怎么用SetROP2(R2_NOTXORPEN)擦除不了先前画的矩形？？

[zhangxinkuku]

在MFC 鼠标移动事件响应如下：
void CMoveWindowTestDlg::OnMouseMove(UINT nFlags, CPoint point)
{
// TODO: Add your message handler code here and/or call default
if (m_isCapture==TRUE)
{
m_hasPicture=TRUE;
CClientDC dc(this);
CPen pen(PS_SOLID,1,RGB(255,0,0));
DeleteObject(dc.SelectObject(pen));

int drawMode=dc.SetROP2(R2_NOTXORPEN);
m_endPoint.x=point.x;
m_endPoint.y=point.y;

dc.MoveTo(m_startPoint);
dc.LineTo(m_endPoint.x,m_startPoint.y);
dc.LineTo(m_endPoint.x,m_endPoint.y);
dc.LineTo(m_startPoint.x,m_endPoint.y);
dc.LineTo(m_startPoint.x,m_startPoint.y);
/*dc.LineTo(point);*/
//dc.SetROP2(drawMode);
}
CDialog::OnMouseMove(nFlags, point);
}

怎么执行后没擦除先前画的矩形 望高手解释下

[wltg2001]

直接调用Invalidate不就行了。

[无边1]

只画了一次，要画两次，画矩形用rectangle方便点

dc.Rectangle( startPoint.x, startPoint.y, m_endPoint.x, m_endPoint.y );
dc.Rectangle( startPoint.x, startPoint.y, point.x, point.y );

m_endPoint.x=point.x;
m_endPoint.y=point.y;

[无边1]

if (m_isCapture==TRUE)
{
m_hasPicture=TRUE;
CClientDC dc(this);
CPen pen(PS_SOLID,1,RGB(255,0,0));
DeleteObject(dc.SelectObject(pen));
int drawMode=dc.SetROP2(R2_NOTXORPEN);

dc.Rectangle( startPoint.x, startPoint.y, m_endPoint.x, m_endPoint.y );
dc.Rectangle( startPoint.x, startPoint.y, point.x, point.y );
m_endPoint.x=point.x;
m_endPoint.y=point.y;
//dc.SetROP2(drawMode);
}

[stoones]

3楼正解，用SetROP2消除画图轨迹，要画两次，你为什么用那么复杂的方法画矩形啊，直接用Rectangle就行了。

[schlafenhamster]

是不是SetROP2(dc,R2_XORPEN);