Each application uses a Window Server session to communicate with the Window Server.
Through the session, the application may control and interrogate
its own windows
which events it wishes to receive
all other window groups connected to the Window Server
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 CActive::RunL() member
function of an active object.
The RWsSession class represents a session from
the client to the Window Server. Through an RWsSession, 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.
The RWsSession is a client-server session derived from RSessionBase.
In a typical application, an RWsSession owns a single window
group, but the Window Server architecture allows more than one window
group per session. An application owns several windows. See Window
Groups and Applications.
The Window Server session delivers events to the application via three event streams. A typical application handles each stream using an active object. See Window Server Client-Side Events.
The application draws to its windows using a CWindowGc.
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 Flush() and SetAutoFlush() functions
are part of the RWsSession API. The RWsBuffer is
privately owned by an RWsSession and is not as such part
of the API. See Client-Side
Buffer