Qwt plot utility classes collection and compatibility functions. More...

#include "qwt_global.h"
#include <qsize.h>
#include "qwt_plot_factory.h"
#include "qwt_plot_item_info.h"
#include "qwt_plot_data_access.h"
#include "qwt_plot_transform.h"
#include "qwt_plot_styling.h"
#include "qwt_pyplot.h"

Functions
QSize QWT_EXPORT	qwtExpandedToGlobalStrut (const QSize &size)
	Expand a size to the global strut (Qt5/Qt6 compatibility function)

Detailed Description

Qwt plot utility classes collection and compatibility functions.

This file provides two main features:

Forward includes for plot utility classes: Including this file gives access to all Qwt plot utility classes at once. These utility classes replace the deprecated Qwt::plotItemColor() function with more powerful and type-safe functionality.
Qt version compatibility function: qwtExpandedToGlobalStrut() handles the globalStrut API difference between Qt 5 and Qt 6, primarily used internally by Qwt widget classes.

Plot Utility Classes

Since Qwt 7.x, the following 5 dedicated utility classes are recommended for working with plot items:

QwtPlotFactory: Factory methods for creating plot items (curves, bars, markers, etc.)
QwtPlotItemInfo: Type queries for determining item types and basic information
QwtPlotDataAccess: Data access for reading and writing plot item data
QwtPlotTransform: Coordinate transformations between pixel and data coordinates
QwtPlotStyling: Style operations for getting/setting colors, pens, brushes, etc.

All classes are in the Qwt namespace and provide type-safe, rtti-dispatched APIs that are safer and more efficient than the old dynamic_cast approach.

Example

#include <qwt_utils.h>
 
// Create a plot
QwtPlot* plot = new QwtPlot();
 
// Create a curve using factory method
QVector<QPointF> points = {{0,0}, {1,1}, {2,4}};
QwtPlotCurve* curve = QwtPlotFactory::createCurve(plot, "Temperature", points);
 
// Query type
if (QwtPlotItemInfo::isSeriesItem(item)) {
    // Handle series item
}
 
// Read data
QVector<QPointF> data = QwtPlotDataAccess::xySamples(curve);
 
// Set style
QwtPlotStyling::setColor(curve, Qt::blue);
QwtPlotStyling::setPenWidth(curve, 2.0);
 
// Coordinate transformation
QPointF plotPos = QwtPlotTransform::toPlotCoordinates(plot, screenPos);

Guide

If you were using Qwt::plotItemColor(), you should now use QwtPlotStyling::color():

// Old way (deprecated)
QColor color = Qwt::plotItemColor(item);
 
// New way (recommended)
QColor color = QwtPlotStyling::color(item);

The new approach supports more plot item types and uses rtti dispatch instead of dynamic_cast for better performance.

Note: The qwtExpandedToGlobalStrut() function is retained for internal Qwt use only. Application code should not call this function directly.

Function Documentation

◆ qwtExpandedToGlobalStrut()

QSize QWT_EXPORT qwtExpandedToGlobalStrut ( const QSize & size )

Expand a size to the global strut (Qt5/Qt6 compatibility function)

In Qt 5.0-5.14, QApplication::globalStrut() returns the application-defined minimum widget size. This function expands the given size to at least that minimum size.

In Qt 5.15+ and Qt 6, globalStrut() has been removed and this function returns the original size unchanged.

Parameters

size	Original size