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-->  <!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"><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></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 e.g. 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 9.4 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><colspec colname="col2"></colspec>

<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 (i.e., 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>