Similary, top level layouts are set on container widgets ( QGroupBox) or on pages of page-based container widgets ( QTabWidget, QToolBox and QStackedWidget), respectively. To apply a layout, you can select your choice of layout from the toolbar shown on the left, or from the context menu shown below. To check if you have set a top level layout, preview your widget and attempt to resize the window by dragging the size grip.

A top level layout is necessary to ensure that your widgets will resize correctly when its window is resized. The form's top level layout can be set by clearing the selection (click the left mouse button on the form itself) and applying a layout. To break a layout, press Ctrl+0 or choose Break Layout from the form's context menu, the Form menu or the main toolbar. For an introduction to the Qt layout system, refer to Layout Management. For example, to achieve a typical dialog layout with a horizontal row of buttons, the dialog elements can be laid out using a vertical box layout with a horizontal box layout containing the buttons at the bottom. Layouts can be nested to form a hierarchy. Spacers can be added to the layout to influence the geometries of the widgets. Once widgets have been inserted into a layout, it is not possible to move and resize them individually because the layout itself controls the geometry of each widget within it, taking account of the hints provided by spacers. Placing objects in a layout also ensures that they will be resized correctly when the form is resized. This ensures that the objects will be displayed properly when the form is previewed or used in an application.

Before a form can be used, the objects on the form need to be placed into layouts.

Chief architect layout border templates