\subsection{Introduction}
-Before version 2.0 of wxWindows, events were handled by the application
+Before version 2.0 of wxWidgets, events were handled by the application
either by supplying callback functions, or by overriding virtual member
functions such as {\bf OnSize}.
-From wxWindows 2.0, {\it event tables} are used instead, with a few exceptions.
+From wxWidgets 2.0, {\it event tables} are used instead, with a few exceptions.
-An event table is placed in an implementation file to tell wxWindows how to map
+An event table is placed in an implementation file to tell wxWidgets how to map
events to member functions. These member functions are not virtual functions, but
-they all similar in form: they take a single wxEvent-derived argument, and have a void return
+they are all similar in form: they take a single wxEvent-derived argument, and have a void return
type.
Here's an example of an event table.
END_EVENT_TABLE()
\end{verbatim}
-The first two entries map menu commands to two different member functions. The EVT\_SIZE macro
-doesn't need a window identifier, since normally you are only interested in the
-current window's size events. (In fact you could intercept a particular window's size event
-by using EVT\_CUSTOM(wxEVT\_SIZE, id, func).)
-
-The EVT\_BUTTON macro demonstrates that the originating event does not have to come from
-the window class implementing the event table - if the event source is a button within a panel within a frame, this will still
-work, because event tables are searched up through the hierarchy of windows. In this
-case, the button's event table will be searched, then the parent panel's, then the frame's.
-
-As mentioned before, the member functions that handle events do not have to be virtual.
-Indeed, the member functions should not be virtual as the event handler ignores that
-the functions are virtual, i.e. overriding a virtual member function in a derived class
-will not have any effect.
-These member functions take an event argument, and the class of event differs according
-to the type of event and the class of the originating window. For size
-events, \helpref{wxSizeEvent}{wxsizeevent} is used. For menu commands and most control
-commands (such as button presses), \helpref{wxCommandEvent}{wxcommandevent} is used.
-When controls get more complicated, then specific event classes are used, such
-as \helpref{wxTreeEvent}{wxtreeevent} for events from \helpref{wxTreeCtrl}{wxtreectrl} windows.
-
-As well as the event table in the implementation file, there must be a DECLARE\_EVENT\_TABLE
-macro in the class definition. For example:
+The first two entries map menu commands to two different member functions. The
+EVT\_SIZE macro doesn't need a window identifier, since normally you are only
+interested in the current window's size events.
+
+The EVT\_BUTTON macro demonstrates that the originating event does not have to
+come from the window class implementing the event table -- if the event source
+is a button within a panel within a frame, this will still work, because event
+tables are searched up through the hierarchy of windows for the command events.
+In this case, the button's event table will be searched, then the parent
+panel's, then the frame's.
+
+As mentioned before, the member functions that handle events do not have to be
+virtual. Indeed, the member functions should not be virtual as the event
+handler ignores that the functions are virtual, i.e. overriding a virtual
+member function in a derived class will not have any effect. These member
+functions take an event argument, and the class of event differs according to
+the type of event and the class of the originating window. For size events,
+\helpref{wxSizeEvent}{wxsizeevent} is used. For menu commands and most
+control commands (such as button presses),
+\helpref{wxCommandEvent}{wxcommandevent} is used. When controls get more
+complicated, then specific event classes are used, such as
+\helpref{wxTreeEvent}{wxtreeevent} for events from
+\helpref{wxTreeCtrl}{wxtreectrl} windows.
+
+As well as the event table in the implementation file, there must also be a
+DECLARE\_EVENT\_TABLE macro somewhere in the class declaration. For example:
{\small%
\begin{verbatim}
-class MyFrame: public wxFrame {
-
- DECLARE_DYNAMIC_CLASS(MyFrame)
-
+class MyFrame : public wxFrame
+{
public:
...
void OnExit(wxCommandEvent& event);
void OnSize(wxSizeEvent& event);
+
protected:
int m_count;
...
+
DECLARE_EVENT_TABLE()
};
\end{verbatim}
}%
+Note that this macro may occur in any section of the class (public, protected
+or private) but that it is probably better to insert it at the end, as shown,
+because this macro implicitly changes the access to protected which may be
+quite unexpected if there is anything following it.
+
+Finally, if you don't like using macros for static initialization of the event
+tables you may also use \helpref{wxEvtHandler::Connect}{wxevthandlerconnect} to
+connect the events to the handlers dynamically, during run-time. See the
+\helpref{event sample}{sampleevent} for an example of doing it.
+
+
\subsection{How events are processed}\label{eventprocessing}
-When an event is received from the windowing system, wxWindows calls \helpref{wxEvtHandler::ProcessEvent}{wxevthandlerprocessevent} on
-the first event handler object belonging to the window generating the event.
+When an event is received from the windowing system, wxWidgets calls
+\helpref{wxEvtHandler::ProcessEvent}{wxevthandlerprocessevent} on the first
+event handler object belonging to the window generating the event.
-It may be noted that wxWindows' event processing system implements something
+It may be noted that wxWidgets' event processing system implements something
very close to virtual methods in normal C++, i.e. it is possible to alter
the behaviour of a class by overriding its event handling functions. In
many cases this works even for changing the behaviour of native controls.
handler for key events using EVT\_KEY\_DOWN. This would indeed prevent
any key events from being sent to the native control - which might not be
what is desired. In this case the event handler function has to call Skip()
-so as to indicate that it did NOT handle the event at all.
+so as to indicate that the search for the event handler should continue.
+
+To summarize, instead of explicitly calling the base class version as you
+would have done with C++ virtual functions (i.e. {\it wxTextCtrl::OnChar()}),
+you should instead call \helpref{Skip}{wxeventskip}.
In practice, this would look like this if the derived text control only
accepts 'a' to 'z' and 'A' to 'Z':
if ( isalpha( event.KeyCode() ) )
{
// key code is within legal range. we call event.Skip() so the
- // event can be processed either in the base wxWindows class
+ // event can be processed either in the base wxWidgets class
// or the native control.
-
- event.Skip();
+
+ event.Skip();
}
else
{
// illegal key hit. we don't call event.Skip() so the
// event is not processed anywhere else.
-
+
wxBell();
}
}
\item If the object is disabled (via a call to \helpref{wxEvtHandler::SetEvtHandlerEnabled}{wxevthandlersetevthandlerenabled})
the function skips to step (6).
\item If the object is a wxWindow, {\bf ProcessEvent} is recursively called on the window's\rtfsp
-\helpref{wxValidator}{wxvalidator}. If this returns TRUE, the function exits.
+\helpref{wxValidator}{wxvalidator}. If this returns true, the function exits.
\item {\bf 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.
\item 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.
-\item If the object is a wxWindow and the event is a wxCommandEvent, {\bf ProcessEvent} is
-recursively applied to the parent window's event handler. If this returns TRUE, the function exits.
+\item If the object is a wxWindow and the event is set to set to propagate (in the library only
+wxCommandEvent based events are set to propagate), {\bf ProcessEvent} is recursively applied
+to the parent window's event handler. If this returns true, the function exits.
\item Finally, {\bf ProcessEvent} is called on the wxApp object.
\end{enumerate}
+{\bf Pay close attention to Step 5.} People often overlook or get
+confused by this powerful feature of the wxWidgets event processing
+system. To put it a different way, events set to propagate
+(\helpref{See: wxEvent::ShouldPropagate}{wxeventshouldpropagate})
+(most likely derived either directly or indirectly from wxCommandEvent)
+will travel up the containment hierarchy from child to parent until the
+maximal propagation level is reached or an event handler is found that
+doesn't call \helpref{event.Skip()}{wxeventskip}.
+
+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
+\helpref{SetExtraStyle(wxWS\_EX\_BLOCK\_EVENTS)}{wxwindowsetextrastyle}
+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 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
+\helpref{wxEvent::IsCommandEvent}{wxeventiscommandevent} 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:
+handler in the libary itself. 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:
\begin{twocollist}\itemsep=0pt
\twocolitem{\helpref{wxEvent}{wxevent}}{The event base class}
\twocolitem{\helpref{wxPaintEvent}{wxpaintevent}}{A paint event}
\twocolitem{\helpref{wxQueryLayoutInfoEvent}{wxquerylayoutinfoevent}}{Used to query layout information}
\twocolitem{\helpref{wxSizeEvent}{wxsizeevent}}{A size event}
+\twocolitem{\helpref{wxScrollWinEvent}{wxscrollwinevent}}{A scroll event sent by a scrolled window (not a scroll bar)}
\twocolitem{\helpref{wxSysColourChangedEvent}{wxsyscolourchangedevent}}{A system colour change event}
\twocolitem{\helpref{wxUpdateUIEvent}{wxupdateuievent}}{A user interface update event}
\end{twocollist}
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. See next section.
+all events (or any selection of them) to the parent window.
+
+% VZ: it doesn't work like this, but just in case we ever reenable this
+% behaviour, I leave it here
+%
+% \subsection{Redirection of command events to the window with the focus}
+%
+% The usual upward search through the window hierarchy for command event
+% handlers does not always meet an application's requirements. Say you have two
+% wxTextCtrl windows in a frame, plus a toolbar with Cut, Copy and Paste
+% buttons. To avoid the need to define event handlers in the frame
+% and redirect them explicitly to the window with the focus, command events
+% are sent to the window with the focus first, for
+% menu and toolbar command and UI update events only. This means that
+% each window can handle its own commands and UI updates independently. In
+% fact wxTextCtrl can handle Cut, Copy, Paste, Undo and Redo commands and UI update
+% requests, so no extra coding is required to support them in your menus and
+% toolbars.
\subsection{Pluggable event handlers}
\subsection{Window identifiers}\label{windowids}
-\index{identifiers}\index{wxID}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's 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.
+\index{identifiers}\index{wxID}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 {\tt 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 {\tt wxID\_ANY} to a window constructor, an identifier will be
+generated for you automatically by wxWidgets. This is useful when you don't
+care about the exact identifier either because you're not going to process the
+events from the control being created at all or because you process the events
+from all controls in one place (in which case you should specify {\tt wxID\_ANY}
+in the event table or \helpref{wxEvtHandler::Connect}{wxevthandlerconnect} call
+as well. The automatically generated identifiers are always negative and so
+will never conflict with the user-specified identifiers which must be always
+positive.
+
+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.
\begin{verbatim}
+#define wxID_ANY -1
+
#define wxID_LOWEST 4999
#define wxID_OPEN 5000
#define wxID_FIND 5034
#define wxID_DUPLICATE 5035
#define wxID_SELECTALL 5036
+#define wxID_DELETE 5037
+#define wxID_REPLACE 5038
+#define wxID_REPLACE_ALL 5039
+#define wxID_PROPERTIES 5040
+
+#define wxID_VIEW_DETAILS 5041
+#define wxID_VIEW_LARGEICONS 5042
+#define wxID_VIEW_SMALLICONS 5043
+#define wxID_VIEW_LIST 5044
+#define wxID_VIEW_SORTDATE 5045
+#define wxID_VIEW_SORTNAME 5046
+#define wxID_VIEW_SORTSIZE 5047
+#define wxID_VIEW_SORTTYPE 5048
#define wxID_FILE1 5050
#define wxID_FILE2 5051
\twocolitem{\helpref{wxDropFilesEvent}{wxdropfilesevent}}{The EVT\_DROP\_FILES macros handles
file drop events.}
\twocolitem{\helpref{wxEraseEvent}{wxeraseevent}}{The EVT\_ERASE\_BACKGROUND macro is used to handle window erase requests.}
-\twocolitem{\helpref{wxFocusEvent}{wxfocusevent}}{The EVT\_SET\_FOCUS and EVT\_KILL\_FOCUS macros are used to handle keybaord focus events.}
-\twocolitem{\helpref{wxKeyEvent}{wxkeyevent}}{EVT\_CHAR and EVT\_CHAR\_HOOK macros handle keyboard
-input for any window.}
+\twocolitem{\helpref{wxFocusEvent}{wxfocusevent}}{The EVT\_SET\_FOCUS and EVT\_KILL\_FOCUS macros are used to handle keyboard focus events.}
+\twocolitem{\helpref{wxKeyEvent}{wxkeyevent}}{EVT\_CHAR, EVT\_KEY\_DOWN and
+EVT\_KEY\_UP macros handle keyboard input for any window.}
\twocolitem{\helpref{wxIdleEvent}{wxidleevent}}{The EVT\_IDLE macro handle application idle events
(to process background tasks, for example).}
\twocolitem{\helpref{wxInitDialogEvent}{wxinitdialogevent}}{The EVT\_INIT\_DIALOG macro is used
\twocolitem{\helpref{wxMouseEvent}{wxmouseevent}}{Mouse event macros can handle either individual
mouse events or all mouse events.}
\twocolitem{\helpref{wxMoveEvent}{wxmoveevent}}{The EVT\_MOVE macro is used to handle a window move.}
-\twocolitem{\helpref{wxUpdateUIEvent}{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.}
\twocolitem{\helpref{wxPaintEvent}{wxpaintevent}}{The EVT\_PAINT macro is used to handle window paint requests.}
-\twocolitem{\helpref{wxScrollEvent}{wxscrollevent}}{These macros are used to handle scroll events from
-windows, \helpref{wxScrollBar}{wxscrollbar}, and \helpref{wxSpinButton}{wxspinbutton}.}
+\twocolitem{\helpref{wxScrollEvent}{wxscrollevent}}{These macros are used to handle scroll events from
+\helpref{wxScrollBar}{wxscrollbar}, \helpref{wxSlider}{wxslider},and \helpref{wxSpinButton}{wxspinbutton}.}
\twocolitem{\helpref{wxSizeEvent}{wxsizeevent}}{The EVT\_SIZE macro is used to handle a window resize.}
+\twocolitem{\helpref{wxSplitterEvent}{wxsplitterevent}}{The EVT\_SPLITTER\_SASH\_POS\_CHANGED, EVT\_SPLITTER\_UNSPLIT
+and EVT\_SPLITTER\_DCLICK macros are used to handle the various splitter window events.}
\twocolitem{\helpref{wxSysColourChangedEvent}{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).}
\twocolitem{\helpref{wxTreeEvent}{wxtreeevent}}{These macros handle \helpref{wxTreeCtrl}{wxtreectrl} events.}
+\twocolitem{\helpref{wxUpdateUIEvent}{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.}
\end{twocollist}
projects / wxWidgets.git / blobdiff