//需要显示的文字信息
const char* str = "This is a bug";

//保存现场
gpHandle->save();

//当前屏幕
CGContextRef context = gpHandle->getContext();
//坐标转化
CGContextSetTextMatrix(context, CGAffineTransformMakeScale(1.0, -1.0));
//字体信息
CGContextSelectFont(context, "Helvetica", 30 * 4.41718, kCGEncodingMacRoman);
//显示文字
CGContextShowTextAtPoint(context, prct->left, prct->top, str, strlen(str));

//还原现场
gpHandle->restore();