#include<afxwin.h>

 class CMyApp :public CWinApp

 {

 public:

     virtual BOOL InitInstance();

 };

 class CMainWindow:public CFrameWnd

 {

 protected:

     BOOL m_bTracking; //标志：鼠标按下为真，否则为假

     BOOL m_bCaptureEndabled;//初始化为真，由OnNcLButtonDown()切换，以便用来打开或关闭鼠标捕获对程序影响

     CPoint m_ptFrom;

     CPoint m_ptTo;

     void InverLine(CDC* pDC,CPoint ptFrom,CPoint ptTo);

 public:

     CMainWindow();

 protected:

     afx_msg void OnLButtonDown(UINT nFlags,CPoint point);

     afx_msg void OnLButtonUp(UINT nFlags,CPoint point);

     afx_msg void OnMouseMove(UINT nFlags,CPoint point);

     afx_msg void OnNcLButtonDown(UINT nHitTest,CPoint point);

     DECLARE_MESSAGE_MAP();

 };

 #include <afxwin.h>

 #include "MouseCap.h"

 CMyApp myApp;

 BOOL CMyApp::InitInstance(){

     m_pMainWnd=new CMainWindow;

     m_pMainWnd->ShowWindow(m_nCmdShow);

     m_pMainWnd->UpdateWindow();

     return TRUE;

 }

 BEGIN_MESSAGE_MAP(CMainWindow,CFrameWnd)

     ON_WM_LBUTTONDOWN()

     ON_WM_LBUTTONUP()

     ON_WM_MOUSEMOVE()

     ON_WM_NCLBUTTONDOWN()

 END_MESSAGE_MAP()

 CMainWindow::CMainWindow(){

     m_bTracking = FALSE;

     m_bCaptureEndabled=TRUE;

     CString strWndClass = AfxRegisterWndClass(

         ,

         AfxGetApp()->LoadStandardCursor(IDC_CROSS),

         (HBRUSH)(COLOR_WINDOW+),

         AfxGetApp()->LoadStandardIcon(IDI_WINLOGO)

         );

     Create(strWndClass,_T("捕获鼠标_橡皮筋操作"));

 }

 void CMainWindow::OnLButtonDown(UINT nFlags,CPoint point){

     m_ptFrom=point;

     m_ptTo=point;

     m_bTracking=TRUE;

     if(m_bCaptureEndabled)

         SetCapture();

 }

 void CMainWindow::OnMouseMove(UINT nFlags,CPoint point){

     if(m_bTracking){

         CClientDC dc(this);

         InverLine(&dc,m_ptFrom,m_ptTo);//清除原来的

         InverLine(&dc,m_ptFrom,point);//画一条新的

         m_ptTo=point;

     }

 }

 void CMainWindow::OnLButtonUp(UINT nFlags,CPoint point){

     if(m_bTracking){

         m_bTracking=FALSE;

         if(GetCapture()==this)

             ::ReleaseCapture();

         CClientDC dc(this);

         InverLine(&dc,m_ptFrom,m_ptTo);//清除原来的

         CPen pen(PS_DASHDOTDOT,,RGB(,,));//画一条红的

         dc.SelectObject(&pen);

         dc.MoveTo(m_ptFrom);

         dc.LineTo(point);

     }

 }

 //单击标题栏激活CFrameWnd::OnNcLButtonDown(nHitTest,point)处理程序

 void CMainWindow::OnNcLButtonDown(UINT nHitTest,CPoint point){

     if(nHitTest==HTCAPTION){

         m_bCaptureEndabled=m_bCaptureEndabled ? FALSE:TRUE;

         SetWindowText(m_bCaptureEndabled ?

             _T("能够"):_T("不能"));

     }

     CFrameWnd::OnNcLButtonDown(nHitTest,point);

 }

 void CMainWindow::InverLine(CDC* pDC,CPoint ptFrom,CPoint ptTo){

     int nOldMode=pDC->SetROP2(R2_NOT);//这种绘图模式保证一条清除一条新的

     pDC->MoveTo(ptFrom);

     pDC->LineTo(ptTo);

     pDC->SetROP2(nOldMode);

 }