Legacy Maemo 5 Documentation/Human Interface Guidelines/Usability Principles
| This article is legacy documentation, and is superseded by Forum Nokia documentation.
The Forum Nokia documentation is available as the Hildon 2.2 UI style guide, Fremantle master layout guide and the Hildon 2.2 widget UI specification
This section gives some basic principles that are core to the development of touch interfaces and mobile applications. Concepts introduced later in this document build upon the principles in this section. The principles present in the Principles Section of GNOME HIG, although not so related to mobile applications, are also very useful reference and you should be familiar with them as well.
Mobile devices have a wide variety of available hardware. For example, some devices have special buttons to raise the volume, to call a menu, to navigate through the menus, and so on. Other devices may not have any of these buttons. Because of this diversity, avoid using icons or actions that are intimately related to a specific device or brand. For example, do not use a mouse icon with one of its buttons highlighted to suggest the user to click. Also, avoid messages that mention specific hardware features like "Use the menu button to..." (unless you are referring to a graphical button). The developer only controls the software's user interface and cannot depend on any particular hardware features.
 Size Matters
A mobile device is neither a desktop nor a laptop computer. Screen size is an obvious and important difference. Small size screens make the interaction with an application a very different experience than working with a standard computer screen.
Remember that mobile device screens are not only small, but they vary widely in size and dimensions. Do not assume that your user's device will have the same screen size as the one you are using. Some devices have a landscape display while others have a portrait display. Some are even able to change the display orientation. Mobile applications must adapt to all these displays. Avoid fixed-sized application widgets. For example, instead of defining a fixed size for example for a button, let Hildon itself adapt that button to the label and screen layout.
Hildon is designed for touch interfaces and if you wish your application to be finger-friendly, be aware of the size of the widgets with which the user interacts. Small touch surfaces, such as small buttons, are difficult and frustrating to use.
 Using Fingers
Being designed to be used by fingers, Hildon also requires some changes in what comes to the widget's placement in the application. For example, consider an application divided in two columns, the left one that displays information, and the right one that holds control widgets. If the users are left-handed, they may cover up the display area with their fingers when touching the control widgets. Letting the users choose the position of the mentioned areas is good but a better approach is to place the control widgets in the bottom and the information on top of them, if possible.
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