QLineEdit::inputMethodEvent () called twice if enter first letter

class LineEdit : public QLineEdit { 
Q_OBJECT 
public: 
   LineEdit(QWidget *parent = 0) : QLineEdit(parent) {} 
protected: 
    void inputMethodEvent(QInputMethodEvent *e) 
    { 
        QString preedtingStr = e->preeditString(); 
        QString commitStr = e->commitString(); 
        QLineEdit::inputMethodEvent(e); 
    } 
}

If I enter the first character, for example "A" - inputMethodEvent() will be called twice, and the text is saved:

1. In the first call preeditingStr is "A" and commitStr is "";
2. In the second call preeditingStr is "" and commitStr is "A";
3. onTextChanged() was emited

If I enter the second character, for example, "B" - inputMethodEvent () will be called once:

1. In the first call preeditingStr is "B" and commitStr is "";

If I enter the third character, for example "C" - inputMethodEvent() will be called once:

1. In the first call preeditingStr is "C" and commitStr is "";

If I enter space - inputMethodEvent() will be called twice, and the text is saved:

1. In the first call preeditingStr is "A" and commitStr is "";
2. In the second call preeditingStr is "" and commitStr is "A";
3. onTextChanged() was emited