请问一下这程序有什么问题?

Question

请问一下这程序有什么问题，我想实现，点击“直线”－“DDA算法生成直线”然后在窗口内点击鼠标生成一条直线。源代码在附件里

Answer 1

switch(pdoc->m_iMenuSelect)
{
case ID_DDALINE:
case ID_BRESENHAMLINE:
case ID_MIDPOINTLINE:
void CGraphicView::OnLButtonUp(UINT nFlags, CPoint point) 
{
// TODO: Add your message handler code here and/or call default
    CGraphicDoc *pdoc = GetDocument();
CClientDC dc(this);
CPoint s, e;
CRect rect;
double radius;
int r;
switch(pdoc->m_iMenuSelect)
{
case ID_DDALINE:
case ID_BRESENHAMLINE:
case ID_MIDPOINTLINE:
pdoc->m_pointEnd = point; //请同学们实现算法 
MyDrawLine(pdoc->m_pointStart, pdoc->m_pointEnd);


}
CView::OnLButtonUp(nFlags, point);
}

Answer 2

在OnMouseMove()中先擦除先前画的线,然后新画一条,你的算法会很慢的CDC::SetROP2();好好看看书吧,别急 temppen.CreatePen (PS_DOT,0,RGB(255,200,200));
mvcdc->SelectObject (&temppen);
mvcdc->SetROP2 (R2_NOTXORPEN);
mvcdc->MoveTo (firstpoint);
mvcdc->LineTo (secondpoint);
secondpoint = point;
mvcdc->MoveTo (firstpoint);
mvcdc->LineTo (secondpoint);
temppen.DeleteObject ();