QTabWidget - Catching move events

[RobC]

Hey all,

Would it be possible to catch the event of a tab being moved in a QTabWidget?

Lets say, in a horrible example, we have 5 tabs. I dynamically change the tab text to include "1 - ", "2 - " etc for all the tabs in their current order. If the user moves a tab, would it be possible to catch that, and rename all the tabs so the number order is still correct?

If I try this using the 'currentChanged' signal, I believe the index is being changed and thus causes a nasty crash.

[Spitfire]

Hmmm I think that currentChanged() is not be emitted when you move the tab, only when you click on a new one after the tab has been moved.

[RobC]

A very good point. I hadn't tried that when experimenting.

So, ideally a signal on the move - but there isn't one?

[Spitfire]

I don't think there is.

You could try subclassing the QTabWidget and reimplement void QTabWidget::tabInserted ( int index ) [virtual protected], maybe you can emit the signal from there.

[RobC]

No such luck. It emits a signal when the form is first set, but nothing after that point. I guess it doesn't get used when the tabs are moved. I've tried several ways, to no avail.

Time for Plan B. Well, a cup of tea and then Plan B.

[norobro]

So, ideally a signal on the move - but there isn't one?

See QTabBar::tabMoved(int, int). QTabWidget::tabBar() is protected so you will still need to subclass QTabWidget.

[RobC]

Forgive the question, but how do I reimplement QTabBar if I subclass QTabWidget?

[norobro]

You don't need to reimplement QTabBar. You just need to be able to call the protected function tabBar() which you can do in a subclass of QTabWidget.

Using your example:

#include <QtGui>
class TabWidget : public QTabWidget
{
Q_OBJECT
public:
    TabWidget() {
        setMinimumSize(300,100);
        setMovable(true);
        for(int i=0;i<5;++i)
            addTab(new QWidget,QString("Tab %1").arg(i+1));
        connect(tabBar(),SIGNAL(tabMoved(int,int)),this,SLOT(relabelTabs(int,int)));
    }
public slots:
    void relabelTabs(int /* from */, int /* to */){
        for(int i=0;i<count();++i)
            setTabText(i,QString("Tab %1").arg(i+1));
    }
};
 
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    TabWidget tw;
    tw.show();
    app.exec();
}
#include "main.moc"

#include <QtGui>
class TabWidget : public QTabWidget
{
Q_OBJECT
public:
    TabWidget() {
        setMinimumSize(300,100);
        setMovable(true);
        for(int i=0;i<5;++i)
            addTab(new QWidget,QString("Tab %1").arg(i+1));
        connect(tabBar(),SIGNAL(tabMoved(int,int)),this,SLOT(relabelTabs(int,int)));
    }
public slots:
    void relabelTabs(int /* from */, int /* to */){
        for(int i=0;i<count();++i)
            setTabText(i,QString("Tab %1").arg(i+1));
    }
};

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    TabWidget tw;
    tw.show();
    app.exec();
}
#include "main.moc"

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HTH

[RobC]

Ah, I getcha. Sorted. Thanks for the help folks!

[norobro]

You're welcome.

Rather than iterating over all of the tabs, here's a better version of the slot:

void relabelTabs(int from, int to){
        QString hold= tabText(from);
        setTabText(from,tabText(to));
        setTabText(to,hold);
}

void relabelTabs(int from, int to){
        QString hold= tabText(from);
        setTabText(from,tabText(to));
        setTabText(to,hold);
}

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