下面是简单的 用鼠标绘制一条直线 的代码  运行过程中 绘制直线反映很慢  谁能帮忙看看啊  谢谢诶






#include "stdafx.h"
#include "sffg.h"

#include "sffgDoc.h"
#include "sffgView.h"

#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif

/////////////////////////////////////////////////////////////////////////////
// CSffgView

IMPLEMENT_DYNCREATE(CSffgView, CView)

BEGIN_MESSAGE_MAP(CSffgView, CView)
    //{{AFX_MSG_MAP(CSffgView)
    ON_COMMAND(ID_LINE, OnLine)
    ON_COMMAND(ID_NLINE, OnNline)
    ON_WM_LBUTTONDOWN()
    ON_UPDATE_COMMAND_UI(ID_LINE, OnUpdateLine)
    //}}AFX_MSG_MAP
    // Standard printing commands
    ON_COMMAND(ID_FILE_PRINT, CView::OnFilePrint)
    ON_COMMAND(ID_FILE_PRINT_DIRECT, CView::OnFilePrint)
    ON_COMMAND(ID_FILE_PRINT_PREVIEW, CView::OnFilePrintPreview)
END_MESSAGE_MAP()

/////////////////////////////////////////////////////////////////////////////
// CSffgView construction/destruction

CSffgView::CSffgView()
{
    // TODO: add construction code here
    m_bLine=FALSE;
    m_startX=m_startY=0;
    m_step=0;

}

CSffgView::~CSffgView()
{
}

BOOL CSffgView::PreCreateWindow(CREATESTRUCT& cs)
{
    // TODO: Modify the Window class or styles here by modifying
    //  the CREATESTRUCT cs

    return CView::PreCreateWindow(cs);
}

/////////////////////////////////////////////////////////////////////////////
// CSffgView drawing

void CSffgView::OnDraw(CDC* pDC)
{
    CSffgDoc* pDoc = GetDocument();
    ASSERT_VALID(pDoc);
    // TODO: add draw code for native data here
}

/////////////////////////////////////////////////////////////////////////////
// CSffgView printing

BOOL CSffgView::OnPreparePrinting(CPrintInfo* pInfo)
{
    // default preparation
    return DoPreparePrinting(pInfo);
}

void CSffgView::OnBeginPrinting(CDC* /*pDC*/, CPrintInfo* /*pInfo*/)
{
    // TODO: add extra initialization before printing
}

void CSffgView::OnEndPrinting(CDC* /*pDC*/, CPrintInfo* /*pInfo*/)
{
    // TODO: add cleanup after printing
}

/////////////////////////////////////////////////////////////////////////////
// CSffgView diagnostics

#ifdef _DEBUG
void CSffgView::AssertValid() const
{
    CView::AssertValid();
}

void CSffgView::Dump(CDumpContext& dc) const
{
    CView::Dump(dc);
}

CSffgDoc* CSffgView::GetDocument() // non-debug version is inline
{
    ASSERT(m_pDocument->IsKindOf(RUNTIME_CLASS(CSffgDoc)));
    return (CSffgDoc*)m_pDocument;
}
#endif //_DEBUG

/////////////////////////////////////////////////////////////////////////////
// CSffgView message handlers

void CSffgView::OnLine()
{
    // TODO: Add your command handler code here
    CClientDC dc(this);
    m_bLine=TRUE;
    //dc.TextOut(100,100,"shif");
   
}

void CSffgView::OnNline()
{
    // TODO: Add your command handler code here
    CClientDC dc(this);
    m_bLine=FALSE;
   
}

void CSffgView::OnLButtonDown(UINT nFlags, CPoint point)
{
    // TODO: Add your message handler code here and/or call default
    CClientDC dc(this);
    if(m_bLine)
    {
        if(m_step==0)
        {
            m_startX=point.x;
            m_startY=point.y;
            m_step++;
        }
        else
        {
            dc.MoveTo(m_startX,m_startY);
            dc.LineTo(point.x,point.y);
            m_step=0;
        }
    }

   
    CView::OnLButtonDown(nFlags, point);
}

void CSffgView::OnUpdateLine(CCmdUI* pCmdUI)
{
    // TODO: Add your command update UI handler code here
    pCmdUI->SetRadio(m_bLine);
   
}

延迟的厉害啊 截了一张图说明一下：

当我在画直线后面加上一行文本输出的代码后就没有延迟的情况了；（估计其他代码也行）

如果没有那行代码 就会有延迟现象！ 不解中.....