[游戏学习25] MFC 橡皮筋画线效果

>_<:这是给出窗口内外不同情况的处理展示的例子。

>_<:MouseCap.h

 #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();
 };

>_<:MouceCap.cpp

 #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);
 }