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QCPItemTracer Class Reference

Item that sticks to QCPGraph data points. More...

#include <plot2d.h>

Inheritance diagram for QCPItemTracer:
QCPAbstractItem QCPLayerable

Public Types

enum  TracerStyle {
  tsNone, tsPlus, tsCrosshair, tsCircle,

Public Member Functions

 QCPItemTracer (QCustomPlot *parentPlot)
virtual ~QCPItemTracer ()
QPen pen () const
QPen selectedPen () const
QBrush brush () const
QBrush selectedBrush () const
double size () const
TracerStyle style () const
QCPGraphgraph () const
double graphKey () const
bool interpolating () const
void setPen (const QPen &pen)
void setSelectedPen (const QPen &pen)
void setBrush (const QBrush &brush)
void setSelectedBrush (const QBrush &brush)
void setSize (double size)
void setStyle (TracerStyle style)
void setGraph (QCPGraph *graph)
void setGraphKey (double key)
void setInterpolating (bool enabled)
virtual double selectTest (const QPointF &pos) const
void updatePosition ()
- Public Member Functions inherited from QCPAbstractItem
 QCPAbstractItem (QCustomPlot *parentPlot)
virtual ~QCPAbstractItem ()
bool clipToAxisRect () const
QCPAxisclipKeyAxis () const
QCPAxisclipValueAxis () const
bool selectable () const
bool selected () const
void setClipToAxisRect (bool clip)
void setClipAxes (QCPAxis *keyAxis, QCPAxis *valueAxis)
void setClipKeyAxis (QCPAxis *axis)
void setClipValueAxis (QCPAxis *axis)
void setSelectable (bool selectable)
void setSelected (bool selected)
QList< QCPItemPosition * > positions () const
QList< QCPItemAnchor * > anchors () const
QCPItemPositionposition (const QString &name) const
QCPItemAnchoranchor (const QString &name) const
bool hasAnchor (const QString &name) const
- Public Member Functions inherited from QCPLayerable
 QCPLayerable (QCustomPlot *parentPlot)
 ~QCPLayerable ()
bool visible () const
QCustomPlotparentPlot () const
QCPLayerlayer () const
bool antialiased () const
void setVisible (bool on)
bool setLayer (QCPLayer *layer)
bool setLayer (const QString &layerName)
void setAntialiased (bool enabled)

Public Attributes

QCPItemPosition *const position

Protected Member Functions

virtual void draw (QCPPainter *painter)
QPen mainPen () const
QBrush mainBrush () const
- Protected Member Functions inherited from QCPAbstractItem
virtual QRect clipRect () const
virtual void applyDefaultAntialiasingHint (QCPPainter *painter) const
double distSqrToLine (const QPointF &start, const QPointF &end, const QPointF &point) const
double rectSelectTest (const QRectF &rect, const QPointF &pos, bool filledRect) const
virtual QPointF anchorPixelPoint (int anchorId) const
QCPItemPositioncreatePosition (const QString &name)
QCPItemAnchorcreateAnchor (const QString &name, int anchorId)
- Protected Member Functions inherited from QCPLayerable
bool moveToLayer (QCPLayer *layer, bool prepend)
void applyAntialiasingHint (QCPPainter *painter, bool localAntialiased, QCP::AntialiasedElement overrideElement) const

Protected Attributes

QPen mPen
QPen mSelectedPen
QBrush mBrush
QBrush mSelectedBrush
double mSize
TracerStyle mStyle
double mGraphKey
bool mInterpolating
- Protected Attributes inherited from QCPAbstractItem
bool mClipToAxisRect
bool mSelectable
bool mSelected
QList< QCPItemPosition * > mPositions
QList< QCPItemAnchor * > mAnchors
- Protected Attributes inherited from QCPLayerable
bool mVisible
bool mAntialiased

Additional Inherited Members

- Signals inherited from QCPAbstractItem
void selectionChanged (bool selected)

Detailed Description

Item that sticks to QCPGraph data points.

Tracer example. Blue dotted circles are anchors, solid blue discs are positions.

The tracer can be connected with a QCPGraph via setGraph. Then it will automatically adopt the coordinate axes of the graph and update its position to be on the graph's data. This means the key stays controllable via setGraphKey, but the value will follow the graph data. If a QCPGraph is connected, note that setting the coordinates directly via position will have no effect, i.e. be overriden in the next redraw (this is when the coodinate update happens).

If the specified key in setGraphKey is outside the key bounds of the graph, the tracer will stay at the respective end of the graph.

With setInterpolating you may specify whether the tracer may only stay exactly on data points or whether it interpolates data points linearly, if given a key that lies between two data points of the graph.

The tracer has different visual styles, see setStyle. It is also possible to make the tracer have no own visual appearance (set the style to tsNone), and just connect other item positions to the tracer position (used as an anchor) via QCPItemPosition::setParentAnchor.

The tracer position is only automatically updated upon redraws. This means when, for example, the data of the graph changes and you immediately afterwards (without a redraw) read the position coordinates of the tracer, they will not reflect the updated data of the graph. In this case you should call updatePosition manually, prior to reading the tracer coordinates.

Member Enumeration Documentation

The different visual appearances a tracer item can have. Some styles size may be controlled with setSize.

See Also

The tracer is not visible.


A plus shaped crosshair with limited size.


A plus shaped crosshair which spans the complete axis rect.


A circle.


A square.

Constructor & Destructor Documentation

QCPItemTracer::QCPItemTracer ( QCustomPlot parentPlot)

Creates a tracer item and sets default values.

The constructed item can be added to the plot with QCustomPlot::addItem.

QCPItemTracer::~QCPItemTracer ( )

Member Function Documentation

QBrush QCPItemTracer::brush ( ) const
void QCPItemTracer::draw ( QCPPainter painter)

Implements QCPAbstractItem.

QCPGraph* QCPItemTracer::graph ( ) const
double QCPItemTracer::graphKey ( ) const
bool QCPItemTracer::interpolating ( ) const
QBrush QCPItemTracer::mainBrush ( ) const
QPen QCPItemTracer::mainPen ( ) const
QPen QCPItemTracer::pen ( ) const
QBrush QCPItemTracer::selectedBrush ( ) const
QPen QCPItemTracer::selectedPen ( ) const
double QCPItemTracer::selectTest ( const QPointF &  pos) const

This function is used to decide whether a click hits an item or not.

pos is a point in pixel coordinates on the QCustomPlot surface. This function returns the shortest pixel distance of this point to the item. If the item is either invisible or the distance couldn't be determined, -1.0 is returned. setSelectable has no influence on the return value of this function.

If the item is represented not by single lines but by an area like QCPItemRect or QCPItemText, a click inside the area returns a constant value greater zero (typically 99% of the selectionTolerance of the parent QCustomPlot). If the click lies outside the area, this function returns -1.0.

Providing a constant value for area objects allows selecting line objects even when they are obscured by such area objects, by clicking close to the lines (i.e. closer than 0.99*selectionTolerance).

The actual setting of the selection state is not done by this function. This is handled by the parent QCustomPlot when the mouseReleaseEvent occurs.

See Also
setSelected, QCustomPlot::setInteractions

Implements QCPAbstractItem.

void QCPItemTracer::setBrush ( const QBrush &  brush)

Sets the brush that will be used to draw any fills of the tracer

See Also
setSelectedBrush, setPen
void QCPItemTracer::setGraph ( QCPGraph graph)

Sets the QCPGraph this tracer sticks to. The tracer position will be set to type QCPItemPosition::ptPlotCoords and the axes will be set to the axes of graph.

To free the tracer from any graph, set graph to 0. The tracer position can then be placed freely like any other item position. This is the state the tracer will assume when its graph gets deleted while still attached to it.

See Also
void QCPItemTracer::setGraphKey ( double  key)

Sets the key of the graph's data point the tracer will be positioned at. This is the only free cordinate of a tracer when attached to a graph.

Depending on setInterpolating, the tracer will be either positioned on the data point closest to key, or will stay exactly at key and interpolate the value linearly.

See Also
setGraph, setInterpolating
void QCPItemTracer::setInterpolating ( bool  enabled)

Sets whether the value of the graph's data points shall be interpolated, when positioning the tracer.

If enabled is set to false and a key is given with setGraphKey, the tracer is placed on the data point of the graph which is closest to the key, but which is not necessarily exactly there. If enabled is true, the tracer will be positioned exactly at the specified key, and the appropriate value will be interpolated from the graph's data points linearly.

See Also
setGraph, setGraphKey
void QCPItemTracer::setPen ( const QPen &  pen)

Sets the pen that will be used to draw the line of the tracer

See Also
setSelectedPen, setBrush
void QCPItemTracer::setSelectedBrush ( const QBrush &  brush)

Sets the brush that will be used to draw any fills of the tracer, when selected.

See Also
setBrush, setSelected
void QCPItemTracer::setSelectedPen ( const QPen &  pen)

Sets the pen that will be used to draw the line of the tracer when selected

See Also
setPen, setSelected
void QCPItemTracer::setSize ( double  size)

Sets the size of the tracer in pixels, if the style supports setting a size (e.g. tsSquare does, tsCrosshair does not).

void QCPItemTracer::setStyle ( QCPItemTracer::TracerStyle  style)

Sets the style/visual appearance of the tracer.

If you only want to use the tracer position as an anchor for other items, set style to tsNone.

double QCPItemTracer::size ( ) const
TracerStyle QCPItemTracer::style ( ) const
void QCPItemTracer::updatePosition ( )

If the tracer is connected with a graph (setGraph), this function updates the tracer's position to reside on the graph data, depending on the configured key (setGraphKey).

It is called automatically on every redraw and normally doesn't need to be called manually. One exception is when you want to read the tracer coordinates via position and are not sure that the graph's data (or the tracer key with setGraphKey) hasn't changed since the last redraw. In that situation, call this function before accessing position, to make sure you don't get out-of-date coordinates.

If there is no graph set on this tracer, this function does nothing.

Member Data Documentation

QBrush QCPItemTracer::mBrush
QCPGraph* QCPItemTracer::mGraph
double QCPItemTracer::mGraphKey
bool QCPItemTracer::mInterpolating
QPen QCPItemTracer::mPen
QBrush QCPItemTracer::mSelectedBrush
QPen QCPItemTracer::mSelectedPen
double QCPItemTracer::mSize
TracerStyle QCPItemTracer::mStyle
QCPItemPosition* const QCPItemTracer::position

The documentation for this class was generated from the following files: