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another batch of topic overviews reviewing (letters e,f)

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git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@52022 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
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Francesco Montorsi
2008-02-24 00:47:29 +00:00
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docs/doxygen/overviews/eventhandling.h
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@@ -1,5 +1,5 @@
/////////////////////////////////////////////////////////////////////////////
// Name: eventhandling
// Name: eventhandling.h
// Purpose: topic overview
// Author: wxWidgets team
// RCS-ID: $Id$
@@ -8,28 +8,34 @@
/*!
@page eventhandling_overview Event handling overview
@page overview_eventhandling Event handling overview
Classes: #wxEvtHandler, #wxWindow, #wxEvent
#Introduction
@ref eventprocessing_overview
@ref progevent_overview
@ref pluggablehandlers_overview
@ref windowids_overview
@ref eventmacros_overview
@ref customevents_overview
@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_macros -->
@li @ref overview_eventhandling_pluggable
@li @ref overview_eventhandling_winid
@section eventintroduction Introduction
<hr>
@section overview_eventhandling_introduction Introduction
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.
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.
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.
@code
@@ -44,24 +50,25 @@
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,
#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 events from
#wxTreeCtrl windows.
#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
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:
@@ -85,30 +92,36 @@
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 wxEvtHandler::Connect to
connect the events to the handlers dynamically, during run-time. See the
@ref sampleevent_overview for an example of doing it.
@section eventprocessing How events are processed
@section overview_eventhandling_processing How events are processed
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.
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.
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.
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 #Skip.
In practice, this would look like this if the derived text control only
accepts 'a' to 'z' and 'A' to 'Z':
@@ -133,33 +146,31 @@
}
@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.
If the object is disabled (via a call to wxEvtHandler::SetEvtHandlerEnabled)
the function skips to step (6).
If the object is a wxWindow, @b ProcessEvent is recursively called on the window's
#wxValidator. If this returns @true, the function exits.
@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.
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.
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.
Finally, @b ProcessEvent is called on the wxApp object.
@b Pay close attention to Step 5. People often overlook or get
<b>Pay close attention to Step 5</b>. 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
(@ref eventshouldpropagate_overview)
(see @ref overview_eventhandling_propagate)
(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 #event.Skip().
doesn't call @c event.Skip().
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
@@ -172,228 +183,44 @@
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)
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.
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,
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:
#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
#wxSetCursorEvent
Used for special cursor processing based on current mouse position
#wxSizeEvent
A size event
#wxScrollWinEvent
A scroll event sent by a scrolled window (not a scroll bar)
#wxSysColourChangedEvent
A system colour change event
@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
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
@@ -402,126 +229,44 @@
all events (or any selection of them) to the parent window.
@section progevent Events generated by the user vs programmatically generated events
@section overview_eventhandling_prog Events generated by the user 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 events only for
the user-generated events. The only @b exceptions to this rule are:
(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
@li wxNotebook::AdvanceSelection: No event-free alternatives
@li wxNotebook::DeletePage: No event-free alternatives
@li wxNotebook::SetSelection: Use wxNotebook::ChangeSelection instead, as
wxNotebook::SetSelection is deprecated
@li wxTreeCtrl::Delete: No event-free alternatives
@li wxTreeCtrl::DeleteAllItems: No event-free alternatives
@li wxTreeCtrl::EditLabel: No event-free alternatives
@li All #wxTextCtrl methods
wxTextCtrl::ChangeValue can be used instead of wxTextCtrl::SetValue but the other
functions, such as #Replace or #WriteText don't have event-free equivalents.
wxNotebook::AddPage
No event-free alternatives
wxNotebook::AdvanceSelection
No event-free alternatives
wxNotebook::DeletePage
No event-free alternatives
wxNotebook::SetSelection
Use wxNotebook::ChangeSelection instead, as wxNotebook::SetSelection is deprecated
wxTreeCtrl::Delete
No event-free alternatives
wxTreeCtrl::DeleteAllItems
No event-free alternatives
wxTreeCtrl::EditLabel
No event-free alternatives
All #wxTextCtrl methods
wxTextCtrl::ChangeValue can be used instead
of wxTextCtrl::SetValue but the other functions,
such as #Replace or #WriteText
don't have event-free equivalents
@section pluggablehandlers Pluggable event handlers
@section overview_eventhandling_pluggable Pluggable event handlers
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
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 instances of the same event handler class (but different
objects as the same event handler object shouldn't be used more than once) to
handle events from instances of different widget classes. If you ever have to call a window's event handler
handle events from instances of different widget 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
@@ -536,7 +281,9 @@
to form a chain of event handlers, where each handler processes a different
range of events independently from the other handlers.
@section windowids Window identifiers
@section overview_eventhandling_winid Window identifiers
Window identifiers are integers, and are used to
uniquely determine window identity in the event system (though you can use it
@@ -545,6 +292,7 @@
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.
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
@@ -554,6 +302,7 @@
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.
@@ -624,7 +373,14 @@
@endcode
@section eventmacros Event macros summary
<!--
NOTE: this list is incomplete and it's a trouble to maintain it!
we must find an automatic way to generate it
@section overview_eventhandling_macros Event macros summary
@b Macros listed by event class
The documentation for specific event macros is organised by event class. Please refer
@@ -875,21 +631,24 @@
toolbars and controls.
-->
@section overview_eventhandling_custom Custom event summary
@section customevents Custom event summary
@subsection overview_eventhandling_custom_general General approach
@b 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:
@@ -909,7 +668,10 @@
applications where you have to give the event type ID an explicit value.
See also the @ref sampleevent_overview for an example of code
defining and working with the custom event types.
@b Using existing event classes
@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
@@ -919,7 +681,6 @@
@code
DECLARE_EVENT_TYPE(wxEVT_MY_EVENT, -1)
DEFINE_EVENT_TYPE(wxEVT_MY_EVENT)
// user code intercepting the event
@@ -951,88 +712,32 @@
@endcode
@b Generic event table macros
@subsection overview_eventhandling_custom_generic Generic event table macros
@beginTable
@row2col{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.}
@row2col{EVT_CUSTOM_RANGE(event\, id1\, id2\, func),
The same as EVT_CUSTOM, but responds to a range of window identifiers.}
@row2col{EVT_COMMAND(id\, event\, func),
The same as EVT_CUSTOM, but expects a member function with a
wxCommandEvent argument.}
@row2col{EVT_COMMAND_RANGE(id1\, id2\, event\, func),
The same as EVT_CUSTOM_RANGE, but
expects a member function with a wxCommandEvent argument.}
@row2col{EVT_NOTIFY(event\, id\, func),
The same as EVT_CUSTOM, but
expects a member function with a wxNotifyEvent argument.}
@row2col{EVT_NOTIFY_RANGE(event\, id1\, id2\, func),
The same as EVT_CUSTOM_RANGE, but
expects a member function with a wxNotifyEvent argument.}
@endTable
@subsection overview_eventhandling_custom_ownclass Defining your own event class
@b 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.
@b EVT_CUSTOM_RANGE(event, id1, id2, func)
The same as EVT_CUSTOM,
but responds to a range of window identifiers.
@b EVT_COMMAND(id, event, func)
The same as EVT_CUSTOM, but
expects a member function with a wxCommandEvent argument.
@b EVT_COMMAND_RANGE(id1, id2, event, func)
The same as EVT_CUSTOM_RANGE, but
expects a member function with a wxCommandEvent argument.
@b EVT_NOTIFY(event, id, func)
The same as EVT_CUSTOM, but
expects a member function with a wxNotifyEvent argument.
@b EVT_NOTIFY_RANGE(event, id1, id2, func)
The same as EVT_CUSTOM_RANGE, but
expects a member function with a wxNotifyEvent argument.
@b 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
@@ -1098,6 +803,5 @@
}
@endcode
*/
*/