QComboBox aligment issue

[AndyBrice]

I have a QWidget that contains a QHBoxLayout, that layout contains 2 QComboBoxes. On Mac this widget does not correctly align horizontally with another QComboBox in the same QFormLayout. Even if one of the QComboBoxes in the QWidget is hidden. It is only a few pixels out, but it looks ugly.

WriteModeWidget::WriteModeWidget( QWidget* parent )
: QWidget( parent )
{
    QSizePolicy sp = sizePolicy();
    sp.setHorizontalPolicy( QSizePolicy::Preferred );
    sp.setHorizontalStretch( 1 );
    setSizePolicy( sp );

    QHBoxLayout* hLayout = new QHBoxLayout( this );
    hLayout->setSpacing( 1 );
    hLayout->setContentsMargins( 0, 0, 0, 0 );

    m_writeModeCombo = new QComboBox( this );
    hLayout->addWidget( m_writeModeCombo );

    m_fileSheetComboBox = new QComboBox( this );
    hLayout->addWidget( m_fileSheetComboBox );
}

I've tried setting the QWidget margin and (using a stylesheet) padding. But that doesn't fix it. It looks fine on Windows. Any ideas?

[Christian Ehrlicher]

You have to set the margins of your WriteModeWidget to 0

[AndyBrice]

I tried calling:

setContents( 0, 0, 0, 0 );

In the WriteModeWidget constructor. But it didn't seem to make any difference.

[Christian Ehrlicher]

@AndyBrice said in QComboBox aligment issue:

setContents( 0, 0, 0, 0 );

QWidget has no such function.

Maybe there is another widget involved - we can't see it. Please provide a minimal, compilable example so we can take a better look on it.

[AndyBrice]

@Christian-Ehrlicher Sorry, I meant:

QWidget::setContentsMargins( 0, 0, 0, 0 );

[AndyBrice]

Here is a simplified version of the code:

#include "mainwidget.h"
#include <QApplication>
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWidget w( nullptr );
    w.show();
    return a.exec();
}

#include <QWidget>
class MainWidget : public QWidget
{
    Q_OBJECT
public:
    MainWidget( QWidget *parent );
};

#include "mainwidget.h"
#include <QFormLayout>
#include <QComboBox>
class DualComboBox : public QWidget
{
public:
    DualComboBox( QWidget* parent, bool showSecondCombo );
 };

DualComboBox::DualComboBox( QWidget* parent )
: QWidget( parent )
{
        QHBoxLayout* hLayout = new QHBoxLayout( this );
        hLayout->setSpacing( 1 );
        hLayout->setContentsMargins( 0, 0, 0, 0 );
    
        QComboBox* combo1 = new QComboBox( this );
        combo1->addItem( "QComboBox" );
        hLayout->addWidget( combo1 );
    
        QComboBox* combo2 = new QComboBox( this );
        combo2->addItem( "QComboBox" );
        hLayout->addWidget( combo2 );
    
        if ( !showSecondCombo )
            combo2->hide();
}

MainWidget::MainWidget( QWidget *parent )
    : QWidget( parent )
{
        QFormLayout* fLaypout = new QFormLayout( this );
        fLaypout->setFieldGrowthPolicy( QFormLayout::ExpandingFieldsGrow );
    
        DualComboBox* dualComboBox1 = new DualComboBox( this, true );
        fLaypout->addRow( "DualComboBox1", dualComboBox1 );
    
        DualComboBox* dualComboBox2 = new DualComboBox( this, false );
        fLaypout->addRow( "DualComboBox2", dualComboBox2 );
    
        QComboBox* combo = new QComboBox( this );
        combo->addItem( "QComboBox" );
        fLaypout->addRow( "QComboBox", combo );
}

This is what it looks like on Mac. Notice that the left alignment is not quite right.

[Christian Ehrlicher]

The code had a little glitch. Did you try it with a QGridLayout?
It does work fine on Linux therefore I would suggest you to create a Qt bug entry (if possible, otherwise I can do it for you). But please try with QGridlayout first to see if it's the layout component.

#include <QtWidgets>

class DualComboBox : public QWidget
{
public:
    DualComboBox( QWidget* parent, bool showSecondCombo )
        : QWidget( parent )
    {
        QHBoxLayout* hLayout = new QHBoxLayout( this );
        hLayout->setSpacing( 1 );
        hLayout->setContentsMargins( 0, 0, 0, 0 );

        QComboBox* combo1 = new QComboBox( this );
        combo1->addItem( "QComboBox" );
        hLayout->addWidget( combo1 );

        QComboBox* combo2 = new QComboBox( this );
        combo2->addItem( "QComboBox" );
        hLayout->addWidget( combo2 );

        if ( !showSecondCombo )
            combo2->hide();
    }
};

class MainWidget : public QWidget
{
public:
    MainWidget( QWidget *parent )
        : QWidget( parent )
    {
        QFormLayout* fLaypout = new QFormLayout( this );
        fLaypout->setFieldGrowthPolicy( QFormLayout::ExpandingFieldsGrow );

        DualComboBox* dualComboBox1 = new DualComboBox( this, true );
        fLaypout->addRow( "DualComboBox1", dualComboBox1 );

        DualComboBox* dualComboBox2 = new DualComboBox( this, false );
        fLaypout->addRow( "DualComboBox2", dualComboBox2 );

        QComboBox* combo = new QComboBox( this );
        combo->addItem( "QComboBox" );
        fLaypout->addRow( "QComboBox", combo );
    }
};


int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWidget w( nullptr );
    w.show();
    return a.exec();
}

[Bonnie]

I've tried in MacOS.
QComboBox does always have some margins even you set all of the layout's content margins to 0.
I didn't use the OP's code, just made a similar ui by the designer, in both QGridLayout and QFormLayout.

[AndyBrice]

@Christian-Ehrlicher said in QComboBox aligment issue:

The code had a little glitch.

It was 4 different files, rather than 1 file.

Did you try it with a QGridLayout?

Yes. Same issue.

It does work fine on Linux

It is fine on Windows as well.

therefore I would suggest you to create a Qt bug entry

I will. Thx.