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authorQt by Nokia <qt-info@nokia.com>2011-04-27 12:05:43 +0200
committeraxis <qt-info@nokia.com>2011-04-27 12:05:43 +0200
commit38be0d13830efd2d98281c645c3a60afe05ffece (patch)
tree6ea73f3ec77f7d153333779883e8120f82820abe /src/gui/painting/qpaintdevice.qdoc
Initial import from the monolithic Qt.
This is the beginning of revision history for this module. If you want to look at revision history older than this, please refer to the Qt Git wiki for how to use Git history grafting. At the time of writing, this wiki is located here: http://qt.gitorious.org/qt/pages/GitIntroductionWithQt If you have already performed the grafting and you don't see any history beyond this commit, try running "git log" with the "--follow" argument. Branched from the monolithic repo, Qt master branch, at commit 896db169ea224deb96c59ce8af800d019de63f12
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+/****************************************************************************
+**
+** 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.
+**
+** $QT_BEGIN_LICENSE:FDL$
+** No Commercial Usage
+** This file contains pre-release code and may not be distributed.
+** You may use this file in accordance with the terms and conditions
+** contained in the Technology Preview License Agreement accompanying
+** this package.
+**
+** 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.
+**
+** If you have questions regarding the use of this file, please contact
+** Nokia at qt-info@nokia.com.
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+/*!
+ \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()
+*/