Version: 3.1.1
wxEvtHandler Class Reference

#include <wx/event.h>

+ Inheritance diagram for wxEvtHandler:

Detailed Description

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 it is imperative that the wxEvtHandler(-derived) class is the first class inherited such that the this pointer for the overall object will be identical to the this pointer of the wxEvtHandler portion.

Library:  wxBase
Category:  Events
See also
How Events are Processed, wxEventBlocker, wxEventLoopBase

Public Member Functions

 wxEvtHandler ()
 Constructor. More...
 
virtual ~wxEvtHandler ()
 Destructor. More...
 
Event queuing and processing
virtual void QueueEvent (wxEvent *event)
 Queue event for a later processing. More...
 
virtual void AddPendingEvent (const wxEvent &event)
 Post an event to be processed later. More...
 
template<typename T , typename T1 , ... >
void CallAfter (void(T::*method)(T1,...), T1 x1,...)
 Asynchronously call the given method. More...
 
template<typename T >
void CallAfter (const T &functor)
 Asynchronously call the given functor. More...
 
virtual bool ProcessEvent (wxEvent &event)
 Processes an event, searching event tables and calling zero or more suitable event handler function(s). More...
 
bool ProcessEventLocally (wxEvent &event)
 Try to process the event in this handler and all those chained to it. More...
 
bool SafelyProcessEvent (wxEvent &event)
 Processes an event by calling ProcessEvent() and handles any exceptions that occur in the process. More...
 
void ProcessPendingEvents ()
 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 wxCHECK will fail. More...
 
void DeletePendingEvents ()
 Deletes all events queued on this event handler using QueueEvent() or AddPendingEvent(). More...
 
Connecting and disconnecting
void Connect (int id, int lastId, wxEventType eventType, wxObjectEventFunction function, wxObject *userData=NULL, wxEvtHandler *eventSink=NULL)
 Connects the given function dynamically with the event handler, id and event type. More...
 
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. More...
 
void Connect (wxEventType eventType, wxObjectEventFunction function, wxObject *userData=NULL, wxEvtHandler *eventSink=NULL)
 See the Connect(int, int, wxEventType, wxObjectEventFunction, wxObject*, wxEvtHandler*) overload for more info. More...
 
bool Disconnect (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. More...
 
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. More...
 
bool Disconnect (int id, int lastId, wxEventType eventType, wxObjectEventFunction function=NULL, wxObject *userData=NULL, wxEvtHandler *eventSink=NULL)
 See the Disconnect(wxEventType, wxObjectEventFunction, wxObject*, wxEvtHandler*) overload for more info. More...
 
Binding and Unbinding
template<typename EventTag , typename Functor >
void Bind (const EventTag &eventType, Functor functor, int id=wxID_ANY, int lastId=wxID_ANY, wxObject *userData=NULL)
 Binds the given function, functor or method dynamically with the event. More...
 
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)
 See the Bind<>(const EventTag&, Functor, int, int, wxObject*) overload for more info. More...
 
template<typename EventTag , typename Functor >
bool Unbind (const EventTag &eventType, Functor functor, 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. More...
 
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)
 See the Unbind<>(const EventTag&, Functor, int, int, wxObject*) overload for more info. More...
 
User-supplied data
void * GetClientData () const
 Returns user-supplied client data. More...
 
wxClientDataGetClientObject () const
 Returns a pointer to the user-supplied client data object. More...
 
void SetClientData (void *data)
 Sets user-supplied client data. More...
 
void SetClientObject (wxClientData *data)
 Set the client data object. More...
 
Event handler chaining

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

bool GetEvtHandlerEnabled () const
 Returns true if the event handler is enabled, false otherwise. More...
 
wxEvtHandlerGetNextHandler () const
 Returns the pointer to the next handler in the chain. More...
 
wxEvtHandlerGetPreviousHandler () const
 Returns the pointer to the previous handler in the chain. More...
 
void SetEvtHandlerEnabled (bool enabled)
 Enables or disables the event handler. More...
 
virtual void SetNextHandler (wxEvtHandler *handler)
 Sets the pointer to the next handler. More...
 
virtual void SetPreviousHandler (wxEvtHandler *handler)
 Sets the pointer to the previous handler. More...
 
void Unlink ()
 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). More...
 
bool IsUnlinked () const
 Returns true if the next and the previous handler pointers of this event handler instance are NULL. More...
 
- Public Member Functions inherited from wxObject
 wxObject ()
 Default ctor; initializes to NULL the internal reference data. More...
 
 wxObject (const wxObject &other)
 Copy ctor. More...
 
virtual ~wxObject ()
 Destructor. More...
 
virtual wxClassInfoGetClassInfo () const
 This virtual function is redefined for every class that requires run-time type information, when using the wxDECLARE_CLASS macro (or similar). More...
 
wxObjectRefDataGetRefData () const
 Returns the wxObject::m_refData pointer, i.e. the data referenced by this object. More...
 
bool IsKindOf (const wxClassInfo *info) const
 Determines whether this class is a subclass of (or the same class as) the given class. More...
 
bool IsSameAs (const wxObject &obj) const
 Returns true if this object has the same data pointer as obj. More...
 
void Ref (const wxObject &clone)
 Makes this object refer to the data in clone. More...
 
void SetRefData (wxObjectRefData *data)
 Sets the wxObject::m_refData pointer. More...
 
void UnRef ()
 Decrements the reference count in the associated data, and if it is zero, deletes the data. More...
 
void UnShare ()
 This is the same of AllocExclusive() but this method is public. More...
 
void operator delete (void *buf)
 The delete operator is defined for debugging versions of the library only, when the identifier WXDEBUG is defined. More...
 
void * operator new (size_t size, const wxString &filename=NULL, int lineNum=0)
 The new operator is defined for debugging versions of the library only, when the identifier WXDEBUG is defined. More...
 

Static Public Member Functions

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.

static void AddFilter (wxEventFilter *filter)
 Add an event filter whose FilterEvent() method will be called for each and every event processed by wxWidgets. More...
 
static void RemoveFilter (wxEventFilter *filter)
 Remove a filter previously installed with AddFilter(). More...
 

Protected Member Functions

virtual bool TryBefore (wxEvent &event)
 Method called by ProcessEvent() before examining this object event tables. More...
 
virtual bool TryAfter (wxEvent &event)
 Method called by ProcessEvent() as last resort. More...
 
- Protected Member Functions inherited from wxObject
void AllocExclusive ()
 Ensure that this object's data is not shared with any other object. More...
 
virtual wxObjectRefDataCreateRefData () const
 Creates a new instance of the wxObjectRefData-derived class specific to this object and returns it. More...
 
virtual wxObjectRefDataCloneRefData (const wxObjectRefData *data) const
 Creates a new instance of the wxObjectRefData-derived class specific to this object and initializes it copying data. More...
 

Additional Inherited Members

- Protected Attributes inherited from wxObject
wxObjectRefDatam_refData
 Pointer to an object which is the object's reference-counted data. More...
 

Constructor & Destructor Documentation

wxEvtHandler::wxEvtHandler ( )

Constructor.

virtual wxEvtHandler::~wxEvtHandler ( )
virtual

Destructor.

If the handler is part of a chain, the destructor will unlink itself (see Unlink()).

Member Function Documentation

static void wxEvtHandler::AddFilter ( wxEventFilter filter)
static

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
virtual void wxEvtHandler::AddPendingEvent ( const wxEvent event)
virtual

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 event object and its copy made internally by this function share the same string buffer internally. Use QueueEvent() to avoid this.

A copy of 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.

Parameters
eventEvent to add to the pending events queue.

Reimplemented in wxWindow.

template<typename EventTag , typename Functor >
void wxEvtHandler::Bind ( const EventTag &  eventType,
Functor  functor,
int  id = wxID_ANY,
int  lastId = wxID_ANY,
wxObject userData = NULL 
)

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 Dynamic Event Handling for more detailed explanation of this function and the Event Sample sample for usage examples.

Parameters
eventTypeThe event type to be associated with this event handler.
functorThe event handler functor. This can be an ordinary function but also an arbitrary functor like boost::function<>.
idThe first ID of the identifier range to be associated with the event handler.
lastIdThe last ID of the identifier range to be associated with the event handler.
userDataOptional 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 also
Caveats When Not Using C++ RTTI
Since
2.9.0
template<typename EventTag , typename Class , typename EventArg , typename EventHandler >
void wxEvtHandler::Bind ( const EventTag &  eventType,
void(Class::*)(EventArg &)  method,
EventHandler *  handler,
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.

Parameters
eventTypeThe event type to be associated with this event handler.
methodThe event handler method. This can be an arbitrary method (doesn't need to be from a wxEvtHandler derived class).
handlerObject 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.
idThe first ID of the identifier range to be associated with the event handler.
lastIdThe last ID of the identifier range to be associated with the event handler.
userDataOptional 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 also
Caveats When Not Using C++ RTTI
Since
2.9.0
template<typename T , typename T1 , ... >
void wxEvtHandler::CallAfter ( void(T::*)(T1,...)  method,
T1  x1,
  ... 
)

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:

class MyFrame : public wxFrame {
void OnClick(wxMouseEvent& event) {
CallAfter(&MyFrame::ShowPosition, event.GetPosition());
}
void ShowPosition(const wxPoint& pos) {
wxString::Format("Perform click at (%d, %d)?",
pos.x, pos.y), "", wxYES_NO) == wxYES )
{
... do take this click into account ...
}
}
};
Parameters
methodThe method to call.
x1The (optional) first parameter to pass to the method. Currently, 0, 1 or 2 parameters can be passed. If you need to pass more than 2 arguments, you can use the CallAfter<T>(const T& fn) overload that can call any functor.
Note
This method is not available with Visual C++ before version 8 (Visual Studio 2005) as earlier versions of the compiler don't have the required support for C++ templates to implement it.
Since
2.9.5
template<typename T >
void wxEvtHandler::CallAfter ( const T &  functor)

Asynchronously call the given functor.

Calling this function on an object schedules an asynchronous call to the functor 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 function showing this message dialog after the current event handler completes.

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.

This overload is particularly useful in combination with C++11 lambdas:

wxGetApp().CallAfter([]{
wxBell();
});
Parameters
functorThe functor to call.
Note
This method is not available with Visual C++ before version 8 (Visual Studio 2005) as earlier versions of the compiler don't have the required support for C++ templates to implement it.
Since
3.0
void wxEvtHandler::Connect ( int  id,
int  lastId,
wxEventType  eventType,
wxObjectEventFunction  function,
wxObject userData = NULL,
wxEvtHandler eventSink = NULL 
)

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 eventSink when connecting to an event of a different object.

See Dynamic Event Handling for more detailed explanation of this function and the Event Sample sample for usage examples.

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

Parameters
idThe first ID of the identifier range to be associated with the event handler function.
lastIdThe last ID of the identifier range to be associated with the event handler function.
eventTypeThe event type to be associated with this event handler.
functionThe event handler function. Note that this function should be explicitly converted to the correct type which can be done using a macro called wxFooEventHandler for the handler for any wxFooEvent.
userDataOptional 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.
eventSinkObject 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, this is used.

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

See also
Bind<>()
void wxEvtHandler::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 can be used to attach an event handler to a single source ID:

Example:

frame->Connect( wxID_EXIT,
wxCommandEventHandler(MyFrame::OnQuit) );

wxPerl Note: Not supported by wxPerl.

void wxEvtHandler::Connect ( 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.

wxPerl Note: Not supported by wxPerl.

void wxEvtHandler::DeletePendingEvents ( )

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).

bool wxEvtHandler::Disconnect ( 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.

Parameters
eventTypeThe event type associated with this event handler.
functionThe event handler function.
userDataData associated with the event table entry.
eventSinkObject whose member function should be called.

wxPerl Note: Not supported by wxPerl.

bool wxEvtHandler::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 the additional id parameter.

wxPerl Note: Not supported by wxPerl.

bool wxEvtHandler::Disconnect ( int  id,
int  lastId,
wxEventType  eventType,
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.

wxPerl Note: In wxPerl this function takes 3 arguments: id, lastid, type.

void* wxEvtHandler::GetClientData ( ) const

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 also
SetClientData()
wxClientData* wxEvtHandler::GetClientObject ( ) const

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

See also
SetClientObject(), wxClientData
bool wxEvtHandler::GetEvtHandlerEnabled ( ) const

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

See also
SetEvtHandlerEnabled()
wxEvtHandler* wxEvtHandler::GetNextHandler ( ) const

Returns the pointer to the next handler in the chain.

See also
SetNextHandler(), GetPreviousHandler(), SetPreviousHandler(), wxWindow::PushEventHandler, wxWindow::PopEventHandler
wxEvtHandler* wxEvtHandler::GetPreviousHandler ( ) const

Returns the pointer to the previous handler in the chain.

See also
SetPreviousHandler(), GetNextHandler(), SetNextHandler(), wxWindow::PushEventHandler, wxWindow::PopEventHandler
bool wxEvtHandler::IsUnlinked ( ) const

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

Since
2.9.0
See also
SetPreviousHandler(), SetNextHandler()
virtual bool wxEvtHandler::ProcessEvent ( wxEvent event)
virtual

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:

  1. wxApp::FilterEvent() is called. If it returns anything but -1 (default) the processing stops here.
  2. TryBefore() is called (this is where wxValidator are taken into account for wxWindow objects). If this returns true, the function exits.
  3. If the object is disabled (via a call to wxEvtHandler::SetEvtHandlerEnabled) the function skips to step (7).
  4. Dynamic event table of the handlers bound using Bind<>() is searched in the most-recently-bound to the most-early-bound order. 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.
  5. Static events table of the handlers bound using event table macros is searched for this event handler in the order of appearance of event table macros in the source code. 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.
  6. 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():
    overview_events_chain.png
    (referring to the image, if A->ProcessEvent is called and it doesn't handle the event, 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.
  7. 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.

Parameters
eventEvent to process.
Returns
true if a suitable event handler function was found and executed, and the function did not call wxEvent::Skip.

Reimplemented in wxWindow.

bool wxEvtHandler::ProcessEventLocally ( 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
Parameters
eventEvent to process.
Returns
true if this handler of one of those chained to it processed the event.
void wxEvtHandler::ProcessPendingEvents ( )

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 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.

virtual void wxEvtHandler::QueueEvent ( wxEvent event)
virtual

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 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 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:

void FunctionInAWorkerThread(const wxString& str)
{
// NOT evt->SetString(str) as this would be a shallow copy
evt->SetString(str.c_str()); // make a deep copy
}

Note that you can use wxThreadEvent instead of wxCommandEvent to avoid this problem:

void FunctionInAWorkerThread(const wxString& str)
{
evt.SetString(str);
// wxThreadEvent::Clone() makes sure that the internal wxString
// member is not shared by other wxString instances:
}

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
Parameters
eventA heap-allocated event to be queued, QueueEvent() takes ownership of it. This parameter shouldn't be NULL.

Reimplemented in wxWindow.

static void wxEvtHandler::RemoveFilter ( wxEventFilter filter)
static

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
bool wxEvtHandler::SafelyProcessEvent ( 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.

Parameters
eventEvent to process.
Returns
true if the event was processed, false if no handler was found or an exception was thrown.
See also
wxWindow::HandleWindowEvent
void wxEvtHandler::SetClientData ( void *  data)

Sets user-supplied client data.

Parameters
dataData 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 also
GetClientData()
void wxEvtHandler::SetClientObject ( wxClientData data)

Set the client data object.

Any previous object will be deleted.

See also
GetClientObject(), wxClientData
void wxEvtHandler::SetEvtHandlerEnabled ( bool  enabled)

Enables or disables the event handler.

Parameters
enabledtrue 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 also
GetEvtHandlerEnabled()
virtual void wxEvtHandler::SetNextHandler ( wxEvtHandler handler)
virtual

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:
handlerA->SetNextHandler(handlerB);
handlerB->SetPreviousHandler(handlerA);
Parameters
handlerThe event handler to be set as the next handler. Cannot be NULL.
See also
How Events are Processed

Reimplemented in wxWindow.

virtual void wxEvtHandler::SetPreviousHandler ( wxEvtHandler handler)
virtual

Sets the pointer to the previous handler.

All remarks about SetNextHandler() apply to this function as well.

Parameters
handlerThe event handler to be set as the previous handler. Cannot be NULL.
See also
How Events are Processed

Reimplemented in wxWindow.

virtual bool wxEvtHandler::TryAfter ( wxEvent event)
protectedvirtual

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:

class MyClass : public BaseClass // inheriting from wxEvtHandler
{
...
protected:
virtual bool TryAfter(wxEvent& event)
{
if ( BaseClass::TryAfter(event) )
return true;
return MyPostProcess(event);
}
};
See also
ProcessEvent()
virtual bool wxEvtHandler::TryBefore ( wxEvent event)
protectedvirtual

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:

class MyClass : public BaseClass // inheriting from wxEvtHandler
{
...
protected:
virtual bool TryBefore(wxEvent& event)
{
if ( MyPreProcess(event) )
return true;
return BaseClass::TryBefore(event);
}
};
See also
ProcessEvent()
template<typename EventTag , typename Functor >
bool wxEvtHandler::Unbind ( const EventTag &  eventType,
Functor  functor,
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.

Note
Currently functors are compared by their address which, unfortunately, doesn't work correctly if the same address is reused for two different functor objects. Because of this, using Unbind() is not recommended if there are multiple functors using the same eventType and id and lastId as a wrong one could be unbound.
Parameters
eventTypeThe event type associated with this event handler.
functorThe event handler functor. This can be an ordinary function but also an arbitrary functor like boost::function<>.
idThe first ID of the identifier range associated with the event handler.
lastIdThe last ID of the identifier range associated with the event handler.
userDataData associated with the event table entry.
See also
Caveats When Not Using C++ RTTI
Since
2.9.0
template<typename EventTag , typename Class , typename EventArg , typename EventHandler >
bool wxEvtHandler::Unbind ( const EventTag &  eventType,
void(Class::*)(EventArg &)  method,
EventHandler *  handler,
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..

Parameters
eventTypeThe event type associated with this event handler.
methodThe event handler method associated with this event.
handlerObject whose method was called.
idThe first ID of the identifier range associated with the event handler.
lastIdThe last ID of the identifier range associated with the event handler.
userDataData associated with the event table entry.
See also
Caveats When Not Using C++ RTTI
Since
2.9.0
void wxEvtHandler::Unlink ( )

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:

evthandler_unlink_before.png

then after calling B->Unlink() you'll have:

evthandler_unlink_after.png
Since
2.9.0