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    Nokia Corporation - initial contribution.+
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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-ACC71D0D-32C4-5DAF-B4D9-66013A073FD4" xml:lang="en"><title>Synchronising+
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FEP Instantiations</title><shortdesc>This topic describes how to synchronize settings across different+
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instances of the same FEP.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>+
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<p>As mentioned previously, the FEP architecture has been designed so that+
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each running application has its own instance of the current FEP. <codeph>CCoeFep</codeph> provides+
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support for synchronizing attributes across all of these instances, so that+
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when one instance changes the value of an attribute, the others are automatically+
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updated. In order for this to happen, the FEP has to do several things. </p>+
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<ul>+
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<li id="GUID-EC8E4D77-BE0E-5A5E-87B0-817109AD5D44"><p>Override the four pure+
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virtual functions that <xref href="GUID-ADAA039A-7BF3-3B06-8486-2E3604C2633D.dita"><apiname>CCoeFep</apiname></xref> inherits from <xref href="GUID-B0007B23-6745-31BE-A832-9ACA4C12E3E6.dita"><apiname>MFepAttributeStore</apiname></xref>: <codeph>NumberOfAttributes()</codeph>, <codeph>AttributeAtIndex()</codeph>, <codeph>WriteAttributeDataToStreamL()</codeph> and <codeph>ReadAttributeDataFromStreamL()</codeph>. <codeph>NumberOfAttributes()</codeph> should return the number of attributes that are to be synchronized across+
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all instances of the FEP, <codeph>AttributeAtIndex()</codeph> should return+
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the UID of the specified attribute, and <codeph>WriteAttributeDataToStreamL()</codeph> and <codeph>ReadAttributeDataFromStreamL()</codeph> should+
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write/read the specified attribute’s data to/from the provided stream. </p> </li>+
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<li id="GUID-0163FF77-8495-5812-AF0D-2FB9AB376EC5"><p>When the object of the <xref href="GUID-ADAA039A-7BF3-3B06-8486-2E3604C2633D.dita"><apiname>CCoeFep</apiname></xref> -derived+
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class has been fully constructed, call <codeph>CCoeFep::ReadAllAttributesL()</codeph>.+
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This calls the <codeph>ReadAttributeDataFromStreamL()</codeph> virtual function+
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for each of the UIDs that the FEP requires to be synchronized (as specified+
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by <codeph>NumberOfAttributes()</codeph> and <codeph>AttributeAtIndex()</codeph>). </p> </li>+
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<li id="GUID-E4435F88-8C8F-5E93-8587-101DBCA7FA03"><p>After internally changing+
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the value of an attribute that is to be synchronized, call <codeph>CCoeFep::WriteAttributeDataAndBroadcastL()</codeph> to+
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propagate that change to all the other instances of the FEP. The parameter+
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identifies the attributes that are to be synchronized, using UIDs. See the+
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Symbian website for information on how to be allocated UIDs. </p> </li>+
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</ul>+
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<p>The purpose of the <codeph>SynchronouslyExecuteSettingsDialogL()</codeph> exported+
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function, which the FEP must provide, is to launch a dialog that allows the+
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user to change any settings specific to that FEP. As mentioned above, there+
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is no guarantee that any instance of that particular FEP exists when this+
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function is called. In order for the dialog launched by <codeph>SynchronouslyExecuteSettingsDialogL()</codeph> to+
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be able to edit settings that are required to be synchronized across all running+
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applications, the dialog class must derive from <xref href="GUID-270424BB-124B-39FF-9CDA-5CAFB5407FAE.dita"><apiname>MFepAttributeStorer</apiname></xref>.+
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The dialog class’ implementation of <xref href="GUID-270424BB-124B-39FF-9CDA-5CAFB5407FAE.dita"><apiname>MFepAttributeStorer</apiname></xref> ’s+
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virtual functions should be the same as the <xref href="GUID-ADAA039A-7BF3-3B06-8486-2E3604C2633D.dita"><apiname>CCoeFep</apiname></xref> -derived+
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class’ implementation of them. For an example of this, see TFEP1Plugin. When+
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the dialog is launched it needs to call <codeph>MFepAttributeStorer::ReadAllAttributesL()</codeph> to+
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correctly initialize all the settings. Conversely, the settings in the dialog+
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are committed by calling <codeph>MFepAttributeStorer::WriteAttributeDataAndBroadcastL()</codeph>. </p>+
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</conbody></concept>+
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