Question

I was looking at the example here, and was wondering if there is no memory leaks. I have red the article talking about the subjet mem leak on delete. However while QWidgets do retain ownership of the of the widget added to the, the layout do not.

It seems from the QT code that the parent with the layout, gets the ownership of all the widgets for this layout. However i could not seen any reference of this in docs.

Window::Window()
{
 editor = new QTextEdit();
 QPushButton *sendButton = new QPushButton(tr("&Send message"));

 connect(sendButton, SIGNAL(clicked()), this, SLOT(sendMessage()));

 QHBoxLayout *buttonLayout = new QHBoxLayout();
 buttonLayout->addStretch();
 buttonLayout->addWidget(sendButton);
 buttonLayout->addStretch();

 QVBoxLayout *layout = new QVBoxLayout(this);
 layout->addWidget(editor);
 layout->addLayout(buttonLayout);

 setWindowTitle(tr("Custom Type Sending"));
}

Answer 1

From Layout Management:

Tips for Using Layouts

When you use a layout, you do not need to pass a parent when
constructing the child widgets. The layout will automatically
reparent the widgets (using QWidget::setParent()) so that they are
children of the widget on which the layout is installed.

Note: Widgets in a layout are children of the widget on which the
layout is installed, not of the layout itself. Widgets can only have
other widgets as parent, not layouts.

You can nest layouts using addLayout() on a layout; the inner layout
then becomes a child of the layout it is inserted into.