求助：一个画线的问题。

Question

怎样用鼠标在屏幕上画一条线？（如折线，直线，弧线）
然后在线的两侧画出平形线？最好能给出具体代码。我先谢谢各位高手啦！

Answer 1

void C***::Draw(CDC* pDC)
{
OnPrepareDC(pDC , NULL);
//略去画笔选择代码
CPoint p1(10 , 50);
CPoint p2(10 + 50 , 50);
pDC->MoveTo(p1);
pDC->LineTo(p2);
}

Answer 2

在WM_LBUTTONDOWN事件记录起点，在WM_MOUSEMOVE事件调用InvalidateRect(...)重绘，在WM_LBUTTONUP事件中设置终点，创建平行线。

Answer 3

楼上二位都说得很对，另外建议楼主看一本叫做《Visual C++ 6.0编程实例与技巧》，机工出的，我当年就受益于此书，只是这本书有点早了

Answer 4

思路如 grasshopperliu(老前辈) 
所说！

Answer 5

你说的这个问题就是找斜率.void CWrcimageView::VerticalPoint(CPoint FirstPoint,CPoint SecondPoint ,int nOffSet,CPoint *pFirstPoint,CPoint *pSecondPoint)
{
if(FirstPoint.y==SecondPoint.y)
{ pFirstPoint->y=FirstPoint.y-nOffSet/2;
pSecondPoint->y=FirstPoint.y+nOffSet/2;
pFirstPoint->x=pSecondPoint->x=FirstPoint.x;
return ;
}

if(FirstPoint.x==SecondPoint.x)
{ pFirstPoint->x=FirstPoint.x-nOffSet/2;
pSecondPoint->x=FirstPoint.x+nOffSet/2;
pFirstPoint->y=pSecondPoint->y=FirstPoint.y;
return ;
}
double k;
k=(double)(SecondPoint.y-FirstPoint.y)/(SecondPoint.x-FirstPoint.x);

pFirstPoint->y=(int)((double)1/2*nOffSet*sqrt(1/(1+k*k))+FirstPoint.y+0.5);
pSecondPoint->y=2*FirstPoint.y-pFirstPoint->y;
pFirstPoint->x=(int)(FirstPoint.x-(double)1/2*k*(pFirstPoint->y-pSecondPoint->y)+0.5);
pSecondPoint->x=2*FirstPoint.x-pFirstPoint->x;
//当FistPoint.x-SecondPoint.x等2或-2时会出现两点相等的情况,这时按坚直线处理
if(*pFirstPoint==*pSecondPoint)
{
pFirstPoint->x=FirstPoint.x-nOffSet/2;
pSecondPoint->x=FirstPoint.x+nOffSet/2;
pFirstPoint->y=pSecondPoint->y=FirstPoint.y;

}
return ;
}