鼠标追踪线该如何处理

Question

在mousmove消息中获取鼠标的坐标并且画出十字标记线，应该怎么处理这个线，在下次鼠标移动到新位置时，擦除刚画的线

Answer 1

你好，

>应该怎么处理这个线，在下次鼠标移动到新位置时，擦除刚画的线

你可以在 mousemove响应中添加如下参考代码, 注意一定要调用Invalidate()，这个方法会发送WM_PAINT 消息从而使窗体重绘。

Invalidate();

UpdateWindow();

CDC* pDC = GetDC();

pDC->MoveTo(point.x-m_Halflength,point.y);

pDC->LineTo(point.x+m_Halflength,point.y);

pDC->MoveTo(point.x,point.y-m_Halflength);

pDC->LineTo(point.x,point.y+m_Halflength);

ReleaseDC(pDC);

如果我不调用Invalidate（），我的运行结果如下：

类似问题，你还 可以参考以下相似问题的讨论链接：

http://bbs.csdn.net/topics/310045545

May

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Answer 2

CPoint m_pt;
void CAEATDlg::OnMouseMove(UINT nFlags, CPoint point)
{
	// TODO: Add your message handler code here and/or call default
	m_pt = point;
	InvalidateRect(NULL);
	UpdateWindow();

	CDialog::OnMouseMove(nFlags, point);
}

void CAEATDlg::OnPaint()
{
	CPaintDC dc(this); // device context for painting
	
#define BASE_POINT_CX	20
#define BASE_POINT_CY	20
	CPoint pt1, pt2, pt3, pt4;
	pt1.x = m_pt.x - BASE_POINT_CX;
	pt1.y = m_pt.y;
	pt2.x = m_pt.x + BASE_POINT_CX;
	pt2.y = m_pt.y;

	pt3.x = m_pt.x;
	pt3.y = m_pt.y - BASE_POINT_CY;
	pt4.x = m_pt.x;
	pt4.y = m_pt.y + BASE_POINT_CY;

	dc.MoveTo(pt1);
	dc.LineTo(pt2);
	dc.MoveTo(pt3);
	dc.LineTo(pt4);
}

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Visual C++ enthusiast, like network programming and driver development. At present is being engaged in the WinCE/Windows Mobile platform embedded development.

Answer 3

May 的方法并不能取得完整的鼠标滑动轨迹WM_MOUSEMOVE值受当前进程运行效率和采样率影响，如果绘制鼠标轨迹的话会得到弯曲的线而非连续平滑的曲线，但windows提供了补偿机制它将鼠标移动实际轨迹存到一块区域内，通过GetMouseMovePointsEx可获取