KWayland::Client::ShmPool Class Reference

#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 const
QMetaObject::Connection	connect (const QObject *sender, const char *signal, const char *method, Qt::ConnectionType type) const const
void	deleteLater ()
void	destroyed (QObject *obj)
bool	disconnect (const char *signal, const QObject *receiver, const char *method) const const
bool	disconnect (const QObject *receiver, const char *method) const const
void	dumpObjectInfo ()
void	dumpObjectInfo () const const
void	dumpObjectTree ()
void	dumpObjectTree () const const
QList< QByteArray >	dynamicPropertyNames () const const
virtual bool	event (QEvent *e)
virtual bool	eventFilter (QObject *watched, QEvent *event)
T	findChild (const QString &name, Qt::FindChildOptions options) const const
QList< T >	findChildren (const QString &name, Qt::FindChildOptions options) const const
QList< T >	findChildren (const QRegExp &regExp, Qt::FindChildOptions options) const const
QList< T >	findChildren (const QRegularExpression &re, Qt::FindChildOptions options) const const
bool	inherits (const char *className) const const
void	installEventFilter (QObject *filterObj)
bool	isWidgetType () const const
bool	isWindowType () const const
void	killTimer (int id)
virtual const QMetaObject *	metaObject () const const
void	moveToThread (QThread *targetThread)
QString	objectName () const const
void	objectNameChanged (const QString &objectName)
QObject *	parent () const const
QVariant	property (const char *name) const const
	Q_CLASSINFO (Name, Value)
	Q_DISABLE_COPY (Class)
	Q_DISABLE_COPY_MOVE (Class)
	Q_DISABLE_MOVE (Class)
	Q_EMIT Q_EMIT
	Q_ENUM (...)
	Q_ENUM_NS (...)
	Q_ENUMS (...)
	Q_FLAG (...)
	Q_FLAG_NS (...)
	Q_FLAGS (...)
	Q_GADGET Q_GADGET
	Q_INTERFACES (...)
	Q_INVOKABLE Q_INVOKABLE
	Q_NAMESPACE Q_NAMESPACE
	Q_NAMESPACE_EXPORT (EXPORT_MACRO)
	Q_OBJECT Q_OBJECT
	Q_PROPERTY (...)
	Q_REVISION Q_REVISION
	Q_SET_OBJECT_NAME (Object)
	Q_SIGNAL Q_SIGNAL
	Q_SIGNALS Q_SIGNALS
	Q_SLOT Q_SLOT
	Q_SLOTS Q_SLOTS
T	qFindChild (const QObject *obj, const QString &name)
QList< T >	qFindChildren (const QObject *obj, const QRegExp &regExp)
QList< T >	qFindChildren (const QObject *obj, const QString &name)
T	qobject_cast (QObject *object)
T	qobject_cast (const QObject *object)
	QT_NO_NARROWING_CONVERSIONS_IN_CONNECT QT_NO_NARROWING_CONVERSIONS_IN_CONNECT
void	removeEventFilter (QObject *obj)
void	setObjectName (const QString &name)
void	setParent (QObject *parent)
bool	setProperty (const char *name, const QVariant &value)
bool	signalsBlocked () const const
int	startTimer (int interval, Qt::TimerType timerType)
int	startTimer (std::chrono::milliseconds time, Qt::TimerType timerType)
QThread *	thread () const 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)
Public Attributes inherited from QObject
typedef	QObjectList
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 const
int	receivers (const char *signal) const const
QObject *	sender () const const
int	senderSignalIndex () const 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 115 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 172 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 191 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 77 of file shm_pool.cpp.

EventQueue * KWayland::Client::ShmPool::eventQueue

(

)

Returns

The event queue to use for creating a Buffer.

Definition at line 107 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 218 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 260 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 63 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 102 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 94 of file shm_pool.cpp.

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

• shm_pool.h
• shm_pool.cpp