is there anybody to explain of sizepolicy?



  • i worte some test code to understand different of sizepolicy.


    QHBoxLayout *layout = new QHBoxLayout();
    layout->setContentsMargins(0,0,0,0);
    
    QPushButton *button1 = new QPushButton("minimun", this);
    button1->setSizePolicy(QSizePolicy::Minimum, QSizePolicy::Fixed);
    
    QPushButton *button2 = new QPushButton("preferred", this);
    button2->setSizePolicy(QSizePolicy::Preferred, QSizePolicy::Fixed);
    
    QPushButton *button3 = new QPushButton("maximum", this);
    button3->setSizePolicy(QSizePolicy::Maximum, QSizePolicy::Fixed);
    
    layout->addWidget(button1);
    layout->addWidget(button2);
    layout->addWidget(button3);
    
    this->setLayout(layout);
    

    Alt text

    i know difference of maximum and minimum,
    but i don't understand difference of minimum and preferred,
    because the stretching behavior of minimum is as same as it of preferred.

    i did read manpage serveral time, but i can't understand.

    is there anybody to explain of sizepolicy?

    thank you.


  • Moderators

    Hi, and welcome to the Qt Dev Net!

    • Minimum: The widget is not allowed to be smaller than its sizeHint().
    • Preferred: The widget is allowed to be smaller than its sizeHint().

    This is described at http://doc.qt.io/qt-5/qsizepolicy.html#Policy-enum


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