[Qt] 事件机制（四）

滚轮事件：滚动滚轮实现窗口大小缩放

widget.h中增加：

protected:
    void wheelEvent(QWheelEvent *event) Q_DECL_OVERRIDE;
    void extendWindowsSize();
    void shrinkWindowsSize();
private:
    int m_originalWidth;
    int m_originalHeight;

widget.cpp中增加：

Widget::Widget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Widget)
{
    ...
    m_originalWidth=this->width();
    m_originalHeight=this->height();
}
void Widget::wheelEvent(QWheelEvent *event){
    QWidget::wheelEvent(event);
    QPoint scroll = event->angleDelta();
    if(scroll.y()>0){
        extendWindowsSize();
    }else{
        shrinkWindowsSize();
    }
}
void Widget::extendWindowsSize(){
    if(this->width()>m_originalWidth+300){
        return;
    }
    this->setMaximumSize(this->width()+10,this->height()+10);
    this->setMinimumSize(this->width()+10,this->height()+10);
}
void Widget::shrinkWindowsSize(){
    if(this->width()<m_originalWidth-300){
        return;
    }
    this->setMinimumSize(this->width()-10,this->height()-10);
    this->setMaximumSize(this->width()-10,this->height()-10);
}

参考：

https://blog.csdn.net/qq78442761/article/details/85104679

https://blog.csdn.net/qq78442761/article/details/81503006

void setResizeAnchor(ViewportAnchor anchor);

QGraphicsView::AnchorViewCenter