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    12 <concept id="GUID-FCEDC338-61CA-5D10-A8DB-E44A3EBBDE5E" xml:lang="en"><title>Front

    13 End Processor Overview</title><prolog><metadata><keywords/></metadata></prolog><conbody>

    14 <section id="GUID-4DBE2888-BC56-417E-B12F-520A9AFF5CBE"><title>Purpose</title> <p>Front End Processors, or FEPs, enable users

    15 to input characters that are not on the device keyboard. For most phones a

    16 FEP is essential for entering anything anything other than numbers. Typically

    17 FEPs are used for processing multi-tap keypad input, predictive text, handwriting

    18 recognition, voice recognition and character selection. </p> </section>

    19 <section id="GUID-CB4AD573-8695-4BE0-A40D-DCB813AD313C"><title>Architectural relationships</title> <p>FEPs are ECOM plugins

    20 that implement the FEP interface. They typically use the UI Control Framework

    21 to intercept key and pointer events which are processed as necessary and the

    22 output sent to the current application. Applications do not need to be aware

    23 that a FEP is present. </p> <p>Note that until the introduction of <xref href="GUID-4BFEDD79-9502-526A-BA7B-97550A6F0601.dita">Platform

    24 Security</xref> FEPs were implemented as polymorphic DLLs. Significantly,

    25 under Platsec, FEPs require a capability of <b>All - Tcb</b> as they may be

    26 loaded by any application. </p> </section>

    27 <section id="GUID-DDA8FA60-B059-45ED-98FE-BA0C274BFC36"><title>Description</title> <p>The API has five key concepts: FEP

    28 base, control input capability, FEP-aware text editor, foreground observer

    29 and focus observer. </p> <p><b>FEP Base</b> </p> <p>The FEP

    30 base, <xref href="GUID-ADAA039A-7BF3-3B06-8486-2E3604C2633D.dita"><apiname>CCoeFep</apiname></xref>, is the abstract base class from which a

    31 FEP is derived. A FEP is typically implemented to have a window owning control,

    32 the standard Symbian OS means of receiving input events. The UI Control Framework

    33 uses a control stack to determine the order in which controls are offered

    34 key events. A FEP places its control on the stack with a high priority such

    35 that it has first access to key events. </p> <fig id="GUID-55FA95ED-227B-560E-98B4-CCFB8E42A216">

    36 <title>                 FEP Base               </title>

    37 <image href="GUID-DD3A519B-26D5-5920-BEF3-16273A661448_d0e16898_href.png" placement="inline"/>

    38 </fig> <p>The Window Server provides support for windows that float above

    39 other windows in the application. This allows a FEP to have a visible presence. </p> <p>Each

    40 running application has its own instance of the current FEP. Support is provided

    41 for synchronising attributes across all instances so that there appears to

    42 be only one. </p> <p><b>Control input-capabilities</b> </p> <p>A FEP must

    43 be able to discover the input-capabilities of the target control(s) to determine

    44 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

    45 text editors</b> </p> <p>A text-editing control can be designed to be closely

    46 integrated with a FEP by implementing <xref href="GUID-A5D563D6-A99A-31DF-B844-5F94EF5FFE87.dita"><apiname>MCoeFepAwareTextEditor</apiname></xref>.

    47 Most of the Symbian provided editing controls do this. The use of in-line

    48 editing in FEP aware editors can mean that a FEP has no obvious visible presence

    49 at all. </p> <p><b>Foreground observer</b> </p> <p>A FEP can implement an

    50 observer interface to be notified when the application goes into the foreground

    51 or background. The foreground observer is <xref href="GUID-2CAC79B0-8BD3-3961-A162-75B004AEE5FC.dita"><apiname>MCoeForegroundObserver</apiname></xref>. </p> <p><b>Focus

    52 observer</b> </p> <p>A FEP can implement an observer to be notified when controls

    53 under the FEP gain or lose focus. The FEP can then discover the input-capabilities

    54 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>

    55 <section id="GUID-90026D68-1FB6-4190-B0A8-9CDD0B1C6C18"><title>See also</title> <p><xref href="GUID-37E8A48E-09B8-5958-9263-B33EDAE3F7C6.dita">UI

    56 Control Framework Overview</xref>  </p> </section>

    57 </conbody></concept>