override minimumSize function

[niko]

Hello,

I'm trying to override the minimumSize-Function of a widget
(so it can't be resized smaller than this size)

class test : public QLabel {
public:
    test(QString s, QWidget* p=0): QLabel(s, p) {}
    QSize minimumSizeHint() const {
      qDebug() << "minSizeHint";
      return QSize(300, 200);
    }
    QSize minimumSize () const
    {
      qDebug() << "minSize";
      return QSize(300, 200);
    }
};
 
int main(int argc, char* argv[])
{
  QApplication app(argc, argv);
    test l(QString("foo"));
    //l.setMinimumSize(200, 200); //works!
    l.show();
    return app.exec();
}

class test : public QLabel {
public:
    test(QString s, QWidget* p=0): QLabel(s, p) {}
    QSize minimumSizeHint() const {
      qDebug() << "minSizeHint";
      return QSize(300, 200);
    }
    QSize minimumSize () const
    {
      qDebug() << "minSize";
      return QSize(300, 200);
    }
};

int main(int argc, char* argv[])
{
  QApplication app(argc, argv);
    test l(QString("foo"));
    //l.setMinimumSize(200, 200); //works!
    l.show();
    return app.exec();
}

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The functions minimumSize and minimumSizeHint are never called
If I use setMinimumSize it works.

What do I make wrong?
thanks,
niko

[jpn]

Minimum size is a property of QWidget. The getter QWidget::minimumSize() is not virtual and can therefore not be overridden.

[niko]

oh, ok... thanks for that hint.

but minimumSizeHint is a virtual function; I just chcked the Qt-Source:

virtual QSize minimumSizeHint() const;

virtual QSize minimumSizeHint() const;

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But i found out why minimumSizeHint isn't working: I don't use a Layout in my test - it only works with a layout! (strange??)

my fixed code:

int main(int argc, char* argv[])
{
  QApplication app(argc, argv);
  QWidget window;
  QVBoxLayout layout;
  window.setLayout(&layout);
  test testLabel(QString("foo"));
  layout.addWidget(&testLabel);
  window.show();
  return app.exec();
}

int main(int argc, char* argv[])
{
  QApplication app(argc, argv);
  QWidget window;
  QVBoxLayout layout;
  window.setLayout(&layout);
  test testLabel(QString("foo"));
  layout.addWidget(&testLabel);
  window.show();
  return app.exec();
}

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...is there a reason for this behavior or is it a bug in Qt?
(i guess in real applications it doesn't matter - as layouts always will be used)

niko

[wysota]

But i found out why minimumSizeHint isn't working: I don't use a Layout in my test - it only works with a layout! (strange??)
...is there a reason for this behavior or is it a bug in Qt?

It's a way Qt is designed - sizeHints are only relevant when a widget is in layout. See the docs:

The default implementation of sizeHint() returns an invalid size if there is no layout for this widget, and returns the layout's preferred size otherwise.

[niko]

ok, as always, much thanks for your answers...

niko