[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：

 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()<m_originalWidth-300){
27         return;
28     }
29     this->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