Qwt examples

Hi to all! Some time ago I downloaded Qwt. All OK. Compiling OK. Installing OK.
A troubles with using in project was resolved successfully. But I need a histogram.
Well, there is an example present in source code. Good. Building... OK.
Trying to start examples one by one.
bode - segmentation fault :confused:
cpuplot - symbol lookup error: ./cpuplot: undefined symbol: _ZNK9QwtLegend4findEPK20QwtLegendItemManager ????
curvedemo1, curvedemo1 - segmentation fault :confused: :mad:
data_plot - segmentation fault :-/
dials - ok :-D
event_filter - ok :-)
histogram - segmentation fault :-/
radio - ok :-D
realtime - segmentation fault :-/
simple - segmentation fault :-/
sliders - ok :-D
spectrogram - segmentation fault >:-/
sysinfo - ok :-)

So, it`s a pity, but I can`t see most interesting examples. Well. I`m trying to write a histogram for my project. Step by step I`m trying to understand what`s wrong with example "histogram". As I understood there are no class like QwtHistogram. So, in example I have

Code:

---

class HistogramItem: public QwtPlotItem
{
public:
    explicit HistogramItem(const QString &title = QString::null);
    explicit HistogramItem(const QwtText &title);
    virtual ~HistogramItem();
 
    void setData(const QwtIntervalData &data);
    const QwtIntervalData &data() const;
 
    void setColor(const QColor &);
    QColor color() const;
 
    virtual QwtDoubleRect boundingRect() const;
 
    virtual int rtti() const;
 
    virtual void draw(QPainter *, const QwtScaleMap &xMap, 
        const QwtScaleMap &yMap, const QRect &) const;
 
    void setBaseline(double reference);
    double baseline() const;
 
    enum HistogramAttribute
    {
        Auto = 0,
        Xfy = 1
    };
 
    void setHistogramAttribute(HistogramAttribute, bool on = true);
    bool testHistogramAttribute(HistogramAttribute) const;
 
protected:
    virtual void drawBar(QPainter *,
        Qt::Orientation o, const QRect &) const;
 
private:
    void init();
 
    class PrivateData;
    PrivateData *d_data;
};

---

I wrote a test as copy of example:

Code:

---

#include <stdlib.h>
#include <qapplication.h>
#include <qpen.h>
#include <qwt_plot.h>
#include <qwt_plot_grid.h>
#include <qwt_plot_marker.h>
#include <qwt_interval_data.h>
#include "histogram_item.h"
 
int main(int argc, char **argv)
{
    QApplication a(argc, argv);
 
    QwtPlot* plot = new QwtPlot(0);
    plot->setCanvasBackground(QColor(Qt::white));
    plot->setTitle("Histogram");
 
    QwtPlotGrid *grid = new QwtPlotGrid;
    grid->enableXMin(true);
    grid->enableYMin(true);
    grid->setMajPen(QPen(Qt::black, 0, Qt::DotLine));
    grid->setMinPen(QPen(Qt::gray, 0 , Qt::DotLine));
    grid->attach(plot);
 
    HistogramItem *histogram = new HistogramItem();
    histogram->setColor(Qt::darkCyan);
 
    const int numValues = 20;
 
    QwtArray<QwtDoubleInterval> intervals(numValues);
    QwtArray<double> values(numValues);
 
    double pos = 0.0;
    for ( int i = 0; i < (int)intervals.size(); i++ )
    {
        const int width = 5 + rand() % 15;
        const int value = rand() % 100;
 
        intervals[i] = QwtDoubleInterval(pos, pos + double(width));
        values[i] = value; 
 
        pos += width;
    }
 
    histogram->setData(QwtIntervalData(intervals, values));
    histogram->attach(plot);
 
    plot->setAxisScale(QwtPlot::yLeft, 0.0, 100.0);
    plot->setAxisScale(QwtPlot::xBottom, 0.0, pos);
    plot->replot();
 
#if QT_VERSION < 0x040000
    a.setMainWidget(&plot);
#endif
 
    plot->resize(600,400);
    plot->show();
 
    return a.exec(); 
}

---

and got segmentation fault in return a.exec();

Can you help me? Were is problem may be? May be another way present to make histogram?
Thanks a lot everyone!

I can't help with your seg faults but if you are interested in a histogram, I am using the QwtPlotHistogram which is in the SVN development trunk (5.2). I have found it quite useful.

-Dean

Quote:

---

Originally Posted by DKL1972

I can't help with your seg faults but if you are interested in a histogram, I am using the QwtPlotHistogram which is in the SVN development trunk (5.2). I have found it quite useful.
-Dean

---

Thanks a lot! All OK, but at

Code:

---

QwtPlotHistogram *histogram = new QwtPlotHistogram();

---

I`ve got:
/home/Andrei/Projects/Rados/RadosSeparatorQT/RadosSeparatorQT: symbol lookup error: /home/Andrei/Projects/Rados/RadosSeparatorQT/RadosSeparatorQT: undefined symbol: _ZN16QwtPlotHistogramC1ERK7QString
Trying to to understand this...

I is seems that I`ve got dynamically linking problem...
my *.pro file:

Code:

---

QWT_ROOT = qwt
 
include( $${QWT_ROOT}/qwtconfig.pri )
 
SUFFIX_STR =
VVERSION = $$[QT_VERSION]
isEmpty(VVERSION) {
 
    # Qt 3
    debug {
        SUFFIX_STR = $${DEBUG_SUFFIX}
    }
    else {
        SUFFIX_STR = $${RELEASE_SUFFIX}
    }
}
else {
    CONFIG(debug, debug|release) {
        SUFFIX_STR = $${DEBUG_SUFFIX}
    }
    else {
        SUFFIX_STR = $${RELEASE_SUFFIX}
    }
}
 
INCLUDEPATH += $${QWT_ROOT}/src
DEPENDPATH  += $${QWT_ROOT}/src
QWTLIB       = qwt$${SUFFIX_STR}
LIBS        += -L$${QWT_ROOT}/lib -l$${QWTLIB}
 
TEMPLATE = app
TARGET = RadosSeparatorQT
QT += core \
    gui \
    xml \
    network \
    thread
HEADERS += header1.h \
header2.h \
... 
 
SOURCES += source1.cpp \
source2.cpp \
... 
FORMS += Form1.ui \
    Form2.ui \
...
RESOURCES += Resource.qrc

---

is it correct?

Another variant of *.pro file

Code:

---

INCLUDEPATH += qwt/src
unix:LIBS    += -L/qwt/lib -llibqwt
TEMPLATE = app
TARGET = RadosSeparatorQT
QT += core \
    gui \
    xml \
    network \
    thread
HEADERS += header1.h \
header2.h \
...
SOURCES += source1.cpp \
source2.cpp \
...
FORMS += Form1.ui \
    Form2.ui \
...
RESOURCES += Resource.qrc

---

So. I`ve got from from SVN development trunk version 5.2. Before compile and install I changed in qwt.pri CONFIG += QwtDll to CONFIG -= QwtDll. And as result I have libqwt.a (instead of libqwt-5.2.so). Static library. While compiling and installing no any problems. I`ve copied lib and src subdirectory into qwt subdirectory of my project. While compiling project no any trouble. A trouble at linking!

Code:

---

cd '/home/Andrei/Projects/Rados/RadosSeparatorQT' && LC_MESSAGES="C" LC_CTYPE="C" gmake -k 
linking RadosSeparatorQT (g++)
/usr/bin/ld: cannot find -llibqwt
collect2: ld returned 1 exit status
gmake: *** [RadosSeparatorQT] Error 1
gmake: Target `first' not remade because of errors.
*** Exited with status: 2 ***

---

Why it can`t find library? A path to it is correct.

Quote:

---

Originally Posted by 31512

unix:LIBS += -L/qwt/lib -llibqwt

---

It should be:

unix:LIBS += -L/qwt/lib -lqwt

Quote:

---

Originally Posted by jacek

It should be:

unix:LIBS += -L/qwt/lib -lqwt

---

My respect to you! It works! It must be admitted that, the truth is that I am old stupid monkey! Can you explain why it should be -L/qwt/lib -lqwt, but not -L/qwt/lib -llibqwt?

All was good until I wrote

Code:

---

WidgetFrameCommonView::WidgetFrameCommonView( QWidget *parent )
    : QWidget( parent )
{
	setupUi( this );
 
        QwtPlotHistogram *histogram = new QwtPlotHistogram();
        //histogram->setStyle(QwtPlotHistogram::Columns);
        //histogram->setPen(QPen(Qt::black));
        //histogram->setBrush(QBrush(Qt::gray));
        //histogram->attach(Plot);
        //Plot->replot();
 
	CommonInfoPanel->SetBackGroundColor( Qt::lightGray );
	SeparatorsPanelsPanel->SetBackGroundColor( Qt::gray );
	gridLayout->setContentsMargins( 0, 0, 0, 0 );
	gridLayout->setSpacing( 0 );
}

---

linking RadosSeparatorQT (g++)
WidgetFrameCommonView.o: In function `WidgetFrameCommonView':
/home/Andrei/Projects/Rados/RadosSeparatorQT/Frames/WidgetFrameCommonView.cpp:9: undefined reference to `QwtPlotHistogram::QwtPlotHistogram(QString const&)'
/home/Andrei/Projects/Rados/RadosSeparatorQT/Frames/WidgetFrameCommonView.cpp:9: undefined reference to `QwtPlotHistogram::QwtPlotHistogram(QString const&)'
collect2: ld returned 1 exit status
gmake: *** [RadosSeparatorQT] Error 1
gmake: Target `first' not remade because of errors.
*** Exited with status: 2 ***

Without

Code:

---

QwtPlotHistogram *histogram = new QwtPlotHistogram();

---

linking is successful. As I understood class QwtPlotHistogram have some bugs?

Code:

---

class QWT_EXPORT QwtPlotHistogram: public QwtPlotSeriesItem<QwtIntervalSample>
{
public:
    enum CurveStyle
    {
        NoCurve,
 
        Outline,
 
        Columns,
        Lines,
 
        UserCurve = 100
    };
 
    explicit QwtPlotHistogram(const QString &title = QString::null);
    explicit QwtPlotHistogram(const QwtText &title);
    virtual ~QwtPlotHistogram();
 
    ...
};
#endif

---

Histogram example was compiled and linked successfully. Executed successfully too. I`m perplexed... My program still generating link errors.

OK. Problem solved successfully. Including examples.pri (with some modifications) to *.pro file of my project makes wonder...

Quote:

---

Originally Posted by 31512

Can you explain why it should be -L/qwt/lib -lqwt, but not -L/qwt/lib -llibqwt?

---

It's UNIX naming convention. All library file names start with "lib", so somebody in the Olde Days decided to skip it in linker options.

Quote:

---

Originally Posted by jacek

It's UNIX naming convention. All library file names start with "lib", so somebody in the Olde Days decided to skip it in linker options.

---

Thanks a lot! Live and learn... RTFM for me. :)