Layout spacing

AndyBrice

When I run the code below I get these buttons, with big vertical spaces on Mac:

#include <QVBoxLayout>
#include <QPushButton>

class Buttons : public QWidget
{
public:
    Buttons( QWidget* parent );
};

Buttons::Buttons( QWidget* parent )
    :QWidget( parent )
{
    setContentsMargins( 0, 0, 0, 0 );

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

    QPushButton* button1 = new QPushButton( QString( "Button 1" ), this );
    button1->setAttribute( Qt::WA_MacSmallSize );
    hLayout->addWidget( button1 );

    QPushButton* button2 = new QPushButton( QString( "Button 2" ), this );
    button2->setAttribute( Qt::WA_MacSmallSize );
    hLayout->addWidget( button2 );
}

class MainWindow : public QWidget
{
    Q_OBJECT
public:
    MainWindow(QWidget *parent = nullptr);
};

MainWindow::MainWindow(QWidget *parent)
    : QWidget(parent)
{
    setContentsMargins( 0, 0, 0, 0 );

    QVBoxLayout* v1Layout = new QVBoxLayout( this );
    v1Layout->setContentsMargins( 0, 0, 0, 0 );
    v1Layout->setMargin( 0 );
    v1Layout->setSpacing( 0 );
    for ( int i = 0; i < 10; i++ )
    {
        Buttons* buttons = new Buttons( this );
        v1Layout->addWidget( buttons );
    }
}

I can't work out how to get rid of the vertical spacing between buttons. Note that I don't seem to have the same problem on Windows.

If I replace the Buttons class with a simple QButton, then the extra spacing disappears.

So it seems to be something to do with the QHBoxLayout. Any ideas?

I am using Qt 5.15.2.

AndyBrice

I tried:

setAttribute( QT::WA_LayoutUsesWidgetRect);

On each QPushButton. But it didn't make a difference.

JoeCFD

Add vertical spacer to push them up?

AndyBrice

Adding a spacer or stretch at the end of the vertical layout doesn't seem to make a difference.

AndyBrice

I can push the buttons closer together by setting in the Buttons constructor for Mac:

setContentsMargins( 0, 0, 0, -4 );

That seems like a very ugly solution though!

JoeCFD

@AndyBrice Your code may behave differently on other OS. What will happen if you resize your app? Even -4 may need to be scaled if it is set in full screen mode.

Play with the factor in the spacer to see if there is any help. Sometimes I have to raise the factor to get what I want.
Another idea would be to make your layout inside Qt Designer to see if it works there. If it works, generate the layout code. Copy it into your code.