Replacing deprecated QtSignalMapper class to forward Signals in Qt5

sandro4912

I have this code which makes a mdi window written for Qt 4:

class MdiWindow : public QMainWindow
{
    Q_OBJECT
...
private:
    QWorkspace* workspace
    QSignalMapper* mapper
}


MdiWindow::MdiWindow( QWidget *parent ) : QMainWindow( parent )
{
  ...

  workspace = new QWorkspace;
  setCentralWidget( workspace );
  
  connect( workspace, SIGNAL(windowActivated(QWidget *)), this, SLOT(enableActions()));
  mapper = new QSignalMapper( this );
  connect( mapper, SIGNAL(mapped(QWidget*)), workspace, SLOT(setActiveWindow(QWidget*)) );

  ....
}

According to the documentation QWorkspace should be replaced with QMdiArea.

I did that and wrote the first connect like this:

connect(workspace, &QMdiArea::subWindowActivated,
        this, &MdiWindow::enableActions);

But what about QSignalMapper also that is also deprecated.

So how can i update this line:

mapper = new QSignalMapper( this );
connect( mapper, SIGNAL(mapped(QWidget*)), workspace, SLOT(setActiveWindow(QWidget*)) );

I read QSignalMapper can be replaced with lamdas but how in this case?
If i understand right mapper forwards all the signals from this to workspaces active window?

SGaist

Hi,

What signal do you connect to the mapper ?

sandro4912

What do you mean with that theres only these two lines going on in the constructor:

mapper = new QSignalMapper( this );
connect( mapper, SIGNAL(mapped(QWidget*)), workspace, SLOT(setActiveWindow(QWidget*)) );

Doesn't the mapper forward all the signals from class `MdiWindow`` here?

In midi Window iI have several QAction

...
private:

    QMdiArea* workspace;
    QSignalMapper* mapper;

    QAction *newAction;
    QAction *closeAction;
    QAction *exitAction;

    QAction *cutAction;
    QAction *copyAction;
    QAction *pasteAction;
...

I thought by creation of QSignalMapper with this it knows about them....

SGaist

No it doesn't. How would it know what you want exactly to connect ? That's not the goal of this class.

Take a look at the example of QSignalMapper's documentation.

But from what you wrote, it simply hasn't been used at all and you can remove it from your code.

sandro4912

found later int the code it gets used like this:

void MdiWindow::updateWindowList()
{
windowMenu->clear();

windowMenu->addAction(tileAction);
windowMenu->addAction(cascadeAction);
windowMenu->addSeparator();
windowMenu->addAction(nextAction);
windowMenu->addAction(previousAction);
windowMenu->addAction(separatorAction);

auto i = 1;
for (auto &window : workspace->subWindowList()) {
    QString text;
    
    if (i<10) {
        text = QString("&%1 %2").arg(i++).arg(window->windowTitle());    
    }
    else{
        text = window->windowTitle();
    }
    
    auto action = windowMenu->addAction(text);
    action->setCheckable(true);
    action->setChecked(window->widget() == activeDocument());
    
            
    connect(action, &QAction::triggered, mapper, map);
    mapper->setMapping(action, w); 
}

}

So how to get rid of the mapper here?

    connect(action, &QAction::triggered, mapper, map);
    mapper->setMapping(action, w);

SGaist

Something like:

connect(action, &QAction::triggered, [=] { setActiveWindow(window); });

sandro4912

@SGaist said in Replacing deprecated QtSignalMapper class to forward Signals in Qt5:

connect(action, &QAction::triggered, [=] { setActiveWindow(window); });

that works. But then comming back to the constrcutor lines. How to ged rid of them:

mapper = new QSignalMapper( this );
connect( mapper, SIGNAL(mapped(QWidget*)), workspace, SLOT(setActiveWindow(QWidget*)) );

Christian Ehrlicher

@sandro4912 said in Replacing deprecated QtSignalMapper class to forward Signals in Qt5:

How to ged rid of them:

You don't need it at all anymore with the solution @SGaist suggested...

sandro4912

yes now its working even without. I had some other crash when in ported from QWorkspace to QMdiWindow but know everything works. thanks.

Christian Ehrlicher

The please mark this thread as solved, thx :)