The Q3PaintDeviceMetrics class provides information about a paint device. 更多...
| 头： | #include <Q3PaintDeviceMetrics> |
| Q3PaintDeviceMetrics (const QPaintDevice * pd ) | |
| int | depth () const |
| int | height () const |
| int | heightMM () const |
| int | logicalDpiX () const |
| int | logicalDpiY () const |
| int | numColors () const |
| int | width () const |
| int | widthMM () const |
The Q3PaintDeviceMetrics 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:
Q3PaintDeviceMetrics pdm(myWidget); double aspect = (double)pdm.widthMM() / (double)pdm.heightMM();
Q3PaintDeviceMetrics contains methods to provide the width and height of a device in both pixels ( width () 和 height ()) and millimeters ( widthMM () 和 heightMM ()), the number of colors the device supports ( numColors ()), the number of bit planes ( depth ()), and the resolution of the device ( logicalDpiX () 和 logicalDpiY ()).
It is not always possible for Q3PaintDeviceMetrics 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?
Constructs a metric for the paint device pd .
返回描绘设备的位深度 (位平面的数量)。
返回描绘设备的高度，以默认坐标系单位为单位 (如：像素对于 QPixmap and QWidget ).
Returns the height of the paint device, measured in millimeters.
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.
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.
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.
返回描绘设备的宽度，以默认坐标系单位为单位 (如：像素对于 QPixmap and QWidget ).
Returns the width of the paint device, measured in millimeters.
