Qt grid layout not displaying correctly in scroll area

Question

I have a grid layout with a bunch of QPushButtons and my own flavor of QToolButtons in it. My dialog is displaying to my taste except when I happen to have too many buttons in it which causes the grid to expand beyond the screen size. So I want to add a scroll bar.

I've already read a bunch a questions/solutions about scroll bars and QtGridLayout but after implementing this accepted solution for example qdialog with scrollarea and gridlayout all my buttons (which should have their size fixed - corresponding code omitted below for clarity) get shrunk to a stupid size. Also, when I resize my dialog, the scroll area resizes accordingly, but the grid inside it doesn't. What am I missing?

NOTE: I have tried all sorts of ways to fix the various dimensions, basically everything works without the scroll area, but as soon as I put things in the scroll area, the grid cells get automatically and nonsensically resized...

void createDatabaseWindow()
{
    _database_widget = new QDialog;
    QVBoxLayout* layout(new QVBoxLayout);
    _database_layout = new QGridLayout;

    QLabel* text(new QLabel("some text"));
    layout->addWidget(text);

    QVBoxLayout* vlayout(new QVBoxLayout);
    _new_user_button = new QPushButton("New User");
    vlayout->addWidget(_new_user_button);
    QPushButton* cancel_button(SM_NEW QPushButton("Cancel"));
    vlayout->addWidget(cancel_button);
    _database_layout->addLayout(vlayout, 0, 0);

    std::vector<Result> database = getWholeDatabase();
    for (int i = 0; i < database.size(); i++){
        myQToolButton* button(new myQToolButton(database[i]));
        _database_layout->addWidget(button, (i + 1) / N_ROWS_DATABASE, (i + 1) % N_ROWS_DATABASE);
    }

    // the following comes from an accepted solution, but doesn't work for me...

    //Create a widget and set its layout as your new layout created above
    QWidget *viewport = new QWidget;
    viewport->setLayout(_database_layout);

    //Add the viewport to the scroll area
    QScrollArea *scrollArea = new QScrollArea;
    scrollArea->setWidget(viewport);

    //Add the scroll area to your main window's layout
    layout->addWidget(scrollArea);

    _database_widget->setLayout(layout);


}

Julien Julien · Accepted Answer · 2015-10-19T02:15:33

Got it! The problem was dynamic change in the grid layout content. The magic line that fixes everything is:

_database_layout->setSizeConstraint(QLayout::SetMinAndMaxSize);

Qt grid layout not displaying correctly in scroll area

1 Answers