#ifndef WIDGET_H
#define WIDGET_H

#include "ui_widget.h"

class Widget : public QWidget, private Ui::mainWidget
{
    Q_OBJECT
    
public:
    explicit Widget(QWidget *parent = 0);
};

#endif // WIDGET_H

#include "widget.h"
Widget::Widget(QWidget *parent) :
    QWidget(parent)
{
    setupUi(this);
}

#ifndef MYWIDGET_H
#define MYWIDGET_H

#include <QWidget>
#include <QPainter>

class MyWidget : public QWidget
{
    Q_OBJECT
public:
    explicit MyWidget(QWidget *parent = 0);
    
signals:
    
public slots:
    
protected:
    void paintEvent(QPaintEvent *);
    QPainter paint;
};

#endif // MYWIDGET_H

#include "mywidget.h"

MyWidget::MyWidget(QWidget *parent) :
    QWidget(parent)
{
}

void MyWidget::paintEvent(QPaintEvent *)
{

    int w = this->width();
    int h = this->height();

    QPainter p(this);
    //p.drawLine(0,0,w, h);
    p.drawLine(w/2, 0, w/2, h);
    p.drawLine(0, h/2, w, h/2);
    for(int i = 10; i < h; i+=10)
    {
        p.drawLine(w/2 - 1, i, w/2 + 1, i);
    }
    for(int i = 10; i < w; i+=10)
    {
        p.drawLine(i, h/2 - 1, i, h/2 + 1);
    }
}

#include <QtGui/QApplication>
#include "widget.h"

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Widget w;
    w.show();
    
    return a.exec();
}

#ifndef UI_WIDGET_H
#define UI_WIDGET_H

#include <QtCore/QVariant>
#include <QtGui/QAction>
#include <QtGui/QApplication>
#include <QtGui/QButtonGroup>
#include <QtGui/QHeaderView>
#include <QtGui/QPushButton>
#include <QtGui/QWidget>
#include "mywidget.h"

QT_BEGIN_NAMESPACE

class Ui_mainWidget
{
public:
    MyWidget *drawWidget;
    QPushButton *pushButton;

    void setupUi(QWidget *mainWidget)
    {
        if (mainWidget->objectName().isEmpty())
            mainWidget->setObjectName(QString::fromUtf8("mainWidget"));
        mainWidget->resize(531, 300);
        drawWidget = new MyWidget(mainWidget);
        drawWidget->setObjectName(QString::fromUtf8("drawWidget"));
        drawWidget->setGeometry(QRect(60, 50, 261, 211));
        pushButton = new QPushButton(mainWidget);
        pushButton->setObjectName(QString::fromUtf8("pushButton"));
        pushButton->setGeometry(QRect(380, 70, 98, 27));

        retranslateUi(mainWidget);

        QMetaObject::connectSlotsByName(mainWidget);
    } // setupUi

    void retranslateUi(QWidget *mainWidget)
    {
        mainWidget->setWindowTitle(QApplication::translate("mainWidget", "Widget", 0, QApplication::UnicodeUTF8));
        pushButton->setText(QApplication::translate("mainWidget", "do it", 0, QApplication::UnicodeUTF8));
    } // retranslateUi

};

namespace Ui {
    class mainWidget: public Ui_mainWidget {};
} // namespace Ui

QT_END_NAMESPACE

#endif // UI_WIDGET_H