive any itemsUpdated() signal for these items.

See also: requestItems(), insertItems(), itemsAvailable()

◆ referenceBuffer()

void QPlatformSharedGraphicsCache::referenceBuffer ( void * bufferId )

pure virtual

Registers a reference to the buffer bufferId.

See also: dereferenceBuffer()

◆ releaseItems()

void QPlatformSharedGraphicsCache::releaseItems	(	const QByteArray &	cacheId,
		const QList< quint32 > &	itemIds
	)

pure virtual

Releases the reference to the items in itemIds from the cache named cacheId.

This should only be called when all references to the items have been released by the user, and they are no longer needed.

◆ requestBatchStarted()

bool QPlatformSharedGraphicsCache::requestBatchStarted ( ) const

pure virtual

Returns true if a request batch has previously been started using beginRequestBatch() and not yet stopped using endRequestBatch().

See also: beginRequestBatch(), endRequestBatch()

◆ requestItems()

void QPlatformSharedGraphicsCache::requestItems	(	const QByteArray &	cacheId,
		const QList< quint32 > &	itemIds
	)

pure virtual

Requests all the items in itemIds from the cache with the name cacheId.

If any or all of the items are available in the cache, one or more itemsAvailable() signals will be emitted corresponding to the items. If the cache does not contain all of the items in question, then an itemsMissing() signal will be emitted corresponding to the missing items. The user is at this point expected to call insertItems() to insert the missing items into the cache. If the inserted items have previously been requested by the user, at which point an itemsAvailable() signal will be emitted corresponding to the items.

Before requesting items from a cache, the user must call ensureCacheInitialized() with the correct parameters for the cache.

◆ sizeOfBuffer()

QSize QPlatformSharedGraphicsCache::sizeOfBuffer ( void * bufferId )

pure virtual

Returns the size of the buffer bufferId.

See also: textureIdForBuffer(), eglImageForBuffer()

◆ textureIdForBuffer()

uint QPlatformSharedGraphicsCache::textureIdForBuffer ( void * bufferId )

pure virtual

Returns an OpenGL texture ID corresponding to the buffer bufferId, which has previously been passed through signals itemsAvailable() or itemsUpdated().

The relevant OpenGL context should be current when calling this function.

See also: eglImageForBuffer(), sizeOfBuffer()

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

qtbase/src/gui/kernel/qplatformsharedgraphicscache.h
qtbase/src/gui/kernel/qplatformsharedgraphicscache.cpp

Public Types

Signals

Public Member Functions

Additional Inherited Members

Detailed Description

Member Enumeration Documentation

◆ BufferType

◆ PixelFormat

Constructor & Destructor Documentation

◆ QPlatformSharedGraphicsCache()

Member Function Documentation

◆ beginRequestBatch()

◆ dereferenceBuffer()

◆ eglImageForBuffer()

◆ endRequestBatch()

◆ ensureCacheInitialized()

◆ insertItems()

◆ itemsAvailable

◆ itemsInvalidated

◆ itemsMissing

◆ itemsUpdated

◆ referenceBuffer()

◆ releaseItems()

◆ requestBatchStarted()

◆ requestItems()

◆ sizeOfBuffer()

◆ textureIdForBuffer()