CODEWITHSUNDEEP
qt
spraff
spraff

Reputation: 33385

Why does QComboBox ignore its fixed vertical size policy?

I have a widget with two stacked layers. The first looks like this, which is fine:

enter image description here

The second looks like this, which is wrong.

enter image description here

Here is complete code which produces the widget and prints the size policies.

#include <QtWidgets>

int main (int argc, char ** argv)
{
    QApplication app (argc, argv);

    QWidget w;
    auto stack = new QStackedWidget ();
    QWidget * labelbox = new QWidget ();
    QWidget * combobox = new QComboBox ();
    QWidget * label = new QLabel ("Label");
    QWidget * button = new QPushButton ("Button");
    QWidget * date = new QDateTimeEdit ();

    auto gl = new QGridLayout (& w);
    auto hl = new QHBoxLayout (labelbox);

    hl -> addWidget (label);
    hl -> addWidget (button);

    stack -> addWidget (labelbox);
    stack -> addWidget (combobox);
    stack -> setCurrentIndex (1); // 0 is the good layer, 1 is the bad

    gl -> addWidget (date);
    gl -> addWidget (stack, 0, 1);

    w .setMinimumSize (300, 200);
    w .show ();

    for (auto x : {(QWidget *) stack, labelbox, combobox, label, button, date})
    {
        qWarning ()
            << x -> metaObject () -> className ()
            << x -> sizePolicy ();
    }
    return app .exec ();
}

The stdout is as follows:

QStackedWidget QSizePolicy(horizontalPolicy = 5, verticalPolicy = 5)
QWidget        QSizePolicy(horizontalPolicy = 5, verticalPolicy = 5)
QComboBox      QSizePolicy(horizontalPolicy = 5, verticalPolicy = 0)
QLabel         QSizePolicy(horizontalPolicy = 1, verticalPolicy = 5)
QPushButton    QSizePolicy(horizontalPolicy = 1, verticalPolicy = 0)
QDateTimeEdit  QSizePolicy(horizontalPolicy = 1, verticalPolicy = 0)

The documentation for these values is:

QSizePolicy::Fixed      = 0 The QWidget::sizeHint() is the only acceptable alternative, so the widget can never grow or shrink (e.g. the vertical direction of a push button).
QSizePolicy::GrowFlag   = 1 The widget can grow beyond its size hint if necessary.
QSizePolicy::ExpandFlag = 2 The widget should get as much space as possible.
QSizePolicy::ShrinkFlag = 4 The widget can shrink below its size hint if necessary.
QSizePolicy::IgnoreFlag = 8 The widget's size hint is ignored. The widget will get as much space as possible.

So it looks like the vertical size policies are Fixed except for the QStackedWidget, the QWidget which contains the label and button, and the QLabel, which all have GrowFlag|ShrinkFlag.

Why does the QComboBox grow vertically, despite its Fixed policy? Why does this not happen to the QPushButton or the QDateTimeEdit?

This happens with Qt 4.8 and Qt 5.1 on Ubuntu 15.04.

Upvotes: 2

Views: 1312

Answers (1)

kh25
kh25

Reputation: 1298

You are assigning the combo box directly to the QStackedWidget but haven't added it to a QLayout first. Assign it to a layout, add this layout to a QWidget and then add this QWidget to the QStackedWidget.

Example:

QWidget * combowidget = new QWidget ();
QWidget * combobox = new QComboBox ();

auto vl = new QVBoxLayout (combowidget);

vl->addWidget(combobox);
stack->addWidget (combowidget);

Upvotes: 3

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