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1 <?xml version="1.0" encoding="utf-8"?> |
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2 <!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. --> |
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3 <!-- This component and the accompanying materials are made available under the terms of the License |
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4 "Eclipse Public License v1.0" which accompanies this distribution, |
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5 and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". --> |
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6 <!-- Initial Contributors: |
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7 Nokia Corporation - initial contribution. |
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8 Contributors: |
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9 --> |
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10 <!DOCTYPE concept |
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11 PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"> |
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12 <concept id="GUID-FCEDC338-61CA-5D10-A8DB-E44A3EBBDE5E" xml:lang="en"><title>Front |
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13 End Processor Overview</title><prolog><metadata><keywords/></metadata></prolog><conbody> |
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14 <section id="GUID-4DBE2888-BC56-417E-B12F-520A9AFF5CBE"><title>Purpose</title> <p>Front |
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15 End Processors, or FEPs, enable users to input characters that are not on |
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16 the device keyboard. For most phones a FEP is essential for entering anything |
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17 anything other than numbers. Typically FEPs are used for processing multi-tap |
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18 keypad input, predictive text, handwriting recognition, voice recognition |
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19 and character selection. </p> </section> |
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20 <section id="GUID-CB4AD573-8695-4BE0-A40D-DCB813AD313C"><title>Architectural |
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21 relationships</title> <p>FEPs are ECOM plugins that implement the FEP interface. |
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22 They typically use the UI Control Framework to intercept key and pointer events |
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23 which are processed as necessary and the output sent to the current application. |
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24 Applications do not need to be aware that a FEP is present. </p> <p>Note that |
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25 until the introduction of <xref href="GUID-4BFEDD79-9502-526A-BA7B-97550A6F0601.dita">Platform |
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26 Security</xref> FEPs were implemented as polymorphic DLLs. Significantly, |
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27 under Platsec, FEPs require a capability of <b>All - Tcb</b> as they may be |
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28 loaded by any application. </p> </section> |
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29 <section id="GUID-DDA8FA60-B059-45ED-98FE-BA0C274BFC36"><title>Description</title> <p>The |
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30 API has five key concepts: FEP base, control input capability, FEP-aware text |
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31 editor, foreground observer and focus observer. </p> <p><b>FEP Base</b> </p> <p>The |
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32 FEP base, <xref href="GUID-ADAA039A-7BF3-3B06-8486-2E3604C2633D.dita"><apiname>CCoeFep</apiname></xref>, is the abstract base class from which |
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33 a FEP is derived. A FEP is typically implemented to have a window owning control, |
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34 the standard means of receiving input events. The UI Control Framework uses |
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35 a control stack to determine the order in which controls are offered key events. |
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36 A FEP places its control on the stack with a high priority such that it has |
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37 first access to key events. </p> <fig id="GUID-55FA95ED-227B-560E-98B4-CCFB8E42A216"> |
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38 <title> FEP Base </title> |
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39 <image href="GUID-DD3A519B-26D5-5920-BEF3-16273A661448_d0e49491_href.png" placement="inline"/> |
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40 </fig> <p>The Window Server provides support for windows that float above |
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41 other windows in the application. This allows a FEP to have a visible presence. </p> <p>Each |
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42 running application has its own instance of the current FEP. Support is provided |
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43 for synchronising attributes across all instances so that there appears to |
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44 be only one. </p> <p><b>Control input-capabilities</b> </p> <p>A FEP must |
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45 be able to discover the input-capabilities of the target control(s) to determine |
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46 what output is appropriate. Input capabilities are provided by <xref href="GUID-BB7D0D56-1713-3DC0-BDA0-3CA1F0462BE2.dita"><apiname>TCoeInputCapabilities</apiname></xref>. </p> <p><b>FEP-aware |
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47 text editors</b> </p> <p>A text-editing control can be designed to be closely |
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48 integrated with a FEP by implementing <xref href="GUID-A5D563D6-A99A-31DF-B844-5F94EF5FFE87.dita"><apiname>MCoeFepAwareTextEditor</apiname></xref>. |
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49 Most of the Symbian provided editing controls do this. The use of in-line |
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50 editing in FEP aware editors can mean that a FEP has no obvious visible presence |
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51 at all. </p> <p><b>Foreground observer</b> </p> <p>A FEP can implement an |
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52 observer interface to be notified when the application goes into the foreground |
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53 or background. The foreground observer is <xref href="GUID-2CAC79B0-8BD3-3961-A162-75B004AEE5FC.dita"><apiname>MCoeForegroundObserver</apiname></xref>. </p> <p><b>Focus |
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54 observer</b> </p> <p>A FEP can implement an observer to be notified when controls |
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55 under the FEP gain or lose focus. The FEP can then discover the input-capabilities |
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56 of the current target control(s). The focus observer is <xref href="GUID-E591B7D7-ED56-3CEF-883F-7091D5833731.dita"><apiname>MCoeFocusObserver</apiname></xref>. </p> </section> |
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57 <section id="GUID-90026D68-1FB6-4190-B0A8-9CDD0B1C6C18"><title>See also</title> <p><xref href="GUID-37E8A48E-09B8-5958-9263-B33EDAE3F7C6.dita">UI Control Framework Overview</xref> </p> </section> |
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58 </conbody></concept> |