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.
-E.g. it is possible to filter out a number of key events sent by the
+For example it is possible to filter out a number of key events sent by the
system to a native text control by overriding wxTextCtrl and defining a
-handler for key events using EVT_KEY_DOWN. This would in-deed prevent
+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':
// key code is within legal range. we call event.Skip() so the
// event can be processed either in the base wxWindows 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();
}
}
-
\end{verbatim}
}%
\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 wxWindows event processing
+system. To put it a different way, events derived either directly or
+indirectly from wxCommandEvent will travel up the containment
+heirarchy from child to parent until an event handler is found that
+doesn't call event.Skip(). Events not derived from wxCommandEvent are
+sent only to the window they occurred in and then stop.
+
+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 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
\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}}{An 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}
In some cases, it might be desired by the programmer to get a certain number
-of system events in a parent window, e.g. all key events sent to, but not
+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.
+
+\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}
to form a chain of event handlers, where each handler processes a different
range of events independently from the other handlers.
-\subsection{Event macros summary}\label{eventmacros}
+\subsection{Window identifiers}\label{windowids}
-\wxheading{Specifying an event table}
+\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.
-\twocolwidtha{8cm}%
-\begin{twocollist}\itemsep=0pt
-\twocolitem{\windowstyle{EVT\_CUSTOM(eventId, 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.}
-\twocolitem{\windowstyle{EVT\_CUSTOM\_RANGE(eventId, id1, id2, func)}}{The same as EVT\_CUSTOM,
-but responds to a range of window identifiers.}
-\end{twocollist}
+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.
+
+\begin{verbatim}
+#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
+\end{verbatim}
+
+\subsection{Event macros summary}\label{eventmacros}
\wxheading{Generic event table macros}
\twocolwidtha{8cm}%
\begin{twocollist}\itemsep=0pt
-\twocolitem{\windowstyle{EVT\_CUSTOM(eventId, id, func)}}{Allows you to add a custom event table
+\twocolitem{\windowstyle{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.}
-\twocolitem{\windowstyle{EVT\_CUSTOM\_RANGE(eventId, id1, id2, func)}}{The same as EVT\_CUSTOM,
+\twocolitem{\windowstyle{EVT\_CUSTOM\_RANGE(event, id1, id2, func)}}{The same as EVT\_CUSTOM,
but responds to a range of window identifiers.}
-\twocolitem{\windowstyle{EVT\_COMMAND(eventId, id, func)}}{The same as EVT\_CUSTOM, but
+\twocolitem{\windowstyle{EVT\_COMMAND(id, event, func)}}{The same as EVT\_CUSTOM, but
expects a member function with a wxCommandEvent argument.}
-\twocolitem{\windowstyle{EVT\_COMMAND\_RANGE(eventId, id1, id2, func)}}{The same as EVT\_CUSTOM\_RANGE, but
+\twocolitem{\windowstyle{EVT\_COMMAND\_RANGE(id1, id2, event, func)}}{The same as EVT\_CUSTOM\_RANGE, but
expects a member function with a wxCommandEvent argument.}
\end{twocollist}
\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}.}
+\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\_DOUBLECLICKED 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