Add QScrollArea to QDialog

[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.

[Rachol]

Ok, now it is easy

There are couple of ways to solve your problem.

1. The easiest way would be to place a layout inside your MixerStrip class and then place all the widgets inside the layout instead of hardcoding all coordinates.
2. Re-implement minimumSizeHint and maximumSizeHint. You could return the same value that you return in your sizeHint implementation.

[cpsmusic]

Ok, now it is easy

There are couple of ways to solve your problem.

1. The easiest way would be to place a layout inside your MixerStrip class and then place all the widgets inside the layout instead of hardcoding all coordinates.
2. Re-implement minimumSizeHint and maximumSizeHint. You could return the same value that you return in your sizeHint implementation.

I tried the second suggestion (see below) however the widgets are still spread out.

#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;
}
 
QSize MixerStrip::minimumSizeHint() const
{
 
    QSize size(70,300);
 
    return size;
}
 
QSize MixerStrip::maximumSize()
{
    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;
}

QSize MixerStrip::minimumSizeHint() const
{

    QSize size(70,300);

    return size;
}

QSize MixerStrip::maximumSize()
{
    QSize size(70,300);

    return size;
}

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[Santosh Reddy]

Ok, I hope this should fix your problem for sure.

When you implement size hints on your MixerStrip, then you don't need to set it to fixed size explicitly. Just remove the following statement at the end of MixerStrip Ctor, you should be done, worrying.

//setFixedSize(size());

//setFixedSize(size());

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[cpsmusic]

Thanks, that last change solved the problem! Thanks very much, the people on this forum are very helpful.