SetSizeConstraint gives Segmentation fault.

[indy]

I am reading the book "C++ GUI programming with QT4" and I have a problem with the example of the Shape-Changing dialogs in chapter 2. I followed the tutorial by designing the GUI with designer and building the project in Eclipse. Everything compiles fine. The problem is with the constructor of the dialog box.

SortDialog::SortDialog(QWidget *parent)
        : QDialog(parent)
{
    setupUi(this);
 
    secondaryGroupBox->hide();
    tertiaryGroupBox->hide();
    layout()->setSizeConstraint(QLayout::SetFixedSize);
    setColoumnRange('A', 'Z');
}

SortDialog::SortDialog(QWidget *parent)
        : QDialog(parent)
{
    setupUi(this);

    secondaryGroupBox->hide();
    tertiaryGroupBox->hide();
    layout()->setSizeConstraint(QLayout::SetFixedSize);
    setColoumnRange('A', 'Z');
}

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When I add the line

layout()->setSizeConstraint(QLayout::SetFixedSize);

layout()->setSizeConstraint(QLayout::SetFixedSize);

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the project compiles but when I try to run the executable I get Segmentation fault. Without that line the program runs ok but of course the dialog doesn't resize.

I am using Linux with KDE. Can anyone explain what is wrong please?

[jacek]

Do you have a top-level layout on that dialog?

[indy]

Thank you, that was it. I did a Layout->Layout in a grid and then it ran fine. The strange thing is that I could not reproduce the same layout using designer. I did it with the Qt plugin for Eclipse. I hope with experience will avoid such mistakes in the future but is there any way to ensure that there is always a top level layout?

[jacek]

is there any way to ensure that there is always a top level layout?

You don't have to use layouts, so Qt Designer doesn't know whether it's OK or not if you did't add the top-level layout. Although it warns you about a missing top-level layout when you try to save an .ui file with spacers.

I simply test all m .ui files before saving them.