长QString 根据所需宽度自动判断换行示例

在做打印程序时，先开始用了 宽度 /字体宽度 = 每行个数  的办法，发现对于不同宽度的混合字体的字符串，输出效果一塌糊涂。
于是采用了一个笨办法。对每个字体进行宽度判定，存入到一个临时 linestr ,当linestr的宽度大于设置值时，换行。行个数计算器清零。


QString text = "abckadamlamsdfloi";
    text += "MMs1 may optionally also include a foundry name, e.g. (The Qt 2.x syntax, i.e. , is also supported.)";
    text += "If the family is available from more than one foundry and the foundry isn't specified, an arbitrary foundry is chosen. If the family isn't available a family will be set using the font matching algorithm.";
        text += "也是随着时间的积累，对Qt的认识慢慢深刻，这里希望刚会使用Qt的同志们心里问自己几个问题,";
        text += "你是否知道Qt和Qt creator的区别？你对qmake的理解？Qt中信号与槽机制是同步还是异步？";

    int width = 700; // 纸张宽度或其他宽度 ，为像素值
    QFont font = QApplication::font();

    QFontMetrics fmt = QFontMetrics(font);
    int textLength = text.length();
    QList<QString> textRows ;
    QString entity = text;
    QString linestr ;
    int entitywidth = fmt.width(entity);
    // 文本小于纸张宽度，说明只有一行。
    if(entitywidth  < width){
        qDebug() << "textWidth =" <<entitywidth;
        qDebug()<<"textLength=: " << textLength;
        textRows.append(entity);
        qDebug()<<  textRows;
        return;

    }
    // 多行时
    int count =0;   //  每行的字个数，超过设定的宽度时，归零。
    int index =0;  //  读取字符串的个数，读完所有字符时，存最后一行数据，退出。
    for ( ; ; )
    {
        linestr = entity.left(count);
        if(index ==textLength-1){
            qDebug() << "end of the text.index =" << index;
            textRows.append(linestr);
             qDebug() << "final row text count =" <<count;
            break;
        }
        int textwidth = fmt.width(linestr);

        if(textwidth > width)
        {
            textRows.append(linestr);
            entity.remove(0,count);
            qDebug() << "row text count =" <<count;
            count = 0;
        }

        if(entity.isEmpty())
        {
            qDebug() << "count = " << count <<"index =:"<< index;
            qDebug() <<" entity is empty";
            break;
        }
        count ++;
        index ++;
    }

    qDebug()<<  textRows;