绘图后的虚框怎么取消

[elegant87]

我在练习画图，画直线，矩形，椭圆，我用到了虚框，开始画的时候有个虚框，但是画完后还有，
我的问题是怎么让画完图后虚框消失！
下面是我的程序：

void CGraphicView::OnLButtonDown(UINT nFlags, CPoint point) 
{
	// TODO: Add your message handler code here and/or call default
	m_ptOrigin=point;
	m_bDraw=TRUE;

	m_pre.left=point.x;  
    m_pre.top=point.y;  
    m_pre.right=point.x;  
    m_pre.bottom=point.y;  
   
    m_new.left=point.x;  
    m_new.top=point.y;  
    m_new.right=point.x;  
    m_new.bottom=point.y;   
	CView::OnLButtonDown(nFlags, point);
}
void CGraphicView::OnLButtonUp(UINT nFlags, CPoint point) 
{
	// TODO: Add your message handler code here and/or call default
	m_bDraw=FALSE;
	CClientDC dc(this);
	CPen pen(PS_SOLID,3,RGB(255,0,0));
	dc.SelectObject(&pen);
	dc.SetROP2(R2_COPYPEN);  
	switch(m_nDrawType)
	{
	case 1:
		dc.SetPixel(point,RGB(255,0,0));
		break;
	case 2:
		dc.MoveTo(m_ptOrigin);
		dc.LineTo(point);
		break;
	case 3:
		dc.Rectangle(CRect(m_ptOrigin,point));
		break;
	case 4:
		dc.Ellipse(CRect(m_ptOrigin,point));
		break;
	}
	CView::OnLButtonUp(nFlags, point);
}
void CGraphicView::OnMouseMove(UINT nFlags, CPoint point) 
{
	// TODO: Add your message handler code here and/or call default
	if(m_bDraw)
	{
		CClientDC dc(this);
    	dc.SetROP2(R2_XORPEN);    //设置虚框模式
		dc.DrawFocusRect(&m_pre);
        m_new.right=point.x;  
        m_new.bottom=point.y;  
        dc.DrawFocusRect(&m_new);//画新矩形 
        m_pre.right=m_new.right;  
        m_pre.bottom=m_new.bottom; 
		dc.SetROP2(R2_WHITE);
	}	
    CView::OnMouseMove(nFlags, point);
}

[dirdirdir3]

用异或笔来画,并且需要消失时重新画一次

[Tinary3v0]

在OnMouseMove中使用内存绘图，我想绘图过程一般都需要这样清屏的，因为移动的过程当中wm_paint消息没有被及时触发，
而且就算是及时触发了也会造成屏幕闪烁。
使用内存绘图，因为在内存里面绘制后直接贴图到屏幕上，时间快，因此不会闪烁。
楼主可以参考下面的代码来试试：

CDC *pdc=this->GetDC();　　　//这里是pdc 等同于楼主的&dc
		CDC   MenDC;   
		CBitmap   bm;
		
		CRect rt;
		GetClientRect(&rt);
		MenDC.CreateCompatibleDC(pdc);   
		bm.CreateCompatibleBitmap(pdc,rt.Width(),rt.Height());   
		MenDC.SelectObject(&bm);
		//-------------------------------------------------------------------
                //在这里使用MenDC来绘图，一定要是MenDC（内存ＤＣ）
		//-------------------------------------------------------------------
		pdc->BitBlt(0,0,rt.Width(),rt.Height(),&MenDC,0,0,SRCCOPY);  
		MenDC.DeleteDC();   
		bm.DeleteObject();
		ReleaseDC(pdc);

[cnzdgs]

OnLButtonUp中加入：

    if(m_bDraw)
    {
    CClientDC dc(this);
    dc.SetROP2(R2_XORPEN);
    dc.DrawFocusRect(&m_pre);
    dc.SetROP2(R2_WHITE);
    }

[ilovedrv]

void CGraphicView::OnLButtonUp(UINT nFlags, CPoint point) 
{
  // TODO: Add your message handler code here and/or call default
  m_bDraw=FALSE;
  CClientDC dc(this);

  dc.SetROP2(R2_XORPEN);    //设置虚框模式
  dc.DrawFocusRect(&m_pre);

  CPen pen(PS_SOLID,3,RGB(255,0,0));
  dc.SelectObject(&pen);
  dc.SetROP2(R2_COPYPEN);  
  switch(m_nDrawType)
  {
  case 1:
    dc.SetPixel(point,RGB(255,0,0));
    break;
  case 2:
    dc.MoveTo(m_ptOrigin);
    dc.LineTo(point);
    break;
  case 3:
    dc.Rectangle(CRect(m_ptOrigin,point));
    break;
  case 4:
    dc.Ellipse(CRect(m_ptOrigin,point));
    break;
  }
  CView::OnLButtonUp(nFlags, point);

}

void CGraphicView::OnMouseMove(UINT nFlags, CPoint point) 
{
  // TODO: Add your message handler code here and/or call default
  if(m_bDraw)
  {
    CClientDC dc(this);
    dc.SetROP2(R2_XORPEN);    //设置虚框模式
    if (!m_pre.IsRectEmpty())
      dc.DrawFocusRect(&m_pre);
    m_new.right=point.x;  
    m_new.bottom=point.y;  
    if (!m_new.IsRectEmpty())
      dc.DrawFocusRect(&m_new);//画新矩形 
    m_pre.right=m_new.right;  
    m_pre.bottom=m_new.bottom; 
    dc.SetROP2(R2_WHITE);
  }    
  CView::OnMouseMove(nFlags, point);

}

[ilovedrv]

1. OnLButtonUp里面重绘上次的痕迹

2. OnMouseMove 需要判断绘制的矩形框是否有效

[梧桐168]

脏矩形，这么简单好用的专门用于绘图上的方法，怎么许多人不知道。