#include <QLineEdit>


class ElidedQLineEdit : public QLineEdit  
{  
     Q_OBJECT  
 public:  
     explicit ElidedQLineEdit(QWidget *parent=0);  
     explicit ElidedQLineEdit(const QString &text, QWidget *parent=0);  

     void setText(const QString &text);  
     void setFullText(const QString &text);  
     void setTextLimitShrink(const QString &text, int width);  
     void setTextLimitExpand(const QString &text);  
     QString fullText() const;  




protected:  
    void paintEvent(QPaintEvent *);  
private:  
    void elideText();  
private:  
    QString m_fullText;  
};


ElidedQLineEdit::ElidedQLineEdit(QWidget *parent)  
: QLineEdit(parent)  
{  
    this->setMinimumWidth(0);  
}  


ElidedQLineEdit::ElidedQLineEdit(const QString &text, QWidget *parent)  
: QLineEdit(text, parent), m_fullText(text)  
{  
    this->setMinimumWidth(0);  
}  


void ElidedQLineEdit::setText(const QString &text)  
{  
    setFullText(text);  
}  


void ElidedQLineEdit::setFullText(const QString &text)  
{  
    m_fullText = text;  
    update();  
}  


void ElidedQLineEdit::setTextLimitShrink(const QString &text, int width)  
{  
    this->setMinimumWidth(qMin(this->fontMetrics().width(text), width));  
    setFullText(text);  
}  


void ElidedQLineEdit::setTextLimitExpand(const QString &text)  
{  
    int textWidth = this->fontMetrics().width(text);  
    this->setMaximumWidth(textWidth);  
    setFullText(text);  
}  


QString ElidedQLineEdit::fullText() const  
{  
    return m_fullText;  
}  


void ElidedQLineEdit::paintEvent(QPaintEvent *event)  
{  
    QLineEdit::paintEvent(event);  
    elideText();  
}  


void ElidedQLineEdit::elideText()  
{  
    QFontMetrics fm = this->fontMetrics();  
    int dif = fm.width(m_fullText) - this->width();  
    if (dif > 0) 
    {  
        QString showText = fm.elidedText(m_fullText, Qt::ElideRight, this->width());  
        QLineEdit::setText(showText);    
    } else 
    {  
        QLineEdit::setText(m_fullText);  
    }  
} 
 

http://blog.csdn.net/tujiaw/article/details/44983201  實現了QLabel的子類，使其根據寬度自動加省略點和ToolTip。 但是發現當開始顯示字串的寬度小於QLabel控制元件的寬度時字串會正常顯示，但把QLabel寬度縮小至小於QLabel寬度後，還是會顯示完整的字串，沒有截斷字串並加省略點

實現QLineEdit 子類會根據寬度自動加省略點 就不會出現上面的問題