Why are widgets stacked on top of each other?

Question

Qt

CocomoWidget::CocomoWidget(QWidget* parent) : QWidget(parent) {
    auto scaleLabel = new QLabel("Размер проекта:", this);

    auto scaleSpinBox = new QSpinBox(this);
    scaleSpinBox->setRange(1, 1000000);
    scaleSpinBox->setSingleStep(10);
    scaleSpinBox->setValue(10);
    scaleSpinBox->setSuffix(" KLOC");

    auto scaleLayout = new QHBoxLayout(this);
    scaleLayout->addWidget(scaleLabel);
    scaleLayout->addWidget(scaleSpinBox);

    auto topLayout = new QVBoxLayout(this);
    topLayout->addLayout(scaleLayout);

    this->setLayout(topLayout);
}

Result:

Answer 1

That's how it works. Look at the application console, it probably wrote "QLayout: Attempting to add QLayout "" to CustomWidget "", which already has a layout", because it was set when you specified this as a constructor parameter.

auto scaleLabel = new QLabel("Размер проекта:", this);

    auto scaleSpinBox = new QSpinBox(this);
    scaleSpinBox->setRange(1, 1000000);
    scaleSpinBox->setSingleStep(10);
    scaleSpinBox->setValue(10);
    scaleSpinBox->setSuffix(" KLOC");

    auto scaleLayout = new QHBoxLayout;
    scaleLayout->addWidget(scaleLabel);
    scaleLayout->addWidget(scaleSpinBox);

    auto topLayout = new QVBoxLayout;
    topLayout->addLayout(scaleLayout);

    this->setLayout(topLayout);

PS for widgets, you can also not add parent'a, tk. addWidget calls addItem which will add it.

Answer 2

You only need one empty Layout in which to shove the rest of the Layout.