/**************************************************************************** ** ** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies). ** All rights reserved. ** Contact: Nokia Corporation (qt-info@nokia.com) ** ** This file is part of the documentation of the Qt Toolkit. ** ** $QT_BEGIN_LICENSE:FDL$ ** GNU Free Documentation License ** Alternatively, this file may be used under the terms of the GNU Free ** Documentation License version 1.3 as published by the Free Software ** Foundation and appearing in the file included in the packaging of ** this file. ** ** Other Usage ** Alternatively, this file may be used in accordance with the terms ** and conditions contained in a signed written agreement between you ** and Nokia. ** ** ** ** ** $QT_END_LICENSE$ ** ****************************************************************************/ /*! \class QPaintDevice \brief The QPaintDevice class is the base class of objects that can be painted. \ingroup painting 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 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. \sa QPaintEngine, QPainter, {Coordinate System}, {Paint System} */ /*! \enum QPaintDevice::PaintDeviceMetric Describes the various metrics of a paint device. \value PdmWidth The width of the paint device in default coordinate system units (e.g. pixels for QPixmap and QWidget). See also width(). \value PdmHeight The height of the paint device in default coordinate system units (e.g. pixels for QPixmap and QWidget). See also height(). \value PdmWidthMM The width of the paint device in millimeters. See also widthMM(). \value PdmHeightMM The height of the paint device in millimeters. See also heightMM(). \value PdmNumColors The number of different colors available for the paint device. See also colorCount(). \value PdmDepth The bit depth (number of bit planes) of the paint device. See also depth(). \value PdmDpiX The horizontal resolution of the device in dots per inch. See also logicalDpiX(). \value PdmDpiY The vertical resolution of the device in dots per inch. See also logicalDpiY(). \value PdmPhysicalDpiX The horizontal resolution of the device in dots per inch. See also physicalDpiX(). \value PdmPhysicalDpiY The vertical resolution of the device in dots per inch. See also physicalDpiY(). \sa metric() */ /*! \fn QPaintDevice::QPaintDevice() Constructs a paint device. This constructor can be invoked only from subclasses of QPaintDevice. */ /*! \fn QPaintDevice::~QPaintDevice() Destroys the paint device and frees window system resources. */ /*! \fn int QPaintDevice::devType() const \internal Returns the device type identifier, which is QInternal::Widget if the device is a QWidget, QInternal::Pixmap if it's a QPixmap, QInternal::Printer if it's a QPrinter, QInternal::Picture if it's a QPicture, or QInternal::UnknownDevice in other cases. */ /*! \fn bool QPaintDevice::paintingActive() const 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. \sa QPainter::isActive() */ /*! \fn QPaintEngine *QPaintDevice::paintEngine() const Returns a pointer to the paint engine used for drawing on the device. */ /*! \fn int QPaintDevice::metric(PaintDeviceMetric metric) const Returns the metric information for the given paint device \a metric. \sa PaintDeviceMetric */ /*! \fn int QPaintDevice::width() const Returns the width of the paint device in default coordinate system units (e.g. pixels for QPixmap and QWidget). \sa widthMM() */ /*! \fn int QPaintDevice::height() const Returns the height of the paint device in default coordinate system units (e.g. pixels for QPixmap and QWidget). \sa heightMM() */ /*! \fn int QPaintDevice::widthMM() const 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. \sa width() */ /*! \fn int QPaintDevice::heightMM() const 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. \sa height() */ /*! \fn int QPaintDevice::numColors() const \deprecated Use colorCount() instead. 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. */ /*! \fn int QPaintDevice::colorCount() const 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. */ /*! \fn int QPaintDevice::depth() const Returns the bit depth (number of bit planes) of the paint device. */ /*! \fn int QPaintDevice::logicalDpiX() const 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. \sa logicalDpiY(), physicalDpiX() */ /*! \fn int QPaintDevice::logicalDpiY() const 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. \sa logicalDpiX(), physicalDpiY() */ /*! \fn int QPaintDevice::physicalDpiX() const 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. \sa physicalDpiY(), logicalDpiX() */ /*! \fn int QPaintDevice::physicalDpiY() const 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. \sa physicalDpiX(), logicalDpiY() */