Qt鼠标事件，窗口移动

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include 

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

protected:
    virtual void mouseDoubleClickEvent(QMouseEvent *event);
    virtual void mouseMoveEvent(QMouseEvent *event);
    virtual void mousePressEvent(QMouseEvent *event);
    virtual void mouseReleaseEvent(QMouseEvent *event);
    virtual void wheelEvent(QWheelEvent *event);

private:
    Ui::MainWindow *ui;

    QPoint m_offset; //记录鼠标左键按下时窗口和鼠标的位置偏差
};

#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include 
#include 

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::mouseDoubleClickEvent(QMouseEvent *event)
{
    if(Qt::LeftButton == event->button())
    {
        if(this->isFullScreen())
        {
//            this->showNormal();
            this->setWindowState(Qt::WindowNoState);
        }
        else
        {
//            this->showFullScreen();
            this->setWindowState(Qt::WindowFullScreen);
        }
    }
    else
    {
        QMainWindow::mouseDoubleClickEvent(event);
    }
}

void MainWindow::mouseMoveEvent(QMouseEvent *event)
{
    if(Qt::LeftButton & event->buttons())
    {
        QPoint point;
        point = event->globalPos() - m_offset;
        this->move(point);
    }
    else
    {
        QMainWindow::mouseMoveEvent(event);
    }
}

void MainWindow::mousePressEvent(QMouseEvent *event)
{
    if(Qt::LeftButton == event->button())
    {
        m_offset = event->globalPos() - this->pos(); //记录鼠标和窗口的位置偏差

        //将鼠标形状换成“手”
        QCursor cursor;
        cursor.setShape(Qt::ClosedHandCursor); //“握拳”
//        cursor.setShape(Qt::OpenHandCursor); //"手掌"
        QApplication::setOverrideCursor(cursor);
    }
    else
    {
        QMainWindow::mousePressEvent(event);
    }
}

void MainWindow::mouseReleaseEvent(QMouseEvent *event)
{
    if(Qt::LeftButton == event->button())
    {
        QApplication::restoreOverrideCursor();
    }
    else
    {
        QMainWindow::mouseReleaseEvent(event);
    }
}

void MainWindow::wheelEvent(QWheelEvent *event)
{
    if(event->delta() > 0)
    {
        ui->textEdit->zoomIn(); //目前字体缩放仍有很多限制，并不是每种情况都有效
    }
    else
    {
        ui->textEdit->zoomOut();
    }
}