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playground/curvetracker/CurveTracker.cpp

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+/*****************************************************************************
+ * Qwt Examples - Copyright (C) 2002 Uwe Rathmann
+ * This file may be used under the terms of the 3-clause BSD License
+ *****************************************************************************/
+
+#include "CurveTracker.h"
+
+#include <QwtPickerMachine>
+#include <QwtPlot>
+#include <QwtPlotCurve>
+#include <QwtText>
+
+#include <QPen>
+
+struct compareX
+{
+    inline bool operator()( const double x, const QPointF& pos ) const
+    {
+        return ( x < pos.x() );
+    }
+};
+
+CurveTracker::CurveTracker( QWidget* canvas )
+    : QwtPlotPicker( canvas )
+{
+    setTrackerMode( QwtPlotPicker::ActiveOnly );
+    setRubberBand( VLineRubberBand );
+
+    setStateMachine( new QwtPickerDragPointMachine() );
+}
+
+QRect CurveTracker::trackerRect( const QFont& font ) const
+{
+    QRect r = QwtPlotPicker::trackerRect( font );
+
+    // align r to the first curve
+
+    const QwtPlotItemList curves = plot()->itemList( QwtPlotItem::Rtti_PlotCurve );
+    if ( curves.size() > 0 )
+    {
+        QPointF pos = invTransform( trackerPosition() );
+
+        const QLineF line = curveLineAt(
+            static_cast< const QwtPlotCurve* >( curves[0] ), pos.x() );
+        if ( !line.isNull() )
+        {
+            const double curveY = line.pointAt(
+                ( pos.x() - line.p1().x() ) / line.dx() ).y();
+
+            pos.setY( curveY );
+            pos = transform( pos );
+
+            r.moveBottom( pos.y() );
+        }
+    }
+
+    return r;
+}
+
+QwtText CurveTracker::trackerTextF( const QPointF& pos ) const
+{
+    QwtText trackerText;
+
+    trackerText.setColor( Qt::black );
+
+    QColor c( "#333333" );
+    trackerText.setBorderPen( QPen( c, 2 ) );
+    c.setAlpha( 200 );
+    trackerText.setBackgroundBrush( c );
+
+    QString info;
+
+    const QwtPlotItemList curves =
+        plot()->itemList( QwtPlotItem::Rtti_PlotCurve );
+
+    for ( int i = 0; i < curves.size(); i++ )
+    {
+        const QString curveInfo = curveInfoAt(
+            static_cast< const QwtPlotCurve* >( curves[i] ), pos );
+
+        if ( !curveInfo.isEmpty() )
+        {
+            if ( !info.isEmpty() )
+                info += "<br>";
+
+            info += curveInfo;
+        }
+    }
+
+    trackerText.setText( info );
+    return trackerText;
+}
+
+QString CurveTracker::curveInfoAt(
+    const QwtPlotCurve* curve, const QPointF& pos ) const
+{
+    const QLineF line = curveLineAt( curve, pos.x() );
+    if ( line.isNull() )
+        return QString();
+
+    const double y = line.pointAt(
+        ( pos.x() - line.p1().x() ) / line.dx() ).y();
+
+    QString info( "<font color=" "%1" ">%2</font>" );
+    return info.arg( curve->pen().color().name() ).arg( y );
+}
+
+QLineF CurveTracker::curveLineAt(
+    const QwtPlotCurve* curve, double x ) const
+{
+    QLineF line;
+
+    if ( curve->dataSize() >= 2 )
+    {
+        const QRectF br = curve->boundingRect();
+        if ( ( br.width() > 0 ) && ( x >= br.left() ) && ( x <= br.right() ) )
+        {
+            int index = qwtUpperSampleIndex< QPointF >(
+                *curve->data(), x, compareX() );
+
+            if ( index == -1 &&
+                x == curve->sample( curve->dataSize() - 1 ).x() )
+            {
+                // the last sample is excluded from qwtUpperSampleIndex
+                index = curve->dataSize() - 1;
+            }
+
+            if ( index > 0 )
+            {
+                line.setP1( curve->sample( index - 1 ) );
+                line.setP2( curve->sample( index ) );
+            }
+        }
+    }
+
+    return line;
+}