General events

All events generated by the window server, except redraw events and priority key events, are delivered to the client in a TWsEvent which is requested asynchronously by the RWsSession::EventReady() function. When this request completes, it is handled by an active object CActive::RunL() function which must use RWsSession::GetEvent() to get the TWsEvent representing the event. The TWsEvent::Type() function is used to identify the event type which can then retrieve the appropriate type of data. Event types may be grouped as follows:

• those relating to the system, e.g. switch-on

  see How to process system-related events

• those relating to a window group, e.g. focus lost or gained, key code, key up or down

  see How to process window-group related events

• those relating to a window, e.g. a pointer event

  For this type of event the TWsEvent::Handle() function may be used to identify the window. Each window, when created by the client, is given a handle which the client uses to identify the window associated with a particular event.

  see How to process window-related events

Certain event types are not automatically delivered to the window server session: if they are required they must be explicitly requested by a window. The window server session will then receive the events, with a handle to the window that requested them, and the handle can be used to invoke a member function of the window that requested the events. Events that must be requested in this way are of the following types:

• on events, e.g. when the machine is powered up, either by pressing the On key, opening the case, touching the screen or an alarm going off

  UseRWindowTreeNode::EnableOnEvents() to instruct the server to report system switch on events to this window.

• window group changed events

  Use RWindowTreeNode::EnableGroupChangeEvents() to instruct the window server to report group-change events to this window. These events will typically be of interest to a shell or similar application, for example to notify it that it should update its list of running applications

• modifier changed events, i.e., when one of the modifier keys is pressed or released

  Use RWindowTreeNode::EnableModifierChangedEvents() to instruct the window server to report modifier changed events to this window. Values for the modifier keys are defined in TEventModifier.

• focus changed events

  Use RWindowTreeNode::EnableFocusChangeEvents() to instruct the window server to report when the window group with focus changes.

• error message events, e.g., out of memory messages

  useRWindowTreeNode::EnableFocusChangedEvents() to instruct the window server to report error message events.

If several windows associated with a window server session request notification of the same event, then the event is notified separately to all windows which requested it.

Events of type EEventScreenDeviceChanged are issued if the screen size mode changes. Such events are sent, for example, when the flip on an Ericsson R380 phone is opened or closed. Use EnableScreenChangeEvents() to instruct the window server to report screen change events to a window group.