Qt 5.6 | Qt GUI | C++ Classes | QScreen

Qt 5.6.3 Reference Documentation

# QScreen Class

The QScreen class is used to query screen properties. More...

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

- List of all members, including inherited members

## Properties

- availableGeometry : const QRect
- availableSize : const QSize
- availableVirtualGeometry : const QRect
- availableVirtualSize : const QSize
- depth : const int
- devicePixelRatio : const qreal
- geometry : const QRect
- logicalDotsPerInch : const qreal
- logicalDotsPerInchX : const qreal
- logicalDotsPerInchY : const qreal
- name : const QString

- nativeOrientation : const Qt::ScreenOrientation
- orientation : const Qt::ScreenOrientation
- physicalDotsPerInch : const qreal
- physicalDotsPerInchX : const qreal
- physicalDotsPerInchY : const qreal
- physicalSize : const QSizeF
- primaryOrientation : const Qt::ScreenOrientation
- refreshRate : const qreal
- size : const QSize
- virtualGeometry : const QRect
- virtualSize : const QSize

## Public Functions

| ~QScreen()
int | angleBetween(Qt::ScreenOrientation a, Qt::ScreenOrientation b) const
QRect | availableGeometry() const
QSize | availableSize() const
QRect | availableVirtualGeometry() const
QSize | availableVirtualSize() const
int | depth() const
qreal | devicePixelRatio() const
QRect | geometry() const
QPixmap | grabWindow(WId window, int x = 0, int y = 0, int width = -1, int height = -1)
QPlatformScreen * | handle() const
bool | isLandscape(Qt::ScreenOrientation o) const
bool | isPortrait(Qt::ScreenOrientation o) const
qreal | logicalDotsPerInch() const
qreal | logicalDotsPerInchX() const
qreal | logicalDotsPerInchY() const
QRect | mapBetween(Qt::ScreenOrientation a, Qt::ScreenOrientation b, const QRect &rect) const
QString | name() const
Qt::ScreenOrientation | nativeOrientation() const
Qt::ScreenOrientation | orientation() const
Qt::ScreenOrientations | orientationUpdateMask() const
qreal | physicalDotsPerInch() const
qreal | physicalDotsPerInchX() const
qreal | physicalDotsPerInchY() const
QSizeF | physicalSize() const
Qt::ScreenOrientation | primaryOrientation() const
qreal | refreshRate() const
void | setOrientationUpdateMask(Qt::ScreenOrientations mask)
QSize | size() const
QTransform | transformBetween(Qt::ScreenOrientation a, Qt::ScreenOrientation b, const QRect &target) const
QRect | virtualGeometry() const
QList<QScreen *> | virtualSiblings() const
QSize | virtualSize() const

## Signals

void | availableGeometryChanged(const QRect &geometry)
void | geometryChanged(const QRect &geometry)
void | logicalDotsPerInchChanged(qreal dpi)
void | orientationChanged(Qt::ScreenOrientation orientation)
void | physicalDotsPerInchChanged(qreal dpi)
void | physicalSizeChanged(const QSizeF &size)
void | primaryOrientationChanged(Qt::ScreenOrientation orientation)
void | refreshRateChanged(qreal refreshRate)
void | virtualGeometryChanged(const QRect &rect)

## Detailed Description

The QScreen class is used to query screen properties.

A note on logical vs physical dots per inch: physical DPI is based on the actual physical pixel sizes when available, and is useful for print preview and other cases where it's desirable to know the exact physical dimensions of screen displayed contents.

Logical dots per inch are used to convert font and user interface elements from point sizes to pixel sizes, and might be different from the physical dots per inch. The logical dots per inch are sometimes user-settable in the desktop environment's settings panel, to let the user globally control UI and font sizes in different applications.

## Property Documentation

### availableGeometry : const QRect

This property holds the screen's available geometry in pixels.

The available geometry is the geometry excluding window manager reserved areas such as task bars and system menus.

Access functions:

QRect | availableGeometry() const

Notifier signal:

void | availableGeometryChanged(const QRect &geometry)

### availableSize : const QSize

This property holds the screen's available size in pixels.

The available size is the size excluding window manager reserved areas such as task bars and system menus.

Access functions:

QSize | availableSize() const

Notifier signal:

void | availableGeometryChanged(const QRect &geometry)

### availableVirtualGeometry : const QRect

This property holds the available geometry of the virtual desktop to which this screen belongs.

Returns the available geometry of the virtual desktop corresponding to this screen.

This is the union of the virtual siblings' individual available geometries.

Access functions:

QRect | availableVirtualGeometry() const

Notifier signal:

void | virtualGeometryChanged(const QRect &rect)

See also availableGeometry() and virtualSiblings().

### availableVirtualSize : const QSize

This property holds the available size of the virtual desktop to which this screen belongs.

Returns the available pixel size of the virtual desktop corresponding to this screen.

This is the combined size of the virtual siblings' individual available geometries.

Access functions:

QSize | availableVirtualSize() const

Notifier signal:

void | virtualGeometryChanged(const QRect &rect)

See also availableSize() and virtualSiblings().

### depth : const int

This property holds the color depth of the screen.

Access functions:

int | depth() const

### devicePixelRatio : const qreal

This property holds the screen's ratio between physical pixels and device-independent pixels.

Returns the ratio between physical pixels and device-independent pixels for the screen.

Common values are 1.0 on normal displays and 2.0 on "retina" displays. Higher values are also possible.

This property was introduced in Qt 5.5.

Access functions:

qreal | devicePixelRatio() const

Notifier signal:

void | physicalDotsPerInchChanged(qreal dpi)

See also QWindow::devicePixelRatio() and QGuiApplication::devicePixelRatio().

### geometry : const QRect

This property holds the screen's geometry in pixels.

As an example this might return QRect(0, 0, 1280, 1024), or in a virtual desktop setting QRect(1280, 0, 1280, 1024).

Access functions:

QRect | geometry() const

Notifier signal:

void | geometryChanged(const QRect &geometry)

### logicalDotsPerInch : const qreal

This property holds the number of logical dots or pixels per inch.

This value can be used to convert font point sizes to pixel sizes.

This is a convenience property that's simply the average of the logicalDotsPerInchX and logicalDotsPerInchY properties.

Access functions:

qreal | logicalDotsPerInch() const

Notifier signal:

void | logicalDotsPerInchChanged(qreal dpi)

See also logicalDotsPerInchX() and logicalDotsPerInchY().

### logicalDotsPerInchX : const qreal

This property holds the number of logical dots or pixels per inch in the horizontal direction.

This value is used to convert font point sizes to pixel sizes.

Access functions:

qreal | logicalDotsPerInchX() const

Notifier signal:

void | logicalDotsPerInchChanged(qreal dpi)

See also logicalDotsPerInchY().

### logicalDotsPerInchY : const qreal

This property holds the number of logical dots or pixels per inch in the vertical direction.

This value is used to convert font point sizes to pixel sizes.

Access functions:

qreal | logicalDotsPerInchY() const

Notifier signal:

void | logicalDotsPerInchChanged(qreal dpi)

See also logicalDotsPerInchX().

### name : const QString

This property holds a user presentable string representing the screen.

For example, on X11 these correspond to the XRandr screen names, typically "VGA1", "HDMI1", etc.

Access functions:

QString | name() const

### nativeOrientation : const Qt::ScreenOrientation

This property holds the native screen orientation.

The native orientation of the screen is the orientation where the logo sticker of the device appears the right way up, or Qt::PrimaryOrientation if the platform does not support this functionality.

The native orientation is a property of the hardware, and does not change.

This property was introduced in Qt 5.2.

Access functions:

Qt::ScreenOrientation | nativeOrientation() const

### orientation : const Qt::ScreenOrientation

This property holds the screen orientation.

The screen orientation represents the physical orientation of the display. For example, the screen orientation of a mobile device will change based on how it is being held. A change to the orientation might or might not trigger a change to the primary orientation of the screen.

Changes to this property will be filtered by orientationUpdateMask(), so in order to receive orientation updates the application must first call setOrientationUpdateMask() with a mask of the orientations it wants to receive.

Qt::PrimaryOrientation is never returned.

Access functions:

Qt::ScreenOrientation | orientation() const

Notifier signal:

void | orientationChanged(Qt::ScreenOrientation orientation)

See also primaryOrientation().

### physicalDotsPerInch : const qreal

This property holds the number of physical dots or pixels per inch.

This value represents the pixel density on the screen's display. Depending on what information the underlying system provides the value might not be entirely accurate.

This is a convenience property that's simply the average of the physicalDotsPerInchX and physicalDotsPerInchY properties.

Access functions:

qreal | physicalDotsPerInch() const

Notifier signal:

void | physicalDotsPerInchChanged(qreal dpi)

See also physicalDotsPerInchX() and physicalDotsPerInchY().

### physicalDotsPerInchX : const qreal

This property holds the number of physical dots or pixels per inch in the horizontal direction.

This value represents the actual horizontal pixel density on the screen's display. Depending on what information the underlying system provides the value might not be entirely accurate.

Access functions:

qreal | physicalDotsPerInchX() const

Notifier signal:

void | physicalDotsPerInchChanged(qreal dpi)

See also physicalDotsPerInchY().

### physicalDotsPerInchY : const qreal

This property holds the number of physical dots or pixels per inch in the vertical direction.

This value represents the actual vertical pixel density on the screen's display. Depending on what information the underlying system provides the value might not be entirely accurate.

Access functions:

qreal | physicalDotsPerInchY() const

Notifier signal:

void | physicalDotsPerInchChanged(qreal dpi)

See also physicalDotsPerInchX().

### physicalSize : const QSizeF

This property holds the screen's physical size (in millimeters).

The physical size represents the actual physical dimensions of the screen's display.

Depending on what information the underlying system provides the value might not be entirely accurate.

Access functions:

QSizeF | physicalSize() const

Notifier signal:

void | physicalSizeChanged(const QSizeF &size)

### primaryOrientation : const Qt::ScreenOrientation

This property holds the primary screen orientation.

The primary screen orientation is Qt::LandscapeOrientation if the screen geometry's width is greater than or equal to its height, or Qt::PortraitOrientation otherwise. This property might change when the screen orientation was changed (i.e. when the display is rotated). The behavior is however platform dependent and can often be specified in an application manifest file.

Access functions:

Qt::ScreenOrientation | primaryOrientation() const

Notifier signal:

void | primaryOrientationChanged(Qt::ScreenOrientation orientation)

### refreshRate : const qreal

This property holds the approximate vertical refresh rate of the screen in Hz.

Access functions:

qreal | refreshRate() const

Notifier signal:

void | refreshRateChanged(qreal refreshRate)

### size : const QSize

This property holds the pixel resolution of the screen.

Access functions:

QSize | size() const

Notifier signal:

void | geometryChanged(const QRect &geometry)

### virtualGeometry : const QRect

This property holds the pixel geometry of the virtual desktop to which this screen belongs.

Returns the pixel geometry of the virtual desktop corresponding to this screen.

This is the union of the virtual siblings' individual geometries.

Access functions:

QRect | virtualGeometry() const

Notifier signal:

void | virtualGeometryChanged(const QRect &rect)

See also virtualSiblings().

### virtualSize : const QSize

This property holds the pixel size of the virtual desktop to which this screen belongs.

Returns the pixel size of the virtual desktop corresponding to this screen.

This is the combined size of the virtual siblings' individual geometries.

Access functions:

QSize | virtualSize() const

Notifier signal:

void | virtualGeometryChanged(const QRect &rect)

See also virtualSiblings().

## Member Function Documentation

### QScreen::~QScreen()

Destroys the screen.

### int QScreen::angleBetween(Qt::ScreenOrientation a, Qt::ScreenOrientation b) const

Convenience function to compute the angle of rotation to get from rotation a to rotation b.

The result will be 0, 90, 180, or 270.

Qt::PrimaryOrientation is interpreted as the screen's primaryOrientation().

### QPixmap QScreen::grabWindow(WId window, int x = 0, int y = 0, int width = -1, int height = -1)

Creates and returns a pixmap constructed by grabbing the contents of the given window restricted by QRect(x, y, width, height).

The arguments (x, y) specify the offset in the window, whereas (width, height) specify the area to be copied. If width is negative, the function copies everything to the right border of the window. If height is negative, the function copies everything to the bottom of the window.

The window system identifier (`WId`) can be retrieved using the QWidget::winId() function. The rationale for using a window identifier and not a QWidget, is to enable grabbing of windows that are not part of the application, window system frames, and so on.

The grabWindow() function grabs pixels from the screen, not from the window, i.e. if there is another window partially or entirely over the one you grab, you get pixels from the overlying window, too. The mouse cursor is generally not grabbed.

Note on X11 that if the given window doesn't have the same depth as the root window, and another window partially or entirely obscures the one you grab, you will not get pixels from the overlying window. The contents of the obscured areas in the pixmap will be undefined and uninitialized.

On Windows Vista and above grabbing a layered window, which is created by setting the Qt::WA_TranslucentBackground attribute, will not work. Instead grabbing the desktop widget should work.

Warning: In general, grabbing an area outside the screen is not safe. This depends on the underlying window system.

### QPlatformScreen *QScreen::handle() const

Get the platform screen handle.

### bool QScreen::isLandscape(Qt::ScreenOrientation o) const

Convenience function that returns `true` if o is either landscape or inverted landscape; otherwise returns `false`.

Qt::PrimaryOrientation is interpreted as the screen's primaryOrientation().

### bool QScreen::isPortrait(Qt::ScreenOrientation o) const

Convenience function that returns `true` if o is either portrait or inverted portrait; otherwise returns `false`.

Qt::PrimaryOrientation is interpreted as the screen's primaryOrientation().

### QRect QScreen::mapBetween(Qt::ScreenOrientation a, Qt::ScreenOrientation b, const QRect &rect) const

Maps the rect between two screen orientations.

This will flip the x and y dimensions of the rectangle rect if the orientation a is Qt::PortraitOrientation or Qt::InvertedPortraitOrientation and orientation b is Qt::LandscapeOrientation or Qt::InvertedLandscapeOrientation, or vice versa.

Qt::PrimaryOrientation is interpreted as the screen's primaryOrientation().

### `[signal]` void QScreen::orientationChanged(Qt::ScreenOrientation orientation)

This signal is emitted when the orientation of the screen changes with orientation as an argument.

Note: Notifier signal for property orientation.

See also orientation().

### Qt::ScreenOrientations QScreen::orientationUpdateMask() const

Returns the currently set orientation update mask.

See also setOrientationUpdateMask().

### `[signal]` void QScreen::primaryOrientationChanged(Qt::ScreenOrientation orientation)

This signal is emitted when the primary orientation of the screen changes with orientation as an argument.

Note: Notifier signal for property primaryOrientation.

See also primaryOrientation().

### void QScreen::setOrientationUpdateMask(Qt::ScreenOrientations mask)

Sets the orientations that the application is interested in receiving updates for in conjunction with this screen.

For example, to receive orientation() updates and thus have orientationChanged() signals being emitted for LandscapeOrientation and InvertedLandscapeOrientation, call setOrientationUpdateMask() with mask set to Qt::LandscapeOrientation | Qt::InvertedLandscapeOrientation.

The default, 0, means no orientationChanged() signals are fired.

See also orientationUpdateMask().

### QTransform QScreen::transformBetween(Qt::ScreenOrientation a, Qt::ScreenOrientation b, const QRect &target) const

Convenience function to compute a transform that maps from the coordinate system defined by orientation a into the coordinate system defined by orientation b and target dimensions target.

Example, a is Qt::Landscape, b is Qt::Portrait, and target is QRect(0, 0, w, h) the resulting transform will be such that the point QPoint(0, 0) is mapped to QPoint(0, w), and QPoint(h, w) is mapped to QPoint(0, h). Thus, the landscape coordinate system QRect(0, 0, h, w) is mapped (with a 90 degree rotation) into the portrait coordinate system QRect(0, 0, w, h).

Qt::PrimaryOrientation is interpreted as the screen's primaryOrientation().

### QList<QScreen *> QScreen::virtualSiblings() const

Get the screen's virtual siblings.

The virtual siblings are the screen instances sharing the same virtual desktop. They share a common coordinate system, and windows can freely be moved or positioned across them without having to be re-created.