MFC Dynamic Curves: OnDraw Tutorial

To draw dynamic curves in MFC, you can achieve this by overriding the OnDraw function of the window class. The specific steps are as follows:

1. In the header file of the Window class, define the data structure for the curve that needs to be drawn, for example:

class CMyView : public CView
{
    // 曲线数据结构
    CArray<CPoint, CPoint> m_points;
};

1. Override the OnDraw function in the implementation file of the window class to draw a curve.

void CMyView::OnDraw(CDC* pDC)
{
    CRect rect;
    GetClientRect(&rect);
    
    // 创建画笔
    CPen pen(PS_SOLID, 2, RGB(0, 0, 255));
    CPen* pOldPen = pDC->SelectObject(&pen);
    
    // 绘制曲线
    for (int i = 1; i < m_points.GetSize(); i++)
    {
        pDC->MoveTo(m_points[i - 1]);
        pDC->LineTo(m_points[i]);
    }
    
    pDC->SelectObject(pOldPen);
}

1. Add a function in the window class to update the curve data, and call this function when the curve needs to be updated.

void CMyView::AddPoint(CPoint point)
{
    m_points.Add(point);
    Invalidate();
}

1. Call the AddPoint function where you need to draw a curve, and add a new data point.

void CMyView::OnMouseMove(UINT nFlags, CPoint point)
{
    if (nFlags & MK_LBUTTON)
    {
        AddPoint(point);
    }
}

This allows for the dynamic drawing of curves while the mouse moves.