Classes: wxEvtHandler, wxWindow, wxEvent
Introduction
How events are processed
Pluggable event handlers
Window identifiers
Event macros summary
BEGIN_EVENT_TABLE(MyFrame, wxFrame) EVT_MENU (wxID_EXIT, MyFrame::OnExit) EVT_MENU (DO_TEST, MyFrame::DoTest) EVT_SIZE ( MyFrame::OnSize) EVT_BUTTON (BUTTON1, MyFrame::OnButton1) END_EVENT_TABLE()
class MyFrame: public wxFrame {
DECLARE_DYNAMIC_CLASS(MyFrame)
public:
...
void OnExit(wxCommandEvent& event);
void OnSize(wxSizeEvent& event);
protected:
int m_count;
...
DECLARE_EVENT_TABLE()
};
void MyTextCtrl::OnChar(wxKeyEvent& event)
{
if ( isalpha( event.KeyCode() ) )
{
// キーコードが正当な範囲に収まっている。event.Skip()を呼び出して
// 基底のwxWidgetsクラスまたは元のコントロールのイベントを実行する
// ようにする。
// key code is within legal range. we call event.Skip() so the
// event can be processed either in the base wxWidgets class
// or the native control.
event.Skip();
}
else
{
// 不正なキー。event.Skip()を呼ばずにこれ以上手続きが進行しない
// ようにする。
// illegal key hit. we don't call event.Skip() so the
// event is not processed anywhere else.
wxBell();
}
}
Finally, there is another additional complication (which, in fact, simplifies life of wxWidgets programmers significantly): when propagating the command events upwards to the parent window, the event propagation stops when it reaches the parent dialog, if any. This means that you don't risk to get unexpected events from the dialog controls (which might be left unprocessed by the dialog itself because it doesn't care about them) when a modal dialog is popped up. The events do propagate beyond the frames, however. The rationale for this choice is that there are only a few frames in a typical application and their parent-child relation are well understood by the programmer while it may be very difficult, if not impossible, to track down all the dialogs which may be popped up in a complex program (remember that some are created automatically by wxWidgets). If you need to specify a different behaviour for some reason, you can use SetExtraStyle(wxWS_EX_BLOCK_EVENTS) explicitly to prevent the events from being propagated beyond the given window or unset this flag for the dialogs which have it on by default.
Typically events that deal with a window as a window (size, motion, paint, mouse, keyboard, etc.) are sent only to the window. Events that have a higher level of meaning and/or are generated by the window itself, (button click, menu select, tree expand, etc.) are command events and are sent up to the parent to see if it is interested in the event.
Note that your application may wish to override ProcessEvent to redirect processing of events. This is done in the document/view framework, for example, to allow event handlers to be defined in the document or view. To test for command events (which will probably be the only events you wish to redirect), you may use wxEvent::IsCommandEvent for efficiency, instead of using the slower run-time type system.
As mentioned above, only command events are recursively applied to the parents event handler. As this quite often causes confusion for users, here is a list of system events which will NOT get sent to the parent's event handler:
| wxEvent | The event base class |
| wxActivateEvent | A window or application activation event |
| wxCloseEvent | A close window or end session event |
| wxEraseEvent | An erase background event |
| wxFocusEvent | A window focus event |
| wxKeyEvent | A keypress event |
| wxIdleEvent | An idle event |
| wxInitDialogEvent | A dialog initialisation event |
| wxJoystickEvent | A joystick event |
| wxMenuEvent | A menu event |
| wxMouseEvent | A mouse event |
| wxMoveEvent | A move event |
| wxPaintEvent | A paint event |
| wxQueryLayoutInfoEvent | Used to query layout information |
| wxSizeEvent | A size event |
| wxScrollWinEvent | A scroll event sent by a scrolled window (not a scroll bar) |
| wxSysColourChangedEvent | A system colour change event |
| wxUpdateUIEvent | A user interface update event |
In some cases, it might be desired by the programmer to get a certain number of system events in a parent window, for example all key events sent to, but not used by, the native controls in a dialog. In this case, a special event handler will have to be written that will override ProcessEvent() in order to pass all events (or any selection of them) to the parent window.
In fact, you don't have to derive a new class from a window class if you don't want to. You can derive a new class from wxEvtHandler instead, defining the appropriate event table, and then call wxWindow::SetEventHandler (or, preferably, wxWindow::PushEventHandler) to make this event handler the object that responds to events. This way, you can avoid a lot of class derivation, and use the same event handler object to handle events from instances of different classes. If you ever have to call a window's event handler manually, use the GetEventHandler function to retrieve the window's event handler and use that to call the member function. By default, GetEventHandler returns a pointer to the window itself unless an application has redirected event handling using SetEventHandler or PushEventHandler.
One use of PushEventHandler is to temporarily or permanently change the behaviour of the GUI. For example, you might want to invoke a dialog editor in your application that changes aspects of dialog boxes. You can grab all the input for an existing dialog box, and edit it 'in situ', before restoring its behaviour to normal. So even if the application has derived new classes to customize behaviour, your utility can indulge in a spot of body-snatching. It could be a useful technique for on-line tutorials, too, where you take a user through a serious of steps and don't want them to diverge from the lesson. Here, you can examine the events coming from buttons and windows, and if acceptable, pass them through to the original event handler. Use PushEventHandler/PopEventHandler to form a chain of event handlers, where each handler processes a different range of events independently from the other handlers.
Window identifiers are integers, and are used to uniquely determine window identity in the event system (though you can use it for other purposes). In fact, identifiers do not need to be unique across your entire application just so long as they are unique within a particular context you're interested in, such as a frame and its children. You may use the wxID_OK identifier, for example, on any number of dialogs so long as you don't have several within the same dialog.
If you pass -1 to a window constructor, an identifier will be generated for you, but beware: if things don't respond in the way they should, it could be because of an id conflict. It is safer to supply window ids at all times. Automatic generation of identifiers starts at 1 so may well conflict with your own identifiers.
The following standard identifiers are supplied. You can use wxID_HIGHEST to determine the number above which it is safe to define your own identifiers. Or, you can use identifiers below wxID_LOWEST.
#define wxID_LOWEST 4999 #define wxID_OPEN 5000 #define wxID_CLOSE 5001 #define wxID_NEW 5002 #define wxID_SAVE 5003 #define wxID_SAVEAS 5004 #define wxID_REVERT 5005 #define wxID_EXIT 5006 #define wxID_UNDO 5007 #define wxID_REDO 5008 #define wxID_HELP 5009 #define wxID_PRINT 5010 #define wxID_PRINT_SETUP 5011 #define wxID_PREVIEW 5012 #define wxID_ABOUT 5013 #define wxID_HELP_CONTENTS 5014 #define wxID_HELP_COMMANDS 5015 #define wxID_HELP_PROCEDURES 5016 #define wxID_HELP_CONTEXT 5017 #define wxID_CUT 5030 #define wxID_COPY 5031 #define wxID_PASTE 5032 #define wxID_CLEAR 5033 #define wxID_FIND 5034 #define wxID_DUPLICATE 5035 #define wxID_SELECTALL 5036 #define wxID_FILE1 5050 #define wxID_FILE2 5051 #define wxID_FILE3 5052 #define wxID_FILE4 5053 #define wxID_FILE5 5054 #define wxID_FILE6 5055 #define wxID_FILE7 5056 #define wxID_FILE8 5057 #define wxID_FILE9 5058 #define wxID_OK 5100 #define wxID_CANCEL 5101 #define wxID_APPLY 5102 #define wxID_YES 5103 #define wxID_NO 5104 #define wxID_STATIC 5105 #define wxID_HIGHEST 5999
Generic event table macros
| EVT_CUSTOM(event, id, func) | Allows you to add a custom event table entry by specifying the event identifier (such as wxEVT_SIZE), the window identifier, and a member function to call. |
| EVT_CUSTOM_RANGE(event, id1, id2, func) | The same as EVT_CUSTOM, but responds to a range of window identifiers. |
| EVT_COMMAND(id, event, func) | The same as EVT_CUSTOM, but expects a member function with a wxCommandEvent argument. |
| EVT_COMMAND_RANGE(id1, id2, event, func) | The same as EVT_CUSTOM_RANGE, but expects a member function with a wxCommandEvent argument. |
Macros listed by event class
The documentation for specific event macros is organised by event class. Please refer to these sections for details.
| wxActivateEvent | The EVT_ACTIVATE and EVT_ACTIVATE_APP macros intercept activation and deactivation events. |
| wxCommandEvent | A range of commonly-used control events. |
| wxCloseEvent | The EVT_CLOSE macro handles window closure called via wxWindow::Close. |
| wxDropFilesEvent | The EVT_DROP_FILES macros handles file drop events. |
| wxEraseEvent | The EVT_ERASE_BACKGROUND macro is used to handle window erase requests. |
| wxFocusEvent | The EVT_SET_FOCUS and EVT_KILL_FOCUS macros are used to handle keyboard focus events. |
| wxKeyEvent | EVT_CHAR, EVT_KEY_DOWN and EVT_KEY_UP macros handle keyboard input for any window. |
| wxIdleEvent | The EVT_IDLE macro handle application idle events (to process background tasks, for example). |
| wxInitDialogEvent | The EVT_INIT_DIALOG macro is used to handle dialog initialisation. |
| wxListEvent | These macros handle wxListCtrl events. |
| wxMenuEvent | These macros handle special menu events (not menu commands). |
| wxMouseEvent | Mouse event macros can handle either individual mouse events or all mouse events. |
| wxMoveEvent | The EVT_MOVE macro is used to handle a window move. |
| wxPaintEvent | The EVT_PAINT macro is used to handle window paint requests. |
| wxScrollEvent | These macros are used to handle scroll events from wxScrollBar, wxSlider,and wxSpinButton. |
| wxSizeEvent | The EVT_SIZE macro is used to handle a window resize. |
| wxSplitterEvent | The EVT_SPLITTER_SASH_POS_CHANGED, EVT_SPLITTER_UNSPLIT and EVT_SPLITTER_DCLICK macros are used to handle the various splitter window events. |
| wxSysColourChangedEvent | The EVT_SYS_COLOUR_CHANGED macro is used to handle events informing the application that the user has changed the system colours (Windows only). |
| wxTreeEvent | These macros handle wxTreeCtrl events. |
| wxUpdateUIEvent | The EVT_UPDATE_UI macro is used to handle user interface update pseudo-events, which are generated to give the application the chance to update the visual state of menus, toolbars and controls. |