Add QScrollArea to QDialog

[cpsmusic]

Hi,

Is it possible to create a Qdialog with a QScrollArea?

I've tried the following but neither method works:

QScrollArea scrollArea;
scrollArea.viewport()->setBackgroundRole(QPalette::Dark);
scrollArea.viewport()->setAutoFillBackground(true);
scrollArea.setWindowTitle(QObject::tr("Mixer Strip"));
scrollArea.setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
scrollArea.setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
scrollArea.setParent(this);
scrollArea.show();

QScrollArea scrollArea;
scrollArea.viewport()->setBackgroundRole(QPalette::Dark);
scrollArea.viewport()->setAutoFillBackground(true);
scrollArea.setWindowTitle(QObject::tr("Mixer Strip"));
scrollArea.setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
scrollArea.setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
scrollArea.setParent(this);
scrollArea.show();

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QScrollArea scroll;
scroll.setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
scroll.setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
QWidget *viewport = new QWidget;
scroll.setWidget(viewport);
scroll.setWidgetResizable(true);
QVBoxLayout *l = new QVBoxLayout(viewport);
setLayout(l);
scroll.show();

QScrollArea scroll;
scroll.setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
scroll.setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
QWidget *viewport = new QWidget;
scroll.setWidget(viewport);
scroll.setWidgetResizable(true);
QVBoxLayout *l = new QVBoxLayout(viewport);
setLayout(l);
scroll.show();

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Cheers,

Chris

[Rachol]

The second example seems to be correct, but what is the parent of QScrollArea?

[cpsmusic]

If I change the code to the following I still don't see the QScrollArea:

QScrollArea scroll;
    scroll.setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
    scroll.setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
    QWidget *viewport = new QWidget;
    scroll.setWidget(viewport);
    scroll.setWidgetResizable(true);
    QVBoxLayout *l = new QVBoxLayout(viewport);
    setLayout(l);
    scroll.setParent(this);
    scroll.show();

QScrollArea scroll;
    scroll.setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
    scroll.setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
    QWidget *viewport = new QWidget;
    scroll.setWidget(viewport);
    scroll.setWidgetResizable(true);
    QVBoxLayout *l = new QVBoxLayout(viewport);
    setLayout(l);
    scroll.setParent(this);
    scroll.show();

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[Santosh Reddy]

Create QScrollArea on heap

QScrollArea * scroll = new QScrollArea(this);

QScrollArea * scroll = new QScrollArea(this);

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[cpsmusic]

Hi,

I tried the following:

setWindowTitle("Mixer Strip");
    setMinimumSize(600, 350);
 
    QScrollArea *scroll = new QScrollArea(this);
    scroll->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
    scroll->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
    QWidget *viewport = new QWidget;
    scroll->setWidget(viewport);
    scroll->setWidgetResizable(true);
    QHBoxLayout *l = new QHBoxLayout(viewport);
    setLayout(l);

setWindowTitle("Mixer Strip");
    setMinimumSize(600, 350);

    QScrollArea *scroll = new QScrollArea(this);
    scroll->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
    scroll->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
    QWidget *viewport = new QWidget;
    scroll->setWidget(viewport);
    scroll->setWidgetResizable(true);
    QHBoxLayout *l = new QHBoxLayout(viewport);
    setLayout(l);

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Using this code the scrollbars are visible however they're positioned in the top left corner of the dialog and don't change position when the dialog is resized. I can just makeout the widgets that are added.

Cheers,

Chris

[Santosh Reddy]

If you are adding widgets to QHBoxLayout *l then

QHBoxLayout *l = new QHBoxLayout(viewport);
viewport->setLayout(l);

QHBoxLayout *l = new QHBoxLayout(viewport);
viewport->setLayout(l);

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[cpsmusic]

I tried the following:

QScrollArea *scroll = new QScrollArea(this);
    scroll->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
    scroll->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
    QWidget *viewport = new QWidget;
    scroll->setWidget(viewport);
    scroll->setWidgetResizable(true);
    QHBoxLayout *l = new QHBoxLayout(viewport);
    viewport->setLayout(l);

QScrollArea *scroll = new QScrollArea(this);
    scroll->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
    scroll->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
    QWidget *viewport = new QWidget;
    scroll->setWidget(viewport);
    scroll->setWidgetResizable(true);
    QHBoxLayout *l = new QHBoxLayout(viewport);
    viewport->setLayout(l);

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The scrollbars are visible however they're still not attached to the dialog.

I also tried removing the call to

scroll->setWidget(viewport)

scroll->setWidget(viewport)

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In this case, the scrollbars are visible (and the size of the area they contain is larger) but they're still not attached to the dialog.

[Santosh Reddy]

I think I got you problem, not sure how you are using QDialog, let me put both the ways, check which is applicable to you

1. If sub-classing QDialog, then in the constructor of the sub-calss

MyDialog::MyDialog(QWidget * parent) : QDialog(parent)
{
    QScrollArea *scroll = new QScrollArea(this);
    scroll->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
    scroll->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
 
    QWidget *viewport = new QWidget(this);
    scroll->setWidget(viewport);
    scroll->setWidgetResizable(true);
 
    QHBoxLayout *l = new QHBoxLayout(viewport);
    viewport->setLayout(l);
 
    // add needed widgets to layout "l"
    for(int i = 0; i < 10; i++)
        l->addWidget(new QPushButton());
 
    // Add a layout for QDialog
    QHBoxLayout *dialog_layout = new QHBoxLayout(this);
    dialog_layout->addWidget(scroll); // add scroll to the QDialog's layout
    setLayout(dialog_layout);
 
    // show dialog
    show();
}

MyDialog::MyDialog(QWidget * parent) : QDialog(parent)
{
    QScrollArea *scroll = new QScrollArea(this);
    scroll->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
    scroll->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
	
    QWidget *viewport = new QWidget(this);
    scroll->setWidget(viewport);
    scroll->setWidgetResizable(true);
	
    QHBoxLayout *l = new QHBoxLayout(viewport);
    viewport->setLayout(l);

    // add needed widgets to layout "l"
    for(int i = 0; i < 10; i++)
        l->addWidget(new QPushButton());

    // Add a layout for QDialog
    QHBoxLayout *dialog_layout = new QHBoxLayout(this);
    dialog_layout->addWidget(scroll); // add scroll to the QDialog's layout
    setLayout(dialog_layout);
    
    // show dialog
    show();
}

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1. If using QDialog directly, then

QDialog * dialog = new QDialog(this); //my be you already have this
 
QScrollArea *scroll = new QScrollArea(dialog);
scroll->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
scroll->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
 
QWidget *viewport = new QWidget(dialog);
scroll->setWidget(viewport);
scroll->setWidgetResizable(true);
 
QHBoxLayout *l = new QHBoxLayout(viewport);
viewport->setLayout(l);
 
// add needed widgets to layout "l"
for(int i = 0; i < 10; i++)
	l->addWidget(new QPushButton());
 
// Add a layout for QDialog
QHBoxLayout *dialog_layout = new QHBoxLayout(dialog);
dialog->setLayout(dialog_layout);
dialog->layout()->addWidget(scroll); // add scroll to the QDialog's layout
dialog->show();

QDialog * dialog = new QDialog(this); //my be you already have this

QScrollArea *scroll = new QScrollArea(dialog);
scroll->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
scroll->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOn);

QWidget *viewport = new QWidget(dialog);
scroll->setWidget(viewport);
scroll->setWidgetResizable(true);

QHBoxLayout *l = new QHBoxLayout(viewport);
viewport->setLayout(l);

// add needed widgets to layout "l"
for(int i = 0; i < 10; i++)
	l->addWidget(new QPushButton());

// Add a layout for QDialog
QHBoxLayout *dialog_layout = new QHBoxLayout(dialog);
dialog->setLayout(dialog_layout);
dialog->layout()->addWidget(scroll); // add scroll to the QDialog's layout
dialog->show();

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Edit: your actual problem is you are adding QScrollArea to QDialog, where as you should be adding QScrollArea to QDialog's layout

[cpsmusic]

Thanks, that fixed the problem.

[cpsmusic]

Although I've got the scrollbars showing now, I've run into another problem - the widgets are being spread too widely in the horizontal direction. What I'd like is for the widgets to bunch up on the left hand side of the layout. I tried using a QGridLayout however this didn't fix the problem. The code I'm using is below. One thing, the widget is a custom widget that has a fixed size. I'm implemented the sizeHint method returning the size of the widget.

MixerDialog::MixerDialog(QWidget *parent) :
    QDialog(parent) {
 
    setWindowTitle("Mixer");
    setMinimumSize(600, 350);
 
    QScrollArea *scrollArea = new QScrollArea(this);
    scrollArea->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
    scrollArea->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
 
    QWidget *viewport = new QWidget(this);
    scrollArea->setWidget(viewport);
    scrollArea->setWidgetResizable(true);
 
    QHBoxLayout *hlayout = new QHBoxLayout(viewport);
    hlayout->setMargin(0);
    hlayout->setSpacing(0);
    viewport->setLayout(hlayout);
 
    // add needed widgets to layout "hlayout"
    int numberOfChannels = 10;
    for(int i = 0; i < numberOfChannels; i++) {
        MixerStrip *strip = new MixerStrip;
        hlayout->addWidget(strip);
    }
    hlayout->addStretch();
 
    // Add a layout for QDialog
    QHBoxLayout *dialog_layout = new QHBoxLayout(this);
    dialog_layout->setMargin(0);
    dialog_layout->setSpacing(0);
    dialog_layout->addWidget(scrollArea); // add scrollArea to the QDialog's layout
    setLayout(dialog_layout);
 
    // show dialog
    show();
}

MixerDialog::MixerDialog(QWidget *parent) :
    QDialog(parent) {

    setWindowTitle("Mixer");
    setMinimumSize(600, 350);

    QScrollArea *scrollArea = new QScrollArea(this);
    scrollArea->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
    scrollArea->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOn);

    QWidget *viewport = new QWidget(this);
    scrollArea->setWidget(viewport);
    scrollArea->setWidgetResizable(true);

    QHBoxLayout *hlayout = new QHBoxLayout(viewport);
    hlayout->setMargin(0);
    hlayout->setSpacing(0);
    viewport->setLayout(hlayout);

    // add needed widgets to layout "hlayout"
    int numberOfChannels = 10;
    for(int i = 0; i < numberOfChannels; i++) {
        MixerStrip *strip = new MixerStrip;
        hlayout->addWidget(strip);
    }
    hlayout->addStretch();

    // Add a layout for QDialog
    QHBoxLayout *dialog_layout = new QHBoxLayout(this);
    dialog_layout->setMargin(0);
    dialog_layout->setSpacing(0);
    dialog_layout->addWidget(scrollArea); // add scrollArea to the QDialog's layout
    setLayout(dialog_layout);

    // show dialog
    show();
}

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[Santosh Reddy]

You code should work, hlayout->addStretch(); does the magic...Post a screenshot indicating the of the probelm

[cpsmusic]

Here's a screenshot of how the widgets are being laid out:

Grab.tiff

The addStretch() doesn't seem to push them left.

[Rachol]

Have you tried hlayout->setSizeConstraint ( QLayout::SetFixedSize ); ?

[cpsmusic]

Have you tried hlayout->setSizeConstraint ( QLayout::SetFixedSize ); ?

I just tried what you've suggested however it didn't make any difference.

[Rachol]

Can you try your code with QPushButton instead of MixerStrip and then see if the widgets are being laid out normally?

[Santosh Reddy]

Ok, Your problem seems to be with in mixer widget, set proper size constraint to it, and also don't use any spacers if designing from Qt Designer (i mean don't place spacers in such a position which will cause the mixer widget to fit the area available)

[cpsmusic]

I'm not clear about how to set the size constraint in the widget. I tried adding:

setSizeConstraint ( QLayout::SetFixedSize );

setSizeConstraint ( QLayout::SetFixedSize );

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to the MixerStrip (which inherits from QWidget) but the code won't build.

I'm not using Qt Designer so I don't think that's the problem.

[Rachol]

setSizeConstraint -> this is QLayout API, so of course it won't work. Have you tried what I suggested in my previous post? How did it work? How is your MixerStrip widget implemented?

[Santosh Reddy]

You can use

hlayout.setSizeConstraint(QLayout::SetMinimumSize);

hlayout.setSizeConstraint(QLayout::SetMinimumSize);

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This will set the layout and the containing widget to smallest size possible.

[cpsmusic]

Can you try your code with QPushButton instead of MixerStrip and then see if the widgets are being laid out normally?

If I use QPushButtons they're laid out correctly.

Here's the code for the MixerStrip:

#include "mixerstrip.h"
 
MixerStrip::MixerStrip(QWidget *parent) :
    QWidget(parent)
{
    QSlider *volSlider = new QSlider(Qt::Vertical);
    volSlider->setMinimum(0);
    volSlider->setMaximum(100);
    QPalette pal = volSlider->palette();
    pal.setColor(volSlider->backgroundRole(), QColor(128, 128, 128));
    volSlider->setPalette(pal);
    volSlider->setAutoFillBackground(TRUE);
    volSlider->setGeometry(0,0,20,220);
    volSlider->setParent(this);
 
    Meter *meter = new Meter;
    meter->setGeometry(20,0,50,220);
    meter->setParent(this);
 
    QPushButton *muteButton = new QPushButton("M");
    QPushButton *soloButton = new QPushButton("S");
    muteButton->setCheckable(true);
    soloButton->setCheckable(true);
 
    pal = muteButton->palette();
    pal.setColor(muteButton->backgroundRole(), QColor(128, 128, 128));
    muteButton->setPalette(pal);
    muteButton->setAutoFillBackground(TRUE);
    pal = soloButton->palette();
    pal.setColor(soloButton->backgroundRole(), QColor(128, 128, 128));
    soloButton->setPalette(pal);
    soloButton->setAutoFillBackground(TRUE);
 
    muteButton->setGeometry(0,220,70,20);
    soloButton->setGeometry(0,240,70,20);
    muteButton->setParent(this);
    soloButton->setParent(this);
 
    QSlider *panSlider = new QSlider(Qt::Horizontal);
    panSlider->setMinimum(-100);
    panSlider->setMaximum(100);
    panSlider->setValue(0);
    pal = panSlider->palette();
    pal.setColor(panSlider->backgroundRole(), QColor(128, 128, 128));
    panSlider->setPalette(pal);
    panSlider->setAutoFillBackground(TRUE);
    panSlider->setGeometry(0,260,70,20);
    panSlider->setParent(this);
 
    QLineEdit *trackName = new QLineEdit();
    trackName->setAlignment(Qt::AlignCenter);
    trackName->setText("Track");
    trackName->setGeometry(0,280,70,20);
    trackName->setParent(this);
 
    QObject::connect(volSlider, SIGNAL(valueChanged(int)), meter, SLOT(valueChanged(int)));
    volSlider->setValue(0);
 
    setFixedSize(size());
    //setSizeConstraint ( QLayout::SetFixedSize );
}
 
QSize MixerStrip::sizeHint() const
{
    QSize size(70,300);
 
    return size;
}

#include "mixerstrip.h"

MixerStrip::MixerStrip(QWidget *parent) :
    QWidget(parent)
{
    QSlider *volSlider = new QSlider(Qt::Vertical);
    volSlider->setMinimum(0);
    volSlider->setMaximum(100);
    QPalette pal = volSlider->palette();
    pal.setColor(volSlider->backgroundRole(), QColor(128, 128, 128));
    volSlider->setPalette(pal);
    volSlider->setAutoFillBackground(TRUE);
    volSlider->setGeometry(0,0,20,220);
    volSlider->setParent(this);

    Meter *meter = new Meter;
    meter->setGeometry(20,0,50,220);
    meter->setParent(this);

    QPushButton *muteButton = new QPushButton("M");
    QPushButton *soloButton = new QPushButton("S");
    muteButton->setCheckable(true);
    soloButton->setCheckable(true);

    pal = muteButton->palette();
    pal.setColor(muteButton->backgroundRole(), QColor(128, 128, 128));
    muteButton->setPalette(pal);
    muteButton->setAutoFillBackground(TRUE);
    pal = soloButton->palette();
    pal.setColor(soloButton->backgroundRole(), QColor(128, 128, 128));
    soloButton->setPalette(pal);
    soloButton->setAutoFillBackground(TRUE);

    muteButton->setGeometry(0,220,70,20);
    soloButton->setGeometry(0,240,70,20);
    muteButton->setParent(this);
    soloButton->setParent(this);

    QSlider *panSlider = new QSlider(Qt::Horizontal);
    panSlider->setMinimum(-100);
    panSlider->setMaximum(100);
    panSlider->setValue(0);
    pal = panSlider->palette();
    pal.setColor(panSlider->backgroundRole(), QColor(128, 128, 128));
    panSlider->setPalette(pal);
    panSlider->setAutoFillBackground(TRUE);
    panSlider->setGeometry(0,260,70,20);
    panSlider->setParent(this);

    QLineEdit *trackName = new QLineEdit();
    trackName->setAlignment(Qt::AlignCenter);
    trackName->setText("Track");
    trackName->setGeometry(0,280,70,20);
    trackName->setParent(this);

    QObject::connect(volSlider, SIGNAL(valueChanged(int)), meter, SLOT(valueChanged(int)));
    volSlider->setValue(0);

    setFixedSize(size());
    //setSizeConstraint ( QLayout::SetFixedSize );
}

QSize MixerStrip::sizeHint() const
{
    QSize size(70,300);

    return size;
}

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You can use

hlayout.setSizeConstraint(QLayout::SetMinimumSize);

hlayout.setSizeConstraint(QLayout::SetMinimumSize);

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This will set the layout and the containing widget to smallest size possible.

I tried what you suggested but it still doesn't fix the problem.