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java.lang.Objectcom.trolltech.qt.QSignalEmitter
com.trolltech.qt.QtJambiObject
com.trolltech.qt.gui.QPaintDevice
public abstract class QPaintDevice
The QPaintDevice class is the base class of objects that can be painted.
A paint device is an abstraction of a two-dimensional space that can be drawn 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 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.
Nested Class Summary | |
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static class |
QPaintDevice.PaintDeviceMetric
Describes the various metrics of a paint device. |
Nested classes/interfaces inherited from class com.trolltech.qt.QSignalEmitter |
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QSignalEmitter.Signal0, QSignalEmitter.Signal1<A>, QSignalEmitter.Signal2<A,B>, QSignalEmitter.Signal3<A,B,C>, QSignalEmitter.Signal4<A,B,C,D>, QSignalEmitter.Signal5<A,B,C,D,E>, QSignalEmitter.Signal6<A,B,C,D,E,F>, QSignalEmitter.Signal7<A,B,C,D,E,F,G>, QSignalEmitter.Signal8<A,B,C,D,E,F,G,H>, QSignalEmitter.Signal9<A,B,C,D,E,F,G,H,I> |
Constructor Summary | |
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QPaintDevice()
Constructs a paint device. |
Method Summary | |
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int |
depth()
Returns the bit depth (number of bit planes) of the paint device. |
int |
devType()
This method is used internally by Qt Jambi. |
static QPaintDevice |
fromNativePointer(QNativePointer nativePointer)
This function returns the QPaintDevice instance pointed to by nativePointer |
int |
height()
Returns the height of the paint device in default coordinate system units (e.g. pixels for QPixmap and QWidget). |
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. |
abstract 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.e. someone has called QPainter::begin() but not yet called QPainter::end() for this device; otherwise returns false. |
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.g. pixels for QPixmap and QWidget). |
int |
widthMM()
Returns the width of the paint device in millimeters. |
Methods inherited from class com.trolltech.qt.QtJambiObject |
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dispose, disposed, finalize, reassignNativeResources, tr, tr, tr |
Methods inherited from class com.trolltech.qt.QSignalEmitter |
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blockSignals, disconnect, disconnect, signalsBlocked, signalSender, thread |
Methods inherited from class java.lang.Object |
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clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Methods inherited from interface com.trolltech.qt.QtJambiInterface |
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disableGarbageCollection, nativeId, nativePointer, reenableGarbageCollection, setJavaOwnership |
Constructor Detail |
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public QPaintDevice()
Constructs a paint device. This constructor can be invoked only from subclasses of QPaintDevice.
Method Detail |
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public final int depth()
Returns the bit depth (number of bit planes) of the paint device.
depth
in interface QPaintDeviceInterface
public final int height()
Returns the height of the paint device in default coordinate system units (e.g. pixels for QPixmap and QWidget).
height
in interface QPaintDeviceInterface
public final int heightMM()
Returns the height of the paint device in millimeters.
heightMM
in interface QPaintDeviceInterface
public final int logicalDpiX()
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, but it varies on Windows.
Note that if the logicalDpiX doesn't equal the physicalDpiX, the corresponding QPaintEngine must handle the resolution mapping.
logicalDpiX
in interface QPaintDeviceInterface
public final int logicalDpiY()
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, but it varies on Windows.
Note that if the logicalDpiY doesn't equal the physicalDpiY, the corresponding QPaintEngine must handle the resolution mapping.
logicalDpiY
in interface QPaintDeviceInterface
public final int numColors()
Returns the number of different colors available for the paint device. Since this value is an int, it will not be sufficient to represent the number of colors on 32 bit displays, in this case INT_MAX is returned instead.
numColors
in interface QPaintDeviceInterface
public final boolean paintingActive()
Returns true if the device is currently being painted on, i.e. someone has called QPainter::begin() but not yet called QPainter::end() for this device; otherwise returns false.
paintingActive
in interface QPaintDeviceInterface
public final int physicalDpiX()
Returns the horizontal resolution of the device in dots per inch.
Note that if the physicalDpiX doesn't equal the logicalDpiX, the corresponding QPaintEngine must handle the resolution mapping.
physicalDpiX
in interface QPaintDeviceInterface
public final int physicalDpiY()
Returns the horizontal resolution of the device in dots per inch.
Note that if the physicalDpiY doesn't equal the logicalDpiY, the corresponding QPaintEngine must handle the resolution mapping.
physicalDpiY
in interface QPaintDeviceInterface
public final int width()
Returns the width of the paint device in default coordinate system units (e.g. pixels for QPixmap and QWidget).
width
in interface QPaintDeviceInterface
public final int widthMM()
Returns the width of the paint device in millimeters.
widthMM
in interface QPaintDeviceInterface
public int devType()
This method is used internally by Qt Jambi. Do not use it in your applications.
devType
in interface QPaintDeviceInterface
public int metric(QPaintDevice.PaintDeviceMetric metric)
Returns the metric information for the given paint device metric.
metric
in interface QPaintDeviceInterface
public abstract QPaintEngine paintEngine()
Returns a pointer to the paint engine used for drawing on the device.
paintEngine
in interface QPaintDeviceInterface
public static QPaintDevice fromNativePointer(QNativePointer nativePointer)
nativePointer
- the QNativePointer of which object should be returned.
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