QwtPlotTransform Class Reference

Utility class for coordinate transformations on a QwtPlot. More...

#include <qwt_plot_transform.h>

Static Public Member Functions
static QPointF	transformPoint (const QwtPlot *plot, const QPointF &point, QwtAxisId fromX, QwtAxisId fromY, QwtAxisId toX, QwtAxisId toY)
	Transform a point from one axis pair to another.
static QPainterPath	transformPath (const QwtPlot *plot, const QPainterPath &path, QwtAxisId fromX, QwtAxisId fromY, QwtAxisId toX, QwtAxisId toY)
	Transform a path from one axis pair to another.
static QPointF	toPlotPoint (const QwtPlot *plot, const QPointF &screenPos, QwtAxisId xAxis=QwtAxis::XBottom, QwtAxisId yAxis=QwtAxis::YLeft)
	Convert screen position to data coordinates.
static QPointF	toScreenPoint (const QwtPlot *plot, const QPointF &plotPoint, QwtAxisId xAxis=QwtAxis::XBottom, QwtAxisId yAxis=QwtAxis::YLeft)
	Convert data coordinates to screen position.
static QPointF	onePixelOffset (const QwtPlot *plot, QwtAxisId xAxis=QwtAxis::XBottom, QwtAxisId yAxis=QwtAxis::YLeft)
	Compute the data-coordinate offset for 1 pixel displacement.
static QRectF	visibleRange (const QwtPlot *plot, QwtAxisId xAxis=QwtAxis::XBottom, QwtAxisId yAxis=QwtAxis::YLeft)
	Get the currently visible data range.
static QRectF	totalDataRange (const QwtPlot *plot, bool onlyVisible=true)
	Get the union of all data item bounding rectangles.

Detailed Description

Utility class for coordinate transformations on a QwtPlot.

QwtPlotTransform provides static methods to convert between different coordinate systems, compute pixel offsets, and determine the visible data range. All methods are read-only and do not modify the plot.

Coordinate systems in Qwt:

• Data coordinates: the actual x/y values of the plotted data
• Screen coordinates: pixel positions on the canvas widget
• Cross-axis transformation: converting data from one axis pair to another while preserving the same screen position

QwtPlot* plot = ...;
QRectF visible = Qwt::QwtPlotTransform::visibleRange(plot);
qDebug() << "Visible range:" << visible;
 
// Convert a mouse click to data coordinates
QPointF dataPoint = Qwt::QwtPlotTransform::toPlotPoint(plot, mousePos);

See also

QwtPlot::invTransform(), QwtPlot::transform(), QwtScaleMap

Member Function Documentation

onePixelOffset()

QPointF QwtPlotTransform::onePixelOffset ( const QwtPlot *  plot, QwtAxisId  xAxis = QwtAxis::XBottom, QwtAxisId  yAxis = QwtAxis::YLeft  )

static

Compute the data-coordinate offset for 1 pixel displacement.

Parameters

plot	Plot to query
xAxis	X axis
yAxis	Y axis

Returns

Positive offset in data coordinates that corresponds to 1 pixel at the center of the plot

toPlotPoint()

QPointF QwtPlotTransform::toPlotPoint ( const QwtPlot *  plot, const QPointF &  screenPos, QwtAxisId  xAxis = QwtAxis::XBottom, QwtAxisId  yAxis = QwtAxis::YLeft  )

static

Convert screen position to data coordinates.

Parameters

plot	Plot to query
screenPos	Position in canvas widget pixel coordinates
xAxis	X axis to use for conversion
yAxis	Y axis to use for conversion

Returns

Data coordinates corresponding to the screen position

toScreenPoint()

QPointF QwtPlotTransform::toScreenPoint ( const QwtPlot *  plot, const QPointF &  plotPoint, QwtAxisId  xAxis = QwtAxis::XBottom, QwtAxisId  yAxis = QwtAxis::YLeft  )

static

Convert data coordinates to screen position.

Parameters

plot	Plot to query
plotPoint	Data coordinates
xAxis	X axis to use for conversion
yAxis	Y axis to use for conversion

Returns

Screen position in canvas widget pixel coordinates

totalDataRange()

QRectF QwtPlotTransform::totalDataRange ( const QwtPlot *  plot, bool  onlyVisible = true  )

static

Get the union of all data item bounding rectangles.

Parameters

plot	Plot to query
onlyVisible	If true, only include visible items

Returns

Union of all data bounding rectangles, or an invalid rect if no data items exist

transformPath()

QPainterPath QwtPlotTransform::transformPath ( const QwtPlot *  plot, const QPainterPath &  path, QwtAxisId  fromX, QwtAxisId  fromY, QwtAxisId  toX, QwtAxisId  toY  )

static

Transform a path from one axis pair to another.

Parameters

plot	Plot to query
path	Path in source axis data coordinates
fromX	Source X axis
fromY	Source Y axis
toX	Target X axis
toY	Target Y axis

Returns

Transformed path in target axis data coordinates

transformPoint()

QPointF QwtPlotTransform::transformPoint ( const QwtPlot *  plot, const QPointF &  point, QwtAxisId  fromX, QwtAxisId  fromY, QwtAxisId  toX, QwtAxisId  toY  )

static

Transform a point from one axis pair to another.

Parameters

plot	Plot to query
point	Data coordinates in the source axis system
fromX	Source X axis
fromY	Source Y axis
toX	Target X axis
toY	Target Y axis

Returns

Data coordinates in the target axis system (same screen position)

This method first transforms the data point to screen coordinates using the source axes, then transforms back to data coordinates using the target axes.

visibleRange()

QRectF QwtPlotTransform::visibleRange ( const QwtPlot *  plot, QwtAxisId  xAxis = QwtAxis::XBottom, QwtAxisId  yAxis = QwtAxis::YLeft  )

static

Get the currently visible data range.

Parameters

plot	Plot to query
xAxis	X axis
yAxis	Y axis

Returns

Rectangle in data coordinates representing the visible area

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

• /home/runner/work/QWT/QWT/src/plot/qwt_plot_transform.h
• /home/runner/work/QWT/QWT/src/plot/qwt_plot_transform.cpp