#ifndef __MOUSELINE_H__
#define __MOUSELINE_H__
#include <QWidget>
#include <QVector>
#include <QPoint>
#include <QPainter>
#include <QBrush>
#include <QPen>
#include <QPaintEvent>

class MouseLine: public QWidget {
    public:
        MouseLine(QWidget* p = 0): QWidget(p)
        {

        }
    private:
        QVector<QPoint>        m_points;

    protected:
        void paintEvent(QPaintEvent* ev)
        {
            if(m_points.isEmpty()) QWidget::paintEvent(ev);
            else if(m_points.size() > 1){
                QPainter painter(this);
                painter.setPen(Qt::red);
                QVectorIterator<QPoint> iter(m_points);
                QPoint begin,end;
                end  = iter.next();
                while(iter.hasNext()){
                    begin = end;
                    end = iter.next();
                    painter.drawLine(begin,end);
                }
//                painter.drawLines(m_points);
//                painter.drawLines(m_points.data() + 1, m_points.size()/2 - 1);
            }
        }
        void mousePressEvent(QMouseEvent* ev)
        {
            Qt::MouseButton button = ev->button();
            const QPoint& point = ev->pos();
            if(button == Qt::LeftButton) m_points.append(point);
            else if(button == Qt::RightButton) m_points.clear();
            update();
        }
        void mouseMoveEvent(QMouseEvent* ev)
        {
            m_points.last() = ev->pos();
            update();
        }

};


#endif

#include <QtCore/QEvent>
#include <QtCore/QTimer>
#include <QtGui/QTextEdit>
#include <QtGui/QGridLayout>
#include <QtGui/QVBoxLayout>
#include <QtGui/QPainter>
#include <QtGui/QApplication>
#include <QtGui/QPushButton>
#include <QtDebug>

#include "form.h"

form::form(QWidget *parent) : QMainWindow(parent)
{
    setMinimumSize(200, 180);
    centralwidget = new QWidget(this);
    centralwidget->setObjectName("centralwidget");
    setCentralWidget(centralwidget);

    QTextEdit *textedit = new QTextEdit(centralwidget);
    textedit->setObjectName("textedit");
    QPushButton *btn = new QPushButton("text", this);
    btn->setObjectName("btn");

    QVBoxLayout *vl = new QVBoxLayout(centralwidget);
    vl->addWidget(textedit);
    vl->addWidget(btn);

    centralwidget->setLayout(vl);

    centralwidget->installEventFilter(this);
    textedit->viewport()->installEventFilter(this);
    btn->installEventFilter(this);
}


bool form::eventFilter(QObject *obj, QEvent *event)
{
    if(event->type() == QEvent::Paint) {
        obj->removeEventFilter(this);
        QApplication::sendEvent(obj, event);
        obj->installEventFilter(this);

//        qDebug()<< qobject_cast<QWidget*>(obj)
  //              << qobject_cast<QWidget*>(obj)->geometry()
    //            <<" "
    //            << qobject_cast<QWidget*>(obj)->visibleRegion();

        QPainter p(qobject_cast<QWidget*>(obj));
        p.setPen(Qt::red);
        if(qobject_cast<QWidget*>(obj)->objectName() == "qt_scrollarea_viewport")
            p.setWindow(centralwidget->findChild<QTextEdit*>("textedit")->geometry());
        else
        p.setWindow(qobject_cast<QWidget*>(obj)->geometry());
        p.drawLine(rect().topLeft(), rect().bottomRight());
        return true;
    }
    return false;
}