QPaintDeviceMetrics Class Reference

Detailed Description

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 )

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.

Example: 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.

Examples: action/application.cpp, application/application.cpp, helpviewer/helpwindow.cpp, and mdi/application.cpp.

int QPaintDeviceMetrics::numColors () const

Returns the number of different colors available for the paint device. Since this value is an int will not be sufficient to represent the number of colors on 32 bit displays, in which case INT_MAX is returned instead.

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.

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