QwtPolarGrid - An item which draws scales and grid lines on a polar plot.

NAME

QwtPolarGrid − An item which draws scales and grid lines on a polar plot.

SYNOPSIS

#include <qwt_polar_grid.h>

Inherits QwtPolarItem.

Public Types

enum DisplayFlag { SmartOriginLabel = 1, HideMaxRadiusLabel = 2, ClipAxisBackground = 4, SmartScaleDraw = 8, ClipGridLines = 16 }
enum GridAttribute { AutoScaling = 0x01 }
Grid attributes.
typedef QFlags< DisplayFlag > DisplayFlags
typedef QFlags< GridAttribute > GridAttributes

Public Types inherited from QwtPolarItem

enum RttiValues { Rtti_PolarItem = 0, Rtti_PolarGrid, Rtti_PolarMarker, Rtti_PolarCurve, Rtti_PolarSpectrogram, Rtti_PolarUserItem = 1000 }
Runtime type information.
enum ItemAttribute { Legend = 0x01, AutoScale = 0x02 }
Plot Item Attributes.
enum RenderHint { RenderAntialiased = 0x01 }
Render hints.
typedef QFlags< ItemAttribute > ItemAttributes
typedef QFlags< RenderHint > RenderHints

Public Member Functions

QwtPolarGrid ()
Constructor.
virtual ˜QwtPolarGrid ()
Destructor.
virtual int rtti () const override
void setDisplayFlag (DisplayFlag, bool on=true)
bool testDisplayFlag (DisplayFlag) const
void setGridAttribute (GridAttribute, bool on=true)
Specify an attribute for the grid.
bool testGridAttribute (GridAttribute) const
void showGrid (int scaleId, bool show=true)
bool isGridVisible (int scaleId) const
void showMinorGrid (int scaleId, bool show=true)
bool isMinorGridVisible (int scaleId) const
void showAxis (int axisId, bool show=true)
bool isAxisVisible (int axisId) const
void setPen (const QPen &p)
void setFont (const QFont &)
void setMajorGridPen (const QPen &p)
void setMajorGridPen (int scaleId, const QPen &p)
QPen majorGridPen (int scaleId) const
void setMinorGridPen (const QPen &p)
void setMinorGridPen (int scaleId, const QPen &p)
QPen minorGridPen (int scaleId) const
void setAxisPen (int axisId, const QPen &p)
QPen axisPen (int axisId) const
void setAxisFont (int axisId, const QFont &p)
QFont axisFont (int axisId) const
void setScaleDraw (int axisId, QwtScaleDraw *)
Set a scale draw.
const QwtScaleDraw * scaleDraw (int axisId) const
QwtScaleDraw * scaleDraw (int axisId)
void setAzimuthScaleDraw (QwtRoundScaleDraw *)
Set a scale draw for the azimuth scale.
const QwtRoundScaleDraw * azimuthScaleDraw () const
QwtRoundScaleDraw * azimuthScaleDraw ()
virtual void draw (QPainter *p, const QwtScaleMap &azimuthMap, const QwtScaleMap &radialMap, const QPointF &pole, double radius, const QRectF &rect) const override
virtual void updateScaleDiv (const QwtScaleDiv &azimuthMap, const QwtScaleDiv &radialMap, const QwtInterval &) override
Update the item to changes of the axes scale division.
virtual int marginHint () const override

Public Member Functions inherited from QwtPolarItem

QwtPolarItem (const QwtText &title=QwtText())
virtual ˜QwtPolarItem ()
Destroy the QwtPolarItem.
void attach (QwtPolarPlot *plot)
Attach the item to a plot.
void detach ()
This method detaches a QwtPolarItem from the QwtPolarPlot it has been associated with.
QwtPolarPlot * plot () const
void setTitle (const QString &title)
void setTitle (const QwtText &title)
const QwtText & title () const
void setItemAttribute (ItemAttribute, bool on=true)
bool testItemAttribute (ItemAttribute) const
void setRenderHint (RenderHint, bool on=true)
bool testRenderHint (RenderHint) const
void setRenderThreadCount (uint numThreads)
uint renderThreadCount () const
double z () const
void setZ (double z)
Set the z value.
void show ()
Show the item.
void hide ()
Hide the item.
virtual void setVisible (bool)
bool isVisible () const
virtual void itemChanged ()
virtual void legendChanged ()
virtual QwtInterval boundingInterval (int scaleId) const
void setLegendIconSize (const QSize &)
QSize legendIconSize () const
virtual QList< QwtLegendData > legendData () const
Return all information, that is needed to represent the item on the legend.
virtual QwtGraphic legendIcon (int index, const QSizeF &) const

Protected Member Functions

void drawRays (QPainter *, const QRectF &, const QPointF &pole, double radius, const QwtScaleMap &azimuthMap, const QList< double > &) const
void drawCircles (QPainter *, const QRectF &, const QPointF &pole, const QwtScaleMap &radialMap, const QList< double > &) const
void drawAxis (QPainter *, int axisId) const

Detailed Description

An item which draws scales and grid lines on a polar plot.

The QwtPolarGrid class can be used to draw a coordinate grid. A coordinate grid consists of major and minor gridlines. The locations of the gridlines are determined by the azimuth and radial scale divisions.

QwtPolarGrid is also responsible for drawing the axis representing the scales. It is possible to display 4 radial and one azimuth axis.

Whenever the scale divisions of the plot widget changes the grid is synchronized by updateScaleDiv().

See also

QwtPolarPlot, QwtPolar::Axis

Definition at line 41 of file qwt_polar_grid.h.

Member Typedef Documentation

typedef QFlags<DisplayFlag > QwtPolarGrid::DisplayFlags

An ORed combination of DisplayFlag values.

Definition at line 88 of file qwt_polar_grid.h.

typedef QFlags<GridAttribute > QwtPolarGrid::GridAttributes

An ORed combination of GridAttribute values.

Definition at line 103 of file qwt_polar_grid.h.

Member Enumeration Documentation

enum QwtPolarGrid::DisplayFlag

Mysterious flags trying to avoid conflicts, when painting the scales and grid lines.

The default setting enables all flags.

See also

setDisplayFlag(), testDisplayFlag()

Enumerator
SmartOriginLabel

Try to avoid situations, where the label of the origin is painted over another axis.

HideMaxRadiusLabel

Often the outermost tick of the radial scale is close to the canvas border. With HideMaxRadiusLabel enabled it is not painted.

ClipAxisBackground

The tick labels of the radial scales might be hard to read, when they are painted on top of the radial grid lines ( or on top of a curve/spectrogram ). When ClipAxisBackground the bounding rect of each label is added to the clip region.

SmartScaleDraw

Don’t paint the backbone of the radial axes, when they are very close to a line of the azimuth grid.

ClipGridLines

All grid lines are clipped against the plot area before being painted. When the plot is zoomed in this will have an significant impact on the performance of the painting code.

Definition at line 52 of file qwt_polar_grid.h.

enum QwtPolarGrid::GridAttribute

Grid attributes.

See also

setGridAttributes(), testGridAttributes()

Enumerator
AutoScaling

When AutoScaling is enabled, the radial axes will be adjusted to the interval, that is currently visible on the canvas plot.

Definition at line 94 of file qwt_polar_grid.h.

Constructor & Destructor Documentation

QwtPolarGrid::QwtPolarGrid () [explicit]

Constructor. Enables major and disables minor grid lines. The azimuth and right radial axis are visible. all other axes are hidden. Autoscaling is enabled.

Definition at line 84 of file qwt_polar_grid.cpp.

QwtPolarGrid::˜QwtPolarGrid () [virtual]

Destructor.

Definition at line 157 of file qwt_polar_grid.cpp.

Member Function Documentation

QFont QwtPolarGrid::axisFont (int axisId) const

Returns

Font for the tick labels of a specific axis

Parameters

axisId Axis id (QwtPolar::Axis)

Definition at line 556 of file qwt_polar_grid.cpp.

QPen QwtPolarGrid::axisPen (int axisId) const

Returns

Pen for painting a specific axis

Parameters

axisId Axis id (QwtPolar::Axis)

See also

setAxisPen()

Definition at line 525 of file qwt_polar_grid.cpp.

QwtRoundScaleDraw * QwtPolarGrid::azimuthScaleDraw ()

Returns

Scale draw for the azimuth scale

See also

setAzimuthScaleDraw(), scaleDraw()

Definition at line 1127 of file qwt_polar_grid.cpp.

const QwtRoundScaleDraw * QwtPolarGrid::azimuthScaleDraw () const

Returns

Scale draw for the azimuth scale

See also

setAzimuthScaleDraw(), scaleDraw()

Definition at line 1117 of file qwt_polar_grid.cpp.

void QwtPolarGrid::draw (QPainter * painter, const QwtScaleMap &azimuthMap, const QwtScaleMap & radialMap, const QPointF & pole, doubleradius, const QRectF & canvasRect) const [override], [virtual]

Draw the grid and axes

Parameters

painter Painter
azimuthMap Maps azimuth values to values related to 0.0, M_2PI
radialMap Maps radius values into painter coordinates.
pole Position of the pole in painter coordinates
radius Radius of the complete plot area in painter coordinates
canvasRect Contents rect of the canvas in painter coordinates

Implements QwtPolarItem.

Definition at line 574 of file qwt_polar_grid.cpp.

void QwtPolarGrid::drawAxis (QPainter * painter, int axisId) const[protected]

Paint an axis

Parameters

painter Painter
axisId Axis id (QwtPolar::Axis)

Definition at line 832 of file qwt_polar_grid.cpp.

void QwtPolarGrid::drawCircles (QPainter * painter, const QRectF &canvasRect, const QPointF & pole, const QwtScaleMap & radialMap, constQList< double > & values) const [protected]

Draw circles

Parameters

Returns

Number of pixels, that are necessary to paint the azimuth scale

See also

QwtRoundScaleDraw::extent()

Reimplemented from QwtPolarItem.

Definition at line 1049 of file qwt_polar_grid.cpp.

QPen QwtPolarGrid::minorGridPen (int scaleId) const

Returns

Pen for painting the minor grid lines of a specific scale

Change the display flags

Parameters

flag See DisplayFlag
on true/false

Definition at line 174 of file qwt_polar_grid.cpp.

void QwtPolarGrid::setFont (const QFont & font)

Assign a font for all scale tick labels

Parameters

font Font

See also

setAxisFont()

Definition at line 390 of file qwt_polar_grid.cpp.

Show/Hide grid lines for a scale

Parameters

scaleId Scale id ( QwtPolar::Scale )
show true/false

Definition at line 254 of file qwt_polar_grid.cpp.

void QwtPolarGrid::showMinorGrid (int scaleId, bool show = true)

Show/Hide minor grid lines for a scale

To display minor grid lines. showGrid() needs to be enabled too.

Parameters

scaleId Scale id ( QwtPolar::Scale )
show true/false

See also

showGrid

Definition at line 290 of file qwt_polar_grid.cpp.

bool QwtPolarGrid::testDisplayFlag (DisplayFlag flag) const

Returns

true, if flag is enabled

Parameters

flag See DisplayFlag

Definition at line 191 of file qwt_polar_grid.cpp.

bool QwtPolarGrid::testGridAttribute (GridAttribute attribute) const

Returns

true, if attribute is enabled

See also

GridAttribute, setGridAttribute()

Definition at line 222 of file qwt_polar_grid.cpp.

void QwtPolarGrid::updateScaleDiv (const QwtScaleDiv & azimuthScaleDiv,const QwtScaleDiv & radialScaleDiv, const QwtInterval & interval)[override], [virtual]

Update the item to changes of the axes scale division. If AutoScaling is enabled the radial scale is calculated from the interval, otherwise the scales are adopted to the plot scales.

Parameters

azimuthScaleDiv Scale division of the azimuth-scale
radialScaleDiv Scale division of the radius-axis
interval The interval of the radius-axis, that is visible on the canvas

See also

QwtPolarPlot::setGridAttributes()

Reimplemented from QwtPolarItem.

Definition at line 952 of file qwt_polar_grid.cpp.

Author

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Updated 2026-06-01 - jenkler.se | uex.se