| 1 | /****************************************************************************
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| 2 | **
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| 3 | ** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
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| 4 | ** All rights reserved.
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| 5 | ** Contact: Nokia Corporation (qt-info@nokia.com)
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| 6 | **
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| 7 | ** This file is part of the documentation of the Qt Toolkit.
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| 8 | **
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| 9 | ** $QT_BEGIN_LICENSE:LGPL$
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| 10 | ** Commercial Usage
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| 11 | ** Licensees holding valid Qt Commercial licenses may use this file in
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| 12 | ** accordance with the Qt Commercial License Agreement provided with the
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| 13 | ** Software or, alternatively, in accordance with the terms contained in
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| 14 | ** a written agreement between you and Nokia.
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| 15 | **
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| 16 | ** GNU Lesser General Public License Usage
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| 17 | ** Alternatively, this file may be used under the terms of the GNU Lesser
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| 18 | ** General Public License version 2.1 as published by the Free Software
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| 19 | ** Foundation and appearing in the file LICENSE.LGPL included in the
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| 20 | ** packaging of this file. Please review the following information to
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| 21 | ** ensure the GNU Lesser General Public License version 2.1 requirements
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| 22 | ** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
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| 23 | **
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| 24 | ** In addition, as a special exception, Nokia gives you certain additional
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| 25 | ** rights. These rights are described in the Nokia Qt LGPL Exception
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| 26 | ** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
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| 27 | **
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| 28 | ** GNU General Public License Usage
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| 29 | ** Alternatively, this file may be used under the terms of the GNU
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| 30 | ** General Public License version 3.0 as published by the Free Software
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| 31 | ** Foundation and appearing in the file LICENSE.GPL included in the
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| 32 | ** packaging of this file. Please review the following information to
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| 33 | ** ensure the GNU General Public License version 3.0 requirements will be
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| 34 | ** met: http://www.gnu.org/copyleft/gpl.html.
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| 35 | **
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| 36 | ** If you have questions regarding the use of this file, please contact
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| 37 | ** Nokia at qt-info@nokia.com.
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| 38 | ** $QT_END_LICENSE$
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| 39 | **
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| 40 | ****************************************************************************/
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| 41 |
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| 42 | /*!
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| 43 | \class QPaintDevice
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| 44 | \brief The QPaintDevice class is the base class of objects that
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| 45 | can be painted.
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| 46 |
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| 47 | \ingroup painting
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| 48 |
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| 49 | A paint device is an abstraction of a two-dimensional space that
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| 50 | can be drawn using a QPainter. Its default coordinate system has
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| 51 | its origin located at the top-left position. X increases to the
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| 52 | right and Y increases downwards. The unit is one pixel.
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| 53 |
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| 54 | The drawing capabilities of QPaintDevice are currently implemented
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| 55 | by the QWidget, QImage, QPixmap, QGLPixelBuffer, QPicture, and
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| 56 | QPrinter subclasses.
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| 57 |
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| 58 | To implement support for a new backend, you must derive from
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| 59 | QPaintDevice and reimplement the virtual paintEngine() function to
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| 60 | tell QPainter which paint engine should be used to draw on this
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| 61 | particular device. Note that you also must create a corresponding
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| 62 | paint engine to be able to draw on the device, i.e derive from
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| 63 | QPaintEngine and reimplement its virtual functions.
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| 64 |
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| 65 | \warning Qt requires that a QApplication object exists before
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| 66 | any paint devices can be created. Paint devices access window
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| 67 | system resources, and these resources are not initialized before
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| 68 | an application object is created.
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| 69 |
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| 70 | The QPaintDevice class provides several functions returning the
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| 71 | various device metrics: The depth() function returns its bit depth
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| 72 | (number of bit planes). The height() function returns its height
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| 73 | in default coordinate system units (e.g. pixels for QPixmap and
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| 74 | QWidget) while heightMM() returns the height of the device in
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| 75 | millimeters. Similiarily, the width() and widthMM() functions
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| 76 | return the width of the device in default coordinate system units
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| 77 | and in millimeters, respectively. Alternatively, the protected
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| 78 | metric() function can be used to retrieve the metric information
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| 79 | by specifying the desired PaintDeviceMetric as argument.
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| 80 |
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| 81 | The logicalDpiX() and logicalDpiY() functions return the
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| 82 | horizontal and vertical resolution of the device in dots per
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| 83 | inch. The physicalDpiX() and physicalDpiY() functions also return
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| 84 | the resolution of the device in dots per inch, but note that if
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| 85 | the logical and physical resolution differ, the corresponding
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| 86 | QPaintEngine must handle the mapping. Finally, the colorCount()
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| 87 | function returns the number of different colors available for the
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| 88 | paint device.
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| 89 |
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| 90 | \sa QPaintEngine, QPainter, {The Coordinate System}, {The Paint
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| 91 | System}
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| 92 | */
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| 93 |
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| 94 | /*!
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| 95 | \enum QPaintDevice::PaintDeviceMetric
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| 96 |
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| 97 | Describes the various metrics of a paint device.
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| 98 |
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| 99 | \value PdmWidth The width of the paint device in default
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| 100 | coordinate system units (e.g. pixels for QPixmap and QWidget). See
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| 101 | also width().
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| 102 |
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| 103 | \value PdmHeight The height of the paint device in default
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| 104 | coordinate system units (e.g. pixels for QPixmap and QWidget). See
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| 105 | also height().
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| 106 |
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| 107 | \value PdmWidthMM The width of the paint device in millimeters. See
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| 108 | also widthMM().
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| 109 |
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| 110 | \value PdmHeightMM The height of the paint device in millimeters. See
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| 111 | also heightMM().
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| 112 |
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| 113 | \value PdmNumColors The number of different colors available for
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| 114 | the paint device. See also colorCount().
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| 115 |
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| 116 | \value PdmDepth The bit depth (number of bit planes) of the paint
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| 117 | device. See also depth().
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| 118 |
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| 119 | \value PdmDpiX The horizontal resolution of the device in dots per
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| 120 | inch. See also logicalDpiX().
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| 121 |
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| 122 | \value PdmDpiY The vertical resolution of the device in dots per inch. See
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| 123 | also logicalDpiY().
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| 124 |
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| 125 | \value PdmPhysicalDpiX The horizontal resolution of the device in
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| 126 | dots per inch. See also physicalDpiX().
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| 127 |
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| 128 | \value PdmPhysicalDpiY The vertical resolution of the device in
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| 129 | dots per inch. See also physicalDpiY().
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| 130 |
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| 131 | \sa metric()
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| 132 | */
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| 133 |
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| 134 | /*!
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| 135 | \fn QPaintDevice::QPaintDevice()
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| 136 |
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| 137 | Constructs a paint device. This constructor can be invoked only from
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| 138 | subclasses of QPaintDevice.
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| 139 | */
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| 140 |
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| 141 | /*!
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| 142 | \fn QPaintDevice::~QPaintDevice()
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| 143 |
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| 144 | Destroys the paint device and frees window system resources.
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| 145 | */
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| 146 |
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| 147 | /*!
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| 148 | \fn int QPaintDevice::devType() const
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| 149 |
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| 150 | \internal
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| 151 |
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| 152 | Returns the device type identifier, which is QInternal::Widget
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| 153 | if the device is a QWidget, QInternal::Pixmap if it's a
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| 154 | QPixmap, QInternal::Printer if it's a QPrinter,
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| 155 | QInternal::Picture if it's a QPicture, or
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| 156 | QInternal::UnknownDevice in other cases.
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| 157 | */
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| 158 |
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| 159 | /*!
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| 160 | \fn bool QPaintDevice::paintingActive() const
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| 161 |
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| 162 | Returns true if the device is currently being painted on, i.e. someone has
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| 163 | called QPainter::begin() but not yet called QPainter::end() for
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| 164 | this device; otherwise returns false.
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| 165 |
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| 166 | \sa QPainter::isActive()
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| 167 | */
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| 168 |
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| 169 | /*!
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| 170 | \fn QPaintEngine *QPaintDevice::paintEngine() const
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| 171 |
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| 172 | Returns a pointer to the paint engine used for drawing on the
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| 173 | device.
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| 174 | */
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| 175 |
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| 176 | /*!
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| 177 | \fn int QPaintDevice::metric(PaintDeviceMetric metric) const
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| 178 |
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| 179 | Returns the metric information for the given paint device \a metric.
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| 180 |
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| 181 | \sa PaintDeviceMetric
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| 182 | */
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| 183 |
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| 184 | /*!
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| 185 | \fn int QPaintDevice::width() const
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| 186 |
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| 187 | Returns the width of the paint device in default coordinate system
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| 188 | units (e.g. pixels for QPixmap and QWidget).
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| 189 |
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| 190 | \sa widthMM()
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| 191 | */
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| 192 |
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| 193 | /*!
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| 194 | \fn int QPaintDevice::height() const
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| 195 |
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| 196 | Returns the height of the paint device in default coordinate
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| 197 | system units (e.g. pixels for QPixmap and QWidget).
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| 198 |
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| 199 | \sa heightMM()
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| 200 | */
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| 201 |
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| 202 | /*!
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| 203 | \fn int QPaintDevice::widthMM() const
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| 204 |
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| 205 | Returns the width of the paint device in millimeters. Due to platform
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| 206 | limitations it may not be possible to use this function to determine
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| 207 | the actual physical size of a widget on the screen.
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| 208 |
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| 209 | \sa width()
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| 210 | */
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| 211 |
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| 212 | /*!
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| 213 | \fn int QPaintDevice::heightMM() const
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| 214 |
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| 215 | Returns the height of the paint device in millimeters. Due to platform
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| 216 | limitations it may not be possible to use this function to determine
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| 217 | the actual physical size of a widget on the screen.
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| 218 |
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| 219 | \sa height()
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| 220 | */
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| 221 |
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| 222 | /*!
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| 223 | \fn int QPaintDevice::numColors() const
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| 224 | \deprecated
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| 225 |
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| 226 | Use colorCount() instead.
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| 227 |
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| 228 | Returns the number of different colors available for the paint
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| 229 | device. Since this value is an int, it will not be sufficient to
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| 230 | represent the number of colors on 32 bit displays, in this case
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| 231 | INT_MAX is returned instead.
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| 232 | */
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| 233 |
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| 234 | /*!
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| 235 | \fn int QPaintDevice::colorCount() const
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| 236 |
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| 237 | Returns the number of different colors available for the paint
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| 238 | device. Since this value is an int, it will not be sufficient to
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| 239 | represent the number of colors on 32 bit displays, in this case
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| 240 | INT_MAX is returned instead.
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| 241 | */
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| 242 |
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| 243 | /*!
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| 244 | \fn int QPaintDevice::depth() const
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| 245 |
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| 246 | Returns the bit depth (number of bit planes) of the paint device.
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| 247 | */
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| 248 |
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| 249 | /*!
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| 250 | \fn int QPaintDevice::logicalDpiX() const
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| 251 |
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| 252 | Returns the horizontal resolution of the device in dots per inch,
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| 253 | which is used when computing font sizes. For X11, this is usually
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| 254 | the same as could be computed from widthMM().
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| 255 |
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| 256 | Note that if the logicalDpiX() doesn't equal the physicalDpiX(),
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| 257 | the corresponding QPaintEngine must handle the resolution mapping.
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| 258 |
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| 259 | \sa logicalDpiY(), physicalDpiX()
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| 260 | */
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| 261 |
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| 262 | /*!
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| 263 | \fn int QPaintDevice::logicalDpiY() const
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| 264 |
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| 265 | Returns the vertical resolution of the device in dots per inch,
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| 266 | which is used when computing font sizes. For X11, this is usually
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| 267 | the same as could be computed from heightMM().
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| 268 |
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| 269 | Note that if the logicalDpiY() doesn't equal the physicalDpiY(),
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| 270 | the corresponding QPaintEngine must handle the resolution mapping.
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| 271 |
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| 272 | \sa logicalDpiX(), physicalDpiY()
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| 273 | */
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| 274 |
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| 275 | /*!
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| 276 | \fn int QPaintDevice::physicalDpiX() const
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| 277 |
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| 278 | Returns the horizontal resolution of the device in dots per inch.
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| 279 | For example, when printing, this resolution refers to the physical
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| 280 | printer's resolution. The logical DPI on the other hand, refers to
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| 281 | the resolution used by the actual paint engine.
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| 282 |
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| 283 | Note that if the physicalDpiX() doesn't equal the logicalDpiX(),
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| 284 | the corresponding QPaintEngine must handle the resolution mapping.
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| 285 |
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| 286 | \sa physicalDpiY(), logicalDpiX()
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| 287 | */
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| 288 |
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| 289 | /*!
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| 290 | \fn int QPaintDevice::physicalDpiY() const
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| 291 |
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| 292 | Returns the horizontal resolution of the device in dots per inch.
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| 293 | For example, when printing, this resolution refers to the physical
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| 294 | printer's resolution. The logical DPI on the other hand, refers to
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| 295 | the resolution used by the actual paint engine.
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| 296 |
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| 297 | Note that if the physicalDpiY() doesn't equal the logicalDpiY(),
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| 298 | the corresponding QPaintEngine must handle the resolution mapping.
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| 299 |
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| 300 | \sa physicalDpiX(), logicalDpiY()
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| 301 | */
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