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     7     Nokia Corporation - initial contribution.

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    10 <!DOCTYPE concept

    11   PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">

    12 <concept id="GUID-0174CE72-AEF6-5DA9-A9C5-074781BD544F" xml:lang="en"><title>Window

    13 Server Sessions</title><shortdesc>Each application uses a Window Server session to communicate with

    14 the Window Server. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

    15 <p>Through the session, the application may control and interrogate </p>

    16 <ul>

    17 <li id="GUID-81DEE250-87BC-5C47-91E5-B8E480884111"><p>its own windows </p> </li>

    18 <li id="GUID-7F8F429D-AD79-5634-A815-CE7DB12F2866"><p>which events it wishes

    19 to receive </p> </li>

    20 <li id="GUID-E86BCF17-F124-5CE5-B07B-704BBD020F97"><p>all other window groups

    21 connected to the Window Server </p> </li>

    22 </ul>

    23 <p>The Window Server session provides a low-level interface for application

    24 programs’ use, using asynchronous services. To support an application framework,

    25 these services should be made higher-level, and the asynchronous services

    26 should be encapsulated into active objects. This function is performed by

    27 the UI control framework. The control framework is the basis for the GUI.

    28 Each event is then handled by the <xref href="GUID-067293BF-B28C-3CEC-92F4-1351A795EA7F.dita"><apiname>CActive::RunL()</apiname></xref> member

    29 function of an active object. </p>

    30 <p>The <xref href="GUID-067293BF-B28C-3CEC-92F4-1351A795EA7F.dita"><apiname>RWsSession</apiname></xref> class represents a <keyword>session</keyword> from

    31 the client to the Window Server. Through an <codeph>RWsSession</codeph>, the

    32 client program controls all its own windows, issues asynchronous requests

    33 for up to three types of event, and may in addition control certain system-wide

    34 Window Server behavior. </p>

    35 <p>The <codeph>RWsSession</codeph> is a client-server session derived from <codeph>RSessionBase</codeph>.

    36 In a typical application, an <codeph>RWsSession</codeph> owns a single <keyword>window

    37 group</keyword>, but the Window Server architecture allows more than one window

    38 group per session. An application owns several windows. See <xref href="GUID-D68E0A64-0E8A-5C52-9C5B-93BA3B80C200.dita">Window

    39 Groups and Applications</xref>. </p>

    40 <p>The Window Server session delivers events to the application via three

    41 event streams. A typical application handles each stream using an active object.

    42 See <xref href="GUID-08427065-B8E5-5194-B095-3B5213836BED.dita">Window Server Client-Side

    43 Events</xref>. </p>

    44 <p>The application draws to its windows using a <xref href="GUID-067293BF-B28C-3CEC-92F4-1351A795EA7F.dita"><apiname>CWindowGc</apiname></xref>.

    45 Draw functions are buffered in a client-side buffer in order to minimize client/server

    46 context switches. This buffer is flushed in certain circumstances by the Window

    47 Server and can also be flushed explicitly by the application. The <codeph>Flush()</codeph> and <codeph>SetAutoFlush()</codeph> functions

    48 are part of the <codeph>RWsSession</codeph> API. The <codeph>RWsBuffer</codeph> is

    49 privately owned by an <codeph>RWsSession</codeph> and is not as such part

    50 of the API. See <xref href="GUID-E5CDDA05-CD86-5C44-B9DA-3249D9C14396.dita">Client-Side

    51 Buffer</xref>  </p>

    52 </conbody><related-links>

    53 <link href="GUID-890F06C6-DE32-5EB1-BF0F-D41794F47AE1.dita"><linktext>Active objects</linktext>

    54 </link>

    55 <link href="GUID-1F9A47CE-7F4C-52BD-8823-25D5D1BEF42F.dita"><linktext>Window Server

    56 Client-Side Library                 Concepts</linktext></link>

    57 </related-links></concept>