com.trolltech.qt.gui
Interface QPaintDeviceInterface

All Superinterfaces:

QtJambiInterface

All Known Implementing Classes:

EffectWidget, QAbstractButton, QAbstractItemView, QAbstractPageSetupDialog, QAbstractPrintDialog, QAbstractScrollArea, QAbstractSlider, QAbstractSpinBox, QBitmap, QCalendarWidget, QCheckBox, QColorDialog, QColumnView, QComboBox, QCommandLinkButton, QDateEdit, QDateTimeEdit, QDesktopWidget, QDial, QDialog, QDialogButtonBox, QDockWidget, QDoubleSpinBox, QErrorMessage, QFileDialog, QFocusFrame, QFontComboBox, QFontDialog, QFrame, QGLFramebufferObject, QGLPixelBuffer, QGLWidget, QGraphicsView, QGroupBox, QHeaderView, QImage, QInputDialog, QLabel, QLCDNumber, QLineEdit, QListView, QListWidget, QMainWindow, QMdiArea, QMdiSubWindow, QMenu, QMenuBar, QMessageBox, QPageSetupDialog, QPaintDevice, QPicture, QPixmap, QPlainTextEdit, QPrintDialog, QPrinter, QPrintPreviewDialog, QPrintPreviewWidget, QProgressBar, QProgressDialog, QPushButton, QRadioButton, QRubberBand, QScrollArea, QScrollBar, QSizeGrip, QSlider, QSpinBox, QSplashScreen, QSplitter, QSplitterHandle, QStackedWidget, QStatusBar, QSvgGenerator, QSvgWidget, QTabBar, QTableView, QTableWidget, QTabWidget, QTextBrowser, QTextEdit, QTimeEdit, QToolBar, QToolBox, QToolButton, QTreeView, QTreeWidget, QUndoView, QWebView, QWidget, QWizard, QWizardPage, QWorkspace, SeekSlider, VideoPlayer, VideoWidget, VolumeSlider

public interface QPaintDeviceInterface
extends QtJambiInterface

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.

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

depth

int depth()

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

height

int height()

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

See also:

heightMM().

heightMM

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().

logicalDpiX

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().

logicalDpiY

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().

numColors

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.

paintingActive

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().

physicalDpiX

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().

physicalDpiY

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().

width

int width()

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

See also:

widthMM().

widthMM

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().

metric

int metric(QPaintDevice.PaintDeviceMetric metric)

Returns the metric information for the given paint device metric.

See also:

PaintDeviceMetric .

paintEngine

QPaintEngine paintEngine()

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