In need of an advice of simple line drawing with Qt

[Arvelua]

Hello!

I am a complete newbie what comes to Qt C++ programming. My assignment would be to draw a simple line in a QWidget and frankly I don't know what all I ought to be aware of (header files, QObject...etc) in order to complete this task. I am sorry if this question is answered elsewhere on the forum, yet I couldn't find a solution from here or any Qt related forums nor the Web. I am using QT 4.6.2 and a Qt Creator 1.3.1 on Windows Vista.

I have a designer form, in which I have promoted a class "paint" and created after a header file "paint.h"


The header file (paint.h) looks like:

#ifndef PAINT_H
#define PAINT_H
 
#include <QWidget>
 
class paint : public QWidget
{
  Q_OBJECT
 
  public:
    paint(QWidget *parent = 0);
 
  protected:
    void paintEvent(QPaintEvent *event);
 
};
 
 
#endif // PAINT_H

#ifndef PAINT_H
#define PAINT_H

#include <QWidget>

class paint : public QWidget
{
  Q_OBJECT

  public:
    paint(QWidget *parent = 0);

  protected:
    void paintEvent(QPaintEvent *event);

};


#endif // PAINT_H

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and I have a source file:

#include "paint.h"
#include <QApplication>
#include <QPainter>
#include <QLineF>
 
 
void QWidget::paintEvent ( QPaintEvent * event )
{
 
 QLineF line(10.0, 80.0, 90.0, 20.0);
 
 QPainter painter(this);
 painter.drawLine(line);
 
}

#include "paint.h"
#include <QApplication>
#include <QPainter>
#include <QLineF>


void QWidget::paintEvent ( QPaintEvent * event )
{
    
 QLineF line(10.0, 80.0, 90.0, 20.0);

 QPainter painter(this);
 painter.drawLine(line);
 
}

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Yet this wholeness is invalid and I'm not sure what things are wrong with this. The compiler output looks as following:

.../harjoitus2/draw_line/line1.cpp:7: warning: 'virtual void QWidget::paintEvent(QPaintEvent*)' redeclared without dllimport attribute: previous dllimport ignored
 
c:\Qt\2010.02.1\qt\lib/libqtmaind.a:-1: error: In function `WinMain@16':
 
C:\qt-greenhouse\Trolltech\Code_less_create_more\Trolltech\Code_less_create_more\Troll\4.6\qt\src\winmain/qtmain_win.cpp:131: undefined reference to `qMain(int, char**)'
 
:-1: error: collect2: ld returned 1 exit status

.../harjoitus2/draw_line/line1.cpp:7: warning: 'virtual void QWidget::paintEvent(QPaintEvent*)' redeclared without dllimport attribute: previous dllimport ignored

c:\Qt\2010.02.1\qt\lib/libqtmaind.a:-1: error: In function `WinMain@16':

C:\qt-greenhouse\Trolltech\Code_less_create_more\Trolltech\Code_less_create_more\Troll\4.6\qt\src\winmain/qtmain_win.cpp:131: undefined reference to `qMain(int, char**)'

:-1: error: collect2: ld returned 1 exit status

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I would be very grateful if you would point me out the essential facts of making this simple program to function. Thanks in advance!

[wysota]

It should be paint::paintEvent(...) in line #7 of the second code snippet.

[Arvelua]

Thanks for your reply!

I corrected the line #7, but yet I get these error messages:

c:\Qt\2010.02.1\qt\lib/libqtmaind.a:-1: error: In function `WinMain@16':
 
C:\qt-greenhouse\Trolltech\Code_less_create_more\Trolltech\Code_less_create_more\Troll\4.6\qt\src\winmain/qtmain_win.cpp:131: undefined reference to `qMain(int, char**)'
 
:-1: error: collect2: ld returned 1 exit status

c:\Qt\2010.02.1\qt\lib/libqtmaind.a:-1: error: In function `WinMain@16':

C:\qt-greenhouse\Trolltech\Code_less_create_more\Trolltech\Code_less_create_more\Troll\4.6\qt\src\winmain/qtmain_win.cpp:131: undefined reference to `qMain(int, char**)'

:-1: error: collect2: ld returned 1 exit status

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[wysota]

Did you implement the main() function in your program? Be sure to add the file containing it to your project.

[Arvelua]

Yes, I did it now and the program works as espected. Thanks for your help.