problem with QListWidget::currentRowChanged signal

[mattc]

Hello,
I am experiencing a problem with the QListWidget::currentRowChanged signal when I remove the first element from a QListWidget. Please see my TestWidget class:

// TestWidget.h
//
#include <QWidget>
#include <QMessageBox>
#include <QListWidget>
#include <QVBoxLayout>
#include <QPushButton>
 
class TestWidget: public QWidget
{
    Q_OBJECT
public:
    TestWidget::TestWidget(QWidget* parent = 0):
        QWidget(parent)
    {
        lst = new QListWidget();
        lst->addItem("first");
        lst->addItem("second");
        connect(lst, SIGNAL(currentRowChanged(int)),
                this, SLOT(onRowChanged(int)));
 
        QPushButton* btn = new QPushButton("Remove first row");
        connect(btn, SIGNAL(clicked(bool)),
                this, SLOT(onBtnClicked(bool)));
 
        QVBoxLayout* l = new QVBoxLayout();
        l->addWidget(lst);
        l->addWidget(btn);
 
        setLayout(l);
    }
 
private slots:
    void onRowChanged(int);
    void onBtnClicked(bool);
 
private:
    QListWidget* lst;
};
 
inline void TestWidget::onBtnClicked(bool)
{
    delete lst->takeItem(0); // triggers rowChanged
 
    // current row number == 0 ... Correct
    QMessageBox::information(this, "Debug",
        QString("onBtnClicked: current row number: %1")
            .arg(lst->currentRow()));
}
 
inline void TestWidget::onRowChanged(int i)
{
    // new row number == 1 ... Why?
    QMessageBox::information(this, "Debug",
        QString("onRowChanged: new row number: %1").arg(i));
}

// TestWidget.h
//
#include <QWidget>
#include <QMessageBox>
#include <QListWidget>
#include <QVBoxLayout>
#include <QPushButton>

class TestWidget: public QWidget
{
    Q_OBJECT
public:
    TestWidget::TestWidget(QWidget* parent = 0):
        QWidget(parent)
    {
        lst = new QListWidget();
        lst->addItem("first");
        lst->addItem("second");
        connect(lst, SIGNAL(currentRowChanged(int)),
                this, SLOT(onRowChanged(int)));

        QPushButton* btn = new QPushButton("Remove first row");
        connect(btn, SIGNAL(clicked(bool)),
                this, SLOT(onBtnClicked(bool)));

        QVBoxLayout* l = new QVBoxLayout();
        l->addWidget(lst);
        l->addWidget(btn);

        setLayout(l);
    }

private slots:
    void onRowChanged(int);
    void onBtnClicked(bool);

private:
    QListWidget* lst;
};

inline void TestWidget::onBtnClicked(bool)
{
    delete lst->takeItem(0); // triggers rowChanged

    // current row number == 0 ... Correct
    QMessageBox::information(this, "Debug",
        QString("onBtnClicked: current row number: %1")
            .arg(lst->currentRow()));
}

inline void TestWidget::onRowChanged(int i)
{
    // new row number == 1 ... Why?
    QMessageBox::information(this, "Debug",
        QString("onRowChanged: new row number: %1").arg(i));
}

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The program starts and current row is 0. Then I click the button to remove the first row and rowChanged is triggered with a value of 1. Why? Back from the rowChanged event and the current row is 0 (correct)

Any clues?

Qt 4.6.3
Visual Studio 2008 SP1

[nernst]

Hi,

i would suggest, that by deleting of row 0, row 1 changes to row 0.
And because of this renumbering you get the trigger, that row 1 has changed.

Just a suggestion