MFC CChartCtrl 滚轮缩放

原文来自：MFC그래프 라이브러리, ChartCtrl 마우스 휠 기능 추가

BOOL CChartCtrl::OnMouseWheel(UINT nFlags, short zDelta, CPoint pt)
{
    ScreenToClient(&pt);
    double MinVal = 0;
    double MaxVal = 0;

    double rate = 0.1;

    if (m_bZoomEnabled)
    {
        if (zDelta > 0)
        {
            rate = rate * 1;
        }
        else
        {
            rate = rate * -1;
        }

        double ZoomCenter = 0;

        if (m_pAxes[BottomAxis])
        {
            m_pAxes[BottomAxis]->GetMinMax(MinVal, MaxVal);
            ZoomCenter = m_pAxes[BottomAxis]->ScreenToValue(pt.x);
            MinVal = MinVal + (ZoomCenter - MinVal) * rate;
            MaxVal = MaxVal - (MaxVal - ZoomCenter) * rate;
            m_pAxes[BottomAxis]->SetZoomMinMax(MinVal, MaxVal);
        }

        if (m_pAxes[LeftAxis])
        {
            m_pAxes[LeftAxis]->GetMinMax(MinVal, MaxVal);
            ZoomCenter = m_pAxes[LeftAxis]->ScreenToValue(pt.y);
            MinVal = MinVal + (ZoomCenter - MinVal) * rate;
            MaxVal = MaxVal - (MaxVal - ZoomCenter) * rate;
            m_pAxes[LeftAxis]->SetZoomMinMax(MinVal, MaxVal);
        }

        if (m_pAxes[TopAxis])
        {
            m_pAxes[TopAxis]->GetMinMax(MinVal, MaxVal);
            ZoomCenter = m_pAxes[TopAxis]->ScreenToValue(pt.x);
            MinVal = MinVal + (ZoomCenter - MinVal) * rate;
            MaxVal = MaxVal - (MaxVal - ZoomCenter) * rate;
            m_pAxes[TopAxis]->SetZoomMinMax(MinVal, MaxVal);
        }

        if (m_pAxes[RightAxis])
        {
            m_pAxes[RightAxis]->GetMinMax(MinVal, MaxVal);
            ZoomCenter = m_pAxes[RightAxis]->ScreenToValue(pt.y);
            MinVal = MinVal + (ZoomCenter - MinVal) * rate;
            MaxVal = MaxVal - (MaxVal - ZoomCenter) * rate;
            m_pAxes[RightAxis]->SetZoomMinMax(MinVal, MaxVal);
        }

        RefreshCtrl();

        if (m_PlottingRect.PtInRect(pt))
        {
            TCursorMap::iterator iter = m_mapCursors.begin();
            for (iter; iter != m_mapCursors.end(); iter++)
                iter->second->OnMouseButtonUp(pt);

            Invalidate();
        }

    }

    return CWnd::OnMouseWheel(nFlags, zDelta, pt);
}