The user interface is divided into three levels where the <form> control is the top or outer level containing all user interface objects for either the STN or TFT display, or both because it is possible to create definitions for both STN and TFT displays in the same UI file.
The <form> control defines a number of display panels that are individually presented depending on what is happening in the terminal.
Finally, each panel contains normal controls such as buttons, labels and text boxes.
Figure 15. The structure of the user interface.
