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[wxWidgets.git] / interface / wx / event_base.h

/////////////////////////////////////////////////////////////////////////////
// Name:        interface/wx/event_base.h
// Purpose:     Documentation of wxEvtHandler, wxEvent, wxIdleEvent and other
//              non-GUI event-related classes declared in include/wx/event.h
//              (see interface/wx/event.h for the GUI event classes)
// Author:      wxWidgets team
// RCS-ID:      $Id$
// Licence:     wxWindows licence
/////////////////////////////////////////////////////////////////////////////

/**
    The predefined constants for the number of times we propagate event
    upwards window child-parent chain.
*/
enum wxEventPropagation
{
    /// don't propagate it at all
    wxEVENT_PROPAGATE_NONE = 0,

    /// propagate it until it is processed
    wxEVENT_PROPAGATE_MAX = INT_MAX
};

/**
    The different categories for a wxEvent; see wxEvent::GetEventCategory.

    @note They are used as OR-combinable flags by wxEventLoopBase::YieldFor.
*/
enum wxEventCategory
{
    /**
        This is the category for those events which are generated to update
        the appearance of the GUI but which (usually) do not comport data
        processing, i.e. which do not provide input or output data
        (e.g. size events, scroll events, etc).
        They are events NOT directly generated by the user's input devices.
    */
    wxEVT_CATEGORY_UI = 1,

    /**
        This category groups those events which are generated directly from the
        user through input devices like mouse and keyboard and usually result in
        data to be processed from the application
        (e.g. mouse clicks, key presses, etc).
    */
    wxEVT_CATEGORY_USER_INPUT = 2,

    /// This category is for wxSocketEvent
    wxEVT_CATEGORY_SOCKET = 4,

    /// This category is for wxTimerEvent
    wxEVT_CATEGORY_TIMER = 8,

    /**
        This category is for any event used to send notifications from the
        secondary threads to the main one or in general for notifications among
        different threads (which may or may not be user-generated).
        See e.g. wxThreadEvent.
    */
    wxEVT_CATEGORY_THREAD = 16,

    /**
        This mask is used in wxEventLoopBase::YieldFor to specify that all event
        categories should be processed.
    */
    wxEVT_CATEGORY_ALL =
        wxEVT_CATEGORY_UI|wxEVT_CATEGORY_USER_INPUT|wxEVT_CATEGORY_SOCKET| \
        wxEVT_CATEGORY_TIMER|wxEVT_CATEGORY_THREAD
};

/**
    @class wxEvent

    An event is a structure holding information about an event passed to a
    callback or member function.

    wxEvent used to be a multipurpose event object, and is an abstract base class
    for other event classes (see below).

    For more information about events, see the @ref overview_events overview.

    @beginWxPerlOnly
    In wxPerl custom event classes should be derived from
    @c Wx::PlEvent and @c Wx::PlCommandEvent.
    @endWxPerlOnly

    @library{wxbase}
    @category{events}
    @header{wx/event.h}

    @see wxCommandEvent, wxMouseEvent
*/
class wxEvent : public wxObject
{
public:
    /**
        Constructor.

        Notice that events are usually created by wxWidgets itself and creating
        e.g. a wxPaintEvent in your code and sending it to e.g. a wxTextCtrl
        will not usually affect it at all as native controls have no specific
        knowledge about wxWidgets events. However you may construct objects of
        specific types and pass them to wxEvtHandler::ProcessEvent() if you
        want to create your own custom control and want to process its events
        in the same manner as the standard ones.

        Also please notice that the order of parameters in this constructor is
        different from almost all the derived classes which specify the event
        type as the first argument.

        @param id
            The identifier of the object (window, timer, ...) which generated
            this event.
        @param eventType
            The unique type of event, e.g. @c wxEVT_PAINT, @c wxEVT_SIZE or
            @c wxEVT_COMMAND_BUTTON_CLICKED.
    */
    wxEvent(int id = 0, wxEventType eventType = wxEVT_NULL);

    /**
        Returns a copy of the event.

        Any event that is posted to the wxWidgets event system for later action
        (via wxEvtHandler::AddPendingEvent, wxEvtHandler::QueueEvent or wxPostEvent())
        must implement this method.

        All wxWidgets events fully implement this method, but any derived events
        implemented by the user should also implement this method just in case they
        (or some event derived from them) are ever posted.

        All wxWidgets events implement a copy constructor, so the easiest way of
        implementing the Clone function is to implement a copy constructor for
        a new event (call it MyEvent) and then define the Clone function like this:

        @code
        wxEvent *Clone() const { return new MyEvent(*this); }
        @endcode
    */
    virtual wxEvent* Clone() const = 0;

    /**
        Returns the object (usually a window) associated with the event, if any.
    */
    wxObject* GetEventObject() const;

    /**
        Returns the identifier of the given event type, such as @c wxEVT_COMMAND_BUTTON_CLICKED.
    */
    wxEventType GetEventType() const;

    /**
        Returns a generic category for this event.
        wxEvent implementation returns @c wxEVT_CATEGORY_UI by default.

        This function is used to selectively process events in wxEventLoopBase::YieldFor.
    */
    virtual wxEventCategory GetEventCategory() const;

    /**
        Returns the identifier associated with this event, such as a button command id.
    */
    int GetId() const;

    /**
        Return the user data associated with a dynamically connected event handler.

        wxEvtHandler::Connect() and wxEvtHandler::Bind() allow associating
        optional @c userData pointer with the handler and this method returns
        the value of this pointer.

        The returned pointer is owned by wxWidgets and must not be deleted.

        @since 2.9.5
    */
    wxObject *GetEventUserData() const;

    /**
        Returns @true if the event handler should be skipped, @false otherwise.
    */
    bool GetSkipped() const;

    /**
        Gets the timestamp for the event. The timestamp is the time in milliseconds
        since some fixed moment (not necessarily the standard Unix Epoch, so only
        differences between the timestamps and not their absolute values usually make sense).

        @warning
        wxWidgets returns a non-NULL timestamp only for mouse and key events
        (see wxMouseEvent and wxKeyEvent).
    */
    long GetTimestamp() const;

    /**
        Returns @true if the event is or is derived from wxCommandEvent else it returns @false.

        @note exists only for optimization purposes.
    */
    bool IsCommandEvent() const;

    /**
        Sets the propagation level to the given value (for example returned from an
        earlier call to wxEvent::StopPropagation).
    */
    void ResumePropagation(int propagationLevel);

    /**
        Sets the originating object.
    */
    void SetEventObject(wxObject* object);

    /**
        Sets the event type.
    */
    void SetEventType(wxEventType type);

    /**
        Sets the identifier associated with this event, such as a button command id.
    */
    void SetId(int id);

    /**
        Sets the timestamp for the event.
    */
    void SetTimestamp(long timeStamp = 0);

    /**
        Test if this event should be propagated or not, i.e. if the propagation level
        is currently greater than 0.
    */
    bool ShouldPropagate() const;

    /**
        This method can be used inside an event handler to control whether further
        event handlers bound to this event will be called after the current one returns.

        Without Skip() (or equivalently if Skip(@false) is used), the event will not
        be processed any more. If Skip(@true) is called, the event processing system
        continues searching for a further handler function for this event, even though
        it has been processed already in the current handler.

        In general, it is recommended to skip all non-command events to allow the
        default handling to take place. The command events are, however, normally not
        skipped as usually a single command such as a button click or menu item
        selection must only be processed by one handler.
    */
    void Skip(bool skip = true);

    /**
        Stop the event from propagating to its parent window.

        Returns the old propagation level value which may be later passed to
        ResumePropagation() to allow propagating the event again.
    */
    int StopPropagation();

protected:
    /**
        Indicates how many levels the event can propagate.

        This member is protected and should typically only be set in the constructors
        of the derived classes. It may be temporarily changed by StopPropagation()
        and ResumePropagation() and tested with ShouldPropagate().

        The initial value is set to either @c wxEVENT_PROPAGATE_NONE (by default)
        meaning that the event shouldn't be propagated at all or to
        @c wxEVENT_PROPAGATE_MAX (for command events) meaning that it should be
        propagated as much as necessary.

        Any positive number means that the event should be propagated but no more than
        the given number of times. E.g. the propagation level may be set to 1 to
        propagate the event to its parent only, but not to its grandparent.
    */
    int m_propagationLevel;
};




/**
    @class wxEvtHandler

    A class that can handle events from the windowing system.
    wxWindow is (and therefore all window classes are) derived from this class.

    When events are received, wxEvtHandler invokes the method listed in the
    event table using itself as the object. When using multiple inheritance
    <b>it is imperative that the wxEvtHandler(-derived) class is the first
    class inherited</b> such that the @c this pointer for the overall object
    will be identical to the @c this pointer of the wxEvtHandler portion.

    @library{wxbase}
    @category{events}
    @header{wx/event.h}

    @see @ref overview_events_processing, wxEventBlocker, wxEventLoopBase
*/
class wxEvtHandler : public wxObject, public wxTrackable
{
public:
    /**
        Constructor.
    */
    wxEvtHandler();

    /**
        Destructor.

        If the handler is part of a chain, the destructor will unlink itself
        (see Unlink()).
    */
    virtual ~wxEvtHandler();


    /**
        @name Event queuing and processing
    */
    //@{

    /**
        Queue event for a later processing.

        This method is similar to ProcessEvent() but while the latter is
        synchronous, i.e. the event is processed immediately, before the
        function returns, this one is asynchronous and returns immediately
        while the event will be processed at some later time (usually during
        the next event loop iteration).

        Another important difference is that this method takes ownership of the
        @a event parameter, i.e. it will delete it itself. This implies that
        the event should be allocated on the heap and that the pointer can't be
        used any more after the function returns (as it can be deleted at any
        moment).

        QueueEvent() can be used for inter-thread communication from the worker
        threads to the main thread, it is safe in the sense that it uses
        locking internally and avoids the problem mentioned in AddPendingEvent()
        documentation by ensuring that the @a event object is not used by the
        calling thread any more. Care should still be taken to avoid that some
        fields of this object are used by it, notably any wxString members of
        the event object must not be shallow copies of another wxString object
        as this would result in them still using the same string buffer behind
        the scenes. For example:
        @code
            void FunctionInAWorkerThread(const wxString& str)
            {
                wxCommandEvent* evt = new wxCommandEvent;

                // NOT evt->SetString(str) as this would be a shallow copy
                evt->SetString(str.c_str()); // make a deep copy

                wxTheApp->QueueEvent( evt );
            }
        @endcode

        Note that you can use wxThreadEvent instead of wxCommandEvent
        to avoid this problem:
        @code
            void FunctionInAWorkerThread(const wxString& str)
            {
                wxThreadEvent evt;
                evt->SetString(str);

                // wxThreadEvent::Clone() makes sure that the internal wxString
                // member is not shared by other wxString instances:
                wxTheApp->QueueEvent( evt.Clone() );
            }
        @endcode

        Finally notice that this method automatically wakes up the event loop
        if it is currently idle by calling ::wxWakeUpIdle() so there is no need
        to do it manually when using it.

        @since 2.9.0

        @param event
            A heap-allocated event to be queued, QueueEvent() takes ownership
            of it. This parameter shouldn't be @c NULL.
     */
    virtual void QueueEvent(wxEvent *event);

    /**
        Post an event to be processed later.

        This function is similar to QueueEvent() but can't be used to post
        events from worker threads for the event objects with wxString fields
        (i.e. in practice most of them) because of an unsafe use of the same
        wxString object which happens because the wxString field in the
        original @a event object and its copy made internally by this function
        share the same string buffer internally. Use QueueEvent() to avoid
        this.

        A copy of @a event is made by the function, so the original can be deleted
        as soon as function returns (it is common that the original is created
        on the stack). This requires that the wxEvent::Clone() method be
        implemented by event so that it can be duplicated and stored until it
        gets processed.

        @param event
            Event to add to the pending events queue.
    */
    virtual void AddPendingEvent(const wxEvent& event);

    /**
         Asynchronously call the given method.

         Calling this function on an object schedules an asynchronous call to
         the method specified as CallAfter() argument at a (slightly) later
         time. This is useful when processing some events as certain actions
         typically can't be performed inside their handlers, e.g. you shouldn't
         show a modal dialog from a mouse click event handler as this would
         break the mouse capture state -- but you can call a method showing
         this message dialog after the current event handler completes.

         The method being called must be the method of the object on which
         CallAfter() itself is called.

         Notice that it is safe to use CallAfter() from other, non-GUI,
         threads, but that the method will be always called in the main, GUI,
         thread context.

         Example of use:
         @code
         class MyFrame : public wxFrame {
            void OnClick(wxMouseEvent& event) {
                CallAfter(&MyFrame::ShowPosition, event.GetPosition());
            }

            void ShowPosition(const wxPoint& pos) {
                if ( wxMessageBox(
                        wxString::Format("Perform click at (%d, %d)?",
                                         pos.x, pos.y), "", wxYES_NO) == wxYES )
                {
                    ... do take this click into account ...
                }
            }
         };
         @endcode

         @param method The method to call.
         @param x1 The (optional) first parameter to pass to the method.
         @param x2 The (optional) second parameter to pass to the method.

         Note that currently only up to 2 arguments can be passed.

         @note This method is not available with Visual C++ 6 which doesn't
               have the required support for C++ templates to implement it.

         @since 2.9.5
     */
    template<typename T, typename T1, ...>
    void CallAfter(void (T::*method)(T1, ...), T1 x1, ...);

    /**
        Processes an event, searching event tables and calling zero or more suitable
        event handler function(s).

        Normally, your application would not call this function: it is called in the
        wxWidgets implementation to dispatch incoming user interface events to the
        framework (and application).

        However, you might need to call it if implementing new functionality
        (such as a new control) where you define new event types, as opposed to
        allowing the user to override virtual functions.

        Notice that you don't usually need to override ProcessEvent() to
        customize the event handling, overriding the specially provided
        TryBefore() and TryAfter() functions is usually enough. For example,
        wxMDIParentFrame may override TryBefore() to ensure that the menu
        events are processed in the active child frame before being processed
        in the parent frame itself.

        The normal order of event table searching is as follows:
        -# wxApp::FilterEvent() is called. If it returns anything but @c -1
           (default) the processing stops here.
        -# TryBefore() is called (this is where wxValidator are taken into
           account for wxWindow objects). If this returns @true, the function exits.
        -# If the object is disabled (via a call to wxEvtHandler::SetEvtHandlerEnabled)
           the function skips to step (7).
        -# Dynamic event table of the handlers bound using Bind<>() is
           searched. If a handler is found, it is executed and the function
           returns @true unless the handler used wxEvent::Skip() to indicate
           that it didn't handle the event in which case the search continues.
        -# Static events table of the handlers bound using event table
           macros is searched for this event handler. If this fails, the base
           class event table is tried, and so on until no more tables
           exist or an appropriate function was found. If a handler is found,
           the same logic as in the previous step applies.
        -# The search is applied down the entire chain of event handlers (usually the
           chain has a length of one). This chain can be formed using wxEvtHandler::SetNextHandler():
              @image html overview_events_chain.png
           (referring to the image, if @c A->ProcessEvent is called and it doesn't handle
            the event, @c B->ProcessEvent will be called and so on...).
           Note that in the case of wxWindow you can build a stack of event handlers
           (see wxWindow::PushEventHandler() for more info).
           If any of the handlers of the chain return @true, the function exits.
        -# TryAfter() is called: for the wxWindow object this may propagate the
           event to the window parent (recursively). If the event is still not
           processed, ProcessEvent() on wxTheApp object is called as the last
           step.

        Notice that steps (2)-(6) are performed in ProcessEventLocally()
        which is called by this function.

        @param event
            Event to process.
        @return
            @true if a suitable event handler function was found and executed,
            and the function did not call wxEvent::Skip.

        @see SearchEventTable()
    */
    virtual bool ProcessEvent(wxEvent& event);

    /**
        Try to process the event in this handler and all those chained to it.

        As explained in ProcessEvent() documentation, the event handlers may be
        chained in a doubly-linked list. This function tries to process the
        event in this handler (including performing any pre-processing done in
        TryBefore(), e.g. applying validators) and all those following it in
        the chain until the event is processed or the chain is exhausted.

        This function is called from ProcessEvent() and, in turn, calls
        TryBefore() and TryAfter(). It is not virtual and so cannot be
        overridden but can, and should, be called to forward an event to
        another handler instead of ProcessEvent() which would result in a
        duplicate call to TryAfter(), e.g. resulting in all unprocessed events
        being sent to the application object multiple times.

        @since 2.9.1

        @param event
            Event to process.
        @return
            @true if this handler of one of those chained to it processed the
            event.
     */
    bool ProcessEventLocally(wxEvent& event);

    /**
        Processes an event by calling ProcessEvent() and handles any exceptions
        that occur in the process.
        If an exception is thrown in event handler, wxApp::OnExceptionInMainLoop is called.

        @param event
            Event to process.

        @return @true if the event was processed, @false if no handler was found
                 or an exception was thrown.

        @see wxWindow::HandleWindowEvent
    */
    bool SafelyProcessEvent(wxEvent& event);

    /**
        Processes the pending events previously queued using QueueEvent() or
        AddPendingEvent(); you must call this function only if you are sure
        there are pending events for this handler, otherwise a @c wxCHECK
        will fail.

        The real processing still happens in ProcessEvent() which is called by this
        function.

        Note that this function needs a valid application object (see
        wxAppConsole::GetInstance()) because wxApp holds the list of the event
        handlers with pending events and this function manipulates that list.
    */
    void ProcessPendingEvents();

    /**
        Deletes all events queued on this event handler using QueueEvent() or
        AddPendingEvent().

        Use with care because the events which are deleted are (obviously) not
        processed and this may have unwanted consequences (e.g. user actions events
        will be lost).
    */
    void DeletePendingEvents();

    /**
        Searches the event table, executing an event handler function if an appropriate
        one is found.

        @param table
            Event table to be searched.
        @param event
            Event to be matched against an event table entry.

        @return @true if a suitable event handler function was found and
                 executed, and the function did not call wxEvent::Skip.

        @remarks This function looks through the object's event table and tries
                 to find an entry that will match the event.
                 An entry will match if:
                 @li The event type matches, and
                 @li the identifier or identifier range matches, or the event table
                     entry's identifier is zero.

                 If a suitable function is called but calls wxEvent::Skip, this
                 function will fail, and searching will continue.

         @todo this function in the header is listed as an "implementation only" function;
               are we sure we want to document it?

        @see ProcessEvent()
    */
    virtual bool SearchEventTable(wxEventTable& table,
                                  wxEvent& event);

    //@}


    /**
        @name Connecting and disconnecting
    */
    //@{

    /**
        Connects the given function dynamically with the event handler, id and
        event type.

        Notice that Bind() provides a more flexible and safer way to do the
        same thing as Connect(), please use it in any new code -- while
        Connect() is not formally deprecated due to its existing widespread
        usage, it has no advantages compared to Bind().

        This is an alternative to the use of static event tables. It is more
        flexible as it allows to connect events generated by some object to an
        event handler defined in a different object of a different class (which
        is impossible to do directly with the event tables -- the events can be
        only handled in another object if they are propagated upwards to it).
        Do make sure to specify the correct @a eventSink when connecting to an
        event of a different object.

        See @ref overview_events_bind for more detailed explanation
        of this function and the @ref page_samples_event sample for usage
        examples.

        This specific overload allows you to connect an event handler to a @e range
        of @e source IDs.
        Do not confuse @e source IDs with event @e types: source IDs identify the
        event generator objects (typically wxMenuItem or wxWindow objects) while the
        event @e type identify which type of events should be handled by the
        given @e function (an event generator object may generate many different
        types of events!).

        @param id
            The first ID of the identifier range to be associated with the event
            handler function.
        @param lastId
            The last ID of the identifier range to be associated with the event
            handler function.
        @param eventType
            The event type to be associated with this event handler.
        @param function
            The event handler function. Note that this function should
            be explicitly converted to the correct type which can be done using a macro
            called @c wxFooEventHandler for the handler for any @c wxFooEvent.
        @param userData
            Optional data to be associated with the event table entry.
            wxWidgets will take ownership of this pointer, i.e. it will be
            destroyed when the event handler is disconnected or at the program
            termination. This pointer can be retrieved using
            wxEvent::GetEventUserData() later.
        @param eventSink
            Object whose member function should be called. It must be specified
            when connecting an event generated by one object to a member
            function of a different object. If it is omitted, @c this is used.

        @beginWxPerlOnly
        In wxPerl this function takes 4 arguments: @a id, @a lastid,
        @a type, @a method; if @a method is undef, the handler is
        disconnected.}
        @endWxPerlOnly

        @see Bind<>()
    */
    void Connect(int id, int lastId, wxEventType eventType,
                 wxObjectEventFunction function,
                 wxObject* userData = NULL,
                 wxEvtHandler* eventSink = NULL);

    /**
        See the Connect(int, int, wxEventType, wxObjectEventFunction, wxObject*, wxEvtHandler*)
        overload for more info.

        This overload can be used to attach an event handler to a single source ID:

        Example:
        @code
        frame->Connect( wxID_EXIT,
                        wxEVT_COMMAND_MENU_SELECTED,
                        wxCommandEventHandler(MyFrame::OnQuit) );
        @endcode

        @beginWxPerlOnly
        Not supported by wxPerl.
        @endWxPerlOnly
    */
    void Connect(int id, wxEventType eventType,
                 wxObjectEventFunction function,
                 wxObject* userData = NULL,
                 wxEvtHandler* eventSink = NULL);

    /**
        See the Connect(int, int, wxEventType, wxObjectEventFunction, wxObject*, wxEvtHandler*)
        overload for more info.

        This overload will connect the given event handler so that regardless of the
        ID of the event source, the handler will be called.

        @beginWxPerlOnly
        Not supported by wxPerl.
        @endWxPerlOnly
    */
    void Connect(wxEventType eventType,
                 wxObjectEventFunction function,
                 wxObject* userData = NULL,
                 wxEvtHandler* eventSink = NULL);

    /**
        Disconnects the given function dynamically from the event handler, using the
        specified parameters as search criteria and returning @true if a matching
        function has been found and removed.

        This method can only disconnect functions which have been added using the
        Connect() method. There is no way to disconnect functions connected using
        the (static) event tables.

        @param eventType
            The event type associated with this event handler.
        @param function
            The event handler function.
        @param userData
            Data associated with the event table entry.
        @param eventSink
            Object whose member function should be called.

        @beginWxPerlOnly
        Not supported by wxPerl.
        @endWxPerlOnly
    */
    bool Disconnect(wxEventType eventType,
                    wxObjectEventFunction function,
                    wxObject* userData = NULL,
                    wxEvtHandler* eventSink = NULL);

    /**
        See the Disconnect(wxEventType, wxObjectEventFunction, wxObject*, wxEvtHandler*)
        overload for more info.

        This overload takes the additional @a id parameter.

        @beginWxPerlOnly
        Not supported by wxPerl.
        @endWxPerlOnly
    */
    bool Disconnect(int id = wxID_ANY,
                    wxEventType eventType = wxEVT_NULL,
                    wxObjectEventFunction function = NULL,
                    wxObject* userData = NULL,
                    wxEvtHandler* eventSink = NULL);

    /**
        See the Disconnect(wxEventType, wxObjectEventFunction, wxObject*, wxEvtHandler*)
        overload for more info.

        This overload takes an additional range of source IDs.

        @beginWxPerlOnly
        In wxPerl this function takes 3 arguments: @a id,
        @a lastid, @a type.
        @endWxPerlOnly
    */
    bool Disconnect(int id, int lastId,
                    wxEventType eventType,
                    wxObjectEventFunction function = NULL,
                    wxObject* userData = NULL,
                    wxEvtHandler* eventSink = NULL);
    //@}


    /**
        @name Binding and Unbinding
    */
    //@{

    /**
        Binds the given function, functor or method dynamically with the event.

        This offers basically the same functionality as Connect(), but it is
        more flexible as it also allows you to use ordinary functions and
        arbitrary functors as event handlers. It is also less restrictive then
        Connect() because you can use an arbitrary method as an event handler,
        whereas Connect() requires a wxEvtHandler derived handler.

        See @ref overview_events_bind for more detailed explanation
        of this function and the @ref page_samples_event sample for usage
        examples.

        @param eventType
            The event type to be associated with this event handler.
        @param functor
            The event handler functor. This can be an ordinary function but also
            an arbitrary functor like boost::function<>.
        @param id
            The first ID of the identifier range to be associated with the event
            handler.
        @param lastId
            The last ID of the identifier range to be associated with the event
            handler.
        @param userData
            Optional data to be associated with the event table entry.
            wxWidgets will take ownership of this pointer, i.e. it will be
            destroyed when the event handler is disconnected or at the program
            termination. This pointer can be retrieved using
            wxEvent::GetEventUserData() later.

        @see @ref overview_cpp_rtti_disabled

        @since 2.9.0
    */
    template <typename EventTag, typename Functor>
    void Bind(const EventTag& eventType,
              Functor functor,
              int id = wxID_ANY,
              int lastId = wxID_ANY,
              wxObject *userData = NULL);

    /**
        See the Bind<>(const EventTag&, Functor, int, int, wxObject*) overload for
        more info.

        This overload will bind the given method as the event handler.

        @param eventType
            The event type to be associated with this event handler.
        @param method
            The event handler method. This can be an arbitrary method (doesn't need
            to be from a wxEvtHandler derived class).
        @param handler
            Object whose method should be called. It must always be specified
            so it can be checked at compile time whether the given method is an
            actual member of the given handler.
        @param id
            The first ID of the identifier range to be associated with the event
            handler.
        @param lastId
            The last ID of the identifier range to be associated with the event
            handler.
        @param userData
            Optional data to be associated with the event table entry.
            wxWidgets will take ownership of this pointer, i.e. it will be
            destroyed when the event handler is disconnected or at the program
            termination. This pointer can be retrieved using
            wxEvent::GetEventUserData() later.

        @see @ref overview_cpp_rtti_disabled

        @since 2.9.0
    */
    template <typename EventTag, typename Class, typename EventArg, typename EventHandler>
    void Bind(const EventTag &eventType,
              void (Class::*method)(EventArg &),
              EventHandler *handler,
              int id = wxID_ANY,
              int lastId = wxID_ANY,
              wxObject *userData = NULL);
    /**
        Unbinds the given function, functor or method dynamically from the
        event handler, using the specified parameters as search criteria and
        returning @true if a matching function has been found and removed.

        This method can only unbind functions, functors or methods which have
        been added using the Bind<>() method. There is no way to unbind
        functions bound using the (static) event tables.

        @param eventType
            The event type associated with this event handler.
        @param functor
            The event handler functor. This can be an ordinary function but also
            an arbitrary functor like boost::function<>.
        @param id
            The first ID of the identifier range associated with the event
            handler.
        @param lastId
            The last ID of the identifier range associated with the event
            handler.
        @param userData
            Data associated with the event table entry.

        @see @ref overview_cpp_rtti_disabled

        @since 2.9.0
    */
    template <typename EventTag, typename Functor>
    bool Unbind(const EventTag& eventType,
                Functor functor,
                int id = wxID_ANY,
                int lastId = wxID_ANY,
                wxObject *userData = NULL);

    /**
        See the Unbind<>(const EventTag&, Functor, int, int, wxObject*)
        overload for more info.

        This overload unbinds the given method from the event..

        @param eventType
            The event type associated with this event handler.
        @param method
            The event handler method associated with this event.
        @param handler
            Object whose method was called.
        @param id
            The first ID of the identifier range associated with the event
            handler.
        @param lastId
            The last ID of the identifier range associated with the event
            handler.
        @param userData
            Data associated with the event table entry.

        @see @ref overview_cpp_rtti_disabled

        @since 2.9.0
    */
    template <typename EventTag, typename Class, typename EventArg, typename EventHandler>
    bool Unbind(const EventTag &eventType,
                void (Class::*method)(EventArg&),
                EventHandler *handler,
                int id = wxID_ANY,
                int lastId = wxID_ANY,
                wxObject *userData = NULL );
    //@}
    /**
        @name User-supplied data
    */
    //@{

    /**
        Returns user-supplied client data.

        @remarks Normally, any extra data the programmer wishes to associate with
                 the object should be made available by deriving a new class with
                 new data members.

        @see SetClientData()
    */
    void* GetClientData() const;

    /**
        Returns a pointer to the user-supplied client data object.

        @see SetClientObject(), wxClientData
    */
    wxClientData* GetClientObject() const;

    /**
        Sets user-supplied client data.

        @param data
            Data to be associated with the event handler.

        @remarks Normally, any extra data the programmer wishes to associate
                 with the object should be made available by deriving a new
                 class with new data members. You must not call this method
                 and SetClientObject on the same class - only one of them.

        @see GetClientData()
    */
    void SetClientData(void* data);

    /**
        Set the client data object. Any previous object will be deleted.

        @see GetClientObject(), wxClientData
    */
    void SetClientObject(wxClientData* data);

    //@}


    /**
        @name Event handler chaining

        wxEvtHandler can be arranged in a double-linked list of handlers
        which is automatically iterated by ProcessEvent() if needed.
    */
    //@{

    /**
        Returns @true if the event handler is enabled, @false otherwise.

        @see SetEvtHandlerEnabled()
    */
    bool GetEvtHandlerEnabled() const;

    /**
        Returns the pointer to the next handler in the chain.

        @see SetNextHandler(), GetPreviousHandler(), SetPreviousHandler(),
             wxWindow::PushEventHandler, wxWindow::PopEventHandler
    */
    wxEvtHandler* GetNextHandler() const;

    /**
        Returns the pointer to the previous handler in the chain.

        @see SetPreviousHandler(), GetNextHandler(), SetNextHandler(),
             wxWindow::PushEventHandler, wxWindow::PopEventHandler
    */
    wxEvtHandler* GetPreviousHandler() const;

    /**
        Enables or disables the event handler.

        @param enabled
            @true if the event handler is to be enabled, @false if it is to be disabled.

        @remarks You can use this function to avoid having to remove the event
                 handler from the chain, for example when implementing a
                 dialog editor and changing from edit to test mode.

        @see GetEvtHandlerEnabled()
    */
    void SetEvtHandlerEnabled(bool enabled);

    /**
        Sets the pointer to the next handler.

        @remarks
        See ProcessEvent() for more info about how the chains of event handlers
        are internally used.
        Also remember that wxEvtHandler uses double-linked lists and thus if you
        use this function, you should also call SetPreviousHandler() on the
        argument passed to this function:
        @code
            handlerA->SetNextHandler(handlerB);
            handlerB->SetPreviousHandler(handlerA);
        @endcode

        @param handler
            The event handler to be set as the next handler.
            Cannot be @NULL.

        @see @ref overview_events_processing
    */
    virtual void SetNextHandler(wxEvtHandler* handler);

    /**
        Sets the pointer to the previous handler.
        All remarks about SetNextHandler() apply to this function as well.

        @param handler
            The event handler to be set as the previous handler.
            Cannot be @NULL.

        @see @ref overview_events_processing
    */
    virtual void SetPreviousHandler(wxEvtHandler* handler);

    /**
        Unlinks this event handler from the chain it's part of (if any);
        then links the "previous" event handler to the "next" one
        (so that the chain won't be interrupted).

        E.g. if before calling Unlink() you have the following chain:
            @image html evthandler_unlink_before.png
        then after calling @c B->Unlink() you'll have:
            @image html evthandler_unlink_after.png

        @since 2.9.0
    */
    void Unlink();

    /**
        Returns @true if the next and the previous handler pointers of this
        event handler instance are @NULL.

        @since 2.9.0

        @see SetPreviousHandler(), SetNextHandler()
    */
    bool IsUnlinked() const;

    //@}

    /**
        @name Global event filters.

        Methods for working with the global list of event filters.

        Event filters can be defined to pre-process all the events that happen
        in an application, see wxEventFilter documentation for more information.
     */
    //@{

    /**
        Add an event filter whose FilterEvent() method will be called for each
        and every event processed by wxWidgets.

        The filters are called in LIFO order and wxApp is registered as an
        event filter by default. The pointer must remain valid until it's
        removed with RemoveFilter() and is not deleted by wxEvtHandler.

        @since 2.9.3
     */
    static void AddFilter(wxEventFilter* filter);

    /**
        Remove a filter previously installed with AddFilter().

        It's an error to remove a filter that hadn't been previously added or
        was already removed.

        @since 2.9.3
     */
    static void RemoveFilter(wxEventFilter* filter);

    //@}

protected:
    /**
        Method called by ProcessEvent() before examining this object event
        tables.

        This method can be overridden to hook into the event processing logic
        as early as possible. You should usually call the base class version
        when overriding this method, even if wxEvtHandler itself does nothing
        here, some derived classes do use this method, e.g. wxWindow implements
        support for wxValidator in it.

        Example:
        @code
        class MyClass : public BaseClass // inheriting from wxEvtHandler
        {
        ...
        protected:
            virtual bool TryBefore(wxEvent& event)
            {
                if ( MyPreProcess(event) )
                    return true;

                return BaseClass::TryBefore(event);
            }
        };
        @endcode

        @see ProcessEvent()
     */
    virtual bool TryBefore(wxEvent& event);

    /**
        Method called by ProcessEvent() as last resort.

        This method can be overridden to implement post-processing for the
        events which were not processed anywhere else.

        The base class version handles forwarding the unprocessed events to
        wxApp at wxEvtHandler level and propagating them upwards the window
        child-parent chain at wxWindow level and so should usually be called
        when overriding this method:
        @code
        class MyClass : public BaseClass // inheriting from wxEvtHandler
        {
        ...
        protected:
            virtual bool TryAfter(wxEvent& event)
            {
                if ( BaseClass::TryAfter(event) )
                    return true;

                return MyPostProcess(event);
            }
        };
        @endcode

        @see ProcessEvent()
     */
    virtual bool TryAfter(wxEvent& event);
};



/**
    See wxIdleEvent::SetMode() for more info.
*/
enum wxIdleMode
{
        /** Send idle events to all windows */
    wxIDLE_PROCESS_ALL,

        /** Send idle events to windows that have the wxWS_EX_PROCESS_IDLE flag specified */
    wxIDLE_PROCESS_SPECIFIED
};


/**
    @class wxIdleEvent

    This class is used for idle events, which are generated when the system becomes
    idle. Note that, unless you do something specifically, the idle events are not
    sent if the system remains idle once it has become it, e.g. only a single idle
    event will be generated until something else resulting in more normal events
    happens and only then is the next idle event sent again.

    If you need to ensure a continuous stream of idle events, you can either use
    wxIdleEvent::RequestMore method in your handler or call wxWakeUpIdle() periodically
    (for example from a timer event handler), but note that both of these approaches
    (and especially the first one) increase the system load and so should be avoided
    if possible.

    By default, idle events are sent to all windows, including even the hidden
    ones because they may be shown if some condition is met from their @c
    wxEVT_IDLE (or related @c wxEVT_UPDATE_UI) handler. The children of hidden
    windows do not receive idle events however as they can't change their state
    in any way noticeable by the user. Finally, the global wxApp object also
    receives these events, as usual, so it can be used for any global idle time
    processing.

    If sending idle events to all windows is causing a significant overhead in
    your application, you can call wxIdleEvent::SetMode with the value
    wxIDLE_PROCESS_SPECIFIED, and set the wxWS_EX_PROCESS_IDLE extra window
    style for every window which should receive idle events, all the other ones
    will not receive them in this case.

    @beginEventTable{wxIdleEvent}
    @event{EVT_IDLE(func)}
        Process a @c wxEVT_IDLE event.
    @endEventTable

    @library{wxbase}
    @category{events}
    @header{wx/event.h}

    @section sec_delayed_action Delayed Action Mechanism

    wxIdleEvent can be used to perform some action "at slightly later time".
    This can be necessary in several circumstances when, for whatever reason,
    something can't be done in the current event handler. For example, if a
    mouse event handler is called with the mouse button pressed, the mouse can
    be currently captured and some operations with it -- notably capturing it
    again -- might be impossible or lead to undesirable results. If you still
    want to capture it, you can do it from @c wxEVT_IDLE handler when it is
    called the next time instead of doing it immediately.

    This can be achieved in two different ways: when using static event tables,
    you will need a flag indicating to the (always connected) idle event
    handler whether the desired action should be performed. The originally
    called handler would then set it to indicate that it should indeed be done
    and the idle handler itself would reset it to prevent it from doing the
    same action again.

    Using dynamically connected event handlers things are even simpler as the
    original event handler can simply wxEvtHandler::Connect() or
    wxEvtHandler::Bind() the idle event handler which would only be executed
    then and could wxEvtHandler::Disconnect() or wxEvtHandler::Unbind() itself.


    @see @ref overview_events, wxUpdateUIEvent, wxWindow::OnInternalIdle
*/
class wxIdleEvent : public wxEvent
{
public:
    /**
        Constructor.
    */
    wxIdleEvent();

    /**
        Static function returning a value specifying how wxWidgets will send idle
        events: to all windows, or only to those which specify that they
        will process the events.

        @see SetMode().
    */
    static wxIdleMode GetMode();

    /**
        Returns @true if the OnIdle function processing this event requested more
        processing time.

        @see RequestMore()
    */
    bool MoreRequested() const;

    /**
        Tells wxWidgets that more processing is required.

        This function can be called by an OnIdle handler for a window or window event
        handler to indicate that wxApp::OnIdle should forward the OnIdle event once
        more to the application windows.

        If no window calls this function during OnIdle, then the application will
        remain in a passive event loop (not calling OnIdle) until a new event is
        posted to the application by the windowing system.

        @see MoreRequested()
    */
    void RequestMore(bool needMore = true);

    /**
        Static function for specifying how wxWidgets will send idle events: to
        all windows, or only to those which specify that they will process the events.

        @param mode
            Can be one of the ::wxIdleMode values.
            The default is wxIDLE_PROCESS_ALL.
    */
    static void SetMode(wxIdleMode mode);
};



// ============================================================================
// Global functions/macros
// ============================================================================

/** @addtogroup group_funcmacro_events */
//@{

/**
    A value uniquely identifying the type of the event.

    The values of this type should only be created using wxNewEventType().

    See the macro DEFINE_EVENT_TYPE() for more info.

    @see @ref overview_events_introduction
*/
typedef int wxEventType;

/**
    A special event type usually used to indicate that some wxEvent has yet
    no type assigned.
*/
wxEventType wxEVT_NULL;

wxEventType wxEVT_ANY;

/**
    Generates a new unique event type.

    Usually this function is only used by wxDEFINE_EVENT() and not called
    directly.
*/
wxEventType wxNewEventType();

/**
    Define a new event type associated with the specified event class.

    This macro defines a new unique event type @a name associated with the
    event class @a cls.

    For example:
    @code
    wxDEFINE_EVENT(MY_COMMAND_EVENT, wxCommandEvent);

    class MyCustomEvent : public wxEvent { ... };
    wxDEFINE_EVENT(MY_CUSTOM_EVENT, MyCustomEvent);
    @endcode

    @see wxDECLARE_EVENT(), @ref overview_events_custom
 */
#define wxDEFINE_EVENT(name, cls) \
    const wxEventTypeTag< cls > name(wxNewEventType())

/**
    Declares a custom event type.

    This macro declares a variable called @a name which must be defined
    elsewhere using wxDEFINE_EVENT().

    The class @a cls must be the wxEvent-derived class associated with the
    events of this type and its full declaration must be visible from the point
    of use of this macro.

    For example:
    @code
    wxDECLARE_EVENT(MY_COMMAND_EVENT, wxCommandEvent);

    class MyCustomEvent : public wxEvent { ... };
    wxDECLARE_EVENT(MY_CUSTOM_EVENT, MyCustomEvent);
    @endcode
 */
#define wxDECLARE_EVENT(name, cls) \
        wxDECLARE_EXPORTED_EVENT(wxEMPTY_PARAMETER_VALUE, name, cls)

/**
    Variant of wxDECLARE_EVENT() used for event types defined inside a shared
    library.

    This is mostly used by wxWidgets internally, e.g.
    @code
    wxDECLARE_EXPORTED_EVENT(WXDLLIMPEXP_CORE, wxEVT_COMMAND_BUTTON_CLICKED, wxCommandEvent)
    @endcode
 */
#define wxDECLARE_EXPORTED_EVENT( expdecl, name, cls ) \
    extern const expdecl wxEventTypeTag< cls > name;

/**
    Helper macro for definition of custom event table macros.

    This macro must only be used if wxEVENTS_COMPATIBILITY_2_8 is 1, otherwise
    it is better and more clear to just use the address of the function
    directly as this is all this macro does in this case. However it needs to
    explicitly cast @a func to @a functype, which is the type of wxEvtHandler
    member function taking the custom event argument when
    wxEVENTS_COMPATIBILITY_2_8 is 0.

    See wx__DECLARE_EVT0 for an example of use.

    @see @ref overview_events_custom_ownclass
 */
#define wxEVENT_HANDLER_CAST(functype, func) (&func)

/**
    This macro is used to define event table macros for handling custom
    events.

    Example of use:
    @code
    class MyEvent : public wxEvent { ... };

    // note that this is not necessary unless using old compilers: for the
    // reasonably new ones just use &func instead of MyEventHandler(func)
    typedef void (wxEvtHandler::*MyEventFunction)(MyEvent&);
    #define MyEventHandler(func) wxEVENT_HANDLER_CAST(MyEventFunction, func)

    wxDEFINE_EVENT(MY_EVENT_TYPE, MyEvent);

    #define EVT_MY(id, func) \
        wx__DECLARE_EVT1(MY_EVENT_TYPE, id, MyEventHandler(func))

    ...

    wxBEGIN_EVENT_TABLE(MyFrame, wxFrame)
        EVT_MY(wxID_ANY, MyFrame::OnMyEvent)
    wxEND_EVENT_TABLE()
    @endcode

    @param evt
        The event type to handle.
    @param id
        The identifier of events to handle.
    @param fn
        The event handler method.
 */
#define wx__DECLARE_EVT1(evt, id, fn) \
    wx__DECLARE_EVT2(evt, id, wxID_ANY, fn)

/**
    Generalized version of the wx__DECLARE_EVT1() macro taking a range of
    IDs instead of a single one.
    Argument @a id1 is the first identifier of the range, @a id2 is the
    second identifier of the range.
*/
#define wx__DECLARE_EVT2(evt, id1, id2, fn) \
    DECLARE_EVENT_TABLE_ENTRY(evt, id1, id2, fn, NULL),

/**
    Simplified version of the wx__DECLARE_EVT1() macro, to be used when the
    event type must be handled regardless of the ID associated with the
    specific event instances.
*/
#define wx__DECLARE_EVT0(evt, fn) \
    wx__DECLARE_EVT1(evt, wxID_ANY, fn)

/**
    Use this macro inside a class declaration to declare a @e static event table
    for that class.

    In the implementation file you'll need to use the wxBEGIN_EVENT_TABLE()
    and the wxEND_EVENT_TABLE() macros, plus some additional @c EVT_xxx macro
    to capture events.

    Note that this macro requires a final semicolon.

    @see @ref overview_events_eventtables
*/
#define wxDECLARE_EVENT_TABLE()

/**
    Use this macro in a source file to start listing @e static event handlers
    for a specific class.

    Use wxEND_EVENT_TABLE() to terminate the event-declaration block.

    @see @ref overview_events_eventtables
*/
#define wxBEGIN_EVENT_TABLE(theClass, baseClass)

/**
    Use this macro in a source file to end listing @e static event handlers
    for a specific class.

    Use wxBEGIN_EVENT_TABLE() to start the event-declaration block.

    @see @ref overview_events_eventtables
*/
#define wxEND_EVENT_TABLE()

/**
    In a GUI application, this function posts @a event to the specified @e dest
    object using wxEvtHandler::AddPendingEvent().

    Otherwise, it dispatches @a event immediately using
    wxEvtHandler::ProcessEvent(). See the respective documentation for details
    (and caveats). Because of limitation of wxEvtHandler::AddPendingEvent()
    this function is not thread-safe for event objects having wxString fields,
    use wxQueueEvent() instead.

    @header{wx/event.h}
*/
void wxPostEvent(wxEvtHandler* dest, const wxEvent& event);

/**
    Queue an event for processing on the given object.

    This is a wrapper around wxEvtHandler::QueueEvent(), see its documentation
    for more details.

    @header{wx/event.h}

    @param dest
        The object to queue the event on, can't be @c NULL.
    @param event
        The heap-allocated and non-@c NULL event to queue, the function takes
        ownership of it.
 */
void wxQueueEvent(wxEvtHandler* dest, wxEvent *event);


//@}