docs/latex/wx/tevent.tex

   1 \section{Event handling overview}\label{eventhandlingoverview}
   2
   3 Classes: \helpref{wxEvtHandler}{wxevthandler}, \helpref{wxWindow}{wxwindow}, \helpref{wxEvent}{wxevent}
   4
   5 \subsection{Introduction}\label{eventintroduction}
   6
   7 Before version 2.0 of wxWidgets, events were handled by the application
   8 either by supplying callback functions, or by overriding virtual member
   9 functions such as {\bf OnSize}.
  10
  11 From wxWidgets 2.0, {\it event tables} are used instead, with a few exceptions.
  12
  13 An event table is placed in an implementation file to tell wxWidgets how to map
  14 events to member functions. These member functions are not virtual functions, but
  15 they are all similar in form: they take a single wxEvent-derived argument, and have a void return
  16 type.
  17
  18 Here's an example of an event table.
  19
  20 \begin{verbatim}
  21 BEGIN_EVENT_TABLE(MyFrame, wxFrame)
  22   EVT_MENU    (wxID_EXIT, MyFrame::OnExit)
  23   EVT_MENU    (DO_TEST,   MyFrame::DoTest)
  24   EVT_SIZE    (           MyFrame::OnSize)
  25   EVT_BUTTON  (BUTTON1,   MyFrame::OnButton1)
  26 END_EVENT_TABLE()
  27 \end{verbatim}
  28
  29 The first two entries map menu commands to two different member functions. The
  30 EVT\_SIZE macro doesn't need a window identifier, since normally you are only
  31 interested in the current window's size events.
  32
  33 The EVT\_BUTTON macro demonstrates that the originating event does not have to
  34 come from the window class implementing the event table -- if the event source
  35 is a button within a panel within a frame, this will still work, because event
  36 tables are searched up through the hierarchy of windows for the command events.
  37 In this case, the button's event table will be searched, then the parent
  38 panel's, then the frame's.
  39
  40 As mentioned before, the member functions that handle events do not have to be
  41 virtual. Indeed, the member functions should not be virtual as the event
  42 handler ignores that the functions are virtual, i.e. overriding a virtual
  43 member function in a derived class will not have any effect. These member
  44 functions take an event argument, and the class of event differs according to
  45 the type of event and the class of the originating window. For size events,
  46 \helpref{wxSizeEvent}{wxsizeevent} is used. For menu commands and most
  47 control commands (such as button presses),
  48 \helpref{wxCommandEvent}{wxcommandevent} is used. When controls get more
  49 complicated, then specific event classes are used, such as
  50 \helpref{wxTreeEvent}{wxtreeevent} for events from
  51 \helpref{wxTreeCtrl}{wxtreectrl} windows.
  52
  53 As well as the event table in the implementation file, there must also be a
  54 DECLARE\_EVENT\_TABLE macro somewhere in the class declaration. For example:
  55
  56 {\small%
  57 \begin{verbatim}
  58 class MyFrame : public wxFrame
  59 {
  60 public:
  61   ...
  62   void OnExit(wxCommandEvent& event);
  63   void OnSize(wxSizeEvent& event);
  64
  65 protected:
  66   int       m_count;
  67   ...
  68
  69   DECLARE_EVENT_TABLE()
  70 };
  71 \end{verbatim}
  72 }%
  73
  74 Note that this macro may occur in any section of the class (public, protected
  75 or private) but that it is probably better to insert it at the end, as shown,
  76 because this macro implicitly changes the access to protected which may be
  77 quite unexpected if there is anything following it.
  78
  79 Finally, if you don't like using macros for static initialization of the event
  80 tables you may also use \helpref{wxEvtHandler::Connect}{wxevthandlerconnect} to
  81 connect the events to the handlers dynamically, during run-time. See the
  82 \helpref{event sample}{sampleevent} for an example of doing it.
  83
  84
  85 \subsection{How events are processed}\label{eventprocessing}
  86
  87 When an event is received from the windowing system, wxWidgets calls
  88 \helpref{wxEvtHandler::ProcessEvent}{wxevthandlerprocessevent} on the first
  89 event handler object belonging to the window generating the event.
  90
  91 It may be noted that wxWidgets' event processing system implements something
  92 very close to virtual methods in normal C++, i.e. it is possible to alter
  93 the behaviour of a class by overriding its event handling functions. In
  94 many cases this works even for changing the behaviour of native controls.
  95 For example it is possible to filter out a number of key events sent by the
  96 system to a native text control by overriding wxTextCtrl and defining a
  97 handler for key events using EVT\_KEY\_DOWN. This would indeed prevent
  98 any key events from being sent to the native control - which might not be
  99 what is desired. In this case the event handler function has to call Skip()
 100 so as to indicate that the search for the event handler should continue.
 101
 102 To summarize, instead of explicitly calling the base class version as you
 103 would have done with C++ virtual functions (i.e. {\it wxTextCtrl::OnChar()}),
 104 you should instead call \helpref{Skip}{wxeventskip}.
 105
 106 In practice, this would look like this if the derived text control only
 107 accepts 'a' to 'z' and 'A' to 'Z':
 108
 109 {\small%
 110 \begin{verbatim}
 111 void MyTextCtrl::OnChar(wxKeyEvent& event)
 112 {
 113     if ( isalpha( event.KeyCode() ) )
 114     {
 115        // key code is within legal range. we call event.Skip() so the
 116        // event can be processed either in the base wxWidgets class
 117        // or the native control.
 118
 119        event.Skip();
 120     }
 121     else
 122     {
 123        // illegal key hit. we don't call event.Skip() so the
 124        // event is not processed anywhere else.
 125
 126        wxBell();
 127     }
 128 }
 129 \end{verbatim}
 130 }%
 131
 132
 133 The normal order of event table searching by ProcessEvent is as follows:
 134
 135 \begin{enumerate}\itemsep=0pt
 136 \item If the object is disabled (via a call to \helpref{wxEvtHandler::SetEvtHandlerEnabled}{wxevthandlersetevthandlerenabled})
 137 the function skips to step (6).
 138 \item If the object is a wxWindow, {\bf ProcessEvent} is recursively called on the window's\rtfsp
 139 \helpref{wxValidator}{wxvalidator}. If this returns true, the function exits.
 140 \item {\bf SearchEventTable} is called for this event handler. If this fails, the base
 141 class table is tried, and so on until no more tables exist or an appropriate function was found,
 142 in which case the function exits.
 143 \item The search is applied down the entire chain of event handlers (usually the chain has a length
 144 of one). If this succeeds, the function exits.
 145 \item If the object is a wxWindow and the event is set to set to propagate (in the library only
 146 wxCommandEvent based events are set to propagate), {\bf ProcessEvent} is recursively applied
 147 to the parent window's event handler. If this returns true, the function exits.
 148 \item Finally, {\bf ProcessEvent} is called on the wxApp object.
 149 \end{enumerate}
 150
 151 {\bf Pay close attention to Step 5.}  People often overlook or get
 152 confused by this powerful feature of the wxWidgets event processing
 153 system.  To put it a different way, events set to propagate
 154 (\helpref{See: wxEvent::ShouldPropagate}{wxeventshouldpropagate})
 155 (most likely derived either directly or indirectly from wxCommandEvent)
 156 will travel up the containment hierarchy from child to parent until the
 157 maximal propagation level is reached or an event handler is found that
 158 doesn't call \helpref{event.Skip()}{wxeventskip}.
 159
 160 Finally, there is another additional complication (which, in fact, simplifies
 161 life of wxWidgets programmers significantly): when propagating the command
 162 events upwards to the parent window, the event propagation stops when it
 163 reaches the parent dialog, if any. This means that you don't risk to get
 164 unexpected events from the dialog controls (which might be left unprocessed by
 165 the dialog itself because it doesn't care about them) when a modal dialog is
 166 popped up. The events do propagate beyond the frames, however. The rationale
 167 for this choice is that there are only a few frames in a typical application
 168 and their parent-child relation are well understood by the programmer while it
 169 may be very difficult, if not impossible, to track down all the dialogs which
 170 may be popped up in a complex program (remember that some are created
 171 automatically by wxWidgets). If you need to specify a different behaviour for
 172 some reason, you can use
 173 \helpref{SetExtraStyle(wxWS\_EX\_BLOCK\_EVENTS)}{wxwindowsetextrastyle}
 174 explicitly to prevent the events from being propagated beyond the given window
 175 or unset this flag for the dialogs which have it on by default.
 176
 177 Typically events that deal with a window as a window (size, motion,
 178 paint, mouse, keyboard, etc.) are sent only to the window.  Events
 179 that have a higher level of meaning and/or are generated by the window
 180 itself, (button click, menu select, tree expand, etc.) are command
 181 events and are sent up to the parent to see if it is interested in the
 182 event.
 183
 184 Note that your application may wish to override ProcessEvent to redirect processing of
 185 events. This is done in the document/view framework, for example, to allow event handlers
 186 to be defined in the document or view. To test for command events (which will probably
 187 be the only events you wish to redirect), you may use
 188 \helpref{wxEvent::IsCommandEvent}{wxeventiscommandevent} for efficiency,
 189 instead of using the slower run-time type system.
 190
 191 As mentioned above, only command events are recursively applied to the parents event
 192 handler in the library itself. As this quite often causes confusion for users,
 193 here is a list of system events which will NOT get sent to the parent's event handler:
 194
 195 \begin{twocollist}\itemsep=0pt
 196 \twocolitem{\helpref{wxEvent}{wxevent}}{The event base class}
 197 \twocolitem{\helpref{wxActivateEvent}{wxactivateevent}}{A window or application activation event}
 198 \twocolitem{\helpref{wxCloseEvent}{wxcloseevent}}{A close window or end session event}
 199 \twocolitem{\helpref{wxEraseEvent}{wxeraseevent}}{An erase background event}
 200 \twocolitem{\helpref{wxFocusEvent}{wxfocusevent}}{A window focus event}
 201 \twocolitem{\helpref{wxKeyEvent}{wxkeyevent}}{A keypress event}
 202 \twocolitem{\helpref{wxIdleEvent}{wxidleevent}}{An idle event}
 203 \twocolitem{\helpref{wxInitDialogEvent}{wxinitdialogevent}}{A dialog initialisation event}
 204 \twocolitem{\helpref{wxJoystickEvent}{wxjoystickevent}}{A joystick event}
 205 \twocolitem{\helpref{wxMenuEvent}{wxmenuevent}}{A menu event}
 206 \twocolitem{\helpref{wxMouseEvent}{wxmouseevent}}{A mouse event}
 207 \twocolitem{\helpref{wxMoveEvent}{wxmoveevent}}{A move event}
 208 \twocolitem{\helpref{wxPaintEvent}{wxpaintevent}}{A paint event}
 209 \twocolitem{\helpref{wxQueryLayoutInfoEvent}{wxquerylayoutinfoevent}}{Used to query layout information}
 210 \twocolitem{\helpref{wxSetCursorEvent}{wxsetcursorevent}}{Used for special cursor processing based on current mouse position}
 211 \twocolitem{\helpref{wxSizeEvent}{wxsizeevent}}{A size event}
 212 \twocolitem{\helpref{wxScrollWinEvent}{wxscrollwinevent}}{A scroll event sent by a scrolled window (not a scroll bar)}
 213 \twocolitem{\helpref{wxSysColourChangedEvent}{wxsyscolourchangedevent}}{A system colour change event}
 214 \end{twocollist}
 215
 216 In some cases, it might be desired by the programmer to get a certain number
 217 of system events in a parent window, for example all key events sent to, but not
 218 used by, the native controls in a dialog. In this case, a special event handler
 219 will have to be written that will override ProcessEvent() in order to pass
 220 all events (or any selection of them) to the parent window.
 221
 222
 223 \subsection{Events generated by the user vs programmatically generated events}\label{progevent}
 224
 225 While generically \helpref{wxEvents}{wxevent} can be generated both by user
 226 actions (e.g. resize of a \helpref{wxWindow}{wxwindow}) and by calls to functions
 227 (e.g. \helpref{wxWindow::SetSize}{wxwindowsetsize}), wxWidgets controls
 228 normally send \helpref{wxCommandEvent}{wxcommandevent}-derived events only for
 229 the user-generated events. The only {\bf exceptions} to this rule are:
 230
 231 \begin{twocollist}\itemsep=0pt
 232 \twocolitem{\helpref{wxNotebook::AddPage}{wxnotebookaddpage}}{No event-free alternatives}
 233 \twocolitem{\helpref{wxNotebook::AdvanceSelection}{wxnotebookadvanceselection}}{No event-free alternatives}
 234 \twocolitem{\helpref{wxNotebook::DeletePage}{wxnotebookdeletepage}}{No event-free alternatives}
 235 \twocolitem{\helpref{wxNotebook::SetSelection}{wxnotebooksetselection}}{Use \helpref{wxNotebook::ChangeSelection}{wxnotebookchangeselection} instead, as \helpref{wxNotebook::SetSelection}{wxnotebooksetselection} is deprecated}
 236 \twocolitem{\helpref{wxTreeCtrl::Delete}{wxtreectrldelete}}{No event-free alternatives}
 237 \twocolitem{\helpref{wxTreeCtrl::DeleteAllItems}{wxtreectrldeleteallitems}}{No event-free alternatives}
 238 \twocolitem{\helpref{wxTreeCtrl::EditLabel}{wxtreectrleditlabel}}{No event-free alternatives}
 239 \twocolitem{All \helpref{wxTextCtrl}{wxtextctrl} methods}{\helpref{wxTextCtrl::ChangeValue}{wxtextctrlchangevalue} can be used instead
 240 of \helpref{wxTextCtrl::SetValue}{wxtextctrlsetvalue} but the other functions,
 241 such as \helpref{Replace}{wxtextctrlreplace} or \helpref{WriteText}{wxtextctrlwritetext}
 242 don't have event-free equivalents}
 243 \end{twocollist}
 244
 245
 246 % VZ: it doesn't work like this, but just in case we ever reenable this
 247 %     behaviour, I leave it here
 248 %
 249 % \subsection{Redirection of command events to the window with the focus}
 250 %
 251 % The usual upward search through the window hierarchy for command event
 252 % handlers does not always meet an application's requirements. Say you have two
 253 % wxTextCtrl windows in a frame, plus a toolbar with Cut, Copy and Paste
 254 % buttons. To avoid the need to define event handlers in the frame
 255 % and redirect them explicitly to the window with the focus, command events
 256 % are sent to the window with the focus first, for
 257 % menu and toolbar command and UI update events only. This means that
 258 % each window can handle its own commands and UI updates independently. In
 259 % fact wxTextCtrl can handle Cut, Copy, Paste, Undo and Redo commands and UI update
 260 % requests, so no extra coding is required to support them in your menus and
 261 % toolbars.
 262
 263 \subsection{Pluggable event handlers}\label{pluggablehandlers}
 264
 265 In fact, you don't have to derive a new class from a window class
 266 if you don't want to. You can derive a new class from wxEvtHandler instead,
 267 defining the appropriate event table, and then call
 268 \rtfsp\helpref{wxWindow::SetEventHandler}{wxwindowseteventhandler} (or, preferably,
 269 \rtfsp\helpref{wxWindow::PushEventHandler}{wxwindowpusheventhandler}) to make this
 270 event handler the object that responds to events. This way, you can avoid
 271 a lot of class derivation, and use the same event handler object to
 272 handle events from instances of different classes. If you ever have to call a window's event handler
 273 manually, use the GetEventHandler function to retrieve the window's event handler and use that
 274 to call the member function. By default, GetEventHandler returns a pointer to the window itself
 275 unless an application has redirected event handling using SetEventHandler or PushEventHandler.
 276
 277 One use of PushEventHandler is to temporarily or permanently change the
 278 behaviour of the GUI. For example, you might want to invoke a dialog editor
 279 in your application that changes aspects of dialog boxes. You can
 280 grab all the input for an existing dialog box, and edit it `in situ',
 281 before restoring its behaviour to normal. So even if the application
 282 has derived new classes to customize behaviour, your utility can indulge
 283 in a spot of body-snatching. It could be a useful technique for on-line
 284 tutorials, too, where you take a user through a serious of steps and
 285 don't want them to diverge from the lesson. Here, you can examine the events
 286 coming from buttons and windows, and if acceptable, pass them through to
 287 the original event handler. Use PushEventHandler/PopEventHandler
 288 to form a chain of event handlers, where each handler processes a different
 289 range of events independently from the other handlers.
 290
 291 \subsection{Window identifiers}\label{windowids}
 292
 293 \index{identifiers}\index{wxID}Window identifiers are integers, and are used to
 294 uniquely determine window identity in the event system (though you can use it
 295 for other purposes). In fact, identifiers do not need to be unique
 296 across your entire application just so long as they are unique within a
 297 particular context you're interested in, such as a frame and its children. You
 298 may use the {\tt wxID\_OK} identifier, for example, on any number of dialogs so
 299 long as you don't have several within the same dialog.
 300
 301 If you pass {\tt wxID\_ANY} to a window constructor, an identifier will be
 302 generated for you automatically by wxWidgets. This is useful when you don't
 303 care about the exact identifier either because you're not going to process the
 304 events from the control being created at all or because you process the events
 305 from all controls in one place (in which case you should specify {\tt wxID\_ANY}
 306 in the event table or \helpref{wxEvtHandler::Connect}{wxevthandlerconnect} call
 307 as well. The automatically generated identifiers are always negative and so
 308 will never conflict with the user-specified identifiers which must be always
 309 positive.
 310
 311 The following standard identifiers are supplied. You can use wxID\_HIGHEST to
 312 determine the number above which it is safe to define your own identifiers. Or,
 313 you can use identifiers below wxID\_LOWEST.
 314
 315 \begin{verbatim}
 316 #define wxID_ANY                -1
 317
 318 #define wxID_LOWEST             4999
 319
 320 #define wxID_OPEN               5000
 321 #define wxID_CLOSE              5001
 322 #define wxID_NEW                5002
 323 #define wxID_SAVE               5003
 324 #define wxID_SAVEAS             5004
 325 #define wxID_REVERT             5005
 326 #define wxID_EXIT               5006
 327 #define wxID_UNDO               5007
 328 #define wxID_REDO               5008
 329 #define wxID_HELP               5009
 330 #define wxID_PRINT              5010
 331 #define wxID_PRINT_SETUP        5011
 332 #define wxID_PREVIEW            5012
 333 #define wxID_ABOUT              5013
 334 #define wxID_HELP_CONTENTS      5014
 335 #define wxID_HELP_COMMANDS      5015
 336 #define wxID_HELP_PROCEDURES    5016
 337 #define wxID_HELP_CONTEXT       5017
 338
 339 #define wxID_CUT                5030
 340 #define wxID_COPY               5031
 341 #define wxID_PASTE              5032
 342 #define wxID_CLEAR              5033
 343 #define wxID_FIND               5034
 344 #define wxID_DUPLICATE          5035
 345 #define wxID_SELECTALL          5036
 346 #define wxID_DELETE             5037
 347 #define wxID_REPLACE            5038
 348 #define wxID_REPLACE_ALL        5039
 349 #define wxID_PROPERTIES         5040
 350
 351 #define wxID_VIEW_DETAILS       5041
 352 #define wxID_VIEW_LARGEICONS    5042
 353 #define wxID_VIEW_SMALLICONS    5043
 354 #define wxID_VIEW_LIST          5044
 355 #define wxID_VIEW_SORTDATE      5045
 356 #define wxID_VIEW_SORTNAME      5046
 357 #define wxID_VIEW_SORTSIZE      5047
 358 #define wxID_VIEW_SORTTYPE      5048
 359
 360 #define wxID_FILE1              5050
 361 #define wxID_FILE2              5051
 362 #define wxID_FILE3              5052
 363 #define wxID_FILE4              5053
 364 #define wxID_FILE5              5054
 365 #define wxID_FILE6              5055
 366 #define wxID_FILE7              5056
 367 #define wxID_FILE8              5057
 368 #define wxID_FILE9              5058
 369
 370 #define wxID_OK                 5100
 371 #define wxID_CANCEL             5101
 372 #define wxID_APPLY              5102
 373 #define wxID_YES                5103
 374 #define wxID_NO                 5104
 375 #define wxID_STATIC             5105
 376
 377 #define wxID_HIGHEST            5999
 378 \end{verbatim}
 379
 380 \subsection{Event macros summary}\label{eventmacros}
 381
 382 \wxheading{Macros listed by event class}
 383
 384 The documentation for specific event macros is organised by event class. Please refer
 385 to these sections for details.
 386
 387 \twocolwidtha{8cm}%
 388 \begin{twocollist}\itemsep=0pt
 389 \twocolitem{\helpref{wxActivateEvent}{wxactivateevent}}{The EVT\_ACTIVATE and EVT\_ACTIVATE\_APP macros intercept
 390 activation and deactivation events.}
 391 \twocolitem{\helpref{wxCommandEvent}{wxcommandevent}}{A range of commonly-used control events.}
 392 \twocolitem{\helpref{wxCloseEvent}{wxcloseevent}}{The EVT\_CLOSE macro handles window closure
 393 called via \helpref{wxWindow::Close}{wxwindowclose}.}
 394 \twocolitem{\helpref{wxDropFilesEvent}{wxdropfilesevent}}{The EVT\_DROP\_FILES macros handles
 395 file drop events.}
 396 \twocolitem{\helpref{wxEraseEvent}{wxeraseevent}}{The EVT\_ERASE\_BACKGROUND macro is used to handle window erase requests.}
 397 \twocolitem{\helpref{wxFocusEvent}{wxfocusevent}}{The EVT\_SET\_FOCUS and EVT\_KILL\_FOCUS macros are used to handle keyboard focus events.}
 398 \twocolitem{\helpref{wxKeyEvent}{wxkeyevent}}{EVT\_CHAR, EVT\_KEY\_DOWN and
 399 EVT\_KEY\_UP macros handle keyboard input for any window.}
 400 \twocolitem{\helpref{wxIdleEvent}{wxidleevent}}{The EVT\_IDLE macro handle application idle events
 401 (to process background tasks, for example).}
 402 \twocolitem{\helpref{wxInitDialogEvent}{wxinitdialogevent}}{The EVT\_INIT\_DIALOG macro is used
 403 to handle dialog initialisation.}
 404 \twocolitem{\helpref{wxListEvent}{wxlistevent}}{These macros handle \helpref{wxListCtrl}{wxlistctrl} events.}
 405 \twocolitem{\helpref{wxMenuEvent}{wxmenuevent}}{These macros handle special menu events (not menu commands).}
 406 \twocolitem{\helpref{wxMouseEvent}{wxmouseevent}}{Mouse event macros can handle either individual
 407 mouse events or all mouse events.}
 408 \twocolitem{\helpref{wxMoveEvent}{wxmoveevent}}{The EVT\_MOVE macro is used to handle a window move.}
 409 \twocolitem{\helpref{wxPaintEvent}{wxpaintevent}}{The EVT\_PAINT macro is used to handle window paint requests.}
 410 \twocolitem{\helpref{wxScrollEvent}{wxscrollevent}}{These macros are used to handle scroll events from
 411 \helpref{wxScrollBar}{wxscrollbar}, \helpref{wxSlider}{wxslider},and \helpref{wxSpinButton}{wxspinbutton}.}
 412 \twocolitem{\helpref{wxSetCursorEvent}{wxsetcursorevent}}{The EVT\_SET\_CURSOR macro is used for special cursor processing.}
 413 \twocolitem{\helpref{wxSizeEvent}{wxsizeevent}}{The EVT\_SIZE macro is used to handle a window resize.}
 414 \twocolitem{\helpref{wxSplitterEvent}{wxsplitterevent}}{The EVT\_SPLITTER\_SASH\_POS\_CHANGED, EVT\_SPLITTER\_UNSPLIT
 415 and EVT\_SPLITTER\_DCLICK macros are used to handle the various splitter window events.}
 416 \twocolitem{\helpref{wxSysColourChangedEvent}{wxsyscolourchangedevent}}{The EVT\_SYS\_COLOUR\_CHANGED macro is used to handle
 417 events informing the application that the user has changed the system colours (Windows only).}
 418 \twocolitem{\helpref{wxTreeEvent}{wxtreeevent}}{These macros handle \helpref{wxTreeCtrl}{wxtreectrl} events.}
 419 \twocolitem{\helpref{wxUpdateUIEvent}{wxupdateuievent}}{The EVT\_UPDATE\_UI macro is used to handle user interface
 420 update pseudo-events, which are generated to give the application the chance to update the visual state of menus,
 421 toolbars and controls.}
 422 \end{twocollist}
 423
 424 \subsection{Custom event summary}\label{customevents}
 425
 426 \wxheading{General approach}
 427
 428 Since version 2.2.x of wxWidgets, each event type is identified by ID which
 429 is given to the event type {\it at runtime} which makes it possible to add
 430 new event types to the library or application without risking ID clashes
 431 (two different event types mistakingly getting the same event ID). This
 432 event type ID is stored in a struct of type {\bf const wxEventType}.
 433
 434 In order to define a new event type, there are principally two choices.
 435 One is to define a entirely new event class (typically deriving from
 436 \helpref{wxEvent}{wxevent} or \helpref{wxCommandEvent}{wxcommandevent}.
 437 The other is to use the existing event classes and give them an new event
 438 type. You'll have to define and declare a new event type using either way,
 439 and this is done using the following macros:
 440
 441 \begin{verbatim}
 442 // in the header of the source file
 443 BEGIN_DECLARE_EVENT_TYPES()
 444 DECLARE_EVENT_TYPE(name, value)
 445 END_DECLARE_EVENT_TYPES()
 446
 447 // in the implementation
 448 DEFINE_EVENT_TYPE(name)
 449 \end{verbatim}
 450
 451 You can ignore the {\it value} parameter of the DECLARE\_EVENT\_TYPE macro
 452 since it used only for backwards compatibility with wxWidgets 2.0.x based
 453 applications where you have to give the event type ID an explicit value.
 454
 455 See also the \helpref{event sample}{sampleevent} for an example of code
 456 defining and working with the custom event types.
 457
 458 \wxheading{Using existing event classes}
 459
 460 If you just want to use a \helpref{wxCommandEvent}{wxcommandevent} with
 461 a new event type, you can then use one of the generic event table macros
 462 listed below, without having to define a new macro yourself. This also
 463 has the advantage that you won't have to define a new \helpref{wxEvent::Clone()}{wxeventclone}
 464 method for posting events between threads etc. This could look like this
 465 in your code:
 466
 467 {\small%
 468 \begin{verbatim}
 469 DECLARE_EVENT_TYPE(wxEVT_MY_EVENT, -1)
 470
 471 DEFINE_EVENT_TYPE(wxEVT_MY_EVENT)
 472
 473 // user code intercepting the event
 474
 475 BEGIN_EVENT_TABLE(MyFrame, wxFrame)
 476   EVT_MENU    (wxID_EXIT, MyFrame::OnExit)
 477   // ....
 478   EVT_COMMAND  (ID_MY_WINDOW, wxEVT_MY_EVENT, MyFrame::OnMyEvent)
 479 END_EVENT_TABLE()
 480
 481 void MyFrame::OnMyEvent( wxCommandEvent &event )
 482 {
 483     // do something
 484     wxString text = event.GetText();
 485 }
 486
 487
 488 // user code sending the event
 489
 490 void MyWindow::SendEvent()
 491 {
 492     wxCommandEvent event( wxEVT_MY_EVENT, GetId() );
 493     event.SetEventObject( this );
 494     // Give it some contents
 495     event.SetText( wxT("Hallo") );
 496     // Send it
 497     GetEventHandler()->ProcessEvent( event );
 498 }
 499 \end{verbatim}
 500 }%
 501
 502
 503 \wxheading{Generic event table macros}
 504
 505 \twocolwidtha{8cm}%
 506 \begin{twocollist}\itemsep=0pt
 507 \twocolitem{\windowstyle{EVT\_CUSTOM(event, id, func)}}{Allows you to add a custom event table
 508 entry by specifying the event identifier (such as wxEVT\_SIZE), the window identifier,
 509 and a member function to call.}
 510 \twocolitem{\windowstyle{EVT\_CUSTOM\_RANGE(event, id1, id2, func)}}{The same as EVT\_CUSTOM,
 511 but responds to a range of window identifiers.}
 512 \twocolitem{\windowstyle{EVT\_COMMAND(id, event, func)}}{The same as EVT\_CUSTOM, but
 513 expects a member function with a wxCommandEvent argument.}
 514 \twocolitem{\windowstyle{EVT\_COMMAND\_RANGE(id1, id2, event, func)}}{The same as EVT\_CUSTOM\_RANGE, but
 515 expects a member function with a wxCommandEvent argument.}
 516 \twocolitem{\windowstyle{EVT\_NOTIFY(event, id, func)}}{The same as EVT\_CUSTOM, but
 517 expects a member function with a wxNotifyEvent argument.}
 518 \twocolitem{\windowstyle{EVT\_NOTIFY\_RANGE(event, id1, id2, func)}}{The same as EVT\_CUSTOM\_RANGE, but
 519 expects a member function with a wxNotifyEvent argument.}
 520 \end{twocollist}
 521
 522
 523 \wxheading{Defining your own event class}
 524
 525 Under certain circumstances, it will be required to define your own event
 526 class e.g. for sending more complex data from one place to another. Apart
 527 from defining your event class, you will also need to define your own
 528 event table macro (which is quite long). Watch out to put in enough
 529 casts to the inherited event function. Here is an example, taken mostly
 530 from the {\it wxPlot} library, which is in the {\it contrib} section of
 531 the wxWidgets sources.
 532
 533 {\small%
 534 \begin{verbatim}
 535
 536 // code defining event
 537
 538 class wxPlotEvent: public wxNotifyEvent
 539 {
 540 public:
 541     wxPlotEvent( wxEventType commandType = wxEVT_NULL, int id = 0 );
 542
 543     // accessors
 544     wxPlotCurve *GetCurve()
 545         { return m_curve; }
 546
 547     // required for sending with wxPostEvent()
 548     wxEvent* Clone();
 549
 550 private:
 551     wxPlotCurve   *m_curve;
 552 };
 553
 554 DECLARE_EVENT_MACRO( wxEVT_PLOT_ACTION, -1 )
 555
 556 typedef void (wxEvtHandler::*wxPlotEventFunction)(wxPlotEvent&);
 557
 558 #define EVT_PLOT(id, fn) \
 559     DECLARE_EVENT_TABLE_ENTRY( wxEVT_PLOT_ACTION, id, -1, \
 560     (wxObjectEventFunction) (wxEventFunction) (wxCommandEventFunction) (wxNotifyEventFunction) \
 561     wxStaticCastEvent( wxPlotEventFunction, & fn ), (wxObject *) NULL ),
 562
 563
 564 // code implementing the event type and the event class
 565
 566 DEFINE_EVENT_TYPE( wxEVT_PLOT_ACTION )
 567
 568 wxPlotEvent::wxPlotEvent( ...
 569
 570
 571 // user code intercepting the event
 572
 573 BEGIN_EVENT_TABLE(MyFrame, wxFrame)
 574   EVT_PLOT  (ID_MY_WINDOW,  MyFrame::OnPlot)
 575 END_EVENT_TABLE()
 576
 577 void MyFrame::OnPlot( wxPlotEvent &event )
 578 {
 579     wxPlotCurve *curve = event.GetCurve();
 580 }
 581
 582
 583 // user code sending the event
 584
 585 void MyWindow::SendEvent()
 586 {
 587     wxPlotEvent event( wxEVT_PLOT_ACTION, GetId() );
 588     event.SetEventObject( this );
 589     event.SetCurve( m_curve );
 590     GetEventHandler()->ProcessEvent( event );
 591 }
 592
 593 \end{verbatim}
 594 }%
 595