Usability -considerations

diff -r 51a74ef9ed63 -r ae94777fff8f Symbian3/SDK/Source/GUID-056165A7-E8A1-4868-8051-9EC58C5A3342.dita --- a/Symbian3/SDK/Source/GUID-056165A7-E8A1-4868-8051-9EC58C5A3342.dita Wed Mar 31 11:11:55 2010 +0100 +++ b/Symbian3/SDK/Source/GUID-056165A7-E8A1-4868-8051-9EC58C5A3342.dita Fri Jun 11 12:39:03 2010 +0100 @@ -1,69 +1,69 @@ - - - - - -Usability -considerations -

All touch and gestural interfaces have to appear competent and safe. The -interface must appear such that it is not going to misuse users' personal -data or break down. Optimizing system performance is critical here. Low screen -refresh rate and latent images do not give the impression of a trustworthy -touch UI. The use of touch screen and sensors may also increase battery consumption -of mobile devices.

Touch screens consume most power during touch operations, and reducing -unnecessary user interaction can help increase power efficiency. Specifically -with resistive touch screens, avoiding excessively long touch and drag user -actions is recommended. The continuous touch event flow keeps the CPU busy. -The screen lock turns off the touch completely. To learn more about both optimizing -system performance and battery life, see the Power Management section at the Symbian Foundation.

The best products predict the needs of their users and then fulfill those -needs in unexpectedly pleasing ways. Adaptive targets are one way to do this. - Controls that match the users actions well are another way devices can be -clever.

Interaction design

Use appropriate and simple interaction logic:

Navigation and controls must be clear and meaningful to prevent mistakes: -strokes along the touch panel must produce a logical outcome.
The coolest interaction in the world is empty unless it has clear meaning -for the person performing it. When using indirect controls, the UI response -must relate to the action the user is performing.
Meaningful controls are easier to learn and remember.

Touch UI can employ direct or indirect controls, or a combination of both:

Direct controls allow users to simply tap the item they want to manipulate -right on the screen itself, move it, make it bigger, scroll it, and so on. -For more information, see UI -components and Touch -support for common UI components.
Indirect controls use some other means to manipulate an object, for -example, shaking, tilting, flipping, waving and so on. For more information, -see Sensor interaction.
Although Symbian platform allows the use of scrollbars, it is common -to reverse the page scrolling orientation in applications such as browser. -In absence of scrollbars, users will flick or drag the page upwards rather -than pull a scrollbar down to move the page up, that is, to scroll down. In -this case, scrollbars are used as navigation indicators.

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Direct taps and strokes are far easier for the user to understand and pick -up than abstract, indirect ones. A single view must always employ only a few -indirect strokes, so that the controls do not confuse the user.

Visual design

On touch screens, it is important to make a clear distinction between touchable -areas, and non-touchable areas, such as text. Borders, glow effects, or other -indicators can be used to highlight the interaction.Theme design alone -is not sufficient for indicating touch functionality, where one theme may -indicate touch, another may not.