Deleting a Qsplitter

**Elberion** · 15th May 2011, 11:53

Hi, i have a glwidget that renders a cube. I want to have different views of the cube, and that the user can choose how many views it want.
So if he wants dual view for example:

gridGroupBox = new QGroupBox(tr("Grid layout"));
hbox = new QHBoxLayout(this);
splitter1->addWidget(glWidget);
splitter1->addWidget(topright);
hbox->addWidget(splitter1);

So my question is, how do i remove the splitter to go back to single view?
I tride hide, doesnt work, delete later doesnt work. It should be something like.

hbox->removeWidget(splitter);
hbox->addWidget(glWidget);

That doesn't work because the splitter is still there!
Thank u for ur help!
Elbe

**ChrisW67** · 16th May 2011, 00:22

If a QSplitter contains only one widget, or only one visible widget, then the splitter handle is not shown. The QSplitter still exists, and can have widgets re-added. Watch this for 10 seconds:

Qt Code:

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#include <QtGui>
#include <QDebug>
 
class MainWindow: public QMainWindow {
    Q_OBJECT
public:
    MainWindow(QWidget *p = 0): QMainWindow(p) {
        QSplitter *central = new QSplitter(this);
        left = new QLabel("Left", this);
        central->addWidget(left);
        right = new QLabel("Right", this);
        central->addWidget(right);
 
        setCentralWidget(central);
 
        QTimer::singleShot(5000, this, SLOT(removeRight()));
        QTimer::singleShot(10000, this, SLOT(restoreRight()));
    }
public slots:
    void removeRight() {
        qDebug() << "removeRight";
        right->hide();
        // right->deleteLater();  // if you do not need the widget any more
    }
    void restoreRight() {
        qDebug() << "restoreRight";
        right->show();
    }
private:
    QLabel *left;
    QLabel *right;
};
 
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
 
    MainWindow m;
    m.show();
    return app.exec();
}
#include "main.moc"

#include <QtGui>
#include <QDebug>

class MainWindow: public QMainWindow {
    Q_OBJECT
public:
    MainWindow(QWidget *p = 0): QMainWindow(p) {
        QSplitter *central = new QSplitter(this);
        left = new QLabel("Left", this);
        central->addWidget(left);
        right = new QLabel("Right", this);
        central->addWidget(right);

        setCentralWidget(central);

        QTimer::singleShot(5000, this, SLOT(removeRight()));
        QTimer::singleShot(10000, this, SLOT(restoreRight()));
    }
public slots:
    void removeRight() {
        qDebug() << "removeRight";
        right->hide();
        // right->deleteLater();  // if you do not need the widget any more
    }
    void restoreRight() {
        qDebug() << "restoreRight";
        right->show();
    }
private:
    QLabel *left;
    QLabel *right;
};

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    MainWindow m;
    m.show();
    return app.exec();
}
#include "main.moc"

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If you really want the splitter to go away entirely then (in this example):

Qt Code:

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void removeSplitter() {
    qDebug() << "removeSplitter";
    setCentralWidget(left);
    splitter->deleteLater();
    right->deleteLater();
}

void removeSplitter() {
    qDebug() << "removeSplitter";
    setCentralWidget(left);
    splitter->deleteLater();
    right->deleteLater();
}

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**Elberion** · 16th May 2011, 15:03

Thank you very much Chris!
I realized that i was doing splitter.hide() instead of the widgets in the splitter.
So i have 4 views of my scene topleft,topright, botleft and botright.
Single view shows topleft. Dual view shows topleft and topright. Quad view shows all 4.

With your help i can switch now between dual and single view without problem. But when i go into Quad view , Debug shows:
QLayout: Attempting to add QLayout "" to MainWindow "", which already has a layout
and the execution of my program stops.

Why would that be? What am i missing?

Here is part of my code

//In Constructor

Qt Code:

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glWidget = new GLWidget(1);
    topright = new GLWidget(2);
    botleft = new GLWidget(3);
    botright = new GLWidget(4);
 
    old_view=1;
    gridGroupBox = new QGroupBox(tr("Grid layout"));
    hbox = new QHBoxLayout(this);
 
    splitter1 = new QSplitter(Qt::Horizontal, this);
    splitter2 = new QSplitter(Qt::Horizontal, this);
    splitter3 = new QSplitter(Qt::Vertical, this);
 
    splitter1->addWidget(glWidget);
    splitter1->addWidget(topright);
    topright->hide();
    splitter2->addWidget(botleft);
    splitter2->addWidget(botright);
    botleft->hide();
    botright->hide();
    splitter3->addWidget(splitter1);
    splitter3->addWidget(splitter2);
    splitter2->hide();
 
    hbox->addWidget(splitter3);
    gridGroupBox->setLayout(hbox);
    setCentralWidget(gridGroupBox);

glWidget = new GLWidget(1);
    topright = new GLWidget(2);
    botleft = new GLWidget(3);
    botright = new GLWidget(4);

    old_view=1;
    gridGroupBox = new QGroupBox(tr("Grid layout"));
    hbox = new QHBoxLayout(this);

    splitter1 = new QSplitter(Qt::Horizontal, this);
    splitter2 = new QSplitter(Qt::Horizontal, this);
    splitter3 = new QSplitter(Qt::Vertical, this);
   
    splitter1->addWidget(glWidget);
    splitter1->addWidget(topright);
    topright->hide();
    splitter2->addWidget(botleft);
    splitter2->addWidget(botright);
    botleft->hide();
    botright->hide();
    splitter3->addWidget(splitter1);
    splitter3->addWidget(splitter2);
    splitter2->hide();
    
    hbox->addWidget(splitter3);
    gridGroupBox->setLayout(hbox);
    setCentralWidget(gridGroupBox);

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//Slots

Qt Code:

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void MainWindow::setSingleV()
{
    if(old_view==2)
    {
        topright->hide();
 
    }else if(old_view==4)
    {
        topright->hide();
        botleft->hide();
        botright->hide();
        splitter2->hide();
    }
    old_view=1;
}
void MainWindow::setDualView()
{
    if(old_view==1)
    {
        topright->show();
    }else if(old_view==4)
    {
        botleft->hide();
        botright->hide();
        splitter2->hide();
    }
    old_view=2;
}
void MainWindow::setQuadView()
{
    if(old_view==1)
    {
        topright->show();
        botleft->show();
        botright->show();
        splitter2->show();
 
    }else if(old_view==2)
    {
        botleft->show();
        botright->show();
        splitter2->show();
    }
    old_view=4;
}

void MainWindow::setSingleV()
{
    if(old_view==2)
    {
        topright->hide();

    }else if(old_view==4)
    {
        topright->hide();
        botleft->hide();
        botright->hide();
        splitter2->hide();
    }
    old_view=1;
}
void MainWindow::setDualView()
{
    if(old_view==1)
    {
        topright->show();
    }else if(old_view==4)
    {
        botleft->hide();
        botright->hide();
        splitter2->hide();
    }
    old_view=2;
}
void MainWindow::setQuadView()
{
    if(old_view==1)
    {
        topright->show();
        botleft->show();
        botright->show();
        splitter2->show();

    }else if(old_view==2)
    {
        botleft->show();
        botright->show();
        splitter2->show();
    }
    old_view=4;
}

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Thank u very much for ur time!
Elbe

**ChrisW67** · 17th May 2011, 01:21

The warning message about layouts comes about because at line 8 of the constructor you create the layout with the QMainWindow as its parent. When you later add the layout to that window it see that there is already a child layout and informs you (not considering that it is the same layout). This is non-fatal and can be avoided by removing "this" from line 8 (and moving it closer to where it is used at 25).

Nothing else I can see in your code snippets is program life threatening.

What does "my program stops" mean? Crashes with a backtrace in your debugger? Where is the crash originating?

On a widget juggling note... You never need to hide the lower widgets individually: just hide their parent splitter and let them inherit visibility.

Edit:
Make sure that you are not still using deleteLater() on the widgets or splitters and later trying to dereference an invalid pointer.

**Elberion** · 17th May 2011, 17:59

Oh Chris it works so lovely.

I just move what you just said with the layout and voilÃ !

Thank you very much. It was nagging on me quite a long time!

Regards,

Elberion