The QBackingStore class provides a drawing area for QWindow. More...

#include <qbackingstore.h>

Collaboration diagram for QBackingStore:

Public Member Functions
	QBackingStore (QWindow *window)
	Constructs an empty surface for the given top-level window.

	~QBackingStore ()
	Destroys this surface.

QWindow *	window () const
	Returns a pointer to the top-level window associated with this surface.

QPaintDevice *	paintDevice ()
	Returns the paint device for this surface.

void	flush (const QRegion &region, QWindow *window=nullptr, const QPoint &offset=QPoint())
	Flushes the given region from the specified window onto the screen.

void	resize (const QSize &size)
	Sets the size of the window surface to size.

QSize	size () const
	Returns the current size of the window surface.

bool	scroll (const QRegion &area, int dx, int dy)
	Scrolls the given area dx pixels to the right and dy downward; both dx and dy may be negative.

void	beginPaint (const QRegion &)
	Begins painting on the backing store surface in the given region.

void	endPaint ()
	Ends painting.

void	setStaticContents (const QRegion &region)
	Set region as the static contents of this window.

QRegion	staticContents () const
	Returns a QRegion representing the area of the window that has static contents.

bool	hasStaticContents () const
	Returns a boolean indicating if this window has static contents or not.

QPlatformBackingStore *	handle () const
	Returns a pointer to the QPlatformBackingStore implementation.

Detailed Description

The QBackingStore class provides a drawing area for QWindow.

Since: 5.0 \inmodule QtGui

QBackingStore enables the use of QPainter to paint on a QWindow with type RasterSurface. The other way of rendering to a QWindow is through the use of OpenGL with QOpenGLContext.

A QBackingStore contains a buffered representation of the window contents, and thus supports partial updates by using QPainter to only update a sub region of the window contents.

QBackingStore might be used by an application that wants to use QPainter without OpenGL acceleration and without the extra overhead of using the QWidget or QGraphicsView UI stacks. For an example of how to use QBackingStore see the \l{Raster Window Example}.

Definition at line 23 of file qbackingstore.h.

Constructor & Destructor Documentation

◆ QBackingStore()

QBackingStore::QBackingStore ( QWindow * window )

explicit

Constructs an empty surface for the given top-level window.

Definition at line 80 of file qbackingstore.cpp.

References handle(), and window().

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◆ ~QBackingStore()

QBackingStore::~QBackingStore ( )

Destroys this surface.

Definition at line 93 of file qbackingstore.cpp.

References QBackingStorePrivate::platformBackingStore.

Member Function Documentation

◆ beginPaint()

void QBackingStore::beginPaint ( const QRegion & region )

Begins painting on the backing store surface in the given region.

You should call this function before using the paintDevice() to paint.

See also: endPaint(), paintDevice()

Definition at line 116 of file qbackingstore.cpp.

References QBackingStorePrivate::backingStoreDevicePixelRatio(), QPlatformBackingStore::beginPaint(), QImage::data_ptr(), device, QBackingStorePrivate::deviceIndependentToNativeFactor(), QImage::devicePixelRatio(), dpr(), handle(), QBackingStorePrivate::highDpiBackingstore, QInternal::Image, QHighDpiScaling::isActive(), QScopedPointer< T, Cleanup >::isNull(), QPlatformBackingStore::paintDevice(), QScopedPointer< T, Cleanup >::reset(), resize(), QHighDpi::scale(), QImage::setDevicePixelRatio(), QImage::size(), and size().

Referenced by QRasterWindowPrivate::beginPaint(), QVideoWindowPrivate::render(), and QSGSoftwareRenderer::render().

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◆ endPaint()

void QBackingStore::endPaint ( )

Ends painting.

You should call this function after painting with the paintDevice() has ended.

See also: beginPaint(), paintDevice()

Definition at line 173 of file qbackingstore.cpp.

References QPlatformBackingStore::endPaint(), handle(), paintDevice(), and qWarning.

Referenced by QRasterWindowPrivate::endPaint(), QVideoWindowPrivate::render(), and QSGSoftwareRenderer::render().

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◆ flush()

void QBackingStore::flush	(	const QRegion &	region,
		QWindow *	window = nullptr,
		const QPoint &	offset = QPoint() )

Flushes the given region from the specified window onto the screen.

The window must either be the top level window represented by this backingstore, or a non-transient child of that window. Passing \nullptr falls back to using the backingstore's top level window.

If the window is a child window, the region should be in child window coordinates, and the offset should be the child window's offset in relation to the backingstore's top level window.

You should call this function after ending painting with endPaint().

Definition at line 195 of file qbackingstore.cpp.

References QRegion::boundingRect(), QBackingStorePrivate::deviceIndependentToNativeFactor(), QPlatformBackingStore::flush(), handle(), Q_ASSERT, qAbs(), qMax(), qWarning, QHighDpi::scale(), QRect::topLeft(), window(), QPoint::x(), and QPoint::y().