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wxEvtHandler

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

Derived from

wxObject

Include files

<wx/event.h>

See also

Event handling overview

Members

wxEvtHandler::wxEvtHandler
wxEvtHandler::~wxEvtHandler
wxEvtHandler::Connect
wxEvtHandler::Default
wxEvtHandler::GetClientData
wxEvtHandler::GetEvtHandlerEnabled
wxEvtHandler::GetNextHandler
wxEvtHandler::GetPreviousHandler
wxEvtHandler::ProcessEvent
wxEvtHandler::SearchEventTable
wxEvtHandler::SetClientData
wxEvtHandler::SetEvtHandlerEnabled
wxEvtHandler::SetNextHandler
wxEvtHandler::SetPreviousHandler


wxEvtHandler::wxEvtHandler

wxEvtHandler()

Constructor.


wxEvtHandler::~wxEvtHandler

~wxEvtHandler()

Destructor. If the handler is part of a chain, the destructor will unlink itself and restore the previous and next handlers so that they point to each other.


wxEvtHandler::Connect

void Connect(int id, wxEventType eventType, wxObjectEventFunction function, wxObject* userData = NULL)

void Connect(int id, int lastId, wxEventType eventType, wxObjectEventFunction function, wxObject* userData = NULL)

Connects the given function dynamically with the event handler, id and event type. This is an alternative to the use of static event tables. See the 'dynamic' sample for usage.

Parameters

id

lastId

eventType

function

userData

Example

  frame->Connect( wxID_EXIT,
    wxEVT_COMMAND_MENU_SELECTED,
    (wxObjectEventFunction) (wxEventFunction) (wxCommandEventFunction) MyFrame::OnQuit );

wxEvtHandler::Default

virtual long Default()

Invokes default processing if this event handler is a window.

Return value

System dependent.

Remarks

A generic way of delegating processing to the default system behaviour. It calls a platform-dependent default function, with parameters dependent on the event or message parameters originally sent from the windowing system.

Normally the application should call a base member, such as wxWindow::OnChar, which itself may call Default.


wxEvtHandler::GetClientData

char* GetClientData()

Gets 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

wxEvtHandler::SetClientData


wxEvtHandler::GetEvtHandlerEnabled

bool GetEvtHandlerEnabled()

Returns TRUE if the event handler is enabled, FALSE otherwise.

See also

wxEvtHandler::SetEvtHandlerEnabled


wxEvtHandler::GetNextHandler

wxEvtHandler* GetNextHandler()

Gets the pointer to the next handler in the chain.

See also

wxEvtHandler::GetPreviousHandler, wxEvtHandler::SetPreviousHandler, wxEvtHandler::SetNextHandler, wxWindow::PushEventHandler, wxWindow::PopEventHandler


wxEvtHandler::GetPreviousHandler

wxEvtHandler* GetPreviousHandler()

Gets the pointer to the previous handler in the chain.

See also

wxEvtHandler::GetPreviousHandler, wxEvtHandler::SetPreviousHandler, wxEvtHandler::SetPreviousHandler, wxWindow::PushEventHandler, wxWindow::PopEventHandler


wxEvtHandler::ProcessEvent

virtual bool ProcessEvent(wxEvent& event)

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

Parameters

event

Return value

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

Remarks

Normally, your application would not call this function: it is called in the wxWindows 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.

An instance where you might actually override the ProcessEvent function is where you want to direct event processing to event handlers not normally noticed by wxWindows. For example, in the document/view architecture, documents and views are potential event handlers. When an event reaches a frame, ProcessEvent will need to be called on the associated document and view in case event handler functions are associated with these objects. The property classes library (wxProperty) also overrides ProcessEvent for similar reasons.

The normal order of event table searching is as follows:

  1. If the object is disabled (via a call to wxEvtHandler::SetEvtHandlerEnabled) the function skips to step (6).
  2. If the object is a wxWindow, ProcessEvent is recursively called on the window's wxValidator. If this returns TRUE, the function exits.
  3. SearchEventTable is called for this event handler. If this fails, the base class table is tried, and so on until no more tables exist or an appropriate function was found, in which case the function exits.
  4. The search is applied down the entire chain of event handlers (usually the chain has a length of one). If this succeeds, the function exits.
  5. If the object is a wxWindow and the event is a wxCommandEvent, ProcessEvent is recursively applied to the parent window's event handler. If this returns TRUE, the function exits.
  6. Finally, ProcessEvent is called on the wxApp object.

See also

wxEvtHandler::SearchEventTable


wxEvtHandler::SearchEventTable

bool SearchEventTable(wxEventTable& table, wxEvent& event)

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

Parameters

table

event

Return value

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:

  1. The event type matches, and
  2. 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.

See also

wxEvtHandler::ProcessEvent


wxEvtHandler::SetClientData

void SetClientData(char* data)

Sets user-supplied client data.

Parameters

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

wxEvtHandler::GetClientData


wxEvtHandler::SetEvtHandlerEnabled

void SetEvtHandlerEnabled(bool enabled)

Enables or disables the event handler.

Parameters

enabled

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

wxEvtHandler::GetEvtHandlerEnabled


wxEvtHandler::SetNextHandler

void SetNextHandler(wxEvtHandler* handler)

Sets the pointer to the next handler.

Parameters

handler

See also

wxEvtHandler::GetNextHandler, wxEvtHandler::SetPreviousHandler, wxEvtHandler::GetPreviousHandler, wxWindow::PushEventHandler, wxWindow::PopEventHandler


wxEvtHandler::SetPreviousHandler

void SetPreviousHandler(wxEvtHandler* handler)

Sets the pointer to the previous handler.

Parameters

handler

See also

wxEvtHandler::GetPreviousHandler, wxEvtHandler::SetNextHandler, wxEvtHandler::GetNextHandler, wxWindow::PushEventHandler, wxWindow::PopEventHandler