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public interface QPaintDeviceInterface
The QPaintDevice
class is the base class of objects that can be painted. A paint device is an abstraction of a twodimensional space that can be drawn using a QPainter
. Its default coordinate system has its origin located at the topleft 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 QApplication
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 vertical resolution differ, the corresponding QPaintEngine
must handle the mapping. Finally, the numColors()
function returns the number of different colors available for the paint device.
QPaintEngine
, QPainter
, The Coordinate System, and The Paint System.
Method Summary  

int 
depth()
Returns the bit depth (number of bit planes) of the paint device. 
int 
height()
Returns the height of the paint device in default coordinate system units (e. 
int 
heightMM()
Returns the height of the paint device in millimeters. 
int 
logicalDpiX()
Returns the horizontal resolution of the device in dots per inch, which is used when computing font sizes. 
int 
logicalDpiY()
Returns the vertical resolution of the device in dots per inch, which is used when computing font sizes. 
int 
metric(QPaintDevice.PaintDeviceMetric metric)
Returns the metric information for the given paint device metric. 
int 
numColors()
Returns the number of different colors available for the paint device. 
QPaintEngine 
paintEngine()
Returns a pointer to the paint engine used for drawing on the device. 
boolean 
paintingActive()
Returns true if the device is currently being painted on, i. 
int 
physicalDpiX()
Returns the horizontal resolution of the device in dots per inch. 
int 
physicalDpiY()
Returns the horizontal resolution of the device in dots per inch. 
int 
width()
Returns the width of the paint device in default coordinate system units (e. 
int 
widthMM()
Returns the width of the paint device in millimeters. 
Methods inherited from interface com.trolltech.qt.QtJambiInterface 

disableGarbageCollection, nativeId, nativePointer, reenableGarbageCollection, setJavaOwnership 
Method Detail 

int depth()
int height()
QPixmap
and QWidget
). heightMM()
.
int heightMM()
height()
.
int logicalDpiX()
widthMM()
. Note that if the logicalDpiX()
doesn't equal the physicalDpiX()
, the corresponding QPaintEngine
must handle the resolution mapping.
logicalDpiY()
, and physicalDpiX()
.
int logicalDpiY()
heightMM()
. Note that if the logicalDpiY()
doesn't equal the physicalDpiY()
, the corresponding QPaintEngine
must handle the resolution mapping.
logicalDpiX()
, and physicalDpiY()
.
int numColors()
boolean paintingActive()
QPainter::begin()
but not yet called QPainter::end()
for this device; otherwise returns false. QPainter::isActive()
.
int physicalDpiX()
Note that if the physicalDpiX()
doesn't equal the logicalDpiX()
, the corresponding QPaintEngine
must handle the resolution mapping.
physicalDpiY()
, and logicalDpiX()
.
int physicalDpiY()
Note that if the physicalDpiY()
doesn't equal the logicalDpiY()
, the corresponding QPaintEngine
must handle the resolution mapping.
physicalDpiX()
, and logicalDpiY()
.
int width()
QPixmap
and QWidget
). widthMM()
.
int widthMM()
width()
.
int metric(QPaintDevice.PaintDeviceMetric metric)
PaintDeviceMetric
.
QPaintEngine paintEngine()


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