Qt:自定义窗口之窗口缩放

                当我们隐藏了系统窗口后，无法完成对窗口的缩放，这里缩放方法通过重写一些鼠标事件来实现。具体代码如下：

    头文件：

#define PADDING 2

class MainFrame : public QWidget
{
    Q_OBJECT
public:
    MainFrame(QWidget *parent = 0);
    ~MainFrame();

protected:
    void mouseReleaseEvent(QMouseEvent *event);
    void mouseMoveEvent(QMouseEvent *event);
    void mousePressEvent(QMouseEvent *event);

private:
    void region(const QPoint &cursorPoint);
   
private:
    MainWindow *mainwindow = nullptr;
    bool isLeftPressDown;
    QPoint dragPosition;

    enum Direction{
        UP = 0,
        DOWN=1,
        LEFT,
        RIGHT,
        LEFTTOP,
        LEFTBOTTOM,
        RIGHTBOTTOM,
        RIGHTTOP,
        NONE
    };
    Direction dir;
};

     cpp:

void MainFrame::mouseReleaseEvent(QMouseEvent *event)
{
    if(event->button() == Qt::LeftButton) {
        isLeftPressDown = false;

        this->releaseMouse();
        this->setCursor(QCursor(Qt::ArrowCursor));

    }

    QWidget::mouseReleaseEvent(event);
}

void MainFrame::mousePressEvent(QMouseEvent *event)
{
    if(event->button() == Qt::LeftButton){
        isLeftPressDown = true;
        if(dir != NONE) {
            this->mouseGrabber();
        }
    }

    QWidget::mousePressEvent(event);
}

void MainFrame::mouseMoveEvent(QMouseEvent *event)
{
    QPoint gloPoint = event->globalPos();
    QRect rect = this->rect();
    QPoint tl = mapToGlobal(rect.topLeft());
    QPoint rb = mapToGlobal(rect.bottomRight());

    if(!isLeftPressDown) {
        this->region(gloPoint);
    } else {

        if(dir != NONE) {
            QRect rMove(tl, rb);

            switch(dir) {
            case LEFT:
                if(rb.x() - gloPoint.x() <= this->minimumWidth())
                    rMove.setX(tl.x());
                else
                    rMove.setX(gloPoint.x());
                break;
            case RIGHT:
                rMove.setWidth(gloPoint.x() - tl.x());
                break;
            case UP:
                if(rb.y() - gloPoint.y() <= this->minimumHeight())
                    rMove.setY(tl.y());
                else
                    rMove.setY(gloPoint.y());
                break;
            case DOWN:
                rMove.setHeight(gloPoint.y() - tl.y());
                break;
            case LEFTTOP:
                if(rb.x() - gloPoint.x() <= this->minimumWidth())
                    rMove.setX(tl.x());
                else
                    rMove.setX(gloPoint.x());
                if(rb.y() - gloPoint.y() <= this->minimumHeight())
                    rMove.setY(tl.y());
                else
                    rMove.setY(gloPoint.y());
                break;
            case RIGHTTOP:
                rMove.setWidth(gloPoint.x() - tl.x());
                if(rb.y() - gloPoint.y() <= this->minimumHeight())
                    rMove.setY(tl.y());
                else
                    rMove.setY(gloPoint.y());
                break;

            case LEFTBOTTOM:
                rMove.setHeight(gloPoint.y() - tl.y());
                if(rb.x() - gloPoint.x() <= this->minimumWidth())
                    rMove.setX(tl.x());
                else
                    rMove.setX(gloPoint.x());
                break;

            case RIGHTBOTTOM:
                rMove.setWidth(gloPoint.x() - tl.x());
                rMove.setHeight(gloPoint.y() - tl.y());
                break;
            default:

                break;
            }

            this->setGeometry(rMove);
        }
    }

    QWidget::mouseMoveEvent(event);
}

void MainFrame::region(const QPoint &cursorGlobalPoint)
{
    QRect rect = this->rect();
    QPoint tl = mapToGlobal(rect.topLeft());
    QPoint rb = mapToGlobal(rect.bottomRight());
    int x = cursorGlobalPoint.x();
    int y = cursorGlobalPoint.y();

    if(tl.x() + PADDING >= x && tl.x() <= x && tl.y() + PADDING >= y && tl.y() <= y) {
        // 左上角
        dir = LEFTTOP;
        this->setCursor(QCursor(Qt::SizeFDiagCursor));
    } else if(x >= rb.x() - PADDING && x <= rb.x() && y >= rb.y() - PADDING && y <= rb.y()) {
        // 右下角
        dir = RIGHTBOTTOM;
        this->setCursor(QCursor(Qt::SizeFDiagCursor));
    } else if(x <= tl.x() + PADDING && x >= tl.x() && y >= rb.y() - PADDING && y <= rb.y()) {
        //左下角
        dir = LEFTBOTTOM;
        this->setCursor(QCursor(Qt::SizeBDiagCursor));
    } else if(x <= rb.x() && x >= rb.x() - PADDING && y >= tl.y() && y <= tl.y() + PADDING) {
        // 右上角
        dir = RIGHTTOP;
        this->setCursor(QCursor(Qt::SizeBDiagCursor));
    } else if(x <= tl.x() + PADDING && x >= tl.x()) {
        // 左边
        dir = LEFT;
        this->setCursor(QCursor(Qt::SizeHorCursor));
    } else if( x <= rb.x() && x >= rb.x() - PADDING) {
        // 右边
        dir = RIGHT;
        this->setCursor(QCursor(Qt::SizeHorCursor));
    }else if(y >= tl.y() && y <= tl.y() + PADDING){
        // 上边
        dir = UP;
        this->setCursor(QCursor(Qt::SizeVerCursor));
    } else if(y <= rb.y() && y >= rb.y() - PADDING) {
        // 下边
        dir = DOWN;
        this->setCursor(QCursor(Qt::SizeVerCursor));
    }else {
        // 默认
        dir = NONE;
        this->setCursor(QCursor(Qt::ArrowCursor));
    }
}

效果