Q_DECL_OVERRIDE也就是c++的override
# define Q_DECL_OVERRIDE override
在重写虚函数时会用到，
作用是防止写错虚函数：
void keyPressEvent(QKeyEvent *event) Q_DECL_OVERRIDE;
Q_DECL_OVERRIDE
原文：https://www.cnblogs.com/stones-dream/p/9309119.html
