QBackingStore Class | Qt GUI 5.9

Qt 5.9 | Qt GUI | C++ Classes | QBackingStore

Qt 5.9.9 Reference Documentation

# QBackingStore Class

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

Header: | #include <QBackingStore>
qmake: | QT += gui
Since: | Qt 5.0

- List of all members, including inherited members

## Public Functions

| QBackingStore(QWindow *window)
| ~QBackingStore()
void | beginPaint(const QRegion &region)
void | endPaint()
void | flush(const QRegion &region, QWindow *win = Q_NULLPTR, const QPoint &offset = QPoint())
QPlatformBackingStore * | handle() const
bool | hasStaticContents() const
QPaintDevice * | paintDevice()
void | resize(const QSize &size)
bool | scroll(const QRegion &area, int dx, int dy)
void | setStaticContents(const QRegion &region)
QSize | size() const
QRegion | staticContents() const
QWindow * | window() const

## Detailed Description

The QBackingStore class provides a drawing area for QWindow.

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 Raster Window Example.

## Member Function Documentation

### QBackingStore::QBackingStore(QWindow *window)

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

### QBackingStore::~QBackingStore()

Destroys this surface.

### void QBackingStore::beginPaint(const QRegion &region)

This function is called before painting onto the surface begins, with the region in which the painting will occur.

See also endPaint() and paintDevice().

### void QBackingStore::endPaint()

This function is called after painting onto the surface has ended.

See also beginPaint() and paintDevice().

### void QBackingStore::flush(const QRegion &region, QWindow *win = Q_NULLPTR, const QPoint &offset = QPoint())

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

Note that the offset parameter is currently unused.

### QPlatformBackingStore *QBackingStore::handle() const

Returns a pointer to the QPlatformBackingStore implementation

### bool QBackingStore::hasStaticContents() const

Returns a boolean indicating if this window has static contents or not.

### QPaintDevice *QBackingStore::paintDevice()

Implement this function to return the appropriate paint device.

### void QBackingStore::resize(const QSize &size)

Sets the size of the windowsurface to be size.

See also size().

### bool QBackingStore::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.

Returns `true` if the area was scrolled successfully; false otherwise.

### void QBackingStore::setStaticContents(const QRegion &region)

Set region as the static contents of this window.

See also staticContents().

### QSize QBackingStore::size() const

Returns the current size of the windowsurface.

### QRegion QBackingStore::staticContents() const

Returns a pointer to the QRegion that has the static contents of this window.

See also setStaticContents().

### QWindow *QBackingStore::window() const

Returns a pointer to the top-level window associated with this surface.