QPaintDevice

The QPaintDevice class is the base class of objects that can be painted on with QPainter . More…

Inherited by: QBitmap, QImage, QOpenGLPaintDevice, QPagedPaintDevice, QPicture, QPixmap, QGLFramebufferObject, QGLPixelBuffer, QPrinter, QSvgGenerator

Synopsis

Functions

• def colorCount ()

• def depth ()

• def devicePixelRatio ()

• def devicePixelRatioF ()

• def height ()

• def heightMM ()

• def logicalDpiX ()

• def logicalDpiY ()

• def paintingActive ()

• def physicalDpiX ()

• def physicalDpiY ()

• def width ()

• def widthMM ()

Virtual functions

• def devType ()

• def initPainter (painter)

• def metric (metric)

• def paintEngine ()

• def redirected (offset)

• def sharedPainter ()

Static functions

• def devicePixelRatioFScale ()

Detailed Description

A paint device is an abstraction of a two-dimensional space that can be drawn on using a QPainter . Its default coordinate system has its origin located at the top-left position. X increases to the right and Y increases downwards. The unit is one pixel.

The drawing capabilities of QPaintDevice are currently implemented by the QWidget , QImage , QPixmap , QGLPixelBuffer , QPicture , and QPrinter subclasses.

To implement support for a new backend, you must derive from QPaintDevice and reimplement the virtual paintEngine() function to tell QPainter which paint engine should be used to draw on this particular device. Note that you also must create a corresponding paint engine to be able to draw on the device, i.e derive from QPaintEngine and reimplement its virtual functions.

Warning

Qt requires that a QGuiApplication object exists before any paint devices can be created. Paint devices access window system resources, and these resources are not initialized before an application object is created.

The QPaintDevice class provides several functions returning the various device metrics: The depth() function returns its bit depth (number of bit planes). The height() function returns its height in default coordinate system units (e.g. pixels for QPixmap and QWidget ) while heightMM() returns the height of the device in millimeters. Similiarily, the width() and widthMM() functions return the width of the device in default coordinate system units and in millimeters, respectively. Alternatively, the protected metric() function can be used to retrieve the metric information by specifying the desired PaintDeviceMetric as argument.

The logicalDpiX() and logicalDpiY() functions return the horizontal and vertical resolution of the device in dots per inch. The physicalDpiX() and physicalDpiY() functions also return the resolution of the device in dots per inch, but note that if the logical and physical resolution differ, the corresponding QPaintEngine must handle the mapping. Finally, the colorCount() function returns the number of different colors available for the paint device.

See also

QPaintEngine QPainter Coordinate System Paint System

class PySide2.QtGui.QPaintDevice

Constructs a paint device. This constructor can be invoked only from subclasses of QPaintDevice .

PySide2.QtGui.QPaintDevice.PaintDeviceMetric

Describes the various metrics of a paint device.

Constant	Description
QPaintDevice.PdmWidth	The width of the paint device in default coordinate system units (e.g. pixels for QPixmap and QWidget ). See also width() .
QPaintDevice.PdmHeight	The height of the paint device in default coordinate system units (e.g. pixels for QPixmap and QWidget ). See also height() .
QPaintDevice.PdmWidthMM	The width of the paint device in millimeters. See also widthMM() .
QPaintDevice.PdmHeightMM	The height of the paint device in millimeters. See also heightMM() .
QPaintDevice.PdmNumColors	The number of different colors available for the paint device. See also colorCount() .
QPaintDevice.PdmDepth	The bit depth (number of bit planes) of the paint device. See also depth() .
QPaintDevice.PdmDpiX	The horizontal resolution of the device in dots per inch. See also logicalDpiX() .
QPaintDevice.PdmDpiY	The vertical resolution of the device in dots per inch. See also logicalDpiY() .
QPaintDevice.PdmPhysicalDpiX	The horizontal resolution of the device in dots per inch. See also physicalDpiX() .
QPaintDevice.PdmPhysicalDpiY	The vertical resolution of the device in dots per inch. See also physicalDpiY() .
QPaintDevice.PdmDevicePixelRatio	The device pixel ratio for device. Common values are 1 for normal-dpi displays and 2 for high-dpi “retina” displays.
QPaintDevice.PdmDevicePixelRatioScaled	The scaled device pixel ratio for the device. This is identical to , except that the value is scaled by a constant factor in order to support paint devices with fractional scale factors. The constant scaling factor used is . This enum value has been introduced in Qt 5.6.

See also

metric() devicePixelRatioF()

PySide2.QtGui.QPaintDevice.painters

PySide2.QtGui.QPaintDevice.colorCount()

Return type:

int

Returns the number of different colors available for the paint device. If the number of colors available is too great to be represented by the int data type, then INT_MAX will be returned instead.

PySide2.QtGui.QPaintDevice.depth()

Return type:

int

Returns the bit depth (number of bit planes) of the paint device.

PySide2.QtGui.QPaintDevice.devType()

Return type:

int

PySide2.QtGui.QPaintDevice.devicePixelRatio()

Return type:

int

Returns the device pixel ratio for device.

Common values are 1 for normal-dpi displays and 2 for high-dpi “retina” displays.

PySide2.QtGui.QPaintDevice.devicePixelRatioF()

Return type:

float

Returns the device pixel ratio for the device as a floating point number.

static PySide2.QtGui.QPaintDevice.devicePixelRatioFScale()

Return type:

float

PySide2.QtGui.QPaintDevice.height()

Return type:

int

Returns the height of the paint device in default coordinate system units (e.g. pixels for QPixmap and QWidget ).

See also

heightMM()

PySide2.QtGui.QPaintDevice.heightMM()

Return type:

int

Returns the height of the paint device in millimeters. Due to platform limitations it may not be possible to use this function to determine the actual physical size of a widget on the screen.

See also

height()

PySide2.QtGui.QPaintDevice.initPainter(painter)

Parameters:

painter – PySide2.QtGui.QPainter

PySide2.QtGui.QPaintDevice.logicalDpiX()

Return type:

int

Returns the horizontal resolution of the device in dots per inch, which is used when computing font sizes. For X11, this is usually the same as could be computed from widthMM() .

Note that if the doesn’t equal the physicalDpiX() , the corresponding QPaintEngine must handle the resolution mapping.

See also

logicalDpiY() physicalDpiX()

PySide2.QtGui.QPaintDevice.logicalDpiY()

Return type:

int

Returns the vertical resolution of the device in dots per inch, which is used when computing font sizes. For X11, this is usually the same as could be computed from heightMM() .

Note that if the doesn’t equal the physicalDpiY() , the corresponding QPaintEngine must handle the resolution mapping.

See also

logicalDpiX() physicalDpiY()

PySide2.QtGui.QPaintDevice.metric(metric)

Parameters:

metric – PaintDeviceMetric

Return type:

int

Returns the metric information for the given paint device metric .

See also

PaintDeviceMetric

PySide2.QtGui.QPaintDevice.paintEngine()

Return type:

PySide2.QtGui.QPaintEngine

Returns a pointer to the paint engine used for drawing on the device.

PySide2.QtGui.QPaintDevice.paintingActive()

Return type:

bool

Returns true if the device is currently being painted on, i.e. someone has called begin() but not yet called end() for this device; otherwise returns false .

See also

isActive()

PySide2.QtGui.QPaintDevice.physicalDpiX()

Return type:

int

Returns the horizontal resolution of the device in dots per inch. For example, when printing, this resolution refers to the physical printer’s resolution. The logical DPI on the other hand, refers to the resolution used by the actual paint engine.

Note that if the doesn’t equal the logicalDpiX() , the corresponding QPaintEngine must handle the resolution mapping.

See also

physicalDpiY() logicalDpiX()

PySide2.QtGui.QPaintDevice.physicalDpiY()

Return type:

int

Returns the horizontal resolution of the device in dots per inch. For example, when printing, this resolution refers to the physical printer’s resolution. The logical DPI on the other hand, refers to the resolution used by the actual paint engine.

Note that if the doesn’t equal the logicalDpiY() , the corresponding QPaintEngine must handle the resolution mapping.

See also

physicalDpiX() logicalDpiY()

PySide2.QtGui.QPaintDevice.redirected(offset)

Parameters:

offset – PySide2.QtCore.QPoint

Return type:

PySide2.QtGui.QPaintDevice

PySide2.QtGui.QPaintDevice.sharedPainter()

Return type:

PySide2.QtGui.QPainter

PySide2.QtGui.QPaintDevice.width()

Return type:

int

Returns the width of the paint device in default coordinate system units (e.g. pixels for QPixmap and QWidget ).

See also

widthMM()

PySide2.QtGui.QPaintDevice.widthMM()

Return type:

int

Returns the width of the paint device in millimeters. Due to platform limitations it may not be possible to use this function to determine the actual physical size of a widget on the screen.

See also

width()