QPieSlice Class

The QPieSlice class represents a single slice in a pie series. More...

Header: #include <QPieSlice>
CMake: find_package(Qt6 REQUIRED COMPONENTS Graphs)
target_link_libraries(mytarget PRIVATE Qt6::Graphs)
qmake: QT += graphs
Instantiated By: PieSlice
Inherits: QObject

Public Types

enum class LabelPosition { Outside, InsideHorizontal, InsideTangential, InsideNormal }

Properties

Public Functions

QPieSlice(QObject *parent = nullptr)
QPieSlice(const QString &label, qreal value, QObject *parent = nullptr)
virtual ~QPieSlice() override
qreal angleSpan() const
QColor borderColor() const
qreal borderWidth() const
QColor color() const
qreal explodeDistanceFactor() const
bool isExploded() const
bool isLabelVisible() const
QString label() const
qreal labelArmLengthFactor() const
QColor labelColor() const
QFont labelFont() const
QPieSlice::LabelPosition labelPosition()
qreal percentage() const
QPieSeries *series() const
void setBorderColor(QColor color)
void setBorderWidth(qreal borderWidth)
void setColor(QColor color)
void setExplodeDistanceFactor(qreal factor)
void setExploded(bool exploded)
void setLabel(const QString &label)
void setLabelArmLengthFactor(qreal factor)
void setLabelColor(QColor color)
void setLabelFont(const QFont &font)
void setLabelPosition(QPieSlice::LabelPosition position)
void setLabelVisible(bool visible = true)
void setValue(qreal value)
qreal startAngle() const
qreal value() const

Signals

void angleSpanChanged()
void borderColorChanged()
void borderWidthChanged()
void colorChanged()
void explodeDistanceFactorChanged()
void explodedChanged()
void labelArmLengthFactorChanged()
void labelChanged()
void labelColorChanged()
void labelFontChanged()
void labelPositionChanged()
void labelVisibleChanged()
void percentageChanged()
void startAngleChanged()
void valueChanged()

Detailed Description

A pie slice has a value and a label. When the slice is added to a pie series, the QPieSeries object calculates the percentage of the slice compared with the sum of all slices in the series to determine the actual size of the slice in the graph.

By default, the label is hidden. If it is visible, it can be either located outside the slice and connected to it with an arm or centered inside the slice either horizontally or in parallel with the tangential or normal of the slice's arc.

By default, the visual appearance of the slice is set by a theme, but the theme can be overridden by specifying slice properties. However, if the theme is changed after the slices are customized, all customization will be lost.

To enable user interaction with the pie graph, some basic signals are emitted when users click pie slices or hover the mouse over them.

See also QPieSeries.

Member Type Documentation

enum class QPieSlice::LabelPosition

This enum describes the position of the slice label.

ConstantValueDescription
QPieSlice::LabelPosition::Outside0The label is located outside the slice connected to it with an arm. This is the default value.
QPieSlice::LabelPosition::InsideHorizontal1The label is centered within the slice and laid out horizontally.
QPieSlice::LabelPosition::InsideTangential2The label is centered within the slice and rotated to be parallel with the tangential of the slice's arc.
QPieSlice::LabelPosition::InsideNormal3The label is centered within the slice and rotated to be parallel with the normal of the slice's arc.

Property Documentation

[read-only] angleSpan : const qreal

This property holds the span of the slice in degrees. A full pie is 360 degrees, where 0 degrees is at 12 a'clock. Updated automatically once the slice is added to the series.

Access functions:

qreal angleSpan() const

Notifier signal:

void angleSpanChanged()

borderColor : QColor

This property holds the color used to draw the slice border. This is a convenience property for modifying the slice.

Access functions:

QColor borderColor() const
void setBorderColor(QColor color)

Notifier signal:

void borderColorChanged()

See also borderWidth.

borderWidth : qreal

This property holds the width of the slice border. This is a convenience property for modifying the slice border width.

Access functions:

qreal borderWidth() const
void setBorderWidth(qreal borderWidth)

Notifier signal:

void borderWidthChanged()

See also borderColor.

color : QColor

This property holds the fill color of the slice. This is a convenience property for modifying the slice fill color.

Access functions:

QColor color() const
void setColor(QColor color)

Notifier signal:

void colorChanged()

explodeDistanceFactor : qreal

Determines how far away from the pie the slice is exploded.

  • 1.0 means that the distance is the same as the radius.
  • 0.5 means that the distance is half of the radius.

By default, the distance is 0.15

Access functions:

qreal explodeDistanceFactor() const
void setExplodeDistanceFactor(qreal factor)

Notifier signal:

void explodeDistanceFactorChanged()

See also exploded.

exploded : bool

This property holds whether the slice is separated from the pie.

Access functions:

bool isExploded() const
void setExploded(bool exploded)

Notifier signal:

void explodedChanged()

See also explodeDistanceFactor.

label : QString

This property holds the label of the slice.

Note: The string can be HTML formatted.

Access functions:

QString label() const
void setLabel(const QString &label)

Notifier signal:

void labelChanged()

See also labelVisible, labelFont, and labelArmLengthFactor.

labelArmLengthFactor : qreal

This property holds the length of the label arm. The factor is relative to the pie radius. For example:

  • 1.0 means that the length is the same as the radius.
  • 0.5 means that the length is half of the radius.

By default, the arm length is 0.15

Access functions:

qreal labelArmLengthFactor() const
void setLabelArmLengthFactor(qreal factor)

Notifier signal:

void labelArmLengthFactorChanged()

See also label, labelVisible, and labelFont.

labelColor : QColor

This property holds the color used to draw the slice label.

Access functions:

QColor labelColor() const
void setLabelColor(QColor color)

Notifier signal:

void labelColorChanged()

labelFont : QFont

This property holds the font used for drawing the label text.

Access functions:

QFont labelFont() const
void setLabelFont(const QFont &font)

Notifier signal:

void labelFontChanged()

See also label, labelVisible, and labelArmLengthFactor.

labelPosition : LabelPosition

This property holds the position of the slice label.

Access functions:

QPieSlice::LabelPosition labelPosition()
void setLabelPosition(QPieSlice::LabelPosition position)

Notifier signal:

void labelPositionChanged()

See also label and labelVisible.

labelVisible : bool

This property holds the visibility of the slice label. By default, the label is not visible.

Access functions:

bool isLabelVisible() const
void setLabelVisible(bool visible = true)

Notifier signal:

void labelVisibleChanged()

See also label, labelFont, and labelArmLengthFactor.

[read-only] percentage : const qreal

This property holds the percentage of the slice compared to the sum of all slices in the series. The actual value ranges from 0.0 to 1.0. Updated automatically once the slice is added to the series.

Access functions:

qreal percentage() const

Notifier signal:

void percentageChanged()

See also value and QPieSeries::sum.

[read-only] startAngle : const qreal

This property holds the starting angle of this slice in the series it belongs to. A full pie is 360 degrees, where 0 degrees is at 12 a'clock. Updated automatically once the slice is added to the series.

Access functions:

qreal startAngle() const

Notifier signal:

void startAngleChanged()

value : qreal

This property holds the value of the slice.

Note: A negative value is converted to a positive value.

Access functions:

qreal value() const
void setValue(qreal value)

Notifier signal:

void valueChanged()

See also percentage() and QPieSeries::sum().

Member Function Documentation

[explicit] QPieSlice::QPieSlice(QObject *parent = nullptr)

Constructs an empty slice with the parent parent.

See also QPieSeries::append() and QPieSeries::insert().

QPieSlice::QPieSlice(const QString &label, qreal value, QObject *parent = nullptr)

Constructs an empty slice with the specified value, label, and parent.

See also QPieSeries::append() and QPieSeries::insert().

[override virtual noexcept] QPieSlice::~QPieSlice()

Removes the slice. The slice should not be removed if it has been added to a series.

QPieSeries *QPieSlice::series() const

Returns the series that this slice belongs to.

See also QPieSeries::append().

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