X-Git-Url: https://git.saurik.com/wxWidgets.git/blobdiff_plain/dc28cdf8d4d895e953d1710bbf77a065106ff98f..4e15d1caa03346c126015019c1fdf093033ef40b:/docs/doxygen/overviews/eventhandling.h diff --git a/docs/doxygen/overviews/eventhandling.h b/docs/doxygen/overviews/eventhandling.h index e504d6e5d1..405b3e1f36 100644 --- a/docs/doxygen/overviews/eventhandling.h +++ b/docs/doxygen/overviews/eventhandling.h @@ -3,223 +3,542 @@ // Purpose: topic overview // Author: wxWidgets team // RCS-ID: $Id$ -// Licence: wxWindows license +// Licence: wxWindows licence ///////////////////////////////////////////////////////////////////////////// /** -@page overview_eventhandling Event Handling +@page overview_events Events and Event Handling + +@tableofcontents + +Like with all the other GUI frameworks, the control of flow in wxWidgets +applications is event-based: the program normally performs most of its actions +in response to the events generated by the user. These events can be triggered +by using the input devices (such as keyboard, mouse, joystick) directly or, +more commonly, by a standard control which synthesizes such input events into +higher level events: for example, a wxButton can generate a click event when +the user presses the left mouse button on it and then releases it without +pressing @c Esc in the meanwhile. There are also events which don't directly +correspond to the user actions, such as wxTimerEvent or wxSocketEvent. + +But in all cases wxWidgets represents these events in a uniform way and allows +you to handle them in the same way wherever they originate from. And while the +events are normally generated by wxWidgets itself, you can also do this, which +is especially useful when using custom events (see @ref overview_events_custom). + +To be more precise, each event is described by: + - Event type: this is simply a value of type wxEventType which + uniquely identifies the type of the event. For example, clicking on a button, + selecting an item from a list box and pressing a key on the keyboard all + generate events with different event types. + - Event class carried by the event: each event has some information + associated with it and this data is represented by an object of a class + derived from wxEvent. Events of different types can use the same event class, + for example both button click and listbox selection events use wxCommandEvent + class (as do all the other simple control events), but the key press event + uses wxKeyEvent as the information associated with it is different. + - Event source: wxEvent stores the object which generated the event + and, for windows, its identifier (see @ref overview_events_winid). As it is + common to have more than one object generating events of the same type (e.g. a + typical window contains several buttons, all generating the same button click + event), checking the event source object or its id allows to distinguish + between them. + +@see wxEvtHandler, wxWindow, wxEvent + + + +@section overview_events_eventhandling Event Handling + +There are two principal ways to handle events in wxWidgets. One of them uses +event table macros and allows you to define the binding between events +and their handlers only statically, i.e., during program compilation. The other +one uses wxEvtHandler::Bind<>() call and can be used to bind and +unbind, the handlers dynamically, i.e. during run-time depending on some +conditions. It also allows the direct binding of events to: +@li A handler method in another object. +@li An ordinary function like a static method or a global function. +@li An arbitrary functor like boost::function<>. + +The static event tables can only handle events in the object where they are +defined so using Bind<>() is more flexible than using the event tables. On the +other hand, event tables are more succinct and centralize all event handler +bindings in one place. You can either choose a single approach that you find +preferable or freely combine both methods in your program in different classes +or even in one and the same class, although this is probably sufficiently +confusing to be a bad idea. + +Also notice that most of the existing wxWidgets tutorials and discussions use +the event tables because they historically preceded the apparition of dynamic +event handling in wxWidgets. But this absolutely doesn't mean that using the +event tables is the preferred way: handling events dynamically is better in +several aspects and you should strongly consider doing it if you are just +starting with wxWidgets. On the other hand, you still need to know about the +event tables if only because you are going to see them in many samples and +examples. + +So before you make the choice between static event tables and dynamically +connecting the event handlers, let us discuss these two ways in more detail. In +the next section we provide a short introduction to handling the events using +the event tables. Please see @ref overview_events_bind for the discussion of +Bind<>(). + +@subsection overview_events_eventtables Event Handling with Event Tables + +To use an event table you must first decide in which class you wish to +handle the events. The only requirement imposed by wxWidgets is that this class +must derive from wxEvtHandler and so, considering that wxWindow derives from +it, any classes representing windows can handle events. Simple events such as +menu commands are usually processed at the level of a top-level window +containing the menu, so let's suppose that you need to handle some events in @c +MyFrame class deriving from wxFrame. + +First define one or more event handlers. They +are just simple methods of the class that take as a parameter a +reference to an object of a wxEvent-derived class and have no return value (any +return information is passed via the argument, which is why it is non-const). +You also need to insert a macro -Classes: wxEvtHandler, wxWindow, wxEvent - -@li @ref overview_eventhandling_introduction -@li @ref overview_eventhandling_processing -@li @ref overview_eventhandling_prog -@li @ref overview_eventhandling_pluggable -@li @ref overview_eventhandling_winid -@li @ref overview_eventhandling_custom -@li @ref overview_eventhandling_macros +@code +wxDECLARE_EVENT_TABLE() +@endcode +somewhere in the class declaration. It doesn't matter where it appears but +it's customary to put it at the end because the macro changes the access +type internally so it's safest if nothing follows it. The +full class declaration might look like this: -
+@code +class MyFrame : public wxFrame +{ +public: + MyFrame(...) : wxFrame(...) { } + ... -@section overview_eventhandling_introduction Introduction +protected: + int m_whatever; -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 @b OnSize. +private: + // Notice that as the event handlers normally are not called from outside + // the class, they normally are private. In particular they don't need + // to be public. + void OnExit(wxCommandEvent& event); + void OnButton1(wxCommandEvent& event); + void OnSize(wxSizeEvent& event); + + // it's common to call the event handlers OnSomething() but there is no + // obligation to do that; this one is an event handler too: + void DoTest(wxCommandEvent& event); + + wxDECLARE_EVENT_TABLE() +}; +@endcode -From wxWidgets 2.0, @e event tables are used instead, with a few exceptions. -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 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. +Next the event table must be defined and, as with any definition, it must be +placed in an implementation file. The event table tells wxWidgets how to map +events to member functions and in our example it could look like this: @code -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() +wxBEGIN_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) +wxEND_EVENT_TABLE() @endcode -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 +Notice that you must mention a method you want to use for the event handling in +the event table definition; just defining it in MyFrame class is @e not enough. + +Let us now look at the details of this definition: the first line means that we +are defining the event table for MyFrame class and that its base class is +wxFrame, so events not processed by MyFrame will, by default, be handled by +wxFrame. The next four lines define bindings of individual events to their +handlers: the first two of them map menu commands from the items with the +identifiers specified as the first macro parameter to two different member +functions. In the next one, @c EVT_SIZE means that any changes in the size of +the frame will result in calling OnSize() method. Note that this macro doesn't +need a window identifier, since normally you are only interested in the current +window's size events. + +The @c 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, -wxSizeEvent is used. For menu commands and most control commands +(But only command events, so you can't catch mouse move events in a child +control in the parent window in the same way because wxMouseEvent doesn't +derive from wxCommandEvent. See below for how you can do it.) In this case, the +button's event table will be searched, then the parent panel's, then the +frame's. + +Finally, you need to implement the event handlers. As mentioned before, all +event handlers take a wxEvent-derived argument whose exact class differs +according to the type of event and the class of the originating window. For +size events, wxSizeEvent is used. For menu commands and most control commands (such as button presses), wxCommandEvent is used. When controls get more -complicated, then specific event classes are used, such as wxTreeEvent for +complicated, more specific wxCommandEvent-derived event classes providing +additional control-specific information can be used, such as wxTreeEvent for events from 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: +In the simplest possible case an event handler may not use the @c event +parameter at all. For example, @code -class MyFrame : public wxFrame +void MyFrame::OnExit(wxCommandEvent& WXUNUSED(event)) { -public: -... -void OnExit(wxCommandEvent& event); -void OnSize(wxSizeEvent& event); + // when the user selects "Exit" from the menu we should close + Close(true); +} +@endcode -protected: -int m_count; -... +In other cases you may need some information carried by the @c event argument, +as in: -DECLARE_EVENT_TABLE() -}; +@code +void MyFrame::OnSize(wxSizeEvent& event) +{ + wxSize size = event.GetSize(); + + ... update the frame using the new size ... +} @endcode -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. +You will find the details about the event table macros and the corresponding +wxEvent-derived classes in the discussion of each control generating these +events. -Finally, if you don't like using macros for static initialization of the event -tables you may also use wxEvtHandler::Connect to -connect the events to the handlers dynamically, during run-time. See the -@ref page_samples_event for an example of doing it. +@subsection overview_events_bind Dynamic Event Handling +@see @ref overview_cpp_rtti_disabled -@section overview_eventhandling_processing How events are processed +The possibilities of handling events in this way are rather different. +Let us start by looking at the syntax: the first obvious difference is that you +need not use wxDECLARE_EVENT_TABLE() nor wxBEGIN_EVENT_TABLE() and the +associated macros. Instead, in any place in your code, but usually in +the code of the class defining the handler itself (and definitely not in the +global scope as with the event tables), call its Bind<>() method like this: -When an event is received from the windowing system, wxWidgets calls -wxEvtHandler::ProcessEvent on the first -event handler object belonging to the window generating the event. +@code +MyFrame::MyFrame(...) +{ + Bind(wxEVT_COMMAND_MENU_SELECTED, &MyFrame::OnExit, this, wxID_EXIT); +} +@endcode -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. +Note that @c this pointer must be specified here. + +Now let us describe the semantic differences: + + +Let us now look at more examples of how to use different event handlers using +the two overloads of Bind() function: first one for the object methods and the +other one for arbitrary functors (callable objects, including simple functions): + +In addition to using a method of the object generating the event itself, you +can use a method from a completely different object as an event handler: + +@code +void MyFrameHandler::OnFrameExit( wxCommandEvent & ) +{ + // Do something useful. +} + +MyFrameHandler myFrameHandler; + +MyFrame::MyFrame() +{ + Bind( wxEVT_COMMAND_MENU_SELECTED, &MyFrameHandler::OnFrameExit, + &myFrameHandler, wxID_EXIT ); +} +@endcode -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 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 the search for the event handler should continue. +Note that @c MyFrameHandler doesn't need to derive from wxEvtHandler. But +keep in mind that then the lifetime of @c myFrameHandler must be greater than +that of @c MyFrame object -- or at least it needs to be unbound before being +destroyed. -To summarize, instead of explicitly calling the base class version as you -would have done with C++ virtual functions (i.e. @e wxTextCtrl::OnChar()), -you should instead call wxEvent::Skip. -In practice, this would look like this if the derived text control only -accepts 'a' to 'z' and 'A' to 'Z': +To use an ordinary function or a static method as an event handler you would +write something like this: @code -void MyTextCtrl::OnChar(wxKeyEvent& event) +void HandleExit( wxCommandEvent & ) { - if ( isalpha( event.KeyCode() ) ) - { - // 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. + // Do something useful +} - event.Skip(); - } - else - { - // illegal key hit. we don't call event.Skip() so the - // event is not processed anywhere else. +MyFrame::MyFrame() +{ + Bind( wxEVT_COMMAND_MENU_SELECTED, &HandleExit, wxID_EXIT ); +} +@endcode - wxBell(); +And finally you can bind to an arbitrary functor and use it as an event +handler: + +@code + +struct MyFunctor +{ + void operator()( wxCommandEvent & ) + { + // Do something useful } +}; + +MyFunctor myFunctor; + +MyFrame::MyFrame() +{ + Bind( wxEVT_COMMAND_MENU_SELECTED, myFunctor, wxID_EXIT ); } @endcode -The normal order of event table searching by ProcessEvent is as follows: - -@li If the object is disabled (via a call to wxEvtHandler::SetEvtHandlerEnabled) - the function skips to step (6). -@li If the object is a wxWindow, @b ProcessEvent is recursively called on the window's - wxValidator. If this returns @true, the function exits. -@li @b 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. -@li 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. -@li 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), @b ProcessEvent is recursively applied - to the parent window's event handler. If this returns @true, the function exits. -@li Finally, @b ProcessEvent is called on the wxApp object. - -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 -(see wxEvent::ShouldPropagate) -(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 @c event.Skip(). +A common example of a functor is boost::function<>: + +@code +using namespace boost; + +void MyHandler::OnExit( wxCommandEvent & ) +{ + // Do something useful +} + +MyHandler myHandler; + +MyFrame::MyFrame() +{ + function< void ( wxCommandEvent & ) > exitHandler( bind( &MyHandler::OnExit, &myHandler, _1 )); + + Bind( wxEVT_COMMAND_MENU_SELECTED, exitHandler, wxID_EXIT ); +} +@endcode + + +With the aid of boost::bind<>() you can even use methods or functions which +don't quite have the correct signature: + +@code +void MyHandler::OnExit( int exitCode, wxCommandEvent &, wxString goodByeMessage ) +{ + // Do something useful +} + +MyHandler myHandler; + +MyFrame::MyFrame() +{ + function< void ( wxCommandEvent & ) > exitHandler( + bind( &MyHandler::OnExit, &myHandler, EXIT_FAILURE, _1, "Bye" )); + + Bind( wxEVT_COMMAND_MENU_SELECTED, exitHandler, wxID_EXIT ); +} +@endcode + + +To summarize, using Bind<>() requires slightly more typing but is much more +flexible than using static event tables so don't hesitate to use it when you +need this extra power. On the other hand, event tables are still perfectly fine +in simple situations where this extra flexibility is not needed. + + +@section overview_events_processing How Events are Processed + +The previous sections explain how to define event handlers but don't address +the question of how exactly wxWidgets finds the handler to call for the +given event. This section describes the algorithm used in detail. Notice that +you may want to run the @ref page_samples_event while reading this section and +look at its code and the output when the button which can be used to test the +event handlers execution order is clicked to understand it better. + +When an event is received from the windowing system, wxWidgets calls +wxEvtHandler::ProcessEvent() on the first event handler object belonging to the +window generating the event. The normal order of event table searching by +ProcessEvent() is as follows, with the event processing stopping as soon as a +handler is found (unless the handler calls wxEvent::Skip() in which case it +doesn't count as having handled the event and the search continues): +
    +
  1. + Before anything else happens, wxApp::FilterEvent() is called. If it returns + anything but -1 (default), the event handling stops immediately. +
    2. + +
  2. + If this event handler is disabled via a call to + wxEvtHandler::SetEvtHandlerEnabled() the next three steps are skipped and + the event handler resumes at step (5). +
    3. + +
  3. + If the object is a wxWindow and has an associated validator, wxValidator + gets a chance to process the event. +
    4. + +
  4. + The list of dynamically bound event handlers, i.e., those for which + Bind<>() was called, is consulted. Notice that this is done before + checking the static event table entries, so if both a dynamic and a static + event handler match the same event, the static one is never going to be + used unless wxEvent::Skip() is called in the dynamic one. +
    5. + +
  5. + The event table containing all the handlers defined using the event table + macros in this class and its base classes is examined. Notice that this + means that any event handler defined in a base class will be executed at + this step. +
    6. + +
  6. + The event is passed to the next event handler, if any, in the event handler + chain, i.e., the steps (1) to (4) are done for it. Usually there is no next + event handler so the control passes to the next step but see @ref + overview_events_nexthandler for how the next handler may be defined. +
    7. + +
  7. + If the object is a wxWindow and the event is set to propagate (by default + only wxCommandEvent-derived events are set to propagate), then the + processing restarts from the step (1) (and excluding the step (7)) for the + parent window. If this object is not a window but the next handler exists, + the event is passed to its parent if it is a window. This ensures that in a + common case of (possibly several) non-window event handlers pushed on top + of a window, the event eventually reaches the window parent. +
    8. + +
  8. + Finally, i.e., if the event is still not processed, the wxApp object itself + (which derives from wxEvtHandler) gets a last chance to process it. +
    9. +
+ +Please pay close attention to step 6! People often overlook or get +confused by this powerful feature of the wxWidgets event processing system. The +details of event propagation up the window hierarchy are described in the +next section. + +Also please notice that there are additional steps in the event handling for +the windows-making part of wxWidgets document-view framework, i.e., +wxDocParentFrame, wxDocChildFrame and their MDI equivalents wxDocMDIParentFrame +and wxDocMDIChildFrame. The parent frame classes modify step (2) above to +send the events received by them to wxDocManager object first. This object, in +turn, sends the event to the current view and the view itself lets its +associated document process the event first. The child frame classes send +the event directly to the associated view which still forwards it to its +document object. Notice that to avoid remembering the exact order in which the +events are processed in the document-view frame, the simplest, and recommended, +solution is to only handle the events at the view classes level, and not in the +document or document manager classes + + +@subsection overview_events_propagation How Events Propagate Upwards + +As mentioned above, the events of the classes deriving from wxCommandEvent are +propagated by default to the parent window if they are not processed in this +window itself. But although by default only the command events are propagated +like this, other events can be propagated as well because the event handling +code uses wxEvent::ShouldPropagate() to check whether an event should be +propagated. It is also possible to propagate the event only a limited number of +times and not until it is processed (or a top level parent window is reached). 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 +events up to the parent window, the event propagation stops when it +reaches the parent dialog, if any. This means that you don't risk getting 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 difficult, if not impossible, to track down all the dialogs that 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 wxWindow::SetExtraStyle(wxWS_EX_BLOCK_EVENTS) +some reason, you can use wxWindow::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. +or unset this flag for the dialogs that 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 +that have a higher level of meaning 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 in the library 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: - -@li wxEvent: The event base class -@li wxActivateEvent: A window or application activation event -@li wxCloseEvent: A close window or end session event -@li wxEraseEvent: An erase background event -@li wxFocusEvent: A window focus event -@li wxKeyEvent: A keypress event -@li wxIdleEvent: An idle event -@li wxInitDialogEvent: A dialog initialisation event -@li wxJoystickEvent: A joystick event -@li wxMenuEvent: A menu event -@li wxMouseEvent: A mouse event -@li wxMoveEvent: A move event -@li wxPaintEvent: A paint event -@li wxQueryLayoutInfoEvent: Used to query layout information -@li wxSetCursorEvent: Used for special cursor processing based on current mouse position -@li wxSizeEvent: A size event -@li wxScrollWinEvent: A scroll event sent by a scrolled window (not a scroll bar) -@li wxSysColourChangedEvent: A system colour change event +More precisely, as said above, all event classes @b not deriving from wxCommandEvent +(see the wxEvent inheritance map) do @b not propagate upward. 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 @@ -228,11 +547,217 @@ will have to be written that will override ProcessEvent() in order to pass all events (or any selection of them) to the parent window. -@section overview_eventhandling_prog Events generated by the user vs programmatically generated events +@subsection overview_events_nexthandler Event Handlers Chain + +The step 4 of the event propagation algorithm checks for the next handler in +the event handler chain. This chain can be formed using +wxEvtHandler::SetNextHandler(): + @image html overview_events_chain.png +(referring to the image, if @c A->ProcessEvent is called and it doesn't handle + the event, @c B->ProcessEvent will be called and so on...). + +Additionally, in the case of wxWindow you can build a stack (implemented using +wxEvtHandler double-linked list) using wxWindow::PushEventHandler(): + @image html overview_events_winstack.png +(referring to the image, if @c W->ProcessEvent is called, it immediately calls + @c A->ProcessEvent; if nor @c A nor @c B handle the event, then the wxWindow +itself is used -- i.e. the dynamically bind event handlers and static event +table entries of wxWindow are looked as the last possibility, after all pushed +event handlers were tested). + +By default the chain is empty, i.e. there is no next handler. + + +@section overview_events_custom Custom Event Summary + +@subsection overview_events_custom_general General approach + +As each event is uniquely defined by its event type, defining a custom event +starts with defining a new event type for it. This is done using +wxDEFINE_EVENT() macro. As an event type is a variable, it can also be +declared using wxDECLARE_EVENT() if necessary. + +The next thing to do is to decide whether you need to define a custom event +class for events of this type or if you can reuse an existing class, typically +either wxEvent (which doesn't provide any extra information) or wxCommandEvent +(which contains several extra fields and also propagates upwards by default). +Both strategies are described in details below. See also the @ref +page_samples_event for a complete example of code defining and working with the +custom event types. + +Finally, you will need to generate and post your custom events. +Generation is as simple as instancing your custom event class and initializing +its internal fields. +For posting events to a certain event handler there are two possibilities: +using wxEvtHandler::AddPendingEvent or using wxEvtHandler::QueueEvent. +Basically you will need to use the latter when doing inter-thread communication; +when you use only the main thread you can also safely use the former. +Last, note that there are also two simple global wrapper functions associated +to the two wxEvtHandler mentioned functions: wxPostEvent() and wxQueueEvent(). + + +@subsection overview_events_custom_existing Using Existing Event Classes + +If you just want to use a wxCommandEvent with a new event type, use one of the +generic event table macros listed below, without having to define a new event +class yourself. + +Example: + +@code +// this is typically in a header: it just declares MY_EVENT event type +wxDECLARE_EVENT(MY_EVENT, wxCommandEvent); + +// this is a definition so can't be in a header +wxDEFINE_EVENT(MY_EVENT, wxCommandEvent); + +// example of code handling the event with event tables +wxBEGIN_EVENT_TABLE(MyFrame, wxFrame) + EVT_MENU (wxID_EXIT, MyFrame::OnExit) + ... + EVT_COMMAND (ID_MY_WINDOW, MY_EVENT, MyFrame::OnMyEvent) +wxEND_EVENT_TABLE() + +void MyFrame::OnMyEvent(wxCommandEvent& event) +{ + // do something + wxString text = event.GetString(); +} + +// example of code handling the event with Bind<>(): +MyFrame::MyFrame() +{ + Bind(MY_EVENT, &MyFrame::OnMyEvent, this, ID_MY_WINDOW); +} + +// example of code generating the event +void MyWindow::SendEvent() +{ + wxCommandEvent event(MY_EVENT, GetId()); + event.SetEventObject(this); + + // Give it some contents + event.SetString("Hello"); + + // Do send it + ProcessWindowEvent(event); +} +@endcode + + +@subsection overview_events_custom_ownclass Defining Your Own Event Class + +Under certain circumstances, you must define your own event class e.g., for +sending more complex data from one place to another. Apart from defining your +event class, you also need to define your own event table macro if you want to +use event tables for handling events of this type. + +Here is an example: + +@code +// define a new event class +class MyPlotEvent: public wxEvent +{ +public: + MyPlotEvent(wxEventType eventType, int winid, const wxPoint& pos) + : wxEvent(winid, eventType), + m_pos(pos) + { + } + + // accessors + wxPoint GetPoint() const { return m_pos; } + + // implement the base class pure virtual + virtual wxEvent *Clone() const { return new MyPlotEvent(*this); } + +private: + const wxPoint m_pos; +}; + +// we define a single MY_PLOT_CLICKED event type associated with the class +// above but typically you are going to have more than one event type, e.g. you +// could also have MY_PLOT_ZOOMED or MY_PLOT_PANNED &c -- in which case you +// would just add more similar lines here +wxDEFINE_EVENT(MY_PLOT_CLICKED, MyPlotEvent); + + +// if you want to support old compilers you need to use some ugly macros: +typedef void (wxEvtHandler::*MyPlotEventFunction)(MyPlotEvent&); +#define MyPlotEventHandler(func) wxEVENT_HANDLER_CAST(MyPlotEventFunction, func) + +// if your code is only built using reasonably modern compilers, you could just +// do this instead: +#define MyPlotEventHandler(func) (&func) + +// finally define a macro for creating the event table entries for the new +// event type +// +// remember that you don't need this at all if you only use Bind<>() and that +// you can replace MyPlotEventHandler(func) with just &func unless you use a +// really old compiler +#define MY_EVT_PLOT_CLICK(id, func) \ + wx__DECLARE_EVT1(MY_PLOT_CLICKED, id, MyPlotEventHandler(func)) + + +// example of code handling the event (you will use one of these methods, not +// both, of course): +wxBEGIN_EVENT_TABLE(MyFrame, wxFrame) + EVT_PLOT(ID_MY_WINDOW, MyFrame::OnPlot) +wxEND_EVENT_TABLE() + +MyFrame::MyFrame() +{ + Bind(MY_PLOT_CLICKED, &MyFrame::OnPlot, this, ID_MY_WINDOW); +} + +void MyFrame::OnPlot(MyPlotEvent& event) +{ + ... do something with event.GetPoint() ... +} + + +// example of code generating the event: +void MyWindow::SendEvent() +{ + MyPlotEvent event(MY_PLOT_CLICKED, GetId(), wxPoint(...)); + event.SetEventObject(this); + ProcessWindowEvent(event); +} +@endcode + + + +@section overview_events_misc Miscellaneous Notes + +@subsection overview_events_virtual Event Handlers vs Virtual Methods + +It may be noted that wxWidgets' event processing system implements something +close to virtual methods in normal C++ in spirit: both of these mechanisms +allow you to alter the behaviour of the base class by defining the event handling +functions in the derived classes. + +There is however an important difference between the two mechanisms when you +want to invoke the default behaviour, as implemented by the base class, from a +derived class handler. With the virtual functions, you need to call the base +class function directly and you can do it either in the beginning of the +derived class handler function (to post-process the event) or at its end (to +pre-process the event). With the event handlers, you only have the option of +pre-processing the events and in order to still let the default behaviour +happen you must call wxEvent::Skip() and @em not call the base class event +handler directly. In fact, the event handler probably doesn't even exist in the +base class as the default behaviour is often implemented in platform-specific +code by the underlying toolkit or OS itself. But even if it does exist at +wxWidgets level, it should never be called directly as the event handlers are +not part of wxWidgets API and should never be called directly. + + + +@subsection overview_events_prog User Generated Events vs Programmatically Generated Events While generically wxEvents can be generated both by user -actions (e.g. resize of a wxWindow) and by calls to functions -(e.g. wxWindow::SetSize), wxWidgets controls normally send wxCommandEvent-derived +actions (e.g., resize of a wxWindow) and by calls to functions +(e.g., wxWindow::SetSize), wxWidgets controls normally send wxCommandEvent-derived events only for the user-generated events. The only @b exceptions to this rule are: @li wxNotebook::AddPage: No event-free alternatives @@ -251,7 +776,9 @@ equivalents. -@section overview_eventhandling_pluggable Pluggable event handlers +@subsection overview_events_pluggable Pluggable Event Handlers + +TODO: Probably deprecated, Bind() provides a better way to do this 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, @@ -283,112 +810,35 @@ range of events independently from the other handlers. -@section overview_eventhandling_winid Window identifiers +@subsection overview_events_winid Window Identifiers 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 +across your entire application as long they are unique within the particular context you're interested in, such as a frame and its children. You -may use the @c wxID_OK identifier, for example, on any number of dialogs so -long as you don't have several within the same dialog. +may use the @c wxID_OK identifier, for example, on any number of dialogs +as long as you don't have several within the same dialog. If you pass @c 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 +events from the control being created or because you process the events from all controls in one place (in which case you should specify @c wxID_ANY -in the event table or wxEvtHandler::Connect call -as well. The automatically generated identifiers are always negative and so +in the event table or wxEvtHandler::Bind 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. -See @ref page_stdevtid for the list of standard identifiers availabel. +See @ref page_stdevtid for the list of standard identifiers available. 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. -Finally, you can allocate identifiers dynamically using wxNewId() function to. +Finally, you can allocate identifiers dynamically using wxNewId() function too. If you use wxNewId() consistently in your application, you can be sure that -the your identifiers don't conflict accidentally. - - -@section overview_eventhandling_custom Custom event summary - -@subsection overview_eventhandling_custom_general General approach - -Since version 2.2.x of wxWidgets, each event type is identified by ID which -is given to the event type @e at runtime which makes it possible to add -new event types to the library or application without risking ID clashes -(two different event types mistakingly getting the same event ID). This -event type ID is stored in a struct of type @b const wxEventType. - -In order to define a new event type, there are principally two choices. -One is to define a entirely new event class (typically deriving from -wxEvent or wxCommandEvent. - -The other is to use the existing event classes and give them an new event -type. You'll have to define and declare a new event type using either way, -and this is done using the following macros: - -@code -// in the header of the source file -BEGIN_DECLARE_EVENT_TYPES() -DECLARE_EVENT_TYPE(name, value) -END_DECLARE_EVENT_TYPES() - -// in the implementation -DEFINE_EVENT_TYPE(name) -@endcode +your identifiers don't conflict accidentally. -You can ignore the @e value parameter of the DECLARE_EVENT_TYPE macro -since it is used only for backwards compatibility with wxWidgets 2.0.x based -applications where you have to give the event type ID an explicit value. -See also the @ref page_samples_event for an example of code -defining and working with the custom event types. - -@subsection overview_eventhandling_custom_existing Using existing event classes - -If you just want to use a wxCommandEvent with -a new event type, you can then use one of the generic event table macros -listed below, without having to define a new macro yourself. This also -has the advantage that you won't have to define a new wxEvent::Clone() -method for posting events between threads etc. This could look like this -in your code: - -@code -DECLARE_EVENT_TYPE(wxEVT_MY_EVENT, -1) -DEFINE_EVENT_TYPE(wxEVT_MY_EVENT) - -// user code intercepting the event - -BEGIN_EVENT_TABLE(MyFrame, wxFrame) -EVT_MENU (wxID_EXIT, MyFrame::OnExit) -// .... -EVT_COMMAND (ID_MY_WINDOW, wxEVT_MY_EVENT, MyFrame::OnMyEvent) -END_EVENT_TABLE() - -void MyFrame::OnMyEvent( wxCommandEvent ) -{ - // do something - wxString text = event.GetText(); -} - - -// user code sending the event - -void MyWindow::SendEvent() -{ - wxCommandEvent event( wxEVT_MY_EVENT, GetId() ); - event.SetEventObject( this ); - // Give it some contents - event.SetText( wxT("Hallo") ); - // Send it - GetEventHandler()->ProcessEvent( event ); -} -@endcode - - -@subsection overview_eventhandling_custom_generic Generic event table macros +@subsection overview_events_custom_generic Generic Event Table Macros @beginTable @row2col{EVT_CUSTOM(event\, id\, func), @@ -412,80 +862,11 @@ void MyWindow::SendEvent() @endTable -@subsection overview_eventhandling_custom_ownclass Defining your own event class - -Under certain circumstances, it will be required to define your own event -class e.g. for sending more complex data from one place to another. Apart -from defining your event class, you will also need to define your own -event table macro (which is quite long). Watch out to put in enough -casts to the inherited event function. Here is an example: - -@code -// code defining event -class wxPlotEvent: public wxNotifyEvent -{ -public: - wxPlotEvent( wxEventType commandType = wxEVT_NULL, int id = 0 ); - - // accessors - wxPlotCurve *GetCurve() - { return m_curve; } - - // required for sending with wxPostEvent() - virtual wxEvent *Clone() const; - -private: - wxPlotCurve *m_curve; -}; - -DECLARE_EVENT_TYPE( wxEVT_PLOT_ACTION, -1 ) - -typedef void (wxEvtHandler::*wxPlotEventFunction)(wxPlotEvent&); - -#define EVT_PLOT(id, fn) \ - DECLARE_EVENT_TABLE_ENTRY( wxEVT_PLOT_ACTION, id, -1, \ - (wxObjectEventFunction) (wxEventFunction) (wxCommandEventFunction) (wxNotifyEventFunction) \ - wxStaticCastEvent( wxPlotEventFunction, &fn ), (wxObject *) NULL ), - - -// code implementing the event type and the event class - -DEFINE_EVENT_TYPE( wxEVT_PLOT_ACTION ) - -wxPlotEvent::wxPlotEvent( ... - - -// user code intercepting the event - -BEGIN_EVENT_TABLE(MyFrame, wxFrame) -EVT_PLOT (ID_MY_WINDOW, MyFrame::OnPlot) -END_EVENT_TABLE() - -void MyFrame::OnPlot( wxPlotEvent &event ) -{ - wxPlotCurve *curve = event.GetCurve(); -} - - -// user code sending the event - -void MyWindow::SendEvent() -{ - wxPlotEvent event( wxEVT_PLOT_ACTION, GetId() ); - event.SetEventObject( this ); - event.SetCurve( m_curve ); - GetEventHandler()->ProcessEvent( event ); -} -@endcode - - - - -@section overview_eventhandling_macros Event macros summary +@subsection overview_events_list List of wxWidgets Events For the full list of event classes, please see the -@ref page_class_cat_events page. +@ref group_class_events "event classes group page". -*/ +*/