The IShowListHandler-derived classes process IControlEvent events for objects of the class IComboBox. For example, a show list event occurs when the user selects the drop-down button of the combination box.
You can create a handler derived from IShowListHandler and attach it to a combination box or to the combination box's owner window. You do this by calling IHandler::handleEventsFor to pass the combination box or owner window to the show list handler.
When the show list handler receives a show list event, it creates an IControlEvent object and routes that object to the IShowListHandler::listShown virtual function. Override this virtual function to supply your own specialized processing of a show list event.
The following return values from the virtual function specifies whether the show list event is passed on for additional processing:
Constructors & DestructorThe only way to create objects of this class is from a derived class. To enforce this, the only constructor provided for this class is protected. This default constructor can be used by derived classes to create objects of this class. You can destruct objects of this class.
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public:
virtual ~IShowListHandler()
| Windows | OS/2 | AIX |
| Yes | Yes | Yes |
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protected:
IShowListHandler()
Used by derived classes to construct objects of this class. This is the default constructor and accepts no parameters.
| Windows | OS/2 | AIX |
| Yes | Yes | Yes |
Event DispatchingEvent-dispatching members evaluate an event to determine if it is appropriate for this handler object to process it. If it is, it calls the virtual function used to process the event.
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protected:
virtual bool dispatchHandlerEvent(IEvent& event)
If a show list event is received, the appropriate virtual function is called.
| Windows | OS/2 | AIX |
| Yes | Yes | Yes |
Event ProcessingEvent-processing members must be supplied to process a show list event. You can override these virtual members in a derived class.
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protected:
virtual bool listShown(IControlEvent& event) = 0
Derived classes implement this function to process a show list event.
| Windows | OS/2 | AIX |
| Yes | Yes | Yes |
virtual ~IHandler()
virtual IString asDebugInfo() const
virtual IString asString() const
virtual IHandler& disable()
virtual IHandler& enable(bool enable = true)
virtual IHandler& handleEventsFor(IWindow* window)
IHandler()
bool isEnabled() const
virtual IHandler& stopHandlingEventsFor(IWindow* window)
virtual IEventResult defaultProcedure(IEvent& event)
virtual bool dispatchHandlerEvent(IEvent& event) = 0