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<!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. -->+
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<!-- This component and the accompanying materials are made available under the terms of the License +
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<!-- Initial Contributors:+
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    Nokia Corporation - initial contribution.+
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Contributors: +
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-->+
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<!DOCTYPE concept+
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  PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">+
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<concept id="GUID-056165A7-E8A1-4868-8051-9EC58C5A3342" xml:lang="en"><title>Usability+
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considerations</title><prolog><metadata><keywords/></metadata></prolog><conbody>+
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<p>All touch and gestural interfaces have to appear competent and safe. The+
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interface must appear such that it is not going to misuse users' personal+
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data or break down. Optimizing system performance is critical here. Low screen+
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refresh rate and latent images do not give the impression of a trustworthy+
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touch UI. The use of touch screen and sensors may also increase battery consumption+
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of mobile devices.</p>+
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<note><p>Touch screens consume most power during touch operations, and reducing+
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unnecessary user interaction can help increase power efficiency. Specifically+
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with resistive touch screens, avoiding excessively long touch and drag user+
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actions is recommended. The continuous touch event flow keeps the CPU busy.+
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The screen lock turns off the touch completely. To learn more about both optimizing+
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system performance and battery life, see the <xref href="http://developer.symbian.org/wiki/index.php/Power_Management" scope="external">Power Management</xref> section at the Symbian Foundation.</p></note>+
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<p>The best products predict the needs of their users and then fulfill those+
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needs in unexpectedly pleasing ways. Adaptive targets are one way to do this.+
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 Controls that match the users actions well are another way devices can be+
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clever.</p>+
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<p><b>Interaction design</b></p>+
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<p>Use appropriate and simple interaction logic:</p>+
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<ul>+
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<li><p>Navigation and controls must be clear and meaningful to prevent mistakes:+
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strokes along the touch panel must produce a logical outcome. </p></li>+
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<li><p>The coolest interaction in the world is empty unless it has clear meaning+
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for the person performing it. When using indirect controls, the UI response+
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must relate to the action the user is performing. </p></li>+
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<li><p>Meaningful controls are easier to learn and remember. </p></li>+
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</ul>+
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<p>Touch UI can employ direct or indirect controls, or a combination of both:</p>+
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<ul>+
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<li><p>Direct controls allow users to simply tap the item they want to manipulate+
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right on the screen itself, move it, make it bigger, scroll it, and so on.+
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For more information, see <xref href="GUID-CCE6DC36-625C-487C-9AD8-F1BF8E36080A.dita">UI+
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components</xref> and <xref href="GUID-BB8B3A11-0BBC-4759-A7F4-A28C9E70573F.dita">Touch+
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support for common UI components</xref>. </p></li>+
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<li><p>Indirect controls use some other means to manipulate an object, for+
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example, shaking, tilting, flipping, waving and so on. For more information,+
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see <xref href="GUID-AE979B97-5610-42F3-99A7-5A3D66D3C2E6.dita">Sensor interaction</xref>.</p></li>+
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<li><p>Although Symbian platform allows the use of scrollbars, it is common+
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to reverse the page scrolling orientation in applications such as browser.+
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In absence of scrollbars, users will flick or drag the page upwards rather+
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than pull a scrollbar down to move the page up, that is, to scroll down. In+
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this case, scrollbars are used as navigation indicators.</p></li>+
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</ul>+
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<fig id="GUID-604A80CE-CB23-45A9-BC29-A01395CD6A2F">+
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<image href="GUID-EE5937B6-9103-4711-B13B-06A62D56AF79_d0e102012_href.png" scale="60" placement="inline"/>+
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</fig>+
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<p>Direct taps and strokes are far easier for the user to understand and pick+
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up than abstract, indirect ones. A single view must always employ only a few+
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indirect strokes, so that the controls do not confuse the user. </p>+
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<p><b>Visual design</b></p>+
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<p>On touch screens, it is important to make a clear distinction between touchable+
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areas, and non-touchable areas, such as text. Borders, glow effects, or other+
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indicators can be used to highlight the interaction.<note>Theme design alone+
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is not sufficient for indicating touch functionality, where one theme may+
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indicate touch, another may not.</note></p>+
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<p>See also:</p>+
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</conbody></concept>+
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