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

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

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

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

<ul>

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

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

to receive </p> </li>

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

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

</ul>

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

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

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

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

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

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

function of an active object. </p>

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

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

client program controls all its own windows, issues asynchronous requests

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

Window Server behavior. </p>

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

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

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

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

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

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

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

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

Events</xref>. </p>

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

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

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

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

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

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

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

Buffer</xref>  </p>

</conbody><related-links>

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

</link>

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

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