Qt：指定文本宽度，绘画多行文本

void MainWindow::drawMultiLineText(QPainter &painter, const QFont& fnt, const QString& text, int width)
{
    QTextLayout textLayout(text, fnt);
    textLayout.setCacheEnabled(true);
    qreal height = 0;
    qreal lineWidth  = qMax(0, width);
    textLayout.beginLayout();
    QFontMetricsF fm(fnt);
    qreal leading = fm.leading();
    height = -leading;
    while (true)
    {
        QTextLine line = textLayout.createLine();
        if (!line.isValid()) break;
        line.setLineWidth(lineWidth);
        height += leading;
        height = qCeil(height);
        line.setPosition(QPointF(0.0, height));
        height += line.height();
    }
    textLayout.endLayout();

    for (int i = 0; i < textLayout.lineCount(); ++i)
    {
        QTextLine line = textLayout.lineAt(i);
        int start = line.textStart();
        int length = line.textLength();
        QString lineText = text.mid(start, length);
        if(line.naturalTextWidth()>width)
        {
            QString text = fm.elidedText(lineText, Qt::ElideRight, width);
            painter.drawText(QPointF(line.x(), line.y()), text);
            break;
        }
        painter.drawText(QPointF(line.x(), line.y()), lineText);
    }

2.指定宽度和高度，绘画文本

void MainWindow::drawMultiLineText(QPainter &painter, const QFont& fnt, const QString& text, int width, int maxheight)
{
    QTextLayout textLayout(text, fnt);
    textLayout.setCacheEnabled(true);
    qreal height = 50;
    qreal lineWidth  = qMax(0, width);
    textLayout.beginLayout();
    QFontMetricsF fm(fnt);
    qreal leading = fm.leading();
    height -= leading;
    while (true)
    {
        QTextLine line = textLayout.createLine();
        if (!line.isValid()) break;
        line.setLineWidth(lineWidth);
        height += leading;
        line.setPosition(QPointF(0.0, height));
        height += line.height();
    }
    textLayout.endLayout();

    for (int i = 0; i < textLayout.lineCount(); ++i)
    {
        QTextLine line = textLayout.lineAt(i);
        int start = line.textStart();
        if(maxheight < (i+1)*line.height())
        {
            QString lineText = text.mid(start, text.length());
            QString text = fm.elidedText(lineText, Qt::ElideRight, width);
            QPointF fPoint(line.x(), line.y());
            painter.drawText(fPoint, text);
            return;
        }
        int length = line.textLength();
        QString lineText = text.mid(start, length);
        int iTextWidth = qCeil(line.naturalTextWidth());
        if(iTextWidth>width)
        {
            QString text = fm.elidedText(lineText, Qt::ElideRight, width);
            QPointF fPoint(line.x(), line.y());
            painter.drawText(fPoint, text);
            return;
        }
        else
        {
            QPointF fPoint(line.x(), line.y());
            painter.drawText(fPoint, lineText);
        }
    }
}

3.指定行数，绘画文本。

        只需要将指定高度的判断换为行数即可