Remove widget from QStackedWidget and bring it back

[SergeyK12]

Hi!
Im trying to show widget from QStackedWidget in separate window and bring it back after close. (by seParent(nullptr) and show)

When widget is added back and signal to show this widget is emitted, widget is unseen.
But clicking on button manually with connected same slot i can see widget

// show widget in QStackedWidget (_stacked)
        connect(action, &QAction::triggered, [this, plugin](){
            _stacked->setCurrentWidget(plugin);
            plugin->show();
        });

// show widget (plugin) in separate window
        connect(asWindow, &QAction::triggered, [this, action, plugin](){
            plugin->setParent(nullptr);
            plugin->show();
            action->setVisible(false);
        });

// connect with custom signal widget is closed and bring back into stacked
        connect(plugin, &IModuleView::objectWindowIsClosed, [this, action, toolButton](QWidget* w){
            _stacked->addWidget(w);
            action->setVisible(true);
            action->trigger();
        });

Trying to do repaint and updates show that widget is there but is instantly hide.

I also try to clone widget and show it in window when hiding/ showing widget form QStackedWidget (it is worked, but im not sure is simple to clone complex widget)

[Pl45m4]

@SergeyK12 said in Remove widget from QStackedWidget and bring it back:

Trying to do repaint and updates show that widget is there but is instantly hide.

You have probably an issue with the lifetime of your widget.
&IModuleView::objectWindowIsClosed this signal name sounds like you emit the signal when you close the plugin...
Adding the plugin back to the stackedWidget (by triggering the action) might not work then.

This simple example works for me:

#include "widget.h"
#include "ui_widget.h"

#include <QPushButton>
#include <QDebug>


Widget::Widget(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::Widget)
{
    ui->setupUi(this);
    
    QPushButton *pb = new QPushButton("Widget");
    ui->stackedWidget->addWidget(pb);
    ui->stackedWidget->setCurrentWidget(pb);
    
    // pushbutton in UI only to toggle the other button from free floating to be in stackedWidget
    connect(ui->pushButton, &QPushButton::clicked, this, [=](){
        
        if (ui->stackedWidget->currentWidget() == pb) {
            ui->stackedWidget->removeWidget(pb);
            pb->setParent(nullptr);
            qDebug() << "Show standalone";
            pb->show();
        }
        else {
            ui->stackedWidget->addWidget(pb);
            ui->stackedWidget->setCurrentWidget(pb);
            qDebug() << "Add to stackedWidget";
        }
    });
}

Widget::~Widget()
{
    delete ui;
}

}

[SergeyK12]

When i closed widget with cross i suppose that following code will be executed (because i override event)

protected:
    void closeEvent(QCloseEvent *event) override
    {
        emit objectWindowIsClosed(this);
    }

But not only this event happened?

Im trying to connect to this signal to automatically bring widget into _stacked (and emit defaultAction of button), but its only worked when i manually press on button (as in your example).

Could it be a problem with focus on mainwindow (when we click manually its somehow activated )?

Im even seen a layout widget slightly moved when widget back, but its not seen.

[Pl45m4]

@SergeyK12 said in Remove widget from QStackedWidget and bring it back:

But not only this event happened?

The closeEvent is more powerful than your signal. It will complete the process to close/hide the widget.

Now I tried like your way.
I used a more complex widget and emitted a signal in closeEvent.
Afterwards I connected the signal to a lambda to add the transmitted widget pointer again.
And it shows the same behavior as you describe... I only see the widget in my QStackedWidget when I click the button (without the signal in closeEvent).

The explanation is in my first two sentences above.
Even if you emit the signal to move the widget to stackedWidget, the closeEvent will finish and "close" the widget.
And because the closeEvent finishes after the signal is emitted, you don't see the widget in stackedWidget, while everything else seems correct. Therefore you can't bring the widget back up while the closeEvent hasn't finished.

[Edit: See both solutions below: Either delay moving and showing the widget as QStackedWidget page with a timer or ignore the closeEvent as you don't want to actually close the widget. You just want to move it somewhere else while being visible]

@SergeyK12 said in Remove widget from QStackedWidget and bring it back:

protected:
void closeEvent(QCloseEvent *event) override
{
emit objectWindowIsClosed(this);
}

This will fix it:

protected:
    void closeEvent(QCloseEvent *event) override
    {
        // add some bool here to check condition if you want to move to stackedWidget
        // or really close the widget
        if ( moveToStackedWidget ) { 
           emit objectWindowIsClosed(this);
           event->ignore();
        } 
        event->accept();
    }

Edit:

Another solution that will work, but might be a little "hacky":
Detach the move "process" (adding the plugin to stackedWidget) with a QTimer::singleShot lambda.

    connect(plugin, &IModuleView::objectWindowIsClosed, this, [=](QWidget *w) {
        
        // this:
        QTimer::singleShot(0, this, [=]() {
            stackedWidget->addWidget(w);
            stackedWidget->setCurrentWidget(w); // or trigger your QAction here
        });

        // instead of:
        // stackedWidget->addWidget(w);
        // stackedWidget->setCurrentWidget(w);
    });

Then you don't need to ignore the event and can leave the emit objectWindowIsClosed(this); as it is.

For the second idea, I don't know how bad it really is or if this is actually the better way. However it worked for me.

Maybe others can tell :)

Cheers :))

[SergeyK12]

@Pl45m4 said in Remove widget from QStackedWidget and bring it back:

event->ignore();

Amazing!

Thank you very much!

I found out very important thing about Qt!

[Pl45m4]

@SergeyK12

Great, so please mark your topic as solved