实现效果需要处理以下这三个消息:

WM_NCHITTEST WM_SETCURSOR WM_NCLBUTTONDOWN

很多人在问三个函数是做什么用的，下面我大概介绍一下：

OnNcHitTest(UINT nHitTest, CPoint point)是用来测试鼠标的位置，Nc表示非客户区

OnSetCursor(HWND hWnd, UINT nHitTest, UINT message) 是用来设置鼠标状态

OnNcLButtonDown(UINT nHitTest, CPoint point)是用来处理非客户区的鼠标左键点击

有不懂的可以留言交流一下，希望本文章对大家有所帮助

消息处理函数:

UINT CXXXDlg::OnNcHitTest(UINT nHitTest, CPoint point)
...{
 CRect rect;
 GetWindowRect(&rect);
if(point.x<=rect.left+3)
    returnHTLEFT;
elseif(point.x>=rect.right-3)
    returnHTRIGHT;
elseif(point.y<=rect.top+3)
    returnHTTOP;
elseif(point.y>=rect.bottom-3)
    returnHTBOTTOM;
elseif(point.x<=rect.left+10&&point.y<=rect.top+10)
    returnHTTOPLEFT;
elseif(point.x>=rect.right-10&&point.y<=rect.top+10)
    returnHTTOPRIGHT;
elseif(point.x<=rect.left+10&&point.y>=rect.bottom-10)
    returnHTBOTTOMLEFT;
elseif(point.x>=rect.right-10&&point.y>=rect.bottom-10)
    returnHTBOTTOMRIGHT;

 else

    return CDialog::OnNcHitTest(point);
}


BOOL CXXXDlg::OnSetCursor(HWND hWnd, UINT nHitTest, UINT message)
...{
    if(nHitTest==HTCAPTION||nHitTest==HTSYSMENU||
        nHitTest==HTMENU||nHitTest==HTCLIENT)
   ...{
        SetCursor(LoadCursor(NULL, MAKEINTRESOURCE(IDC_ARROW)));
    }
   elseif(nHitTest==HTTOP||nHitTest==HTBOTTOM)
   ...{
        SetCursor(LoadCursor(NULL, MAKEINTRESOURCE(IDC_SIZENS)));
    }
   elseif(nHitTest==HTLEFT||nHitTest==HTRIGHT)
   ...{
        SetCursor(LoadCursor(NULL, MAKEINTRESOURCE(IDC_SIZEWE)));
    }
   elseif(nHitTest==HTTOPLEFT||nHitTest==HTBOTTOMRIGHT)
   ...{
        SetCursor(LoadCursor(NULL, MAKEINTRESOURCE(IDC_SIZENWSE)));
    }
   elseif(nHitTest==HTTOPRIGHT||nHitTest==HTBOTTOMLEFT)
   ...{
        SetCursor(LoadCursor(NULL, MAKEINTRESOURCE(IDC_SIZENESW)));
    }
   else
   ...{
        SetCursor(LoadCursor(NULL, MAKEINTRESOURCE(IDC_ARROW)));
     }
}


voidCXXXDlg::OnNcLButtonDown(UINT nHitTest, CPoint point)
...{
   if(nHitTest==HTTOP)
        SendMessage( WM_SYSCOMMAND, SC_SIZE|WMSZ_TOP, MAKELPARAM(point.x, point.y));
   elseif(nHitTest==HTBOTTOM)
        SendMessage( WM_SYSCOMMAND, SC_SIZE|WMSZ_BOTTOM, MAKELPARAM(point.x, point.y));
   elseif(nHitTest==HTLEFT)
        SendMessage( WM_SYSCOMMAND, SC_SIZE|WMSZ_LEFT, MAKELPARAM(point.x, point.y));
   elseif(nHitTest==HTRIGHT)
        SendMessage( WM_SYSCOMMAND, SC_SIZE|WMSZ_RIGHT, MAKELPARAM(point.x, point.y));
   elseif(nHitTest==HTTOPLEFT)
        SendMessage( WM_SYSCOMMAND, SC_SIZE|WMSZ_TOPLEFT, MAKELPARAM(point.x, point.y));
   elseif(nHitTest==HTTOPRIGHT)
        SendMessage( WM_SYSCOMMAND, SC_SIZE|WMSZ_TOPRIGHT, MAKELPARAM(point.x, point.y));
   elseif(nHitTest==HTBOTTOMLEFT)
        SendMessage( WM_SYSCOMMAND, SC_SIZE|WMSZ_BOTTOMLEFT, MAKELPARAM(point.x, point.y));
   elseif(nHitTest==HTBOTTOMRIGHT)
        SendMessage(WM_SYSCOMMAND, SC_SIZE|WMSZ_BOTTOMRIGHT, MAKELPARAM(point.x, point.y));
}