Help,I want to make a ruler，all the code is here

[duduqq]

Sorry to my bad english，i want the Rect to fill one color,but it is only a little point.why will
like that.

#include  <QApplication>
#include  <QWidget>
#include  <QPixmap>
#include  <QBitmap>
#include  <QPoint>
#include  <QPalette>
#include  <QMouseEvent>
#include  <QPainter>
 
class myclass:public QWidget
{
    public:
        myclass(QWidget *parent = 0);
    protected:
        void mouseMoveEvent(QMouseEvent *e);
        void mousePressEvent(QMouseEvent *e);
    private:
        QPixmap *pixmap;
        QBitmap *bitmap;
        QPainter *painter ;
        QBrush *brush ;
        QPoint last,pos0;
};
myclass::myclass(QWidget *parent)
    : QWidget(parent,Qt::X11BypassWindowManagerHint)
{
    setGeometry(200,200,800,120);
    brush =new QBrush();
    brush->setStyle(Qt::SolidPattern) ;
    brush->setColor(Qt::gray) ;
    pixmap=new QPixmap(800,120);
    painter =new QPainter(pixmap) ;
 
    //painter->setBackgroundMode(Qt::OpaqueMode);
    painter->begin(this) ;
    painter->setBackground(*brush) ;
    painter->setPen(Qt::red) ;
    painter->drawEllipse(10,0,10,10) ;//画了一个小圆圈，运行时可见。
    painter->end() ;
    QPalette palette;
    palette.setBrush(QPalette::Background, QBrush(*pixmap));
    setPalette(palette);
    setMask(*pixmap);
}
void myclass::mouseMoveEvent(QMouseEvent *e)
{
    if (!(e->buttons() & Qt::LeftButton))
        return;
    QPoint newpos = e->globalPos();
    QPoint upleft = pos0 + newpos - last;
    move(upleft);
}
void myclass::mousePressEvent(QMouseEvent *e)
{ 
    if (e->button() == Qt::LeftButton)
    last = e->globalPos();
    pos0 = e->globalPos() - e->pos();
}
 
int main(int argc,char *argv[])
{
    QApplication a(argc,argv);
    myclass w;
    w.showFullScreen();
    return a.exec();
}

#include  <QApplication>
#include  <QWidget>
#include  <QPixmap>
#include  <QBitmap>
#include  <QPoint>
#include  <QPalette>
#include  <QMouseEvent>
#include  <QPainter>

class myclass:public QWidget
{
    public:
        myclass(QWidget *parent = 0);
    protected:
        void mouseMoveEvent(QMouseEvent *e);
        void mousePressEvent(QMouseEvent *e);
    private:
        QPixmap *pixmap;
        QBitmap *bitmap;
        QPainter *painter ;
        QBrush *brush ;
        QPoint last,pos0;
};
myclass::myclass(QWidget *parent)
    : QWidget(parent,Qt::X11BypassWindowManagerHint)
{
    setGeometry(200,200,800,120);
    brush =new QBrush();
    brush->setStyle(Qt::SolidPattern) ;
    brush->setColor(Qt::gray) ;
    pixmap=new QPixmap(800,120);
    painter =new QPainter(pixmap) ;
   
    //painter->setBackgroundMode(Qt::OpaqueMode);
    painter->begin(this) ;
    painter->setBackground(*brush) ;
    painter->setPen(Qt::red) ;
    painter->drawEllipse(10,0,10,10) ;//画了一个小圆圈，运行时可见。
    painter->end() ;
    QPalette palette;
    palette.setBrush(QPalette::Background, QBrush(*pixmap));
    setPalette(palette);
    setMask(*pixmap);
}
void myclass::mouseMoveEvent(QMouseEvent *e)
{
    if (!(e->buttons() & Qt::LeftButton))
        return;
    QPoint newpos = e->globalPos();
    QPoint upleft = pos0 + newpos - last;
    move(upleft);
}
void myclass::mousePressEvent(QMouseEvent *e)
{ 
    if (e->button() == Qt::LeftButton)
    last = e->globalPos();
    pos0 = e->globalPos() - e->pos();
}

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

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