How to declare a window server event handling class

The following example demonstrates how to declare an active object window server event handling class.

• Provide a RunL() function to handle the completion of an asynchronous request, i.e. an event being received.

• Provide a DoCancel() function to implement a cancellation request.

• Provide a function, here called IssueRequest(), to issue a request to window server for events.

• Create a TWsEvent object to store events.

/* An active object that wraps a window server session.
   An event being received causes RunL() to be called,
   where the event is processed. */

class CExampleWsClient : public CActive
          {
public:
 ...

          // Active object protocol
          void RunL ();
          void DoCancel();

          // Issue request to window server for events
          IssueRequest();

private:

          // Access to window server session
          RWsSession& iWs;

          // Access to screen device
          CWsScreenDevice& iScreen;

          // Window server general event
          TWsEvent iWsEvent;
          };

Once the active object has been constructed, a request can be issued. In the following code fragment, the active object provides the function IssueRequest() to invoke the encapsulated event request function. Pass the a TRequestStatus object, iStatus, to the EventReady() function to request window server events from the iWs window server session.

Use the CActive::SetActive() function, to indicate that the active object is currently active.

/* Request window server events */
void CExampleWsClient::IssueRequest()
          {
          iWs.EventReady(&iStatus;); // request an event
          SetActive(); // so we're now active
          }