This category is for any event used to send notifications from the
secondary threads to the main one or in general for notifications among
different threads (which may or may not be user-generated).
+ See e.g. wxThreadEvent.
*/
wxEVT_CATEGORY_THREAD = 16,
@library{wxbase}
@category{events}
- @see @ref overview_events_processing
+ @see @ref overview_events_processing, wxEventBlocker, wxEventLoopBase
*/
class wxEvtHandler : public wxObject
{
fields of this object are used by it, notably any wxString members of
the event object must not be shallow copies of another wxString object
as this would result in them still using the same string buffer behind
- the scenes. For example
+ the scenes. For example:
@code
void FunctionInAWorkerThread(const wxString& str)
{
}
@endcode
+ Note that you can use wxThreadEvent instead of wxCommandEvent
+ to avoid this problem:
+ @code
+ void FunctionInAWorkerThread(const wxString& str)
+ {
+ wxThreadEvent evt;
+ evt->SetString(str);
+
+ // wxThreadEvent::Clone() makes sure that the internal wxString
+ // member is not shared by other wxString instances:
+ wxTheApp->QueueEvent( evt.Clone() );
+ }
+ @endcode
+
Finally notice that this method automatically wakes up the event loop
if it is currently idle by calling ::wxWakeUpIdle() so there is no need
to do it manually when using it.
(such as a new control) where you define new event types, as opposed to
allowing the user to override virtual functions.
- An instance where you might actually override the ProcessEvent() function is where
- you want to direct event processing to event handlers not normally noticed by
- wxWidgets. For example, in the document/view architecture, documents and views
- are potential event handlers. When an event reaches a frame, ProcessEvent() will
- need to be called on the associated document and view in case event handler functions
- are associated with these objects. The property classes library (wxProperty) also
- overrides ProcessEvent() for similar reasons.
+ Notice that you don't usually need to override ProcessEvent() to
+ customize the event handling, overriding the specially provided
+ TryBefore() and TryAfter() functions is usually enough. For example,
+ wxMDIParentFrame may override TryBefore() to ensure that the menu
+ events are processed in the active child frame before being processed
+ in the parent frame itself.
The normal order of event table searching is as follows:
+ -# wxApp::FilterEvent() is called. If it returns anything but @c -1
+ (default) the processing stops here.
-# If the object is disabled (via a call to wxEvtHandler::SetEvtHandlerEnabled)
- the function skips to step (6).
- -# If the object is a wxWindow, ProcessEvent() is recursively called on the
- window's wxValidator. If this returns @true, the function exits.
- -# 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.
+ the function skips to step (7).
+ -# TryBefore() is called (this is where wxValidator are taken into
+ account for wxWindow objects). If this returns @true, the function exits.
+ -# Dynamic event table of the handlers connected using Connect() is
+ searched. If a handler is found, it is executed and the function
+ returns @true unless the handler used wxEvent::Skip() to indicate
+ that it didn't handle the event in which case the search continues.
+ -# Static events table of the handlers connected using event table
+ macros is searched for this event handler. If this fails, the base
+ class event table table is tried, and so on until no more tables
+ exist or an appropriate function was found. If a handler is found,
+ the same logic as in the previous step applies.
-# The search is applied down the entire chain of event handlers (usually the
chain has a length of one). This chain can be formed using wxEvtHandler::SetNextHandler():
@image html overview_events_chain.png
Note that in the case of wxWindow you can build a stack of event handlers
(see wxWindow::PushEventHandler() for more info).
If any of the handlers of the chain return @true, the function exits.
- -# If the object is a wxWindow and the event is a wxCommandEvent, ProcessEvent()
- is recursively applied to the parent window's event handler.
- If this returns @true, the function exits.
- -# Finally, ProcessEvent() is called on the wxApp object.
+ -# TryAfter() is called: for the wxWindow object this may propagate the
+ event to the window parent (recursively). If the event is still not
+ processed, ProcessEvent() on wxTheApp object is called as the last
+ step.
+
+ Notice that steps (2)-(6) are performed in ProcessEventHere() which is
+ called by this function.
@param event
Event to process.
-
- @return @true if a suitable event handler function was found and
- executed, and the function did not call wxEvent::Skip.
+ @return
+ @true if a suitable event handler function was found and executed,
+ and the function did not call wxEvent::Skip.
@see SearchEventTable()
*/
virtual bool ProcessEvent(wxEvent& event);
+ /**
+ Try to process the event in this event handler.
+
+ This method is called from ProcessEvent(), please see the detailed
+ description of the event processing logic there.
+
+ It is @em not virtual and so may not be overridden but it does call
+ virtual TryBefore() which may be overridden.
+
+ @param event
+ Event to process.
+ @return
+ @true if this object itself defines a handler for this event and
+ the handler didn't skip the event.
+ */
+ bool ProcessEventHere(wxEvent& event);
+
/**
Processes an event by calling ProcessEvent() and handles any exceptions
that occur in the process.
@see wxWindow::HandleWindowEvent
*/
bool SafelyProcessEvent(wxEvent& event);
+
+ /**
+ Processes the pending events previously queued using QueueEvent() or
+ AddPendingEvent(); you must call this function only if you are sure
+ there are pending events for this handler, otherwise a @c wxCHECK
+ will fail.
+
+ The real processing still happens in ProcessEvent() which is called by this
+ function.
+
+ Note that this function needs a valid application object (see
+ wxAppConsole::GetInstance()) because wxApp holds the list of the event
+ handlers with pending events and this function manipulates that list.
+ */
+ void ProcessPendingEvents();
+ /**
+ Deletes all events queued on this event handler using QueueEvent() or
+ AddPendingEvent().
+
+ Use with care because the events which are deleted are (obviously) not
+ processed and this may have unwanted consequences (e.g. user actions events
+ will be lost).
+ */
+ void DeletePendingEvents();
+
/**
Searches the event table, executing an event handler function if an appropriate
one is found.
If a suitable function is called but calls wxEvent::Skip, this
function will fail, and searching will continue.
+
+ @todo this function in the header is listed as an "implementation only" function;
+ are we sure we want to document it?
@see ProcessEvent()
*/
bool IsUnlinked() const;
//@}
+
+protected:
+ /**
+ Method called by ProcessEvent() before examining this object event
+ tables.
+
+ This method can be overridden to hook into the event processing logic
+ as early as possible. You should usually call the base class version
+ when overriding this method, even if wxEvtHandler itself does nothing
+ here, some derived classes do use this method, e.g. wxWindow implements
+ support for wxValidator in it.
+
+ Example:
+ @code
+ class MyClass : public BaseClass // inheriting from wxEvtHandler
+ {
+ ...
+ protected:
+ virtual bool TryBefore(wxEvent& event)
+ {
+ if ( MyPreProcess(event) )
+ return true;
+
+ return BaseClass::TryBefore(event);
+ }
+ };
+ @endcode
+
+ @see ProcessEvent(), ProcessEventHere()
+ */
+ virtual bool TryBefore(wxEvent& event);
+
+ /**
+ Method called by ProcessEvent() as last resort.
+
+ This method can be overridden to implement post-processing for the
+ events which were not processed anywhere else.
+
+ The base class version handles forwarding the unprocessed events to
+ wxApp at wxEvtHandler level and propagating them upwards the window
+ child-parent chain at wxWindow level and so should usually be called
+ when overriding this method:
+ @code
+ class MyClass : public BaseClass // inheriting from wxEvtHandler
+ {
+ ...
+ protected:
+ virtual bool TryAfter(wxEvent& event)
+ {
+ if ( BaseClass::TryAfter(event) )
+ return true;
+
+ return MyPostProcess(event);
+ }
+ };
+ @endcode
+
+ @see ProcessEvent(), ProcessEventHere()
+ */
+ virtual bool TryAfter(wxEvent& event);
};
(unless the @c wxEVT_CATEGORY_THREAD is specified - which is never in wx code).
@library{wxcore}
- @category{events}
+ @category{events,threading}
@see @ref overview_thread, wxEventLoopBase::YieldFor
*/
*/
#define wxEVENT_HANDLER_CAST(functype, func) (&func)
-//@{
/**
- These macros are used to define event table macros for handling custom
+ This macro is used to define event table macros for handling custom
events.
Example of use:
The event type to handle.
@param id
The identifier of events to handle.
- @param id1
- The first identifier of the range.
- @param id2
- The second identifier of the range.
@param fn
The event handler method.
*/
-#define wx__DECLARE_EVT2(evt, id1, id2, fn) \
- DECLARE_EVENT_TABLE_ENTRY(evt, id1, id2, fn, NULL),
#define wx__DECLARE_EVT1(evt, id, fn) \
wx__DECLARE_EVT2(evt, id, wxID_ANY, fn)
+
+/**
+ Generalized version of the wx__DECLARE_EVT1() macro taking a range of
+ IDs instead of a single one.
+ Argument @a id1 is the first identifier of the range, @a id2 is the
+ second identifier of the range.
+*/
+#define wx__DECLARE_EVT2(evt, id1, id2, fn) \
+ DECLARE_EVENT_TABLE_ENTRY(evt, id1, id2, fn, NULL),
+
+/**
+ Simplified version of the wx__DECLARE_EVT1() macro, to be used when the
+ event type must be handled regardless of the ID associated with the
+ specific event instances.
+*/
#define wx__DECLARE_EVT0(evt, fn) \
wx__DECLARE_EVT1(evt, wxID_ANY, fn)
-//@}
/**
projects / wxWidgets.git / blobdiff