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<concept id="GUID-8661A7E0-F19A-41F8-9062-FBFAE70CF658" xml:lang="en"><title>Tactile

feedback client API</title><shortdesc>The Tactile feedback client API is used for producing tactile feedback

for different touch events.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<p>The Tactile feedback client API is a library API that has been implemented

with a client-server technique. A major part of the processing is done on

the client side, and thus API calls don't necessarily generate a client-server

transaction immediately. Instead for example, changes to area registry are

buffered, and then transferred to server-side at once.</p>

<p>You can use tactile feedback in, for example, the following cases:</p>

<ul>

<li>When the user starts to scroll with the scroll bar, user can feel and/or

hear when the scroll bar thumb has been caught.</li>

<li>When button is pressed, user can feel and/or hear the button being pressed.</li>

</ul>

<p>The concept of logical feedback type is very important from this API's

point of view. </p>

<p>In practice it means that, for example, you should not try to use this

API for producing vibrator feedback only. Instead, logical feedback types

such as "basic" or "sensitive" are used on this level, and the actual physical

effect then depends on the settings and device configuration. This way the

feedback works in a unified way from the end user point of view in the whole

device.</p>

<section id="GUID-44CAF194-6B6A-4661-AB29-88BF700BBC60"><p>For user experience

guidelines on tactile feedback, see <xref href="GUID-581A8E4B-12BE-41C0-A20E-3087A80FEECF.dita">Tactile

feedback</xref>.</p><p>For information on using the API, see <xref href="GUID-786D76B7-B827-43B7-8202-BA7A7E5EE03E.dita">Providing

tactile feedback for touch events</xref>.</p><p>For the Tactile feedback client

API classes and header files, see Classes and Definitions.</p></section>

<section id="GUID-E44747A5-92BF-4D7A-895C-C469112A4D32"><title>API class structure</title><p>All

functionality of the Tactile feedback client API is provided in the class <xref href="jar:GUID-759FBC7F-5384-4487-8457-A8D4B76F6AA6.jar!/html/classMTouchFeedback.html" format="application/java-archive"><codeph>MTouchFeedback</codeph></xref>.</p></section>

<section id="GUID-0D0648C0-5AAE-48C1-82BD-025D6908E3B1"><title>Constraints</title><p>This

API is valid for all platforms running on Symbian OS v9.4 or later.</p></section>

<section id="GUID-E8D3D7BC-F365-45D7-A4AE-4393CF1B6795"><title>Error handling</title><p>The

leave mechanism of Symbian environment is used to handle memory exhaustion.

The panic mechanism is not used.</p> <p>The table below presents possible

error conditions and responses to them.</p> <table id="GUID-E9186B9F-2C9B-4C09-B054-69D093BBE41D">

<title>Possible error situations when using Tactile Feedback Client API</title>

<tgroup cols="2"><colspec colname="col1"/><colspec colname="col2"/>

<thead>

<row>

<entry>Error situation</entry>

<entry>Response</entry>

</row>

</thead>

<tbody>

<row>

<entry><codeph>SetFeedbackArea</codeph> returns <codeph>KErrNoMemory</codeph> in

case of an OOM situation.</entry>

<entry>This error can usually be ignored by the application.</entry>

</row>

<row>

<entry><codeph>SetFeedbackArea</codeph> returns <codeph>KErrArgument</codeph></entry>

<entry>The given <codeph>CCoeControl</codeph> pointer is a <codeph>NULL</codeph> pointer

or the control does not have any window associated with it (the feedback area

setting is attempted before <codeph>SetContainerWindow</codeph> has been called

on the control).</entry>

</row>

<row>

<entry><codeph>SetFeedbackArea</codeph> returns <codeph>KErrNotSupported</codeph>.</entry>

<entry>The given logical feedback type or triggering event type is out of

range.</entry>

</row>

<row>

<entry>A tactile feedback enabled control is moved with <codeph>CCoeControl::SetPosition</codeph>,

but the feedback area is not moved.</entry>

<entry>The control must override the <codeph>CCoeControl::PositionChanged</codeph> function,

and update the feedback area there the same way as in the <codeph>SizeChanged</codeph> function.</entry>

</row>

<row>

<entry>Area registry updates not are effective fast enough. This might happen

in some applications which use very many frequently running active objects,

so that the <codeph>CIdle</codeph> object used by the implementation of this

API gets no change to run.</entry>

<entry>Use the <codeph>FlushRegistryUpdates</codeph> function for forcing

an update to the server side after doing all updates on the client side.</entry>

</row>

<row>

<entry>A control's feedback areas are not automatically disabled when the

control is dimmed.</entry>

<entry><codeph>CCoeControl::SetMopParent</codeph> has not been called on the

control, and thus the object provider hierarchy is broken.</entry>

</row>

</tbody>

</tgroup>

</table></section>

<section id="GUID-2190CCB3-0569-4A43-A300-BBE83AAD64B6"><title>Memory overhead</title><p>Using

direct feedback does not cause additional memory overhead.</p> <p>Area registry

based feedback consumes approximately 32 bytes for each feedback area.</p></section>

<section id="GUID-F903AC63-2526-4767-B326-56D43344B23B"><title>Extensions

to the API</title><p>New logical feedback types can be added in later releases.

Otherwise the Tactile feedback client API does not explicitly support any

kinds of extensions to it.</p></section>

</conbody></concept>