KWayland - KWayland::Client::ShmPool Class Reference

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KWayland
Client
ShmPool

#include <shm_pool.h>

Inheritance diagram for KWayland::Client::ShmPool:

Signals
void	poolResized ()

void	removed ()

Public Member Functions
	ShmPool (QObject *parent=nullptr)

Buffer::Ptr	createBuffer (const QImage &image)

Buffer::Ptr	createBuffer (const QSize &size, int32_t stride, const void *src, Buffer::Format format=Buffer::Format::ARGB32)

void	destroy ()

EventQueue *	eventQueue ()

Buffer::Ptr	getBuffer (const QSize &size, int32_t stride, Buffer::Format format=Buffer::Format::ARGB32)

bool	isValid () const

void *	poolAddress () const

void	release ()

void	setEventQueue (EventQueue *queue)

void	setup (wl_shm *shm)

wl_shm *	shm ()

Public Member Functions inherited from QObject
	QObject (QObject *parent)

bool	blockSignals (bool block)

const QObjectList &	children () const

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

void	deleteLater ()

void	destroyed (QObject *obj)

bool	disconnect (const char signal, const QObject receiver, const char *method) const

bool	disconnect (const QObject receiver, const char method) const

void	dumpObjectInfo ()

void	dumpObjectTree ()

QList< QByteArray >	dynamicPropertyNames () const

virtual bool	event (QEvent *e)

virtual bool	eventFilter (QObject watched, QEvent event)

T	findChild (const QString &name, QFlags< Qt::FindChildOption > options) const

QList< T >	findChildren (const QString &name, QFlags< Qt::FindChildOption > options) const

QList< T >	findChildren (const QRegExp &regExp, QFlags< Qt::FindChildOption > options) const

QList< T >	findChildren (const QRegularExpression &re, QFlags< Qt::FindChildOption > options) const

bool	inherits (const char *className) const

void	installEventFilter (QObject *filterObj)

bool	isWidgetType () const

bool	isWindowType () const

void	killTimer (int id)

virtual const QMetaObject *	metaObject () const

void	moveToThread (QThread *targetThread)

QString	objectName () const

void	objectNameChanged (const QString &objectName)

QObject *	parent () const

QVariant	property (const char *name) const

void	removeEventFilter (QObject *obj)

void	setObjectName (const QString &name)

void	setParent (QObject *parent)

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

bool	signalsBlocked () const

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

QThread *	thread () const

Additional Inherited Members
Properties inherited from QObject
	objectName

Static Public Member Functions inherited from QObject
QMetaObject::Connection	connect (const QObject sender, const char signal, const QObject receiver, const char method, Qt::ConnectionType type)

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

QMetaObject::Connection	connect (const QObject sender, PointerToMemberFunction signal, const QObject receiver, PointerToMemberFunction method, Qt::ConnectionType type)

QMetaObject::Connection	connect (const QObject *sender, PointerToMemberFunction signal, Functor functor)

QMetaObject::Connection	connect (const QObject sender, PointerToMemberFunction signal, const QObject context, Functor functor, Qt::ConnectionType type)

bool	disconnect (const QMetaObject::Connection &connection)

bool	disconnect (const QObject sender, const char signal, const QObject receiver, const char method)

bool	disconnect (const QObject sender, PointerToMemberFunction signal, const QObject receiver, PointerToMemberFunction method)

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

QString	tr (const char sourceText, const char disambiguation, int n)

QString	trUtf8 (const char sourceText, const char disambiguation, int n)

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

virtual void	connectNotify (const QMetaMethod &signal)

virtual void	customEvent (QEvent *event)

virtual void	disconnectNotify (const QMetaMethod &signal)

bool	isSignalConnected (const QMetaMethod &signal) const

int	receivers (const char *signal) const

QObject *	sender () const

int	senderSignalIndex () const

virtual void	timerEvent (QTimerEvent *event)

Detailed Description

Wrapper class for wl_shm interface.

This class holds a shared memory pool together with the Wayland server.

To use this class one needs to interact with the Registry. There are two possible ways to create a ShmPool instance:

ShmPool *s = registry->createShmPool(name, version);

This creates the ShmPool and sets it up directly. As an alternative this can also be done in a more low level way:

ShmPool *s = new ShmPool;

s->setup(registry->bindShm(name, version));

The ShmPool holds a memory-mapped file from which it provides Buffers. All Buffers are held by the ShmPool and can be reused. Whenever a Buffer is requested the ShmPool tries to reuse an existing Buffer. A Buffer can be reused if the following conditions hold

it's no longer marked as used
the server released the buffer
the size matches
the stride matches
the format matches

The ownership of a Buffer stays with ShmPool. The ShmPool might destroy the Buffer at any given time. Because of that ShmPool only provides QWeakPointer for Buffers. Users should always check whether the pointer is still valid and only promote to a QSharedPointer for a short time, e.g. to set new data.

The ShmPool can provide Buffers for different purposes. One can create a Buffer from an existing QImage. This will use a Buffer with same size, stride and image format as the QImage and copy the content of the QImage into the Buffer. The memory is not shared:

QImage image(24, 24, QImage::Format_ARG32);
image.fill(Qt::transparent);
Buffer::Ptr buffer = s->createBuffer(image);

It is also possible to create a Buffer and copy the content from a generic location. Like above this doesn't share the content but copies it:

QImage image(24, 24, QImage::Format_ARG32);
image.fill(Qt::transparent);
Buffer::Ptr buffer = s->createBuffer(image.size(), image.bytesPerLine(), image.constBits());

Last but not least it is possible to get a Buffer without copying content directly to it. This means an empty area is just reserved and can be used to e.g. share the memory with a QImage:

const QSize size = QSize(24, 24);
const int stride = size.width() * 4;
Buffer::Ptr buffer = s->getBuffer(size, stride, Buffer::Format::RGB32);
if (!buffer) {
    qDebug() << "Didn't get a valid Buffer";
    return;
}
QImage image(buffer.toStrongRef()->address(), size.width(), size.height(), stride, QImage::Format_RGB32);
image.fill(Qt::black);

A Buffer can be attached to a Surface:

Compositor *c = registry.createCompositor(name, version);
Surface *s = c->createSurface();
s->attachBuffer(buffer);
s->damage(QRect(QPoint(0, 0), size));

Once a Buffer is attached to a Surface and the Surface is committed, it might be released by the Wayland server and thus is free to be reused again. If the client code wants to continue using the Buffer it must call Buffer::setUsed on it. This is important if the memory is shared for example with a QImage as the memory buffer for a QImage must remain valid throughout the life time of the QImage:

buffer.toStrongRef()->setUsed(true);

This is also important for the case that the shared memory pool needs to be resized. The ShmPool will automatically resize if it cannot provide a new Buffer. During the resize all existing Buffers are unmapped and any shared objects must be recreated. The ShmPool emits the signal poolResized() after the pool got resized.

See also: Buffer

Definition at line 130 of file shm_pool.h.

Member Function Documentation

Buffer::Ptr KWayland::Client::ShmPool::createBuffer ( const QImage & image )

Provides a Buffer with:

same size as image
same stride as image
same format as image

If the ShmPool fails to provide such a Buffer a null Buffer::Ptr is returned. The content of the image is copied into the buffer. The image and returned Buffer do not share memory.

Parameters

image The image which should be copied into the Buffer

Returns: Buffer with copied content of image in success case, a null Buffer::Ptr otherwise

See also: getBuffer

Definition at line 187 of file shm_pool.cpp.

Buffer::Ptr KWayland::Client::ShmPool::createBuffer	(	const QSize &	size,
		int32_t	stride,
		const void *	src,
		Buffer::Format	format = `Buffer::Format::ARGB32`
	)

Provides a Buffer with size, stride and format.

If the ShmPool fails to provide such a Buffer a null Buffer::Ptr is returned. A memory copy is performed from src into the Buffer. The Buffer does not share memory with src.

Parameters

size	The requested size for the Buffer
stride	The requested stride for the Buffer
src	The source memory location to copy from
format	The requested format for the Buffer

Returns: Buffer with copied content of src in success case, a null Buffer::Ptr otherwise

See also: getBuffer

Definition at line 206 of file shm_pool.cpp.

void KWayland::Client::ShmPool::destroy ( )

Destroys the data held by this ShmPool.

This method is supposed to be used when the connection to the Wayland server goes away. If the connection is not valid anymore, it's not possible to call release anymore as that calls into the Wayland connection and the call would fail. This method cleans up the data, so that the instance can be deleted or set up to a new wl_shm interface once there is a new connection available.

All Buffers are destroyed!

This method is automatically invoked when the Registry which created this ShmPool gets destroyed.

See also: release

Definition at line 93 of file shm_pool.cpp.

EventQueue * KWayland::Client::ShmPool::eventQueue ( )

Returns: The event queue to use for creating a Buffer.

Definition at line 123 of file shm_pool.cpp.

Buffer::Ptr KWayland::Client::ShmPool::getBuffer	(	const QSize &	size,
		int32_t	stride,
		Buffer::Format	format = `Buffer::Format::ARGB32`
	)

Provides a Buffer with size, stride and format.

If the ShmPool fails to provide such a Buffer a null Buffer::Ptr is returned. Unlike with createBuffer there is no memory copy performed. This provides a bare Buffer to be used by the user.

Parameters

size	The requested size for the Buffer
stride	The requested stride for the Buffer
format	The requested format for the Buffer

Returns: Buffer as requested in success case, a null Buffer::Ptr otherwise.

See also: createBuffer

Definition at line 232 of file shm_pool.cpp.

bool KWayland::Client::ShmPool::isValid ( ) const

Returns: true if the ShmPool references a wl_shm interface and the shared memory pool is setup.

Definition at line 275 of file shm_pool.cpp.

void KWayland::Client::ShmPool::poolResized ( )

signal

This signal is emitted whenever the shared memory pool gets resized.

Any used Buffer must be remapped.

void KWayland::Client::ShmPool::release ( )

Releases the wl_shm interface.

After the interface has been released the ShmPool instance is no longer valid and can be setup with another wl_shm interface.

This also destroys the shared memory pool and all Buffers are destroyed.

Definition at line 79 of file shm_pool.cpp.

void KWayland::Client::ShmPool::removed ( )

signal

The corresponding global for this interface on the Registry got removed.

This signal gets only emitted if the Compositor got created by Registry::createShmPool

Since: 5.5

void KWayland::Client::ShmPool::setEventQueue ( EventQueue * queue )

Sets the queue to use for creating a Buffer.

Definition at line 118 of file shm_pool.cpp.

void KWayland::Client::ShmPool::setup ( wl_shm * shm )

Setup this ShmPool to manage the shm.

This also creates the shared memory pool. When using Registry::createShmPool there is no need to call this method.

Definition at line 110 of file shm_pool.cpp.

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

KDE's Doxygen guidelines are available online.

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KWayland::Client::ShmPool

Signals

Public Member Functions

Additional Inherited Members

Detailed Description

Member Function Documentation