Usability +considerations

diff -r 43e37759235e -r 51a74ef9ed63 Symbian3/SDK/Source/GUID-056165A7-E8A1-4868-8051-9EC58C5A3342.dita --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/Symbian3/SDK/Source/GUID-056165A7-E8A1-4868-8051-9EC58C5A3342.dita Wed Mar 31 11:11:55 2010 +0100 @@ -0,0 +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.