C / C++ / MFC

void CMyDLL::OnPaint()
{
        CPaintDC dc(this); // device context for painting
        dc.SetBkColor(RGB(0,0,0));
       
        CRect rect;
        GetClientRect(&rect);
 
        int save = dc.SaveDC();
 
        if(bSetDraw)
        {
                CMemDC mDC(&dc);
 
                //mDC.SetBkColor(RGB(0,0,0));
                mDC.SetMapMode(MM_ANISOTROPIC);
                mDC.SetWindowOrg(rect.BottomRight());
                mDC.SetViewportOrg(0, 0);
                mDC.SetViewportExt(-1, -1);
                mDC.SetWindowExt(1, 1);
                // ********** Background ***********
                // Grid
                if (bActivateGrid)
                {
                        CPen qLinePen(PS_SOLID, 1, RGB(0,139,0));
                        mDC.SelectObject(&qLinePen);
 
                        // Grid - Horizontal lines
                        mDC.MoveTo(1, 0);
                        mDC.LineTo(rect.Width(), 0);
                        int height = rect.Height();
                        int maxlines = height / (int)12.5;
                        for (int i=1;i<=maxlines;i++){
                                int y_axis = (int)((double)i * 12.5);
                                if (y_axis <= rect.Height()) {
                                        mDC.MoveTo(1, y_axis);
                                        mDC.LineTo(rect.Width(), y_axis);
                                }
                        }
 
                        // Grid - Vertical lines
                        mDC.MoveTo(0, 0);
                        mDC.LineTo(0, rect.Height());
                        int width = rect.Width();
                        maxlines = width / (int)12.5;
                        for (int i=1;i<=maxlines;i++){
                                int x_axis = (int)(((double)i * 12.5) - gridOffset);
                                if (x_axis <= rect.Width()) {
                                        mDC.MoveTo(x_axis, 1);
                                        mDC.LineTo(x_axis, rect.Height());
                                }
                        }
 
                        qLinePen.DeleteObject();
                }
                // *********** graphic component ***********
                // based on choice of graph type
                CPen qPolylinePen(PS_SOLID, 1, RGB(0, 255, 0));
                switch (iGraphType)
                {
                case GRAPH_BARS:
                        break;
 
                case GRAPH_LINES:
                        {                              
                                if (vtPoints.capacity() == 1)
                                {
                                        mDC.SelectObject(qPolylinePen);
                                        vectfPoints* pointsline = &vtPoints[0];
                                        mDC.Polyline(&(*pointsline)[0], (int)pointsline->size());
                                        //mDC->PolyPolyline()
                                        qPolylinePen.DeleteObject();
                                }
                        }
                        break;
 
                default:
                        break;
                }
                GDI_FLUSH();
        }
 
        dc.RestoreDC(save);
}