Detailed Description
The QPaintDeviceMetrics class provides information about a
paint device.
Sometimes when drawing graphics it is necessary to obtain
information about the physical characteristics of a paint device.
This class provides the information. For example, to compute the
aspect ratio of a paint device:
QPaintDeviceMetrics pdm( myWidget );
double aspect = (double)pdm.widthMM() / (double)pdm.heightMM();
QPaintDeviceMetrics contains methods to provide the width and
height of a device in both pixels (width() and height()) and
millimeters (widthMM() and heightMM()), the number of colors the
device supports (numColors()), the number of bit planes (depth()),
and the resolution of the device (logicalDpiX() and
logicalDpiY()).
It is not always possible for QPaintDeviceMetrics to compute the
values you ask for, particularly for external devices. The
ultimate example is asking for the resolution of of a QPrinter
that is set to "print to file": who knows what printer that file
will end up on?
See also Graphics Classes and Image Processing Classes.
Member Function Documentation
QPaintDeviceMetrics::QPaintDeviceMetrics ( const QPaintDevice * pd )
Constructs a metric for the paint device pd.
int QPaintDeviceMetrics::depth () const
Returns the bit depth (number of bit planes) of the paint device.
int QPaintDeviceMetrics::height () const
Returns the height of the paint device in default coordinate
system units (e.g. pixels for QPixmap and QWidget).
Examples: action/application.cpp, application/application.cpp, helpviewer/helpwindow.cpp, mdi/application.cpp and qwerty/qwerty.cpp.
int QPaintDeviceMetrics::heightMM () const
Returns the height of the paint device, measured in millimeters.
int QPaintDeviceMetrics::logicalDpiX () const
Returns the horizontal resolution of the device in dots per inch,
which is used when computing font sizes. For X, this is usually
the same as could be computed from widthMM(), but it varies on
Windows.
Examples: helpviewer/helpwindow.cpp and qwerty/qwerty.cpp.
int QPaintDeviceMetrics::logicalDpiY () const
Returns the vertical resolution of the device in dots per inch,
which is used when computing font sizes. For X, this is usually
the same as could be computed from heightMM(), but it varies on
Windows.
Example: helpviewer/helpwindow.cpp.
int QPaintDeviceMetrics::numColors () const
Returns the number of different colors available for the paint
device.
int QPaintDeviceMetrics::width () const
Returns the width of the paint device in default coordinate system
units (e.g. pixels for QPixmap and QWidget).
Examples: action/application.cpp, application/application.cpp, helpviewer/helpwindow.cpp, mdi/application.cpp and qwerty/qwerty.cpp.
int QPaintDeviceMetrics::widthMM () const
Returns the width of the paint device, measured in millimeters.
This file is part of the Qt toolkit.
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