rotating a custom made symbol for QwtPlotCurve

[babu198649]

hi
i have created a customized symbol by subclassing the QwtSymbol class and reimplementing the function,

class feather : public QwtSymbol
{
public:
	void draw(QPainter *painter, const QRect &r) const
	{
		//shape of symbol( |___ )
		QwtPainter::drawLine(painter, r.bottomLeft(), r.topLeft());
		QwtPainter::drawLine(painter, r.bottomLeft(), r.bottomRight());
	}
}

class feather : public QwtSymbol
{
public:
	void draw(QPainter *painter, const QRect &r) const
	{
		//shape of symbol( |___ )
		QwtPainter::drawLine(painter, r.bottomLeft(), r.topLeft());
		QwtPainter::drawLine(painter, r.bottomLeft(), r.bottomRight());
	}
}

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i want to rotate the symbols at some angle. but,i can not use the painter argument for doing this because its co-ordinates are not the co-ordinates of r(argument QRect).

how can i do this.

[Uwe]

i have created a customized symbol by subclassing the QwtSymbol class and reimplementing the function, ...

Note, that you can't customize the symbol of a marker/curve by subclassing, because it gets copied as QwtSymbol. Instead you have to subclass QwtPlotCurve and reimplement QwtPlotCurve::drawSymbols(). In Qwt 5.1-SVN ( svn co https://qwt.svn.sourceforge.net/svnroot/qwt/branches/qwt-5.1 ) you can subclass if you reimplement a QwtSymbol::copy() method.

i want to rotate the symbols at some angle. but,i can not use the painter argument for doing this because its co-ordinates are not the co-ordinates of r(argument QRect).

The QRect is the rectangle ( position + size), where you have to paint your symbol. I'm not sure , what you mean by painter coordinates - maybe its translation ?

It depends on your type of symbol, if QPainter::rotate is the best way to paint it. If you want to use it you might have to set QPainter::translate to the position of your rotation.

HTH,
Uwe

[babu198649]

hi
i have subclassed the QwtPlotCurve like this .

#include <QtGui>
#include "qwt_plot.h"
#include "qwt_plot_curve.h"
#include "qwt_valuelist.h"
#include "qwt_scale_div.h"
#include "qwt_symbol.h"
#include "qwt_painter.h"
class feather : public QwtSymbol
{
public:
 
	void draw(QPainter *painter, const QRect &r) const
	{
		//painter->translate(r.topLeft());
 
		//shape |_|__
		QwtPainter::drawLine(painter, r.bottomLeft(), r.topLeft());
		QwtPainter::drawLine(painter, r.bottomLeft(), r.bottomRight());
		QwtPainter::drawLine(painter, r.right()-r.width()/2, r.bottom(),
				r.right()-r.width()/2, r.top());
	}
};
 
class curve_data : public QwtPlotCurve
{
public:
	void drawSymbols(QPainter *painter, const QwtSymbol &symbol,
			const QwtScaleMap &xMap, const QwtScaleMap &yMap, int from, int to) const
	{
		QRect rect;
		rect.setSize(QwtPainter::metricsMap().screenToLayout(symbol.size()));
 
		for (int i = from; i <= to; i++)
		{
			const int xi = xMap.transform(x(i));
			const int yi = yMap.transform(y(i));
			rect.moveCenter(QPoint(xi, yi));
			painter->setPen(QPen(Qt::blue));
 
			feather f;
			f.draw(painter, rect);
		}
	}
};
 
int main(int argc, char *argv[])
{
	QApplication a(argc, argv);
	QwtPlot *qwt =new QwtPlot;
	qwt->setCanvasBackground(QColor(Qt::white));
 
	//set scale for x-axis
	qwt->setAxisScale(QwtPlot::xBottom, 13, 0);
	qwt->setAxisMaxMajor(QwtPlot::xBottom, 24);
	qwt->setAxisMaxMinor(QwtPlot::xBottom, 0);
 
	//set scale for y-axis
	qwt->setAxisScale(QwtPlot::yLeft, 0, 31);
 
	//create data for curve
	int MAX=12*30;
	double x[MAX], y[MAX];
	int k=1;
	int l=1;
 
	for (int i=0; i<MAX; i++)
	{
		x[i]=k;
		y[i]=l;
		k++;
		if (k>12)
		{
			k=1;
			l++;
		}
	}
 
	//create symbol for curve
	feather sym;
	sym.setStyle(QwtSymbol::Cross);
	sym.setSize(30, 10);
 
	//create curve , set symbol and data to curve 
	curve_data *cur=new curve_data;
	cur->setStyle(QwtPlotCurve::NoCurve);
	cur->setSymbol(sym);
	cur->setData(x, y, MAX);
	cur->attach(qwt);
 
	qwt->resize(800, 600);
	qwt->show();
 
	return a.exec();
}

#include <QtGui>
#include "qwt_plot.h"
#include "qwt_plot_curve.h"
#include "qwt_valuelist.h"
#include "qwt_scale_div.h"
#include "qwt_symbol.h"
#include "qwt_painter.h"
class feather : public QwtSymbol
{
public:

	void draw(QPainter *painter, const QRect &r) const
	{
		//painter->translate(r.topLeft());

		//shape |_|__
		QwtPainter::drawLine(painter, r.bottomLeft(), r.topLeft());
		QwtPainter::drawLine(painter, r.bottomLeft(), r.bottomRight());
		QwtPainter::drawLine(painter, r.right()-r.width()/2, r.bottom(),
				r.right()-r.width()/2, r.top());
	}
};

class curve_data : public QwtPlotCurve
{
public:
	void drawSymbols(QPainter *painter, const QwtSymbol &symbol,
			const QwtScaleMap &xMap, const QwtScaleMap &yMap, int from, int to) const
	{
		QRect rect;
		rect.setSize(QwtPainter::metricsMap().screenToLayout(symbol.size()));

		for (int i = from; i <= to; i++)
		{
			const int xi = xMap.transform(x(i));
			const int yi = yMap.transform(y(i));
			rect.moveCenter(QPoint(xi, yi));
			painter->setPen(QPen(Qt::blue));

			feather f;
			f.draw(painter, rect);
		}
	}
};

int main(int argc, char *argv[])
{
	QApplication a(argc, argv);
	QwtPlot *qwt =new QwtPlot;
	qwt->setCanvasBackground(QColor(Qt::white));

	//set scale for x-axis
	qwt->setAxisScale(QwtPlot::xBottom, 13, 0);
	qwt->setAxisMaxMajor(QwtPlot::xBottom, 24);
	qwt->setAxisMaxMinor(QwtPlot::xBottom, 0);

	//set scale for y-axis
	qwt->setAxisScale(QwtPlot::yLeft, 0, 31);

	//create data for curve
	int MAX=12*30;
	double x[MAX], y[MAX];
	int k=1;
	int l=1;

	for (int i=0; i<MAX; i++)
	{
		x[i]=k;
		y[i]=l;
		k++;
		if (k>12)
		{
			k=1;
			l++;
		}
	}

	//create symbol for curve
	feather sym;
	sym.setStyle(QwtSymbol::Cross);
	sym.setSize(30, 10);

	//create curve , set symbol and data to curve 
	curve_data *cur=new curve_data;
	cur->setStyle(QwtPlotCurve::NoCurve);
	cur->setSymbol(sym);
	cur->setData(x, y, MAX);
	cur->attach(qwt);

	qwt->resize(800, 600);
	qwt->show();

	return a.exec();
}

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i get the symbols , but i need to rotate individual symbols at different angles.

[Uwe]

i get the symbols , but i need to rotate individual symbols at different angles.

You know the position and the size of your symbol and you have control over the painting code.
What is missing ( maybe, that you don't know how to paint something rotated at all ) ?

Uwe

[babu198649]

i have messed with the co-oridnates and now i have corrected it .
thank u.

also i have noticed that the subclassed function of QwtSymbol (draw ) is called twice ,
i have 360 symbols but the draw function is called 720 times.which i have found through global variable.

why is it called twice.

[Uwe]

why is it called twice.

It is called, whenever the content of your plot canvas has to be recreated ( QwtPlot::replot ). Use your debugger set a breakpoint in QwtPlotCurve::drawSymbols() and look at the stack, where you are.

Uwe