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QDial Class Reference
[QtGui module]

The QDial class provides a rounded range control (like a speedometer or potentiometer). More...

Inherits QAbstractSlider.


Detailed Description

The QDial class provides a rounded range control (like a speedometer or potentiometer).

QDial is used when the user needs to control a value within a program-definable range, and the range either wraps around (for example, with angles measured from 0 to 359 degrees) or the dialog layout needs a square widget.

Since QDial inherits from QAbstractSlider, the dial behaves in a similar way to a slider. When wrapping() is false (the default setting) there is no real difference between a slider and a dial. They both share the same signals, slots and member functions. Which one you use depends on the expectations of your users and on the type of application.

The dial initially emits valueChanged() signals continuously while the slider is being moved; you can make it emit the signal less often by disabling the tracking property. The sliderMoved() signal is emitted continuously even when tracking is disabled.

The dial also emits sliderPressed() and sliderReleased() signals when the mouse button is pressed and released. Note that the dial's value can change without these signals being emitted since the keyboard and wheel can also be used to change the value.

Unlike the slider, QDial attempts to draw a "nice" number of notches rather than one per line step. If possible, the number of notches drawn is one per line step, but if there aren't enough pixels to draw every one, QDial will skip notches to try and draw a uniform set (e.g. by drawing every second or third notch).

Like the slider, the dial makes the QAbstractSlider functions setValue(), addLine(), subtractLine(), addPage() and subtractPage() available as slots.

The dial's keyboard interface is fairly simple: The left/up and right/down arrow keys adjust the dial's value by the defined singleStep, Page Up and Page Down by the defined pageStep, and the Home and End keys set the value to the defined minimum and maximum values.

If you are using the mouse wheel to adjust the dial, the increment value is determined by the lesser value of wheelScrollLines multipled by singleStep, and pageStep.

Screenshot of a dial in the Plastique widget style Screenshot of a dial in the Windows XP widget style Screenshot of a dial in the Macintosh widget style
Dials shown in various widget styles (from left to right): Plastique, Windows XP, Macintosh.

Method Documentation

QDial.__init__ (self, QWidget parent = None)

The parent argument, if not None, causes self to be owned by Qt instead of PyQt.

Constructs a dial.

The parent argument is sent to the QAbstractSlider constructor.

bool QDial.event (self, QEvent e)

Reimplemented from QObject.event().

QDial.initStyleOption (self, QStyleOptionSlider option)

Initialize option with the values from this QDial. This method is useful for subclasses when they need a QStyleOptionSlider, but don't want to fill in all the information themselves.

See also QStyleOption.initFrom().

QSize QDial.minimumSizeHint (self)

Reimplemented from QWidget.minimumSizeHint().

QDial.mouseMoveEvent (self, QMouseEvent me)

Reimplemented from QWidget.mouseMoveEvent().

QDial.mousePressEvent (self, QMouseEvent me)

Reimplemented from QWidget.mousePressEvent().

QDial.mouseReleaseEvent (self, QMouseEvent me)

Reimplemented from QWidget.mouseReleaseEvent().

bool QDial.notchesVisible (self)

int QDial.notchSize (self)

float QDial.notchTarget (self)

QDial.paintEvent (self, QPaintEvent pe)

Reimplemented from QWidget.paintEvent().

QDial.resizeEvent (self, QResizeEvent re)

Reimplemented from QWidget.resizeEvent().

QDial.setNotchesVisible (self, bool visible)

This method is also a Qt slot with the C++ signature void setNotchesVisible(bool).

QDial.setNotchTarget (self, float target)

QDial.setWrapping (self, bool on)

This method is also a Qt slot with the C++ signature void setWrapping(bool).

QSize QDial.sizeHint (self)

Reimplemented from QWidget.sizeHint().

QDial.sliderChange (self, QAbstractSlider.SliderChange change)

Reimplemented from QAbstractSlider.sliderChange().

bool QDial.wrapping (self)

PyQt 4.9.4 for WindowsCopyright © Riverbank Computing Ltd and Nokia 2012Qt 4.8.2