C++/Qt4 - QTextEdit - textChanged slot

Hello,

In the QTextEdit the cursor is positioned at the end of the first line of the text, as its supposed to be.
However, if I then press the backspace key, the textChanged() slot gets called twice.
I don't understand why. Perhaps someone could explain.
With text and punctuation keys, the slot gets called once.
Its not a problem for me, I'd just like to know why.
Thanks in advance.

Regards

Code:

void menu::textButton() // slot
{
    if (cm::subSelected == -1) {
        cr::message("Select an item", "Error", 2);
        return;
    }
   prop = new propForm(this);
}

Code:

void menu::editButton() // slot
{
    prop->data->setReadOnly(false);
    prop->data->activateWindow();
    prop->data->moveCursor(QTextCursor::Start);
    prop->data->moveCursor(QTextCursor::EndOfBlock); //end of first line
    prop->data->ensureCursorVisible();
    QWidget *thisOne = QApplication::activeWindow();
    qDebug() << thisOne;
    qDebug() << thisOne->isTopLevel();
    qDebug() << thisOne->isActiveWindow();
}

Code:

propForm.cpp
 
    data = new QTextEdit(this);
    data->setGeometry(0, filePath->height(), this->width(), this->height() - filePath->height());
 
    QString fileName = (cm::mainItem + "/" + cm::subItem);
    filePath->setText(fileName);
 
    QFile file(fileName);
 
    if ( ! (file.open(QIODevice::ReadWrite))) {
        cr::message("Can't open file.", "Error", 2);
        return;
    }
 
    QTextStream in(&file);
    while ( ! in.atEnd()) data->append(in.readLine());
    file.close();
 
    data->setReadOnly(true);
    connect (data, SIGNAL(textChanged()), this, SLOT(textChanged()));
    this->show();

Code:

void propForm::textChanged() // private slot
{
    qDebug() << "text changed";
}

Code:

Output
 
menu(0x7ecc78f0) 
true 
true 
text changed 
text changed

C++/Qt4 - QTextEdit - textChanged slot - Question