Qt Designer's Form Editing Mode

Applying and Breaking Layouts

The simplest way to manage objects is to apply a layout to a group of existing objects. This is achieved by selecting the objects that you need to manage and applying one of the standard layouts from the main toolbar, the Edit menu, or the form's context menu.

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. Instead, you must either break the layout (Ctrl+B or Break Layout) and adjust each object's geometry manually, or you can influence the widget's geometry by resizing the layout. You can also add and remove spacers from the layout to influence the geometries of the widgets.

Inserting objects into a layout Objects can be inserted into an existing layout by dragging them from their current positions and dropping them at the required location. A blue cursor is displayed in the layout as an object is dragged over it to indicate where the object will be added.

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.

Horizontal and Vertical Layouts

The simplest way to arrange objects on a form is to place them in a horizontal or vertical layout. For example, the dialog shown at the beginning of this chapter contains two push buttons and a spacer that can be placed in a horizontal layout; this makes sure that the buttons remain next to each other when more layouts are added to the dialog. In the same way, vertical layouts ensure that each of the widgets within are aligned horizontally.

Horizontal and vertical layouts can be combined, and nested to any depth. However, if you need more control over the placement of objects, you should consider using the grid layout.

The Grid Layout

Complex form layouts can be created by placed objects in a grid layout. This kind of layout gives the form designer much more freedom to arrange widgets on the form, but can result in a much less flexible layout. However, for some kinds of form layout, a grid arrangement is much more suitable than a nested arrangement of horizontal and vertical layouts.

Previewing Forms

Although Qt Designer's forms are accurate representations of the components being edited, it is useful to preview the final appearance while editing. This feature can be activated by opening the Form menu and selecting Preview, or by pressing Ctrl+R when in the form.

The preview shows exactly what the final component will look like when used in an application.

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