QComboxBox different sizes for button and popup

[pablolito]

Hi guys !

I looking for some help about the QComboBox Widget.

I'm trying to build a QComboBox with checkboxes (to allow user to select multiple option easily) and in order to save some space on my user interface, I would like to fix the size of the button, and to allow the popup to expand to fit the size of its contents.

The code I have for now is :

 QComboBox * combo;
 QStandardItem *  item1, * item2;

combo = new QComboBox(ui->tabWidget->widget(0));

this->model = new QStandardItemModel;
item1 = new QStandardItem;
item2 = new QStandardItem;

this->model->insertRow(0, item1);

item1->setText("test");
item1->setFlags(Qt::ItemIsUserCheckable | Qt::ItemIsEnabled);
item1->setData(Qt::Unchecked, Qt::CheckStateRole);


item2->setText("test2 long text aha ah ");
item2->setFlags(Qt::ItemIsUserCheckable | Qt::ItemIsEnabled);
item2->setData(Qt::Unchecked, Qt::CheckStateRole);
this->model->insertRow(1, item2);


combo->setModel(this->model);

combo->view()->setTextElideMode(Qt::ElideNone);
combo->setSizePolicy(QSizePolicy::Fixed, QSizePolicy::Expanding);
combo->setMaximumWidth(50);

combo->show();

This does the job, except for the size of the popup list.

So with this code I have a 50 pixels wide button, but I have no clue on how I can make the popup to expand (I tried to access it by calling combo->view() but without any success).

If someone know how to do this, I would really appreciate some help :)

Thanks in advance !!
Pablo

[Ratzz]

@pablolito
Are you looking for this http://doc.qt.io/qt-4.8/qcombobox.html#showPopup ?

[pablolito]

Actually yes ! thanks a lot ! But I still have a little work to do to get the result I want I guess.

In the showPopup() method I did a :

view()->setSizeAdjustPolicy(QAbstractScrollArea::AdjustToContents);
view()->setMinimumWidth(150);
QComboBox::showPopup();

But I think the setSizeAdjustPolicy() call is not taken into account because the SetMinimumWidth is mandatory if I want the popup list to be resized. is this because of the setMaximumWidth(50); I do previously ?

Also, if possible I looking to have an automatic resize (150 px is just an example, I would like the popup to fit its content size).

Do you know how can I achieve this ?

[Ratzz]

@pablolito
Can you just test with combo->showPopup(); without setting any size .

[pablolito]

@Ratzz

In this case the button take the size of the popup list, even when the popup is hidden.

[Ratzz]

@pablolito
I did not get exactly what problem you are facing .can you explain your screenshot or so?

[pablolito]

Okay.

I modified a little the code, here is what I have now:

CheckBoxList::CheckBoxList( QMap<uint32_t, QString> values, QWidget * parent):
    QComboBox(parent)
{
    QMapIterator<uint32_t, QString> it(values);

    QStandardItem *  item1, * item2;

    this->model = new QStandardItemModel;
    item1 = new QStandardItem;
    item2 = new QStandardItem;

    this->model->insertRow(0, item1);

    item1->setText("test");
    item1->setFlags(Qt::ItemIsUserCheckable | Qt::ItemIsEnabled);
    item1->setData(Qt::Unchecked, Qt::CheckStateRole);


    item2->setText("test2 long text aha ah ");
    item2->setFlags(Qt::ItemIsUserCheckable | Qt::ItemIsEnabled);
    item2->setData(Qt::Unchecked, Qt::CheckStateRole);
    this->model->insertRow(1, item2);


    this->setModel(this->model);

    this->view()->setTextElideMode(Qt::ElideNone);
    this->setSizePolicy(QSizePolicy::Fixed, QSizePolicy::Expanding);
    this->setMaximumWidth(50);
    setModel(this->model);
}

void CheckBoxList::showPopup()
    {
        view()->setSizeAdjustPolicy(QAbstractScrollArea::AdjustToContents);
        view()->setMinimumWidth(150);
        QComboBox::showPopup();

    }

void CheckBoxList::paintEvent(QPaintEvent *)
    {
        QStylePainter painter(this);
        painter.setPen(palette().color(QPalette::Text));

        // draw the combobox frame, focusrect and selected etc.
        QStyleOptionComboBox opt;
        initStyleOption(&opt);

        // if no display text been set , use "..." as default
        if(m_DisplayText.isNull())
            opt.currentText = "...";
        else
            opt.currentText = m_DisplayText;
        painter.drawComplexControl(QStyle::CC_ComboBox, opt);

        // draw the icon and text
        painter.drawControl(QStyle::CE_ComboBoxLabel, opt);
    }

This code give me this result :

This is what I want : a button which is 50px wide and a popup which is wide enough to display all the items. But for now the popup list is 150px wide (fixed) and I would like to have the width to fit the content of the list.

Is it clearer ?

[Ratzz]

@pablolito
You can try with http://doc.qt.io/qt-4.8/qsizepolicy.html#setHorizontalPolicy setting to QSizePolicy::MinimumExpanding .

[pablolito]

@Ratzz

view()->setSizePolicy(QSizePolicy::MinimumExpanding, QSizePolicy::Preferred);

Does the trick :

But the list is a bit too wide and a bit too long... But it wiil be enough for now !

Thanks a lot

[raven-worx]

@pablolito
this should do the calculation you want:

void MyComboBox::showPopup()
{
    //calculate width of all items
    int width = 0;
    const int iconWidth = this->iconSize().width() + 4;
    const QFontMetrics &fontMetrics = this->fontMetrics();

    for( int i = 0; i < this->count(); ++i )
    {
        const int textWidth = fontMetrics.width(this->itemText(i));
        if (this->itemIcon(i).isNull())
            width = (qMax(width, textWidth));
        else
            width = (qMax(width, textWidth + iconWidth));
    }

    QStyleOptionComboBox opt;
    this->initStyleOption(&opt);
    QSize tmpSize(width, 0);
    tmpSize = this->style()->sizeFromContents(QStyle::CT_ComboBox, &opt, tmpSize, this);

    // add width of scrollbar
    int scrollBarWidth = 0;
    if( QAbstractScrollArea* scrollArea = qobject_cast<QAbstractScrollArea*>(this->view()) )
    {
        QScrollBar* vScrollBar = scrollArea->verticalScrollBar();
        vScrollBar->ensurePolished();

        QStyleOptionSlider option;
            option.initFrom(vScrollBar);
            option.subControls = QStyle::SC_None;
            option.activeSubControls = QStyle::SC_None;
            option.orientation = Qt::Vertical;
            option.minimum = vScrollBar->minimum();;
            option.maximum = vScrollBar->maximum();
            option.sliderPosition = vScrollBar->sliderPosition();
            option.sliderValue = vScrollBar->value();
            option.singleStep = vScrollBar->singleStep();
            option.pageStep = vScrollBar->pageStep();
            option.upsideDown = vScrollBar->invertedAppearance();

        scrollBarWidth = vScrollBar->style()->pixelMetric( QStyle::PM_ScrollBarExtent, &option, vScrollBar );
    }

    // set the width to the popup
    this->view()->window()->setFixedWidth( qMax(this->width(),tmpSize.width()+scrollBarWidth) );

    QComboBox::showPopup();
}

[Ratzz]

@pablolito said:

QSizePolicy::MinimumExpanding, QSizePolicy::Preferred

Even i have tried in win7 for long text . does not work here .

    item2->setText("test2 long text aha 123456789012345678901234567890");
    ui->comboBox->view()->setSizePolicy(QSizePolicy::MinimumExpanding, QSizePolicy::Preferred);

[pablolito]

@raven-worx
Thanks a lot !

This does exactly what I want !