With this template you can add a new List Box component to your project. List box is a widget the user can interact with in order to scroll a list of items and select an item from this list. To display the available items the List Box implements a list and list item components. When the user selects an item within the List Box, the component sends signals to associated slot methods where your particular implementation is executed. If the List Box is focused the component can also be controlled by pressing keys on the keyboard or by using hardware buttons.

Components created with this template are intended to be adapted to your particular design expectations. After adding the new List Box you should edit the component, change its appearance and if desired also its behavior. Once you have adapted the component, you can embed instances of this List Box wherever you need in your GUI project. Because it serves as template, it is intentionally kept very simple. Nevertheless, List Boxs created by the template are working widgets. If desired, they can already be used as they are. The following figure demonstrates the default appearance of the List Box created by using the here described component template:

The approach with component templates has two functions. Primarily the templates should simplify the development of new components. Instead of creating the List Box from scratch you can use the available template. The second function is more educative. The template implements fully working List Box component you can investigate and learn about the corresponding programming aspects. The template is well documented. It contains annotations and inline comments with instructions helping you to understand how the component works and how it can be adapted to your particular needs.

This chapter provides an overview how the List Box component template is used within your own application and how you adapt this component according to your particular needs. You will find here also further details concerning the internal implementation of the List Box component.

To create a new List Box component from a template you simply Drag & Drop it between the Templates window and the Composer with an opened unit. This is important in that by using the component templates you add in fact a new class to your project. Classes, in turn, can exist within units only. The following are the typical steps to create a new List Box component from a template:

The List Box template is composed of multiple components: ListBox, ListBoxItem and Example. Here, the ListBoxItem component implements the appearance and the behavior of a single list box item. The ListBox component implements the list itself. For example, it takes care of scrolling and selecting the items. Finally, the Example component implements a simple example demonstrating the usage of the list box.

The new created List Box component appears also accompanied by annotation providing helpful tips how to proceed. If undesired, you can select and delete the annotation.

Once you have created the List Box component, you can use it to assemble more complex components. Technically seen, you embed an instance of the List Box class in-place within some superior GUI component. At the runtime, the superior GUI component takes care of the correct initialization and the displaying of all embedded components, so they appear similarly as you have composed them at the design time.

The following are the typical steps to create a new instance of an already existing List Box component:

As long as the List Box is selected you can inspect and modify its properties conveniently in the Inspector window as demonstrated with the property Bounds in the screenshot below. This is in so far worth mentioning as diverse features of the List Box are controlled by the corresponding properties. If you are not familiar with the concept of a property and the usage of Inspector window, please read first the preceding chapter Compositing component appearance.

The List Box component descends from the Mosaic class Core::Group. Consequently, most of the properties listed in the above screenshot are inherited from this base class. Particular to the List Box are only few following properties:

Property	Description
NoOfItems	The property NoOfItems stores how many items are currently managed within the ListBox. This value should correspond to the number of options the ListBox offers to the user.
OnLoadItem	The property OnLoadItem should refer to a slot method, which will be invoked by the ListBox in order to load an item with its corresponding content. Within the slot method the affected item can be accessed and initialized via variable View.
OnSelect	The property OnSelect can refer to a slot method, which will receive a signal each time the user has selected an item within the ListBox. Thereupon the method's logic will be executed. In the associated slot method you can evaluate SelectedItem to estimate which item has been selected.
Outlet	The property Outlet can refer to any other int32 property the widget should remain synchronized with. When the user selects an item, the affected property is automatically updated to reflect the item's number. On the other hand, when the referred property is modified by another component, the ListBox is automatically notified to remain in sync with the property. This approach follows the Model-View-Controller (MVC) programming paradigm. Here the ListBox represents the view and controller. The property referred via Outlet can be seen as a part of the model. See also Outlet properties.
SelectedItem	The property SelectedItem stores the index of the currently selected item or -1 if no item is selected. The first item has the index 0, the second 1, and so far.

Once added to the component, you can freely move the List Box instance, or you simply grab one of its corners and resize it in this way. You can control the position and the size of the component also by directly modifying its property Bounds. If you want the List Box to appear behind other views you can reorder it explicitly.