MFC鼠标获取DEMO

这里直接贴上MFC window程序设计的代码，然后加上编程需要注意的地方

CMainWindow::CMainWindow ()
{
	m_bTracking = FALSE;
	m_bCaptureEnabled = TRUE;
	//
	// Register a WNDCLASS.
	//
    CString strWndClass = AfxRegisterWndClass (
        0,
        AfxGetApp ()->LoadStandardCursor (IDC_CROSS),	//加载window的十字光标
        (HBRUSH) (COLOR_WINDOW + 1),
        AfxGetApp ()->LoadStandardIcon (IDI_WINLOGO)
    );

	//
	// Create a window.
	//
    Create (strWndClass, _T ("Mouse Capture Demo (Capture Enabled)"));
}

void CMainWindow::OnLButtonDown (UINT nFlags, CPoint point)
{
	//
	// Record the anchor point and set the tracking flag.
	//
    m_ptFrom = point;
    m_ptTo = point;
    m_bTracking = TRUE;

	//
	// If capture is enabled, capture the mouse.
	//
    if (m_bCaptureEnabled)
        SetCapture ();		//这里“捕获”鼠标，意思是即使鼠标不在客户区，也发送鼠标消息到窗口
}

void CMainWindow::OnMouseMove (UINT nFlags, CPoint point)
{
	//
	// If the mouse is moved while we're "tracking" (that is, while a
	// line is being rubber-banded), erase the old rubber-band line and
	// draw a new one.
	//
    if (m_bTracking) {
        CClientDC dc (this);
        InvertLine (&dc, m_ptFrom, m_ptTo);
        InvertLine (&dc, m_ptFrom, point);
        m_ptTo = point;
    }
}

void CMainWindow::OnLButtonUp (UINT nFlags, CPoint point)
{
	//
	// If the left mouse button is released while we're tracking, release
	// the mouse if it's currently captured, erase the last rubber-band
	// line, and draw a thick red line in its place.
	//
 //假如没有捕获鼠标，鼠标在非客户区抬起时，不会发送消息到窗口

 if (m_bTracking) {

       m_bTracking = FALSE;
        if (GetCapture () == this)
            ::ReleaseCapture ();	//假如有捕获鼠标，在这一定要释放掉

        CClientDC dc (this);
        InvertLine (&dc, m_ptFrom, m_ptTo);

        CPen pen (PS_SOLID, 16, RGB (255, 0, 0));
        dc.SelectObject (&pen);

        dc.MoveTo (m_ptFrom);
        dc.LineTo (point);
    }
}

void CMainWindow::OnNcLButtonDown (UINT nHitTest, CPoint point)
{
	//
	// When the window's title bar is clicked with the left mouse button,
	// toggle the capture flag on or off and update the window title.
	//

 //非客户区鼠标左键点击会发送此消息

   if (nHitTest == HTCAPTION) {
        m_bCaptureEnabled = m_bCaptureEnabled ? FALSE : TRUE;
        SetWindowText (m_bCaptureEnabled ?
            _T ("Mouse Capture Demo (Capture Enabled)") :
            _T ("Mouse Capture Demo (Capture Disabled)"));
    }
    CFrameWnd::OnNcLButtonDown (nHitTest, point);	//这里要把消息发给子类，让window去处理，否则鼠标的其他操作会失效
}

void CMainWindow::InvertLine (CDC* pDC, CPoint ptFrom, CPoint ptTo)
{
	//
	// Invert a line of pixels by drawing a line in the R2_NOT drawing mode.
	//
    int nOldMode = pDC->SetROP2 (R2_NOT);	//这是设置前背景渲染模式，R2_NOT是取反

    pDC->MoveTo (ptFrom);
    pDC->LineTo (ptTo);

    pDC->SetROP2 (nOldMode);
}