MFC-SelectObject新对象替换相同类型的对象

    
    HDC hdc = ::GetDC(m_hWnd);
    LOGFONT lf = { 0 };
    lf.lfWeight = 16; //平均宽度
    lf.lfHeight = 40;//字体高度
    lf.lfCharSet = GB2312_CHARSET;
    HFONT hfont = ::CreateFontIndirect(&lf);
    HFONT holdfont= (HFONT)SelectObject(hdc, hfont);//新对象替换相同类型的对象
    /*
    参数1：HDC hdc  DC句柄
    参数2：HGDIOBJ hgdiobj 新对象
            但该对象的句柄必须使用以下函数创建才有效：
            Bitmap(位图)          CreateBitmap, CreateBitmapIndirect, 
                                  CreateCompatibleBitmap, CreateDIBitmap, 
                                  CreateDIBSection
            Brush(画刷)           CreateBrushIndirect, eateDIBPatternBrush,  
                                  CreateDIBPatternBrushPt, CreateHatchBrush,  
                                  CreatePatternBrush, CreateSolidBrush 
            Font(字体)              CreateFont, CreateFontIndirect
            Pen(画笔)               CreatePen, CreatePenIndirect
            Region(区域)             CombineRgn, CreateEllipticRgn, 
                               CreateEllipticRgnIndirect, 
                               CreatePolygonRgn, CreateRectRgn, 
                               CreateRectRgnIndirect
    
    返回值：HGDIOBJ  如果选择对象不是区域并且函数执行成功，那么返回值是被取代的对象的句柄
                    如果选择对象是区域并且函数执行成功，返回如下一值
                    如果发生错误并且选择对象不是一个区域，那么返回值为NULL，否则返回HGDI_ERROR
                    
    */

    
    RECT rect = { 50,50,400,400 };
    int n=DrawText(hdc,_T("GDI测试"),-1,&rect,DT_LEFT);
    
    SelectObject(hdc, holdfont);
    BOOL b=DeleteObject(hfont);  //删除对象