com.trolltech.qt.gui
Class QPaintDevice

java.lang.Object
  extended by com.trolltech.qt.internal.QSignalEmitterInternal
      extended by com.trolltech.qt.QSignalEmitter
          extended by com.trolltech.qt.QtJambiObject
              extended by com.trolltech.qt.gui.QPaintDevice
All Implemented Interfaces:
QPaintDeviceInterface, QtJambiInterface

public abstract class QPaintDevice
extends QtJambiObject
implements QPaintDeviceInterface

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.

See also:
QPaintEngine, QPainter, The Coordinate System, and The Paint System.


Nested Class Summary
static class QPaintDevice.PaintDeviceMetric
          Describes the various metrics of a paint device.
 
Nested classes/interfaces inherited from class com.trolltech.qt.QSignalEmitter
QSignalEmitter.AbstractSignal, QSignalEmitter.PrivateSignal0, QSignalEmitter.PrivateSignal1, QSignalEmitter.PrivateSignal2, QSignalEmitter.PrivateSignal3, QSignalEmitter.PrivateSignal4, QSignalEmitter.PrivateSignal5, QSignalEmitter.PrivateSignal6, QSignalEmitter.PrivateSignal7, QSignalEmitter.PrivateSignal8, QSignalEmitter.PrivateSignal9, QSignalEmitter.Signal0, QSignalEmitter.Signal1, QSignalEmitter.Signal2, QSignalEmitter.Signal3, QSignalEmitter.Signal4, QSignalEmitter.Signal5, QSignalEmitter.Signal6, QSignalEmitter.Signal7, QSignalEmitter.Signal8, QSignalEmitter.Signal9
 
Nested classes/interfaces inherited from class com.trolltech.qt.internal.QSignalEmitterInternal
com.trolltech.qt.internal.QSignalEmitterInternal.AbstractSignalInternal
 
Field Summary
 
Fields inherited from class com.trolltech.qt.internal.QSignalEmitterInternal
currentSender
 
Constructor Summary
QPaintDevice()
          Constructs a paint device.
 
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.
abstract  QPaintEngine paintEngine()
          Returns a pointer to the paint engine used for drawing on the device.
protected  char painters()
           
 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.
protected  void setPainters(char painters)
           
 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 class com.trolltech.qt.QtJambiObject
dispose, disposed, equals, finalize, reassignNativeResources, tr, tr, tr
 
Methods inherited from class com.trolltech.qt.QSignalEmitter
blockSignals, disconnect, disconnect, signalsBlocked, signalSender, thread
 
Methods inherited from class com.trolltech.qt.internal.QSignalEmitterInternal
__qt_signalInitialization
 
Methods inherited from class java.lang.Object
clone, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 
Methods inherited from interface com.trolltech.qt.QtJambiInterface
disableGarbageCollection, nativeId, nativePointer, reenableGarbageCollection, setJavaOwnership
 

Constructor Detail

QPaintDevice

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

Method Detail

depth

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

Specified by:
depth in interface QPaintDeviceInterface

height

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

See also:
heightMM().

Specified by:
height in interface QPaintDeviceInterface

heightMM

public final int heightMM()
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().

Specified by:
heightMM in interface QPaintDeviceInterface

logicalDpiX

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().

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

See also:
logicalDpiY(), and physicalDpiX().

Specified by:
logicalDpiX in interface QPaintDeviceInterface

logicalDpiY

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().

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

See also:
logicalDpiX(), and physicalDpiY().

Specified by:
logicalDpiY in interface QPaintDeviceInterface

numColors

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.

Specified by:
numColors in interface QPaintDeviceInterface

paintingActive

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

See also:
QPainter::isActive().

Specified by:
paintingActive in interface QPaintDeviceInterface

physicalDpiX

public final int physicalDpiX()
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 physicalDpiX() doesn't equal the logicalDpiX(), the corresponding QPaintEngine must handle the resolution mapping.

See also:
physicalDpiY(), and logicalDpiX().

Specified by:
physicalDpiX in interface QPaintDeviceInterface

physicalDpiY

public final int physicalDpiY()
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 physicalDpiY() doesn't equal the logicalDpiY(), the corresponding QPaintEngine must handle the resolution mapping.

See also:
physicalDpiX(), and logicalDpiY().

Specified by:
physicalDpiY in interface QPaintDeviceInterface

width

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

See also:
widthMM().

Specified by:
width in interface QPaintDeviceInterface

widthMM

public final int widthMM()
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().

Specified by:
widthMM in interface QPaintDeviceInterface

metric

public int metric(QPaintDevice.PaintDeviceMetric metric)
Returns the metric information for the given paint device metric.

See also:
PaintDeviceMetric .

Specified by:
metric in interface QPaintDeviceInterface

paintEngine

public abstract QPaintEngine paintEngine()
Returns a pointer to the paint engine used for drawing on the device.

Specified by:
paintEngine in interface QPaintDeviceInterface

setPainters

protected final void setPainters(char painters)

painters

protected final char painters()