Question

error C2440: 'static_cast' : cannot convert from 'LRESULT (__thiscall CchatDlg::* )(CPoint)' to 'UI

error C2440: 'static_cast' : cannot convert from 'LRESULT (__thiscall CchatDlg::* )(CPoint)' to 'UINT (__thiscall CWnd::* )(CPoint)

Answer 1

出现这个错误的原因可是“人力不可抗拒”之原因造成的，因为旧版本的 ON_WM_NCHITTEST 宏使用了

UINT (__thiscall CWzButton::* )(CPoint);

类型的类成员函数指针，其定义如下：

#define ON_WM_NCHITTEST() \

{ WM_NCHITTEST, 0, 0, 0, AfxSig_wp, \

(AFX_PMSG)(AFX_PMSGW)(UINT (AFX_MSG_CALL CWnd::*)(CPoint))&OnNcHitTest },

但是新版本变成了：

#define ON_WM_NCHITTEST() \

{ WM_NCHITTEST, 0, 0, 0, AfxSig_l_p, \

(AFX_PMSG)(AFX_PMSGW) \

(static_cast< LRESULT (AFX_MSG_CALL CWnd::*)(CPoint) > (&ThisClass :: OnNcHitTest)) },

注意返回值类型由UINT改成了LRESULT，再加上static_cast的严格检查，所以就出错了。修改的方法就是将你的OnNcHitTest函数由：

afx_msg UINT OnNcHitTest(CPoint point);

改成：

afx_msg LRESULT OnNcHitTest(CPoint point);