1 \section{\class{wxApp
}}\label{wxapp
}
3 The
{\bf wxApp
} class represents the application itself. It is used
6 \begin{itemize
}\itemsep=
0pt
7 \item set and get application-wide properties;
8 \item implement the windowing system message or event loop;
9 \item initiate application processing via
\helpref{wxApp::OnInit
}{wxapponinit
};
10 \item allow default processing of events not handled by other
11 objects in the application.
14 You should use the macro IMPLEMENT
\_APP(appClass) in your application implementation
15 file to tell wxWidgets how to create an instance of your application class.
17 Use DECLARE
\_APP(appClass) in a header file if you want the wxGetApp function (which returns
18 a reference to your application object) to be visible to other files.
20 \wxheading{Derived from
}
22 \helpref{wxEvtHandler
}{wxevthandler
}\\
23 \helpref{wxObject
}{wxobject
}
25 \wxheading{Include files
}
31 \helpref{wxApp overview
}{wxappoverview
}
33 \latexignore{\rtfignore{\wxheading{Members
}}}
36 \membersection{wxApp::wxApp
}\label{wxappctor
}
38 \func{void
}{wxApp
}{\void}
40 Constructor. Called implicitly with a definition of a wxApp object.
43 \membersection{wxApp::
\destruct{wxApp
}}\label{wxappdtor
}
45 \func{void
}{\destruct{wxApp
}}{\void}
47 Destructor. Will be called implicitly on program exit if the wxApp
48 object is created on the stack.
51 \membersection{wxApp::argc
}\label{wxappargc
}
55 Number of command line arguments (after environment-specific processing).
58 \membersection{wxApp::argv
}\label{wxappargv
}
60 \member{char **
}{argv
}
62 Command line arguments (after environment-specific processing).
65 \membersection{wxApp::CreateLogTarget
}\label{wxappcreatelogtarget
}
67 \func{virtual wxLog*
}{CreateLogTarget
}{\void}
69 Creates a wxLog class for the application to use for logging errors. The default
70 implementation returns a new wxLogGui class.
74 \helpref{wxLog
}{wxlog
}
77 \membersection{wxApp::Dispatch
}\label{wxappdispatch
}
79 \func{virtual void
}{Dispatch
}{\void}
81 Dispatches the next event in the windowing system event queue.
83 This can be used for programming event loops, e.g.
92 \helpref{wxApp::Pending
}{wxapppending
}
95 \membersection{wxApp::FilterEvent
}\label{wxappfilterevent
}
97 \func{int
}{FilterEvent
}{\param{wxEvent\&
}{event
}}
99 This function is called before processing any event and allows the application
100 to preempt the processing of some events. If this method returns $-
1$ the event
101 is processed normally, otherwise either
{\tt true
} or
{\tt false
} should be
102 returned and the event processing stops immediately considering that the event
103 had been already processed (for the former return value) or that it is not
104 going to be processed at all (for the latter one).
107 \membersection{wxApp::ExitMainLoop
}\label{wxappexitmainloop
}
109 \func{virtual void
}{ExitMainLoop
}{\void}
111 Call this to explicitly exit the main message (event) loop.
112 You should normally exit the main loop (and the application) by deleting
116 \membersection{wxApp::GetAppName
}\label{wxappgetappname
}
118 \constfunc{wxString
}{GetAppName
}{\void}
120 Returns the application name.
124 wxWidgets sets this to a reasonable default before
125 calling
\helpref{wxApp::OnInit
}{wxapponinit
}, but the application can reset it at will.
128 \membersection{wxApp::GetAuto3D
}\label{wxappgetauto3d
}
130 \constfunc{bool
}{GetAuto3D
}{\void}
132 Returns true if
3D control mode is on, false otherwise.
136 \helpref{wxApp::SetAuto3D
}{wxappsetauto3d
}
139 \membersection{wxApp::GetClassName
}\label{wxappgetclassname
}
141 \constfunc{wxString
}{GetClassName
}{\void}
143 Gets the class name of the application. The class name may be used in a platform specific
144 manner to refer to the application.
148 \helpref{wxApp::SetClassName
}{wxappsetclassname
}
151 \membersection{wxApp::GetExitOnFrameDelete
}\label{wxappgetexitonframedelete
}
153 \constfunc{bool
}{GetExitOnFrameDelete
}{\void}
155 Returns true if the application will exit when the top-level window is deleted, false
160 \helpref{wxApp::SetExitOnFrameDelete
}{wxappsetexitonframedelete
},\\
161 \helpref{wxApp shutdown overview
}{wxappshutdownoverview
}
164 \membersection{wxApp::GetTopWindow
}\label{wxappgettopwindow
}
166 \constfunc{virtual wxWindow *
}{GetTopWindow
}{\void}
168 Returns a pointer to the top window.
172 If the top window hasn't been set using
\helpref{wxApp::SetTopWindow
}{wxappsettopwindow
}, this
173 function will find the first top-level window (frame or dialog) and return that.
177 \helpref{SetTopWindow
}{wxappsettopwindow
}
180 \membersection{wxApp::GetUseBestVisual
}\label{wxappgetusebestvisual
}
182 \constfunc{bool
}{GetUseBestVisual
}{\void}
184 Returns true if the application will use the best visual on systems that support
185 different visuals, false otherwise.
189 \helpref{SetUseBestVisual
}{wxappsetusebestvisual
}
192 \membersection{wxApp::GetVendorName
}\label{wxappgetvendorname
}
194 \constfunc{wxString
}{GetVendorName
}{\void}
196 Returns the application's vendor name.
199 \membersection{wxApp::IsActive
}\label{wxappisactive
}
201 \constfunc{bool
}{IsActive
}{\void}
203 Returns
\true if the application is active, i.e. if one of its windows is
204 currently in the foreground. If this function returns
\false and you need to
205 attract users attention to the application, you may use
206 \helpref{wxTopLevelWindow::RequestUserAttention
}{wxtoplevelwindowrequestuserattention
}
210 \membersection{wxApp::IsMainLoopRunning
}\label{wxappismainlooprunning
}
212 \constfunc{bool
}{IsMainLoopRunning
}{\void}
214 Returns
\true if the main event loop is currently running, i.e. if the
215 application is inside
\helpref{OnRun
}{wxapponrun
}.
217 This can be useful to test whether the events can be dispatched. For example,
218 if this function returns
\false, non-blocking sockets cannot be used because
219 the events from them would never be processed.
222 \membersection{wxApp::MainLoop
}\label{wxappmainloop
}
224 \func{virtual int
}{MainLoop
}{\void}
226 Called by wxWidgets on creation of the application. Override this if you wish
227 to provide your own (environment-dependent) main loop.
229 \wxheading{Return value
}
231 Returns
0 under X, and the wParam of the WM
\_QUIT message under Windows.
233 %% VZ: OnXXX() functions should *not* be documented
235 %%\membersection{wxApp::OnActivate}\label{wxapponactivate}
237 %%\func{void}{OnActivate}{\param{wxActivateEvent\& }{event}}
239 %%Provide this member function to know whether the application is being
240 %%activated or deactivated (Windows only).
242 %%\wxheading{See also}
244 %%\helpref{wxWindow::OnActivate}{wxwindowonactivate}, \helpref{wxActivateEvent}{wxactivateevent}
246 %%\membersection{wxApp::OnCharHook}\label{wxapponcharhook}
248 %%\func{void}{OnCharHook}{\param{wxKeyEvent\&}{ event}}
250 %%This event handler function is called (under Windows only) to allow the window to intercept keyboard events
251 %%before they are processed by child windows.
253 %%\wxheading{Parameters}
255 %%\docparam{event}{The keypress event.}
257 %%\wxheading{Remarks}
259 %%Use the wxEVT\_CHAR\_HOOK macro in your event table.
261 %%If you use this member, you can selectively consume keypress events by calling\rtfsp
262 %%\helpref{wxEvent::Skip}{wxeventskip} for characters the application is not interested in.
264 %%\wxheading{See also}
266 %%\helpref{wxKeyEvent}{wxkeyevent}, \helpref{wxWindow::OnChar}{wxwindowonchar},\rtfsp
267 %%\helpref{wxWindow::OnCharHook}{wxwindowoncharhook}, \helpref{wxDialog::OnCharHook}{wxdialogoncharhook}
270 \membersection{wxApp::OnAssert
}\label{wxapponassert
}
272 \func{void
}{OnAssert
}{\param{const wxChar
}{*file
},
\param{int
}{line
},
\param{const wxChar
}{*cond
},
\param{const wxChar
}{*msg
}}
274 This function is called when an assert failure occurs, i.e. the condition
275 specified in
\helpref{wxASSERT
}{wxassert
} macro evaluated to
{\tt false
}.
276 It is only called in debug mode (when
{\tt \_\_WXDEBUG\_\_} is defined) as
277 asserts are not left in the release code at all.
279 The base class version show the default assert failure dialog box proposing to
280 the user to stop the program, continue or ignore all subsequent asserts.
282 \wxheading{Parameters
}
284 \docparam{file
}{the name of the source file where the assert occured
}
286 \docparam{line
}{the line number in this file where the assert occured
}
288 \docparam{cond
}{the condition of the failed assert in string form
}
290 \docparam{msg
}{the message specified as argument to
291 \helpref{wxASSERT
\_MSG}{wxassertmsg
} or
\helpref{wxFAIL
\_MSG}{wxfailmsg
}, will
292 be
{\tt NULL
} if just
\helpref{wxASSERT
}{wxassert
} or
\helpref{wxFAIL
}{wxfail
}
296 \membersection{wxApp::OnCmdLineError
}\label{wxapponcmdlineerror
}
298 \func{bool
}{OnCmdLineError
}{\param{wxCmdLineParser\&
}{parser
}}
300 Called when command line parsing fails (i.e. an incorrect command line option
301 was specified by the user). The default behaviour is to show the program usage
302 text and abort the program.
304 Return
{\tt true
} to continue normal execution or
{\tt false
} to return
305 {\tt false
} from
\helpref{OnInit
}{wxapponinit
} thus terminating the program.
309 \helpref{OnInitCmdLine
}{wxapponinitcmdline
}
312 \membersection{wxApp::OnCmdLineHelp
}\label{wxapponcmdlinehelp
}
314 \func{bool
}{OnCmdLineHelp
}{\param{wxCmdLineParser\&
}{parser
}}
316 Called when the help option (
{\tt --help
}) was specified on the command line.
317 The default behaviour is to show the program usage text and abort the program.
319 Return
{\tt true
} to continue normal execution or
{\tt false
} to return
320 {\tt false
} from
\helpref{OnInit
}{wxapponinit
} thus terminating the program.
324 \helpref{OnInitCmdLine
}{wxapponinitcmdline
}
327 \membersection{wxApp::OnCmdLineParsed
}\label{wxapponcmdlineparsed
}
329 \func{bool
}{OnCmdLineParsed
}{\param{wxCmdLineParser\&
}{parser
}}
331 Called after the command line had been successfully parsed. You may override
332 this method to test for the values of the various parameters which could be
333 set from the command line.
335 Don't forget to call the base class version unless you want to suppress
336 processing of the standard command line options.
338 Return
{\tt true
} to continue normal execution or
{\tt false
} to return
339 {\tt false
} from
\helpref{OnInit
}{wxapponinit
} thus terminating the program.
343 \helpref{OnInitCmdLine
}{wxapponinitcmdline
}
346 \membersection{wxApp::OnExceptionInMainLoop
}\label{wxapponexceptioninmainloop
}
348 \func{virtual bool
}{OnExceptionInMainLoop
}{\void}
350 This function is called if an unhandled exception occurs inside the main
351 application event loop. It can return
\true to ignore the exception and to
352 continue running the loop or
\false to exit the loop and terminate the
353 program. In the latter case it can also use C++
\texttt{throw
} keyword to
354 rethrow the current exception.
356 The default behaviour of this function is the latter in all ports except under
357 Windows where a dialog is shown to the user which allows him to choose between
358 the different options. You may override this function in your class to do
359 something more appropriate.
361 Finally note that if the exception is rethrown from here, it can be caught in
362 \helpref{OnUnhandledException
}{wxapponunhandledexception
}.
365 \membersection{wxApp::OnExit
}\label{wxapponexit
}
367 \func{virtual int
}{OnExit
}{\void}
369 Override this member function for any processing which needs to be
370 done as the application is about to exit. OnExit is called after
371 destroying all application windows and controls, but before
372 wxWidgets cleanup. Note that it is not called at all if
373 \helpref{OnInit
}{wxapponinit
} failed.
375 The return value of this function is currently ignored, return the same value
376 as returned by the base class method if you override it.
379 \membersection{wxApp::OnFatalException
}\label{wxapponfatalexception
}
381 \func{void
}{OnFatalException
}{\void}
383 This function may be called if something fatal happens: an unhandled
384 exception under Win32 or a a fatal signal under Unix, for example. However,
385 this will not happen by default: you have to explicitly call
386 \helpref{wxHandleFatalExceptions
}{wxhandlefatalexceptions
} to enable this.
388 Generally speaking, this function should only show a message to the user and
389 return. You may attempt to save unsaved data but this is not guaranteed to
390 work and, in fact, probably won't.
394 \helpref{wxHandleFatalExceptions
}{wxhandlefatalexceptions
}
396 %% VZ: the wxApp event handler are private and should not be documented here!
398 %%\membersection{wxApp::OnIdle}\label{wxapponidle}
400 %%\func{void}{OnIdle}{\param{wxIdleEvent\& }{event}}
402 %%Override this member function for any processing which needs to be done
403 %%when the application is idle. You should call wxApp::OnIdle from your own function,
404 %%since this forwards OnIdle events to windows and also performs garbage collection for
405 %%windows whose destruction has been delayed.
407 %%wxWidgets' strategy for OnIdle processing is as follows. After pending user interface events for an
408 %%application have all been processed, wxWidgets sends an OnIdle event to the application object. wxApp::OnIdle itself
409 %%sends an OnIdle event to each application window, allowing windows to do idle processing such as updating
410 %%their appearance. If either wxApp::OnIdle or a window OnIdle function requested more time, by
411 %%calling \helpref{wxIdleEvent::RequestMore}{wxidleeventrequestmore}, wxWidgets will send another OnIdle
412 %%event to the application object. This will occur in a loop until either a user event is found to be
413 %%pending, or OnIdle requests no more time. Then all pending user events are processed until the system
414 %%goes idle again, when OnIdle is called, and so on.
416 %%\wxheading{See also}
418 %%\helpref{wxWindow::OnIdle}{wxwindowonidle}, \helpref{wxIdleEvent}{wxidleevent},\rtfsp
419 %%\helpref{wxWindow::SendIdleEvents}{wxappsendidleevents}
421 %%\membersection{wxApp::OnEndSession}\label{wxapponendsession}
423 %%\func{void}{OnEndSession}{\param{wxCloseEvent\& }{event}}
425 %%This is an event handler function called when the operating system or GUI session is
426 %%about to close down. The application has a chance to silently save information,
427 %%and can optionally close itself.
429 %%Use the EVT\_END\_SESSION event table macro to handle query end session events.
431 %%The default handler calls \helpref{wxWindow::Close}{wxwindowclose} with a true argument
432 %%(forcing the application to close itself silently).
434 %%\wxheading{Remarks}
436 %%Under X, OnEndSession is called in response to the `die' event.
438 %%Under Windows, OnEndSession is called in response to the WM\_ENDSESSION message.
440 %%\wxheading{See also}
442 %%\helpref{wxWindow::Close}{wxwindowclose},\rtfsp
443 %%\helpref{wxWindow::OnCloseWindow}{wxwindowonclosewindow},\rtfsp
444 %%\helpref{wxCloseEvent}{wxcloseevent},\rtfsp
445 %%\helpref{wxApp::OnQueryEndSession}{wxapponqueryendsession}
448 \membersection{wxApp::OnInit
}\label{wxapponinit
}
450 \func{bool
}{OnInit
}{\void}
452 This must be provided by the application, and will usually create the
453 application's main window, optionally calling
454 \helpref{wxApp::SetTopWindow
}{wxappsettopwindow
}. You may use
455 \helpref{OnExit
}{wxapponexit
} to clean up anything initialized here, provided
456 that the function returns
\true.
458 Notice that if you want to to use the command line processing provided by
459 wxWidgets you have to call the base class version in the derived class
462 Return
\true to continue processing,
\false to exit the application
466 \membersection{wxApp::OnInitCmdLine
}\label{wxapponinitcmdline
}
468 \func{void
}{OnInitCmdLine
}{\param{wxCmdLineParser\&
}{parser
}}
470 Called from
\helpref{OnInit
}{wxapponinit
} and may be used to initialize the
471 parser with the command line options for this application. The base class
472 versions adds support for a few standard options only.
475 \membersection{wxApp::OnQueryEndSession
}\label{wxapponqueryendsession
}
477 \func{void
}{OnQueryEndSession
}{\param{wxCloseEvent\&
}{event
}}
479 This is an event handler function called when the operating system or GUI session is
480 about to close down. Typically, an application will try to save unsaved documents
483 If
\helpref{wxCloseEvent::CanVeto
}{wxcloseeventcanveto
} returns true, the application
484 is allowed to veto the shutdown by calling
\helpref{wxCloseEvent::Veto
}{wxcloseeventveto
}.
485 The application might veto the shutdown after prompting for documents to be saved, and the
486 user has cancelled the save.
488 Use the EVT
\_QUERY\_END\_SESSION event table macro to handle query end session events.
490 You should check whether the application is forcing the deletion of the window
491 using
\helpref{wxCloseEvent::GetForce
}{wxcloseeventgetforce
}. If this is true,
492 destroy the window using
\helpref{wxWindow::Destroy
}{wxwindowdestroy
}.
493 If not, it is up to you whether you respond by destroying the window.
495 The default handler calls
\helpref{wxWindow::Close
}{wxwindowclose
} on the top-level window,
496 and vetoes the shutdown if Close returns false. This will be sufficient for many applications.
500 Under X, OnQueryEndSession is called in response to the `save session' event.
502 Under Windows, OnQueryEndSession is called in response to the WM
\_QUERYENDSESSION message.
506 \helpref{wxWindow::Close
}{wxwindowclose
},
\rtfsp
507 \helpref{wxCloseEvent
}{wxcloseevent
}\rtfsp
510 \membersection{wxApp::OnRun
}\label{wxapponrun
}
512 \func{virtual int
}{OnRun
}{\void}
514 This virtual function is where the execution of a program written in wxWidgets
515 starts. The default implementation just enters the main loop and starts
516 handling the events until it terminates, either because
517 \helpref{ExitMainLoop
}{wxappexitmainloop
} has been explicitly called or because
518 the last frame has been deleted and
519 \helpref{GetExitOnFrameDelete
}{wxappgetexitonframedelete
} flag is
\true (this
522 The return value of this function becomes the exit code of the program, so it
523 should return $
0$ in case of successful termination.
526 \membersection{wxApp::OnUnhandledException
}\label{wxapponunhandledexception
}
528 \func{virtual void
}{OnUnhandledException
}{\void}
530 This function is called when an unhandled C++ exception occurs inside
531 \helpref{OnRun()
}{wxapponrun
} (the exceptions which occur during the program
532 startup and shutdown might not be caught at all).
533 Note that the exception type is lost by now, so if you want to really handle
534 the exception you should override
\helpref{OnRun()
}{wxapponrun
} and put a
535 try/catch clause around the call to the base class version there.
538 \membersection{wxApp::ProcessMessage
}\label{wxappprocessmessage
}
540 \func{bool
}{ProcessMessage
}{\param{WXMSG *
}{msg
}}
542 Windows-only function for processing a message. This function
543 is called from the main message loop, checking for windows that
544 may wish to process it. The function returns true if the message
545 was processed, false otherwise. If you use wxWidgets with another class
546 library with its own message loop, you should make sure that this
547 function is called to allow wxWidgets to receive messages. For example,
548 to allow co-existence with the Microsoft Foundation Classes, override
549 the PreTranslateMessage function:
552 // Provide wxWidgets message loop compatibility
553 BOOL CTheApp::PreTranslateMessage(MSG *msg)
555 if (wxTheApp && wxTheApp->ProcessMessage((WXMSW *)msg))
558 return CWinApp::PreTranslateMessage(msg);
563 \membersection{wxApp::Pending
}\label{wxapppending
}
565 \func{virtual bool
}{Pending
}{\void}
567 Returns true if unprocessed events are in the window system event queue.
571 \helpref{wxApp::Dispatch
}{wxappdispatch
}
574 \membersection{wxApp::SendIdleEvents
}\label{wxappsendidleevents
}
576 \func{bool
}{SendIdleEvents
}{\param{wxWindow*
}{ win
},
\param{wxIdleEvent\&
}{event
}}
578 Sends idle events to a window and its children.
580 Please note that this function is internal to wxWidgets and shouldn't be used
585 These functions poll the top-level windows, and their children, for idle event processing.
586 If true is returned, more OnIdle processing is requested by one or more window.
590 \helpref{wxIdleEvent
}{wxidleevent
}
593 \membersection{wxApp::SetAppName
}\label{wxappsetappname
}
595 \func{void
}{SetAppName
}{\param{const wxString\&
}{name
}}
597 Sets the name of the application. The name may be used in dialogs
598 (for example by the
document/view framework). A default name is set by
603 \helpref{wxApp::GetAppName
}{wxappgetappname
}
606 \membersection{wxApp::SetAuto3D
}\label{wxappsetauto3d
}
608 \func{void
}{SetAuto3D
}{\param{const bool
}{ auto3D
}}
610 Switches automatic
3D controls on or off.
612 \wxheading{Parameters
}
614 \docparam{auto3D
}{If true, all controls will be created with
3D appearances unless
615 overridden for a control or dialog. The default is true
}
619 This has an effect on Windows only.
623 \helpref{wxApp::GetAuto3D
}{wxappgetauto3d
}
626 \membersection{wxApp::SetClassName
}\label{wxappsetclassname
}
628 \func{void
}{SetClassName
}{\param{const wxString\&
}{name
}}
630 Sets the class name of the application. This may be used in a platform specific
631 manner to refer to the application.
635 \helpref{wxApp::GetClassName
}{wxappgetclassname
}
638 \membersection{wxApp::SetExitOnFrameDelete
}\label{wxappsetexitonframedelete
}
640 \func{void
}{SetExitOnFrameDelete
}{\param{bool
}{ flag
}}
642 Allows the programmer to specify whether the application will exit when the
643 top-level frame is deleted.
645 \wxheading{Parameters
}
647 \docparam{flag
}{If true (the default), the application will exit when the top-level frame is
648 deleted. If false, the application will continue to run.
}
652 \helpref{wxApp::GetExitOnFrameDelete
}{wxappgetexitonframedelete
},\\
653 \helpref{wxApp shutdown overview
}{wxappshutdownoverview
}
656 \membersection{wxApp::SetTopWindow
}\label{wxappsettopwindow
}
658 \func{void
}{SetTopWindow
}{\param{wxWindow*
}{window
}}
660 Sets the `top' window. You can call this from within
\helpref{wxApp::OnInit
}{wxapponinit
} to
661 let wxWidgets know which is the main window. You don't have to set the top window;
662 it is only a convenience so that (for example) certain dialogs without parents can use a
663 specific window as the top window. If no top window is specified by the application,
664 wxWidgets just uses the first frame or dialog in its top-level window list, when it
665 needs to use the top window.
667 \wxheading{Parameters
}
669 \docparam{window
}{The new top window.
}
673 \helpref{wxApp::GetTopWindow
}{wxappgettopwindow
},
\helpref{wxApp::OnInit
}{wxapponinit
}
677 \membersection{wxApp::SetVendorName
}\label{wxappsetvendorname
}
679 \func{void
}{SetVendorName
}{\param{const wxString\&
}{name
}}
681 Sets the name of application's vendor. The name will be used
682 in registry access. A default name is set by
687 \helpref{wxApp::GetVendorName
}{wxappgetvendorname
}
690 \membersection{wxApp::SetUseBestVisual
}\label{wxappsetusebestvisual
}
692 \func{void
}{SetUseBestVisual
}{\param{bool
}{ flag
}}
694 Allows the programmer to specify whether the application will use the best visual
695 on systems that support several visual on the same display. This is typically the
696 case under Solaris and IRIX, where the default visual is only
8-bit whereas certain
697 applications are supposed to run in TrueColour mode.
699 Note that this function has to be called in the constructor of the
{\tt wxApp
}
700 instance and won't have any effect when called later on.
702 This function currently only has effect under GTK.
704 \wxheading{Parameters
}
706 \docparam{flag
}{If true, the app will use the best visual.
}
709 \membersection{wxApp::HandleEvent
}\label{wxapphandleevent
}
711 \constfunc{virtual void
}{HandleEvent
}{\param{wxEvtHandler
}{ *handler
},
\param{wxEventFunction
}{ func
},
\param{wxEvent\&
}{event
}}
713 This function simply invokes the given method
\arg{func
} of the specified
714 event handler
\arg{handler
} with the
\arg{event
} as parameter. It exists solely
715 to allow to catch the C++ exceptions which could be thrown by all event
716 handlers in the application in one place: if you want to do this, override this
717 function in your wxApp-derived class and add try/catch clause(s) to it.
720 \membersection{wxApp::Yield
}\label{wxappyield
}
722 \func{bool
}{Yield
}{\param{bool
}{ onlyIfNeeded = false
}}
724 Yields control to pending messages in the windowing system. This can be useful, for example, when a
725 time-consuming process writes to a text window. Without an occasional
726 yield, the text window will not be updated properly, and on systems with
727 cooperative multitasking, such as Windows
3.1 other processes will not respond.
729 Caution should be exercised, however, since yielding may allow the
730 user to perform actions which are not compatible with the current task.
731 Disabling menu items or whole menus during processing can avoid unwanted
732 reentrance of code: see
\helpref{::wxSafeYield
}{wxsafeyield
} for a better
735 Note that Yield() will not flush the message logs. This is intentional as
736 calling Yield() is usually done to quickly update the screen and popping up a
737 message box dialog may be undesirable. If you do wish to flush the log
738 messages immediately (otherwise it will be done during the next idle loop
739 iteration), call
\helpref{wxLog::FlushActive
}{wxlogflushactive
}.
741 Calling Yield() recursively is normally an error and an assert failure is
742 raised in debug build if such situation is detected. However if the the
743 {\it onlyIfNeeded
} parameter is
{\tt true
}, the method will just silently
744 return
{\tt false
} instead.