A 2-D plotting widget. More...

#include <qwt_plot.h>

Inheritance diagram for QwtPlot:

Classes
class	PrivateData

class	ScaleData

Public Types
enum	LegendPosition { LeftLegend , RightLegend , BottomLegend , TopLegend }
	Position of the legend, relative to the canvas. More...

enum	TickDirection { TickOutside = 0 , TickInside = 1 }
	Tick direction enum. More...

enum	Axis { yLeft = QwtAxis::YLeft , yRight = QwtAxis::YRight , xBottom = QwtAxis::XBottom , xTop = QwtAxis::XTop , axisCnt = QwtAxis::AxisPositions }

Public Slots
virtual void	replot ()
	Redraw the plot.

void	autoRefresh ()
	Replots the plot if autoReplot() is enabled.

virtual void	replotAll ()
	Replot all plots.

void	autoRefreshAll ()

Signals
void	itemAttached (QwtPlotItem *plotItem, bool on)
	A signal indicating that an item has been attached/detached.

void	legendDataChanged (const QVariant &itemInfo, const QList< QwtLegendData > &data)
	A signal with the attributes how to update the legend entries for a plot item.

void	parasitePlotAttached (QwtPlot *parasitePlot, bool on)
	Identify the relationship between the parasitic plot and its host plot.

Public Member Functions
	QwtPlot (QWidget *=nullptr)
	Constructor.

	QwtPlot (const QwtText &title, QWidget *=nullptr)

void	setAutoReplot (bool=true)
	Set or reset the autoReplot option.

bool	autoReplot () const
	Check if autoReplot option is enabled.

QString	plotId () const
	Plot ID.

void	setPlotId (const QString &id)

void	setPlotLayout (QwtPlotLayout *)
	Assign a new plot layout.

QwtPlotLayout *	plotLayout ()
	Get the plot's layout.

const QwtPlotLayout *	plotLayout () const
	Get the plot's layout.

void	setTitle (const QString &)
	Change the plot's title.

void	setTitle (const QwtText &)
	Change the plot's title.

QwtText	title () const
	Get the plot's title.

QwtTextLabel *	titleLabel ()
	Get the title label widget.

const QwtTextLabel *	titleLabel () const
	Get the title label widget.

void	setFooter (const QString &)
	Change the footer text.

void	setFooter (const QwtText &)
	Change the footer text.

QwtText	footer () const
	Get the footer text.

QwtTextLabel *	footerLabel ()
	Get the footer label widget.

const QwtTextLabel *	footerLabel () const
	Get the footer label widget.

void	setCanvas (QWidget *)
	Set the drawing canvas of the plot widget.

QWidget *	canvas ()
	Get the plot's canvas.

const QWidget *	canvas () const
	Get the plot's canvas.

void	setCanvasBackground (const QBrush &)
	Change the background of the plotting area.

QBrush	canvasBackground () const
	Nothing else than: canvas()->palette().brush( QPalette::Normal, QPalette::Window);.

void	setColorCycle (const QwtColorCycle &)
	Set the color cycle used for automatic item coloring.

QwtColorCycle	colorCycle () const
	Get the current color cycle.

QColor	nextColorForItem (int rtti)
	Get the next auto-assigned color for a plot item type.

virtual QwtScaleMap	canvasMap (QwtAxisId) const

double	invTransform (QwtAxisId, double pos) const
	Transform the x or y coordinate of a position in the drawing region into a value.

double	transform (QwtAxisId, double value) const
	Transform a value into a coordinate in the plotting region.

bool	isAxisValid (QwtAxisId) const
	Checks if an axis is valid.

void	setAxisVisible (QwtAxisId, bool on=true)
	Hide or show a specified axis.

bool	isAxisVisible (QwtAxisId) const
	Return whether the specified axis is visible.

QwtScaleEngine *	axisScaleEngine (QwtAxisId)
	Return the scale engine for a specific axis.

const QwtScaleEngine *	axisScaleEngine (QwtAxisId) const
	Return the scale engine for a specific axis (const overload)

void	setAxisScaleEngine (QwtAxisId, QwtScaleEngine *)
	Change the scale engine for an axis.

void	setAxisAutoScale (QwtAxisId, bool on=true)
	Enable autoscaling for a specified axis.

bool	axisAutoScale (QwtAxisId) const
	Return whether autoscaling is enabled.

void	setAxisFont (QwtAxisId, const QFont &)
	Change the font of an axis.

QFont	axisFont (QwtAxisId) const
	Return the font of the scale labels for a specified axis.

void	setAxisScale (QwtAxisId, double min, double max, double stepSize=0)
	Disable autoscaling and specify a fixed scale for a selected axis.

void	setAxisScaleDiv (QwtAxisId, const QwtScaleDiv &)
	Disable autoscaling and specify a fixed scale for a selected axis.

void	setAxisScaleDraw (QwtAxisId, QwtScaleDraw *)
	Set a scale draw.

double	axisStepSize (QwtAxisId) const
	Return the step size parameter that has been set in setAxisScale.

QwtInterval	axisInterval (QwtAxisId) const
	Return the current interval of the specified axis.

const QwtScaleDiv &	axisScaleDiv (QwtAxisId) const
	Return the scale division of a specified axis.

const QwtScaleDraw *	axisScaleDraw (QwtAxisId) const
	Return the scale draw of a specified axis.

QwtScaleDraw *	axisScaleDraw (QwtAxisId)
	Return the scale draw of a specified axis.

const QwtScaleWidget *	axisWidget (QwtAxisId) const
	Return the scale widget of the specified axis.

QwtScaleWidget *	axisWidget (QwtAxisId)
	Return the scale widget of the specified axis.

QwtAxisId	visibleXAxisId () const
	Return the currently visible X axis.

QwtAxisId	visibleYAxisId () const
	Return the currently usable Y axis.

void	setAxisLabelAlignment (QwtAxisId, Qt::Alignment)
	Change the alignment of the tick labels.

void	setAxisLabelRotation (QwtAxisId, double rotation)
	Rotate all tick labels.

void	setAxisTitle (QwtAxisId, const QString &)
	Change the title of a specified axis.

void	setAxisTitle (QwtAxisId, const QwtText &)
	Change the title of a specified axis.

QwtText	axisTitle (QwtAxisId) const
	Get the title of a specified axis.

void	setAxisMaxMinor (QwtAxisId, int maxMinor)
	Set the maximum number of minor scale intervals for a specified axis.

int	axisMaxMinor (QwtAxisId) const
	Return the maximum number of minor ticks for a specified axis.

void	setAxisMaxMajor (QwtAxisId, int maxMajor)
	Set the maximum number of major scale intervals for a specified axis.

int	axisMaxMajor (QwtAxisId) const
	Return the maximum number of major ticks for a specified axis.

void	setAxisTickDirection (QwtAxisId axisId, TickDirection direction)
	Set the tick direction for an axis.

TickDirection	axisTickDirection (QwtAxisId axisId) const
	Get the tick direction for an axis.

void	insertLegend (QwtAbstractLegend *, LegendPosition=QwtPlot::RightLegend, double ratio=-1.0)
	Insert a legend.

QwtAbstractLegend *	legend ()
	Get the plot's legend.

const QwtAbstractLegend *	legend () const
	Get the plot's legend.

void	updateLegend ()
	Emit legendDataChanged() for all plot item.

void	updateLegend (const QwtPlotItem *)
	Emit legendDataChanged() for a plot item.

virtual QSize	sizeHint () const override

virtual QSize	minimumSizeHint () const override
	Return a minimum size hint.

virtual void	updateLayout ()
	Adjust plot content to its current size.

virtual void	drawCanvas (QPainter *)
	Redraw the canvas.

void	updateAxes ()
	Rebuild the axes scales.

void	updateCanvasMargins ()
	Update the canvas margins.

virtual void	getCanvasMarginsHint (const QwtScaleMap maps[], const QRectF &canvasRect, double &left, double &top, double &right, double &bottom) const
	Calculate the canvas margins.

virtual bool	event (QEvent *) override
	Adds handling of layout requests.

virtual bool	eventFilter (QObject , QEvent ) override
	Event filter.

virtual void	drawItems (QPainter *, const QRectF &, const QwtScaleMap maps[QwtAxis::AxisPositions]) const
	Redraw the canvas items.

virtual QVariant	itemToInfo (QwtPlotItem *) const
	Build an information, that can be used to identify a plot item on the legend.

virtual QwtPlotItem *	infoToItem (const QVariant &) const
	Identify the plot item according to an item info object, that has bee generated from itemToInfo().

QwtPlot *	createParasitePlot (QwtAxis::Position enableAxis)
	Create parasite axes for this plot.

void	setParasiteShareAxis (QwtAxisId axisId, bool isShare=true)
	Set whether the parasite axis shares the host's specified axis, only valid for parasite axes.

bool	isParasiteShareAxis (QwtAxisId axisId) const
	Query whether the parasite axis shares the host's specified axis.

void	removeParasitePlot (QwtPlot *parasite)
	Remove a parasite plot from this host plot.

QList< QwtPlot * >	parasitePlots () const
	Get all parasite plots associated with this host plot.

QList< QwtPlot * >	plotList (bool descending=false) const
	Return all plots, including the host plot.

QwtPlot *	parasitePlotAt (int index) const
	Get the nth parasite plot.

int	parasitePlotIndex (QwtPlot *parasite) const
	Parasite plot index (level)

QwtPlot *	hostPlot () const
	Get the host plot for this parasite plot.

bool	isParasitePlot () const
	Check if this plot is a parasite plot.

bool	isTopParasitePlot () const
	Whether this is the topmost parasite plot; the topmost parasite's axes are at the outermost layer and are typically updated last.

bool	isHostPlot () const
	Check if this plot is a host plot.

void	setBackgroundColor (const QColor &c)
	Set background color.

QColor	backgroundColor () const
	Get background color.

void	syncAxis (QwtAxisId axis, const QwtPlot *plot)
	Synchronize the axis ranges from the given plot to this plot.

void	rescaleAxes (bool onlyVisibleItems=true, double marginPercent=0.05, QwtAxisId xAxis=QwtPlot::xBottom, QwtAxisId yAxis=QwtPlot::yLeft)
	Rescale axes to fit all data items.

void	setAxisToLogScale (QwtAxisId axisId)
	Set the specified axis to logarithmic scale.

void	setAxisToDateTime (QwtAxisId axisId, Qt::TimeSpec timeSpec=Qt::LocalTime)
	Set the specified axis to date-time scale.

void	setAxisToLinearScale (QwtAxisId axisId)
	Restore the specified axis to linear scale.

void	alignToHost ()
	Align the parasite plot to the host plot.

int	parasitePlotCount () const
	Get the number of parasite plots.

void	updateAxisEdgeMargin (QwtAxisId axisId)
	Recalculate and assign edgeMargin and margin for all layers (host + parasite) axes based on level order.

void	updateAllAxisEdgeMargin ()
	Batch update edge offsets for all axis positions.

void	updateItemsToScaleDiv ()
	Update the scale range of all plot items to match the current axis scales.

void	setEnableScaleBuildinActions (bool on)
	Enable or disable built-in axis event actions.

bool	isEnableScaleBuildinActions () const
	Check if built-in axis event actions are enabled.

void	setupScaleEventDispatcher (QwtPlotScaleEventDispatcher *dispatcher)
	Install the axis event dispatcher.

void	saveAutoReplotState ()
	Save the current autoReplot state.

void	restoreAutoReplotState ()
	Restore the previously saved autoReplot state.

void	panAxis (QwtAxisId axisId, int deltaPixels)
	Pan the specified axis by a given number of pixels.

void	panCanvas (const QPoint &offset)
	Pan the entire canvas by a pixel offset.

void	zoomAxis (QwtAxisId axisId, double factor, const QPoint &centerPosPixels)
	Zoom the axis centered at the specified pixel position.

void	enableAxis (int axisId, bool on=true)

bool	axisEnabled (int axisId) const

Public Member Functions inherited from QwtPlotDict
	QwtPlotDict ()
	Constructor.

void	setAutoDelete (bool)
	Enable/disable auto deletion.

bool	autoDelete () const
	Check if auto deletion is enabled.

const QwtPlotItemList &	itemList () const
	Get the list of all attached plot items.

QwtPlotItemList	itemList (int rtti) const
	Get the list of all attached plot items of a specific type.

void	detachItems (int rtti=QwtPlotItem::Rtti_PlotItem, bool autoDelete=true)
	Detach items from the dictionary.

Protected Member Functions
virtual void	resizeEvent (QResizeEvent *) override
	Resize and update internal layout.

void	addParasitePlot (QwtPlot *parasite)
	Add a parasite plot to this host plot.

void	initParasiteAxes (QwtPlot *parasitePlot) const
	Initialize basic properties of the parasite axes.

void	doLayout ()
	Adjust plot content to its current size.

void	drawInsideTicks (QPainter *, const QRectF &canvasRect, const QwtScaleMap maps[QwtAxis::AxisPositions]) const
	Draw inside ticks for axes with TickInside direction.

Protected Member Functions inherited from QwtPlotDict
void	insertItem (QwtPlotItem *)
	Insert an item into the dictionary.

void	removeItem (QwtPlotItem *)
	Remove an item from the dictionary.

Properties
QBrush	canvasBackground

bool	autoReplot

Friends
class	QwtFigure

class	QwtPlotItem

Detailed Description

A 2-D plotting widget.

QwtPlot is a widget for plotting two-dimensional graphs. An unlimited number of plot items can be displayed on its canvas. Plot items might be curves (QwtPlotCurve), markers (QwtPlotMarker), the grid (QwtPlotGrid), or anything else derived from QwtPlotItem. A plot can have up to four axes, with each plot item attached to an x- and a y axis. The scales at the axes can be explicitly set (QwtScaleDiv), or are calculated from the plot items, using algorithms (QwtScaleEngine) which can be configured separately for each axis.

The simpleplot example is a good starting point to see how to set up a plot widget.

Example: The following example shows (schematically) the most simple way to use QwtPlot. By default, only the left and bottom axes are visible and their scales are computed automatically.
#include <qwt_plot.h>

#include <qwt_plot_curve.h>

QwtPlot *myPlot = new QwtPlot( "Two Curves", parent );

// add curves

QwtPlotCurve *curve1 = new QwtPlotCurve( "Curve 1" );

QwtPlotCurve *curve2 = new QwtPlotCurve( "Curve 2" );

// connect or copy the data to the curves

curve1->setData( ... );

curve2->setData( ... );

curve1->attach( myPlot );

curve2->attach( myPlot );

// finally, refresh the plot

myPlot->replot();

QwtPlotCurve
A plot item, that represents a series of points.
Definition qwt_plot_curve.h:75

QwtPlotCurve::attach
void attach(QwtPlot *plot) override
Attach the curve to a plot.
Definition qwt_plot_curve.cpp:164

QwtPlot
A 2-D plotting widget.
Definition qwt_plot.h:99

QwtPlot::replot
virtual void replot()
Redraw the plot.
Definition qwt_plot.cpp:670

Member Enumeration Documentation

◆ LegendPosition

enum QwtPlot::LegendPosition

Position of the legend, relative to the canvas.

See also: insertLegend()

Enumerator

LeftLegend

The legend will be left from the QwtAxis::YLeft axis.

The legend will be right from the QwtAxis::YRight axis

RightLegend

The legend will be below the footer.

BottomLegend

The legend will be above the title.

◆ TickDirection

enum QwtPlot::TickDirection

Tick direction enum.

Controls whether ticks are drawn inside or outside the canvas. When ticks are inside, they are drawn from the canvas edge toward the interior, while the backbone and labels remain outside.

Enumerator

TickOutside

Ticks are drawn outside the canvas (default behavior)

Ticks are drawn inside the canvas

Constructor & Destructor Documentation

◆ QwtPlot()

QwtPlot::QwtPlot ( QWidget * parent = nullptr )

explicit

Constructor.

Parameters

[in] parent Parent widget

Creates a QwtPlot widget with an empty title.

Constructor with title

Parameters

[in]	title	Title text
[in]	parent	Parent widget

Creates a QwtPlot widget with the specified title.

Destructor

Detaches all plot items and deletes the layout and axis data.

Member Function Documentation

◆ addParasitePlot()

void QwtPlot::addParasitePlot ( QwtPlot * parasite )

protected

Add a parasite plot to this host plot.

This method establishes a parasite relationship where the specified plot will be treated as a parasite of this host plot. The parasite plot will automatically synchronize its geometry with the host plot.

Parameters

parasite Pointer to the parasite QwtPlot

Note: This method is typically called internally by QwtFigure::createParasiteAxes().; The parasite plot should have a transparent background to avoid obscuring the host plot.

// Manually create a parasite relationship
QwtPlot* hostPlot = new QwtPlot;
QwtPlot* parasitePlot = new QwtPlot;
 
// Configure parasite plot
parasitePlot->setAutoFillBackground(false);
parasitePlot->canvas()->setAutoFillBackground(false);
parasitePlot->enableAxis(QwtAxis::YRight, true);
 
// Add parasite to host
hostPlot->addParasitePlot(parasitePlot);

See also: removeParasitePlot(), parasitePlots()

◆ autoRefresh

void QwtPlot::autoRefresh ( )

slot

Replots the plot if autoReplot() is enabled.

This method is called internally when plot properties change and autoReplot is enabled.

◆ autoReplot()

bool QwtPlot::autoReplot ( ) const

Check if autoReplot option is enabled.

Returns: true if the autoReplot option is set

See also: setAutoReplot()

◆ axisAutoScale()

bool QwtPlot::axisAutoScale ( QwtAxisId axisId ) const

Return whether autoscaling is enabled.

Parameters

axisId Axis ID

Returns: true if autoscaling is enabled

◆ axisFont()

QFont QwtPlot::axisFont ( QwtAxisId axisId ) const

Return the font of the scale labels for a specified axis.

Parameters

axisId Axis ID

Returns: Font

◆ axisInterval()

QwtInterval QwtPlot::axisInterval ( QwtAxisId axisId ) const

Return the current interval of the specified axis.

This is only a convenience function for axisScaleDiv( axisId )->interval();

Parameters

axisId Axis ID

Returns: Scale interval

See also: QwtScaleDiv, axisScaleDiv()

◆ axisMaxMajor()

int QwtPlot::axisMaxMajor ( QwtAxisId axisId ) const

Return the maximum number of major ticks for a specified axis.

Parameters

axisId Axis ID

See also: setAxisMaxMajor(), QwtScaleEngine::divideScale()

◆ axisMaxMinor()

int QwtPlot::axisMaxMinor ( QwtAxisId axisId ) const

Return the maximum number of minor ticks for a specified axis.

Parameters

axisId Axis ID

See also: setAxisMaxMinor(), QwtScaleEngine::divideScale()

◆ axisScaleDiv()

const QwtScaleDiv & QwtPlot::axisScaleDiv ( QwtAxisId axisId ) const

Return the scale division of a specified axis.

axisScaleDiv(axisId).lowerBound(), axisScaleDiv(axisId).upperBound() are the current limits of the axis scale.

Parameters

axisId Axis ID

Returns: Scale division

See also: QwtScaleDiv, setAxisScaleDiv(), QwtScaleEngine::divideScale()

◆ axisScaleDraw() [1/2]

QwtScaleDraw * QwtPlot::axisScaleDraw ( QwtAxisId axisId )

Return the scale draw of a specified axis.

Parameters

axisId Axis ID

Returns: Specified scaleDraw for axis, or nullptr if axis is invalid.

◆ axisScaleDraw() [2/2]

const QwtScaleDraw * QwtPlot::axisScaleDraw ( QwtAxisId axisId ) const

Return the scale draw of a specified axis.

Parameters

axisId Axis ID

Returns: Specified scaleDraw for axis, or nullptr if axis is invalid.

◆ axisScaleEngine() [1/2]

QwtScaleEngine * QwtPlot::axisScaleEngine ( QwtAxisId axisId )

Return the scale engine for a specific axis.

Parameters

axisId Axis ID

Returns: Scale engine

◆ axisScaleEngine() [2/2]

const QwtScaleEngine * QwtPlot::axisScaleEngine ( QwtAxisId axisId ) const

Return the scale engine for a specific axis (const overload)

Parameters

axisId Axis ID

Returns: Scale engine

◆ axisStepSize()

double QwtPlot::axisStepSize ( QwtAxisId axisId ) const

Return the step size parameter that has been set in setAxisScale.

This doesn't need to be the step size of the current scale.

Parameters

axisId Axis ID

Returns: step size parameter value

See also: setAxisScale(), QwtScaleEngine::divideScale()

◆ axisTickDirection()

QwtPlot::TickDirection QwtPlot::axisTickDirection ( QwtAxisId axisId ) const

Get the tick direction for an axis.

Parameters

axisId Axis identifier

Returns: Current tick direction

See also: setAxisTickDirection()

◆ axisTitle()

QwtText QwtPlot::axisTitle ( QwtAxisId axisId ) const

Get the title of a specified axis.

Parameters

axisId Axis ID

Returns: Title of a specified axis

◆ axisWidget() [1/2]

QwtScaleWidget * QwtPlot::axisWidget ( QwtAxisId axisId )

Return the scale widget of the specified axis.

Parameters

axisId Axis ID

Returns: Scale widget, or nullptr if axisId is invalid

◆ axisWidget() [2/2]

const QwtScaleWidget * QwtPlot::axisWidget ( QwtAxisId axisId ) const

Return the scale widget of the specified axis.

Parameters

axisId Axis ID

Returns: Scale widget, or nullptr if axisId is invalid

◆ backgroundColor()

QColor QwtPlot::backgroundColor ( ) const

Get background color.

Returns: Background color

◆ canvas() [1/2]

QWidget * QwtPlot::canvas ( )

Get the plot's canvas.

Returns: The plot's canvas widget

◆ canvas() [2/2]

const QWidget * QwtPlot::canvas ( ) const

Get the plot's canvas.

Returns: The plot's canvas widget (const)

◆ canvasBackground()

QBrush QwtPlot::canvasBackground ( ) const

Nothing else than: canvas()->palette().brush( QPalette::Normal, QPalette::Window);.

Returns: Background brush of the plotting area.

See also: setCanvasBackground()

◆ canvasMap()

QwtScaleMap QwtPlot::canvasMap ( QwtAxisId axisId ) const

virtual

Parameters

axisId Axis

Returns: Map for the axis on the canvas. With this map pixel coordinates can translated to plot coordinates and vice versa.

See also: QwtScaleMap, transform(), invTransform()

◆ colorCycle()

QwtColorCycle QwtPlot::colorCycle ( ) const

Get the current color cycle.

Returns: Current color cycle

See also: setColorCycle()

◆ createParasitePlot()

QwtPlot * QwtPlot::createParasitePlot ( QwtAxis::Position enableAxis )

Create parasite axes for this plot.

This method creates a parasite axes that shares the same plotting area as the host plot but with independent axis scaling and labeling. The parasite axes will be positioned exactly on top of the host plot and will automatically synchronize its geometry.

Parameters

enableAxis The axis position to enable on the parasite axes

Returns: Pointer to the created parasite QwtPlot

Return values

nullptr if hostPlot is invalid or not in the figure

Note: A plot cannot be both a parasite and a host at the same time. That is, if a plot is a parasite plot, it is not allowed to create further parasite plots. Calling this function on a parasite plot will return nullptr.

◆ doLayout()

void QwtPlot::doLayout ( )

protected

Adjust plot content to its current size.

The concrete implementation of updateLayout. Before version 7.0, there were no parasite axes. Since the size information of parasite axes fully references the host axes, during the updateLayout process, parasite axes should not perform any actions. Instead, after the host axis's updateLayout finishes, doLayout is executed for all parasite axes.

Therefore, all implementation of updateLayout is extracted into doLayout.

◆ drawCanvas()

void QwtPlot::drawCanvas ( QPainter * painter )

virtual

Redraw the canvas.

Parameters

painter Painter used for drawing

Warning: drawCanvas calls drawItems what is also used for printing. Applications that like to add individual plot items better overload drawItems()

See also: drawItems()

◆ drawInsideTicks()

void QwtPlot::drawInsideTicks	(	QPainter *	painter,
		const QRectF &	canvasRect,
		const QwtScaleMap	maps[QwtAxis::AxisPositions]
	)		const

protected

Draw inside ticks for axes with TickInside direction.

This method is called after drawItems() to draw tick marks that extend from the canvas edge toward the interior.

Parameters

painter	Painter
canvasRect	Canvas rectangle
maps	Scale maps for all axes

◆ drawItems()

void QwtPlot::drawItems	(	QPainter *	painter,
		const QRectF &	canvasRect,
		const QwtScaleMap	maps[QwtAxis::AxisPositions]
	)		const

virtual

Redraw the canvas items.

Parameters

painter	Painter used for drawing
canvasRect	Bounding rectangle where to paint
maps	QwtAxis::AxisCount maps, mapping between plot and paint device coordinates

Note: Usually canvasRect is contentsRect() of the plot canvas. Due to a bug in Qt this rectangle might be wrong for certain frame styles ( f.e QFrame::Box ) and it might be necessary to fix the margins manually using QWidget::setContentsMargins()

◆ event()

bool QwtPlot::event ( QEvent * event )

overridevirtual

Adds handling of layout requests.

Parameters

event Event

Returns: See QFrame::event()

◆ eventFilter()

bool QwtPlot::eventFilter	(	QObject *	object,
		QEvent *	e
	)

overridevirtual

Event filter.

The plot handles the following events for the canvas:

QEvent::Resize The canvas margins might depend on its size
QEvent::ContentsRectChange The layout needs to be recalculated
For parasite axes, the parasite axis filters the host axis dimensions and adjusts its own dimensions

Parameters

object	Object to be filtered
event	Event

Returns: See QFrame::eventFilter()

See also: updateCanvasMargins(), updateLayout()

◆ footer()

QwtText QwtPlot::footer ( ) const

Get the footer text.

Returns: Text of the footer

◆ footerLabel() [1/2]

QwtTextLabel * QwtPlot::footerLabel ( )

Get the footer label widget.

Returns: Footer label widget

◆ footerLabel() [2/2]

const QwtTextLabel * QwtPlot::footerLabel ( ) const

Get the footer label widget.

Returns: Footer label widget (const)

◆ getCanvasMarginsHint()

void QwtPlot::getCanvasMarginsHint	(	const QwtScaleMap	maps[],
		const QRectF &	canvasRect,
		double &	left,
		double &	top,
		double &	right,
		double &	bottom
	)		const

virtual

Calculate the canvas margins.

Parameters

maps	QwtAxis::AxisCount maps, mapping between plot and paint device coordinates
canvasRect	Bounding rectangle where to paint
left	Return parameter for the left margin
top	Return parameter for the top margin
right	Return parameter for the right margin
bottom	Return parameter for the bottom margin

Plot items might indicate, that they need some extra space at the borders of the canvas by the QwtPlotItem::Margins flag.

updateCanvasMargins(), QwtPlotItem::getCanvasMarginHint()

◆ hostPlot()

QwtPlot * QwtPlot::hostPlot ( ) const

Get the host plot for this parasite plot.

This method returns the host plot of this parasite plot, or nullptr if this plot is not a parasite.

Returns: Pointer to the host QwtPlot

Return values

nullptr if this plot is not a parasite plot

See also: isParasitePlot()

◆ infoToItem()

QwtPlotItem * QwtPlot::infoToItem ( const QVariant & itemInfo ) const

virtual

Identify the plot item according to an item info object, that has bee generated from itemToInfo().

The default implementation simply tries to unwrap a QwtPlotItem pointer:

if ( itemInfo.canConvert<QwtPlotItem *>() )

return qvariant_cast<QwtPlotItem *>( itemInfo );

QwtPlotItem

Base class for items on the plot canvas.

Definition qwt_plot_item.h:85

Parameters

itemInfo Plot item

Returns: A plot item, when successful, otherwise a nullptr pointer.

See also: itemToInfo()

◆ initParasiteAxes()

void QwtPlot::initParasiteAxes ( QwtPlot * parasitePlot ) const

protected

Initialize basic properties of the parasite axes.

Parameters

parasitePlot The parasite plot to initialize

◆ insertLegend()

void QwtPlot::insertLegend	(	QwtAbstractLegend *	legend,
		QwtPlot::LegendPosition	pos = `QwtPlot::RightLegend`,
		double	ratio = `-1.0`
	)

Insert a legend.

If the position legend is QwtPlot::LeftLegend or QwtPlot::RightLegend the legend will be organized in one column from top to down. Otherwise the legend items will be placed in a table with a best fit number of columns from left to right.

insertLegend() will set the plot widget as parent for the legend. The legend will be deleted in the destructor of the plot or when another legend is inserted.

Legends, that are not inserted into the layout of the plot widget need to connect to the legendDataChanged() signal. Calling updateLegend() initiates this signal for an initial update. When the application code wants to implement its own layout this also needs to be done for rendering plots to a document ( see QwtPlotRenderer ).

Parameters

legend	Legend
pos	The legend's position. For top/left position the number of columns will be limited to 1, otherwise it will be set to unlimited.
ratio	Ratio between legend and the bounding rectangle of title, canvas and axes. The legend will be shrunk if it would need more space than the given ratio. The ratio is limited to ]0.0 .. 1.0]. In case of <= 0.0 it will be reset to the default ratio. The default vertical/horizontal ratio is 0.33/0.5.

See also: legend(), QwtPlotLayout::legendPosition(), QwtPlotLayout::setLegendPosition()

◆ invTransform()

double QwtPlot::invTransform	(	QwtAxisId	axisId,
		double	pos
	)		const

Transform the x or y coordinate of a position in the drawing region into a value.

Parameters

axisId	Axis ID
pos	position

Returns: Position as axis coordinate

Warning: The position can be an x or a y coordinate, depending on the specified axis.

◆ isAxisValid()

bool QwtPlot::isAxisValid ( QwtAxisId axisId ) const

Checks if an axis is valid.

Parameters

axisId axis ID

Returns: true if the specified axis exists, otherwise false

Note: This method is equivalent to QwtAxis::isValid( axisId ) and simply checks if axisId is one of the values of QwtAxis::Position. It is a placeholder for future releases, where it will be possible to have a customizable number of axes ( multiaxes branch ) at each side.

◆ isAxisVisible()

bool QwtPlot::isAxisVisible ( QwtAxisId axisId ) const

Return whether the specified axis is visible.

Parameters

axisId Axis ID

Returns: true if the axis is visible

◆ isEnableScaleBuildinActions()

bool QwtPlot::isEnableScaleBuildinActions ( ) const

Check if built-in axis event actions are enabled.

Returns: true if enabled

◆ isHostPlot()

bool QwtPlot::isHostPlot ( ) const

Check if this plot is a host plot.

This method returns true if this plot has one or more parasite plots.

A plot is only considered a host if it holds parasite plots.

Note: A plot cannot be both a parasite and a host at the same time, meaning a host itself is not allowed to be parasitic on another plot.

Returns: true if this plot has parasite plots; false if this plot has no parasite plots

See also: isParasitePlot(), parasitePlots()

◆ isParasitePlot()

bool QwtPlot::isParasitePlot ( ) const

Check if this plot is a parasite plot.

This method returns true if this plot is a parasite of another plot.

Returns: true if this plot is a parasite plot; false if this plot is not a parasite plot

See also: isHostPlot(), hostPlot()

◆ isParasiteShareAxis()

bool QwtPlot::isParasiteShareAxis ( QwtAxisId axisId ) const

Query whether the parasite axis shares the host's specified axis.

Parameters

axisId The axis ID to query

Returns: true if the current parasite axis shares the corresponding host axis; false otherwise

See also: setParasiteShareAxis

◆ isTopParasitePlot()

bool QwtPlot::isTopParasitePlot ( ) const

Whether this is the topmost parasite plot; the topmost parasite's axes are at the outermost layer and are typically updated last.

Returns: true if this is the topmost parasite plot

◆ itemAttached

void QwtPlot::itemAttached	(	QwtPlotItem *	plotItem,
		bool	on
	)

signal

A signal indicating that an item has been attached/detached.

Parameters

plotItem	Plot item
on	Attached/Detached

◆ itemToInfo()

QVariant QwtPlot::itemToInfo ( QwtPlotItem * plotItem ) const

virtual

Build an information, that can be used to identify a plot item on the legend.

The default implementation simply wraps the plot item into a QVariant object. When overloading itemToInfo() usually infoToItem() needs to reimplemeted too.

Parameters

plotItem Plot item

Returns: Plot item embedded in a QVariant

See also: infoToItem()

◆ legend() [1/2]

QwtAbstractLegend * QwtPlot::legend ( )

Get the plot's legend.

Returns: The plot's legend

See also: insertLegend()

◆ legend() [2/2]

const QwtAbstractLegend * QwtPlot::legend ( ) const

Get the plot's legend.

Returns: The plot's legend (const)

See also: insertLegend()

◆ legendDataChanged

void QwtPlot::legendDataChanged	(	const QVariant &	itemInfo,
		const QList< QwtLegendData > &	data
	)

signal

A signal with the attributes how to update the legend entries for a plot item.

Parameters

itemInfo	Info about a plot item, built from itemToInfo()
data	Attributes of the entries (usually <= 1) for the plot item.

See also: itemToInfo(), infoToItem(), QwtAbstractLegend::updateLegend()

◆ nextColorForItem()

QColor QwtPlot::nextColorForItem ( int rtti )

Get the next auto-assigned color for a plot item type.

Returns the next color from the color cycle for the given rtti type. Each rtti type maintains an independent counter, so curves and bar charts each start from the first palette color.

Parameters

rtti	The rtti value of the plot item (e.g. QwtPlotItem::Rtti_PlotCurve)

Returns: Next color from the cycle

See also: colorCycle(), QwtPlotItem::rtti()

◆ panAxis()

void QwtPlot::panAxis	(	QwtAxisId	axisId,
		int	deltaPixels
	)

Pan the specified axis by a given number of pixels.

Parameters

axisId	Axis ID (QwtPlot::xBottom, QwtPlot::yLeft, etc.)
deltaPixels	Number of pixels to move

Positive values move right/down, negative values move left/up. For logarithmic axes, coordinate transformations are handled automatically.

Note: This function does not trigger a repaint; the caller must manually call replot

◆ panCanvas()

void QwtPlot::panCanvas ( const QPoint & offset )

Pan the entire canvas by a pixel offset.

Parameters

offset Pixel offset

This method translates all axes (whether enabled or not) by the specified pixel offset, achieving a synchronized panning effect for the entire canvas. Horizontal direction: positive moves right, negative moves left Vertical direction: positive moves down, negative moves up

Note: This function does not trigger a repaint; the caller must manually call replot

◆ parasitePlotAt()

QwtPlot * QwtPlot::parasitePlotAt ( int index ) const

Get the nth parasite plot.

Parameters

index Index

Returns: nullptr if out of range or if this plot is a parasite plot

◆ parasitePlotAttached

void QwtPlot::parasitePlotAttached	(	QwtPlot *	parasitePlot,
		bool	on
	)

signal

Identify the relationship between the parasitic plot and its host plot.

Parameters

parasitePlot	Parasite plot
on	When a parasitic plot is added, on = true. When the parasitic plot is removed, on = false.

Note: This signal is emitted only by the host plot.

◆ parasitePlotCount()

int QwtPlot::parasitePlotCount ( ) const

Get the number of parasite plots.

Returns: 0 if this plot is a parasite plot, otherwise the count of parasite plots

◆ parasitePlotIndex()

int QwtPlot::parasitePlotIndex ( QwtPlot * parasite ) const

Parasite plot index (level)

The parasite level is determined by the order of addition. The first parasite added is at level 0, the second at level 1, and so on. The higher the level, the closer the axis is to the plot boundary.

Parameters

parasite Parasite plot

Returns: -1 if invalid index

Note: If the passed parasite is not a parasite of this plot, returns -1; This function is only valid for host plots; calling it on a parasite plot also returns -1

◆ parasitePlots()

QList< QwtPlot * > QwtPlot::parasitePlots ( ) const

Get all parasite plots associated with this host plot.

This method returns a list of all parasite plots that are associated with this host plot.

Returns: List of parasite QwtPlot pointers

// Get all parasite plots
const QList<QwtPlot*> parasites = hostPlot->parasitePlots();
 
// Perform an operation on all parasite plots
for (QwtPlot* parasite : parasites) {
    parasite->replot();
}

See also: addParasitePlot(), removeParasitePlot()

◆ plotId()

QString QwtPlot::plotId ( ) const

Plot ID.

The plot ID is provided to enable a Figure to identify individual plots during persistence.

For example, after saving a Figure in XML format, it is necessary to know which plots have established axis synchronization signals with which other plots, and which plot boundaries have been aligned. These tasks require locating specific plots, which can be achieved using the plot ID.

Returns: A unique UUID

◆ plotLayout() [1/2]

QwtPlotLayout * QwtPlot::plotLayout ( )

Get the plot's layout.

Returns: The plot's layout

◆ plotLayout() [2/2]

const QwtPlotLayout * QwtPlot::plotLayout ( ) const

Get the plot's layout.

Returns: The plot's layout (const)

◆ plotList()

QList< QwtPlot * > QwtPlot::plotList ( bool descending = false ) const

Return all plots, including the host plot.

descending=false: ascending order, host plot first, lower levels first. descending=true: descending order, host at the end.

Parameters

descending Sort order

Returns: Ordered list of all plots

◆ removeParasitePlot()

void QwtPlot::removeParasitePlot ( QwtPlot * parasite )

Remove a parasite plot from this host plot.

This method removes the parasite relationship between this host plot and the specified plot.

Parameters

parasite Pointer to the parasite QwtPlot to remove

Note: This method does not delete the parasite plot, it only removes the relationship.

// Remove a parasite plot
hostPlot->removeParasitePlot(parasitePlot);
 
// Now the plot is independent and can be used elsewhere

See also: addParasitePlot(), parasitePlots()

◆ replot

void QwtPlot::replot ( )

virtualslot

Redraw the plot.

If the autoReplot option is not set (which is the default) or if any curves are attached to raw data, the plot has to be refreshed explicitly in order to make changes visible.

See also: updateAxes(), setAutoReplot()

◆ rescaleAxes()

void QwtPlot::rescaleAxes	(	bool	onlyVisibleItems = `true`,
		double	marginPercent = `0.05`,
		QwtAxisId	xAxis = `QwtPlot::xBottom`,
		QwtAxisId	yAxis = `QwtPlot::yLeft`
	)

Rescale axes to fit all data items.

This function automatically adjusts the axis ranges to fit all visible data items in the plot. It calculates the bounding rectangle of all plot items and sets appropriate axis scales with optional margins.

Parameters

onlyVisibleItems	If true, only visible items are considered
marginPercent	Percentage of margin to add around the data range
xAxis	The x-axis to rescale (default: QwtPlot::xBottom)
yAxis	The y-axis to rescale (default: QwtPlot::yLeft)

Basic usage:

// Rescale to fit all visible items with default 5% margin

rescaleAxes();

QwtPlot::rescaleAxes

void rescaleAxes(bool onlyVisibleItems=true, double marginPercent=0.05, QwtAxisId xAxis=QwtPlot::xBottom, QwtAxisId yAxis=QwtPlot::yLeft)

Rescale axes to fit all data items.

Definition qwt_plot.cpp:1795

Custom margin:

// Rescale with 10% margin around data

rescaleAxes(true, 0.1);

See also: QwtPlotItem::boundingRect(); QwtPlot::setAxisScale()

◆ resizeEvent()

void QwtPlot::resizeEvent ( QResizeEvent * e )

overrideprotectedvirtual

Resize and update internal layout.

Parameters

e	Resize event

◆ setAutoReplot()

void QwtPlot::setAutoReplot ( bool tf = true )

Set or reset the autoReplot option.

If the autoReplot option is set, the plot will be updated implicitly by manipulating member functions. Since this may be time-consuming, it is recommended to leave this option switched off and call replot() explicitly if necessary.

The autoReplot option is set to false by default, which means that the user has to call replot() in order to make changes visible.

Parameters

tf	`true` or `false`. Defaults to `true`.

See also: replot()

◆ setAxisAutoScale()

void QwtPlot::setAxisAutoScale	(	QwtAxisId	axisId,
		bool	on = `true`
	)

Enable autoscaling for a specified axis.

This member function is used to switch back to autoscaling mode after a fixed scale has been set. Autoscaling is enabled by default.

Parameters

axisId	Axis ID
on	On/Off

See also: setAxisScale(), setAxisScaleDiv(), updateAxes()

Note: The autoscaling flag has no effect until updateAxes() is executed ( called by replot() ).

◆ setAxisFont()

void QwtPlot::setAxisFont	(	QwtAxisId	axisId,
		const QFont &	font
	)

Change the font of an axis.

Parameters

axisId	Axis ID
font	Font

Warning: This function changes the font of the tick labels, not of the axis title.

◆ setAxisLabelAlignment()

void QwtPlot::setAxisLabelAlignment	(	QwtAxisId	axisId,
		Qt::Alignment	alignment
	)

Change the alignment of the tick labels.

Parameters

axisId	Axis ID
alignment	Or'd Qt::AlignmentFlags see <qnamespace.h>

See also: QwtScaleDraw::setLabelAlignment()

◆ setAxisLabelRotation()

void QwtPlot::setAxisLabelRotation	(	QwtAxisId	axisId,
		double	rotation
	)

Rotate all tick labels.

Parameters

axisId	Axis ID
rotation	Angle in degrees. When changing the label rotation, the label alignment might be adjusted too.

See also: QwtScaleDraw::setLabelRotation(), setAxisLabelAlignment()

◆ setAxisMaxMajor()

void QwtPlot::setAxisMaxMajor	(	QwtAxisId	axisId,
		int	maxMajor
	)

Set the maximum number of major scale intervals for a specified axis.

Parameters

axisId	Axis ID
maxMajor	Maximum number of major steps

See also: axisMaxMajor()

◆ setAxisMaxMinor()

void QwtPlot::setAxisMaxMinor	(	QwtAxisId	axisId,
		int	maxMinor
	)

Set the maximum number of minor scale intervals for a specified axis.

Parameters

axisId	Axis ID
maxMinor	Maximum number of minor steps

See also: axisMaxMinor()

◆ setAxisScale()

void QwtPlot::setAxisScale	(	QwtAxisId	axisId,
		double	min,
		double	max,
		double	stepSize = `0`
	)

Disable autoscaling and specify a fixed scale for a selected axis.

In updateAxes() the scale engine calculates a scale division from the specified parameters, that will be assigned to the scale widget. So updates of the scale widget usually happen delayed with the next replot.

Parameters

axisId	Axis ID
min	Minimum of the scale
max	Maximum of the scale
stepSize	Major step size. If `step == 0`, the step size is calculated automatically using the maxMajor setting.

See also: setAxisMaxMajor(), setAxisAutoScale(), axisStepSize(), QwtScaleEngine::divideScale()

◆ setAxisScaleDiv()

void QwtPlot::setAxisScaleDiv	(	QwtAxisId	axisId,
		const QwtScaleDiv &	scaleDiv
	)

Disable autoscaling and specify a fixed scale for a selected axis.

The scale division will be stored locally only until the next call of updateAxes(). So updates of the scale widget usually happen delayed with the next replot.

Parameters

axisId	Axis ID
scaleDiv	Scale division

See also: setAxisScale(), setAxisAutoScale()

◆ setAxisScaleDraw()

void QwtPlot::setAxisScaleDraw	(	QwtAxisId	axisId,
		QwtScaleDraw *	scaleDraw
	)

Set a scale draw.

By passing scaleDraw it is possible to extend QwtScaleDraw functionality and let it take place in QwtPlot. Please note that scaleDraw has to be created with new and will be deleted by the corresponding QwtScale member ( like a child object ).

Parameters

axisId	Axis ID
scaleDraw	Object responsible for drawing scales.

See also: QwtScaleDraw, QwtScaleWidget

Warning: The attributes of scaleDraw will be overwritten by those of the previous QwtScaleDraw.

◆ setAxisScaleEngine()

void QwtPlot::setAxisScaleEngine	(	QwtAxisId	axisId,
		QwtScaleEngine *	scaleEngine
	)

Change the scale engine for an axis.

Parameters

axisId	Axis ID
scaleEngine	Scale engine

Note: The old scale engine will be deleted

See also: axisScaleEngine()

◆ setAxisTickDirection()

void QwtPlot::setAxisTickDirection	(	QwtAxisId	axisId,
		TickDirection	direction
	)

Set the tick direction for an axis.

When set to TickInside, the tick marks are drawn from the canvas edge toward the interior. The outside tick component is disabled on the QwtScaleWidget, and inside ticks are drawn in drawCanvas.

Parameters

axisId	Axis identifier
direction	Tick direction (TickOutside or TickInside)

See also: axisTickDirection()

◆ setAxisTitle() [1/2]

void QwtPlot::setAxisTitle	(	QwtAxisId	axisId,
		const QString &	title
	)

Change the title of a specified axis.

Parameters

axisId	Axis ID
title	axis title

◆ setAxisTitle() [2/2]

void QwtPlot::setAxisTitle	(	QwtAxisId	axisId,
		const QwtText &	title
	)

Change the title of a specified axis.

Parameters

axisId	Axis ID
title	Axis title

◆ setAxisToDateTime()

void QwtPlot::setAxisToDateTime	(	QwtAxisId	axisId,
		Qt::TimeSpec	timeSpec = `Qt::LocalTime`
	)

Set the specified axis to date-time scale.

This method configures the axis to display date-time formatted labels using QwtDateScaleEngine and QwtDateScaleDraw. Data should be provided as milliseconds since epoch (QDateTime::toMSecsSinceEpoch).

Parameters

axisId	Axis identifier, e.g., QwtPlot::xBottom, QwtPlot::yLeft
timeSpec	Time zone specification, defaults to Qt::LocalTime

// Set X axis to UTC date-time scale
plot->setAxisToDateTime(QwtPlot::xBottom, Qt::UTC);
 
QDateTime start = QDateTime::currentDateTime().addSecs(-3600);
QVector<double> timestamps, values;
for (int i = 0; i < 60; ++i) {
    timestamps << start.addSecs(i * 60).toMSecsSinceEpoch(); // per minute
    values << 1.0 + qAbs(qSin(i * 0.2)) * 100;
}
 
QwtPlotCurve *curve = new QwtPlotCurve("Data");
curve->setSamples(timestamps, values);
curve->attach(plot);
plot->setAxisScale(QwtPlot::xBottom, timestamps.first(), timestamps.last());
plot->updateAxes();
plot->replot();

See also: setAxisToLogScale(), setAxisToLinearScale(), QwtDateScaleEngine, QDateTime::toMSecsSinceEpoch()

◆ setAxisToLinearScale()

void QwtPlot::setAxisToLinearScale ( QwtAxisId axisId )

Restore the specified axis to linear scale.

This method replaces the current scale engine and draw with default linear versions. Useful to revert from logarithmic or date-time scales.

Parameters

axisId Axis identifier, e.g., QwtPlot::xBottom, QwtPlot::yLeft

Note: Previous scale engine and draw are deleted automatically.

// Switch back to linear scale after using log scale
plot->setAxisToLinearScale(QwtPlot::yLeft);
plot->updateAxes();
plot->replot();

See also: setAxisToLogScale(), setAxisToDateTime(), QwtLinearScaleEngine

◆ setAxisToLogScale()

void QwtPlot::setAxisToLogScale ( QwtAxisId axisId )

Set the specified axis to logarithmic scale.

This method replaces the current scale engine of the axis with QwtLogScaleEngine, enabling logarithmic scaling. All data values must be greater than zero.

Parameters

axisId Axis identifier, e.g., QwtPlot::xBottom, QwtPlot::yLeft

Note: This method deletes the previous scale engine automatically. Data <= 0 will cause undefined behavior.

// Set Y axis to logarithmic scale
plot->setAxisToLogScale(QwtPlot::yLeft);
 
QVector<double> x = {1, 10, 100, 1000};
QVector<double> y = {1, 100, 10000, 1e6};
QwtPlotCurve *curve = new QwtPlotCurve();
curve->setSamples(x, y);
curve->attach(plot);
plot->replot();

See also: setAxisToDateTime(), setAxisToLinearScale(), QwtLogScaleEngine

◆ setAxisVisible()

void QwtPlot::setAxisVisible	(	QwtAxisId	axisId,
		bool	on = `true`
	)

Hide or show a specified axis.

Curves, markers and other items can be attached to hidden axes, and transformation of screen coordinates into values works as normal.

Only QwtAxis::XBottom and QwtAxis::YLeft are enabled by default.

Parameters

axisId	Axis ID
on	`true` (visible) or `false` (hidden)

◆ setBackgroundColor()

void QwtPlot::setBackgroundColor ( const QColor & c )

Set background color.

Parameters

c Color

◆ setCanvas()

void QwtPlot::setCanvas ( QWidget * canvas )

Set the drawing canvas of the plot widget.

QwtPlot invokes methods of the canvas as meta methods ( see QMetaObject ). In opposite to using conventional C++ techniques like virtual methods they allow to use canvas implementations that are derived from QWidget or QGLWidget.

The following meta methods could be implemented:

replot() When the canvas doesn't offer a replot method, QwtPlot calls update() instead.
borderPath() The border path is necessary to clip the content of the canvas When the canvas doesn't have any special border ( f.e rounded corners ) it is o.k. not to implement this method.

The default canvas is a QwtPlotCanvas

Parameters

canvas Canvas Widget

See also: canvas()

◆ setCanvasBackground()

void QwtPlot::setCanvasBackground ( const QBrush & brush )

Change the background of the plotting area.

Sets brush to QPalette::Window of all color groups of the palette of the canvas. Using canvas()->setPalette() is a more powerful way to set these colors.

Parameters

brush New background brush

See also: canvasBackground()

◆ setColorCycle()

void QwtPlot::setColorCycle ( const QwtColorCycle & colorCycle )

Set the color cycle used for automatic item coloring.

When plot items (curves, bar charts, etc.) are attached without a user-specified pen or brush, they automatically receive a color from this color cycle.

Parameters

colorCycle Color cycle object

See also: colorCycle(), nextColorForItem()

◆ setEnableScaleBuildinActions()

void QwtPlot::setEnableScaleBuildinActions ( bool on )

Enable or disable built-in axis event actions.

Axis events are built-in event actions for axes, primarily including click-to-move-axis, mouse wheel zoom, etc.

Parameters

on	Enable state

◆ setFooter() [1/2]

void QwtPlot::setFooter ( const QString & text )

Change the footer text.

Parameters

[in] text New text of the footer as a string

◆ setFooter() [2/2]

void QwtPlot::setFooter ( const QwtText & text )

Change the footer text.

Parameters

[in] text New text of the footer as a QwtText

◆ setParasiteShareAxis()

void QwtPlot::setParasiteShareAxis	(	QwtAxisId	axisId,
		bool	isShare = `true`
	)

Set whether the parasite axis shares the host's specified axis, only valid for parasite axes.

Parameters

axisId	The axis ID to share (e.g., QwtAxis::YLeft)
isShare	Whether to enable sharing

See also: isParasiteShareAxis

◆ setPlotId()

void QwtPlot::setPlotId ( const QString & id )

set the plot id.

Parameters

id

◆ setPlotLayout()

void QwtPlot::setPlotLayout ( QwtPlotLayout * layout )

Assign a new plot layout.

Parameters

layout Layout()

See also: plotLayout()

◆ setTitle() [1/2]

void QwtPlot::setTitle ( const QString & title )

Change the plot's title.

Parameters

[in] title New title as a string

◆ setTitle() [2/2]

void QwtPlot::setTitle ( const QwtText & title )

Change the plot's title.

Parameters

[in] title New title as a QwtText

◆ setupScaleEventDispatcher()

void QwtPlot::setupScaleEventDispatcher ( QwtPlotScaleEventDispatcher * dispatcher )

Install the axis event dispatcher.

Parameters

dispatcher The event dispatcher to install

◆ sizeHint()

QSize QwtPlot::sizeHint ( ) const

overridevirtual

Returns: Size hint for the plot widget

See also: minimumSizeHint()

◆ syncAxis()

void QwtPlot::syncAxis	(	QwtAxisId	axis,
		const QwtPlot *	plot
	)

Synchronize the axis ranges from the given plot to this plot.

Parameters

axis	Axis ID
plot	Source plot to sync from

◆ title()

QwtText QwtPlot::title ( ) const

Get the plot's title.

Returns: Title of the plot

◆ titleLabel() [1/2]

QwtTextLabel * QwtPlot::titleLabel ( )

Get the title label widget.

Returns: Title label widget

◆ titleLabel() [2/2]

const QwtTextLabel * QwtPlot::titleLabel ( ) const

Get the title label widget.

Returns: Title label widget (const)

◆ transform()

double QwtPlot::transform	(	QwtAxisId	axisId,
		double	value
	)		const

Transform a value into a coordinate in the plotting region.

Parameters

axisId	Axis ID
value	value

Returns: X or Y coordinate in the plotting region corresponding to the value.

◆ updateAllAxisEdgeMargin()

void QwtPlot::updateAllAxisEdgeMargin ( )

Batch update edge offsets for all axis positions.

Sequentially calls updateAxisEdgeMargin(QwtAxisId) for all axis positions (YLeft, YRight, XBottom, XTop) of the current plot instance, automatically synchronizing edgeMargin and margin between the host and all parasite axes, ensuring no overlap between layers and proper alignment of plot areas in multi-axis scenarios.

Typical invocation timing:

After a parasite plot is mounted or removed;
After property changes that affect dimensions, such as axis visibility, label fonts, or tick lengths;
When axis label width/height changes significantly due to host or parasite axis data range changes.
See also
updateAxisEdgeMargin(QwtAxisId)

◆ updateAxes()

void QwtPlot::updateAxes ( )

Rebuild the axes scales.

In case of autoscaling the boundaries of a scale are calculated from the bounding rectangles of all plot items, having the QwtPlotItem::AutoScale flag enabled ( QwtScaleEngine::autoScale() ). Then a scale division is calculated ( QwtScaleEngine::divideScale() ) and assigned to scale widget.

When the scale boundaries have been assigned with setAxisScale() a scale division is calculated ( QwtScaleEngine::divideScale() ) for this interval and assigned to the scale widget.

When the scale has been set explicitly by setAxisScaleDiv() the locally stored scale division gets assigned to the scale widget.

The scale widget indicates modifications by emitting a QwtScaleWidget::scaleDivChanged() signal.

updateAxes() is usually called by replot().

See also: setAxisAutoScale(), setAxisScale(), setAxisScaleDiv(), replot(), QwtPlotItem::boundingRect()

◆ updateAxisEdgeMargin()

void QwtPlot::updateAxisEdgeMargin ( QwtAxisId axisId )

Recalculate and assign edgeMargin and margin for all layers (host + parasite) axes based on level order.

In the Qwt multi-axis system, a host plot can mount any number of parasite plots. Each parasite plot shares the same canvas position as the host but has its own independent axes. To avoid overlap between axis layers, two offsets need to be dynamically calculated for each axis:

edgeMargin – The distance from the current axis to the canvas border, accumulated from the theoretical sizes of all axes at higher levels.
margin – The distance from the current axis to the plot area, accumulated from the theoretical sizes of all axes at lower levels.

Level rules defined here:

The host is always at level 0 (innermost layer);
Parasite plots form levels 1, 2, 3... in the order they are mounted, with larger numbers being closer to the outside of the canvas.

Calculation flow:

Collect the "net" rectangles of the host and all visible parasite axes (with old edgeMargin and margin stripped);
For each level i:
- margin = sum of net rectangle sizes from level 0 to i-1;
- edgeMargin = sum of net rectangle sizes from level i+1 to the last level;
Assign the new values to the corresponding axis's QwtScaleWidget;
The host's margin is preserved (not overwriting values that users may have manually set).

Notes:

If the current axis is not visible or the parasite plot does not use QwtParasitePlotLayout, it is skipped automatically;
All rectangle dimensions within the function are taken as width or height based on axis direction: Y axes (YLeft/YRight) use width, X axes (XBottom/XTop) use height.

Parameters

axisId The axis ID to process

Note: This function only modifies geometric offsets and does not trigger layout or repaint; the caller can subsequently call hostPlot->updateLayout() if needed.

See also: QwtScaleWidget::setEdgeMargin(), QwtScaleWidget::setMargin(), QwtParasitePlotLayout::parasiteScaleRect()

Since: 7.0.4

◆ updateCanvasMargins()

void QwtPlot::updateCanvasMargins ( )

Update the canvas margins.

Plot items might indicate, that they need some extra space at the borders of the canvas by the QwtPlotItem::Margins flag.

getCanvasMarginsHint(), QwtPlotItem::getCanvasMarginHint()

◆ updateItemsToScaleDiv()

void QwtPlot::updateItemsToScaleDiv ( )

Update the scale range of all plot items to match the current axis scales.

This is typically called when axes change, forcing all plot items to update their ranges.

◆ updateLayout()

void QwtPlot::updateLayout ( )

virtual

Adjust plot content to its current size.

See also: resizeEvent()

◆ updateLegend() [1/2]

void QwtPlot::updateLegend ( )

Emit legendDataChanged() for all plot item.

See also: QwtPlotItem::legendData(), legendDataChanged()

◆ updateLegend() [2/2]

void QwtPlot::updateLegend ( const QwtPlotItem * plotItem )

Emit legendDataChanged() for a plot item.

Parameters

plotItem Plot item

See also: QwtPlotItem::legendData(), legendDataChanged()

◆ visibleXAxisId()

QwtAxisId QwtPlot::visibleXAxisId ( ) const

Return the currently visible X axis.

Selection policy (descending priority):

Axis must be visible (isAxisVisible() == true);
If both XBottom and XTop are visible, prefer XBottom;
If only one X axis is visible, return it;
If both are invisible, return default QwtAxis::XBottom.

Returns: Selected X axis ID

◆ visibleYAxisId()

QwtAxisId QwtPlot::visibleYAxisId ( ) const

Return the currently usable Y axis.

Selection policy (descending priority):

Axis must be visible;
If both YLeft and YRight are visible, prefer YLeft;
If only one Y axis is visible, return it;
If both are invisible, return default QwtAxis::YLeft.

Returns: Selected Y axis ID

◆ zoomAxis()

void QwtPlot::zoomAxis	(	QwtAxisId	axisId,
		double	factor,
		const QPoint &	centerPosPixels
	)

Zoom the axis centered at the specified pixel position.

Parameters

axisId	Axis ID
factor	Zoom factor (>1 for zoom in, <1 for zoom out)
centerPosPixels	Pixel position of the zoom center (relative to canvas)

Zoom principle:

Linear axes: zoom centered at the mouse position linearly
Logarithmic axes: zoom centered at the mouse position in the logarithmic domain

Note: This function does not trigger a repaint; the caller must manually call replot

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

/home/runner/work/QWT/QWT/src/plot/qwt_plot.h
/home/runner/work/QWT/QWT/src/plot/qwt_plot.cpp
/home/runner/work/QWT/QWT/src/plot/qwt_plot_axis.cpp

Classes

Public Types

Public Slots

Signals

Public Member Functions

Protected Member Functions

Properties

Friends

Detailed Description

Member Enumeration Documentation

◆ LegendPosition

◆ TickDirection

Constructor & Destructor Documentation

◆ QwtPlot()

Member Function Documentation

◆ addParasitePlot()

◆ autoRefresh

◆ autoReplot()

◆ axisAutoScale()

◆ axisFont()

◆ axisInterval()

◆ axisMaxMajor()

◆ axisMaxMinor()

◆ axisScaleDiv()

◆ axisScaleDraw() [1/2]

◆ axisScaleDraw() [2/2]

◆ axisScaleEngine() [1/2]

◆ axisScaleEngine() [2/2]

◆ axisStepSize()

◆ axisTickDirection()

◆ axisTitle()

◆ axisWidget() [1/2]

◆ axisWidget() [2/2]

◆ backgroundColor()

◆ canvas() [1/2]

◆ canvas() [2/2]

◆ canvasBackground()

◆ canvasMap()

◆ colorCycle()

◆ createParasitePlot()

◆ doLayout()

◆ drawCanvas()

◆ drawInsideTicks()

◆ drawItems()

◆ event()

◆ eventFilter()

◆ footer()

◆ footerLabel() [1/2]

◆ footerLabel() [2/2]

◆ getCanvasMarginsHint()

◆ hostPlot()

◆ infoToItem()

◆ initParasiteAxes()

◆ insertLegend()

◆ invTransform()

◆ isAxisValid()

◆ isAxisVisible()

◆ isEnableScaleBuildinActions()

◆ isHostPlot()

◆ isParasitePlot()

◆ isParasiteShareAxis()

◆ isTopParasitePlot()

◆ itemAttached

◆ itemToInfo()

◆ legend() [1/2]

◆ legend() [2/2]

◆ legendDataChanged

◆ nextColorForItem()

◆ panAxis()

◆ panCanvas()

◆ parasitePlotAt()

◆ parasitePlotAttached

◆ parasitePlotCount()

◆ parasitePlotIndex()

◆ parasitePlots()

◆ plotId()

◆ plotLayout() [1/2]

◆ plotLayout() [2/2]

◆ plotList()

◆ removeParasitePlot()