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：

1 Widget::Widget(QWidget *parent) :
2 QWidget(parent),
3 ui(new Ui::Widget)
4 {
5 …
6 m_originalWidth=this->width();
7 m_originalHeight=this->height();
8 }
9 void Widget::wheelEvent(QWheelEvent *event){
10 QWidget::wheelEvent(event);
11 QPoint scroll = event->angleDelta();
12 if(scroll.y()>0){
13 extendWindowsSize();
14 }else{
15 shrinkWindowsSize();
16 }
17 }
18 void Widget::extendWindowsSize(){
19 if(this->width()>m_originalWidth+300){
20 return;
21 }
22 this->setMaximumSize(this->width()+10,this->height()+10);
23 this->setMinimumSize(this->width()+10,this->height()+10);
24 }
25 void Widget::shrinkWindowsSize(){
26 if(this->width()setMinimumSize(this->width()-10,this->height()-10);
30 this->setMaximumSize(this->width()-10,this->height()-10);
31 }

参考：

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

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

void setResizeAnchor(ViewportAnchor anchor);

QGraphicsView::AnchorViewCenter