app.tex

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continue running the loop or \false to exit the loop and terminate the
program. In the latter case it can also use C++ \texttt{throw} keyword to
rethrow the current exception.

The default behaviour of this function is the latter in all ports except under
Windows where a dialog is shown to the user which allows him to choose between
the different options. You may override this function in your class to do
something more appropriate.

Finally note that if the exception is rethrown from here, it can be caught in 
\helpref{OnUnhandledException}{wxapponunhandledexception}.


\membersection{wxApp::OnExit}\label{wxapponexit}

\func{virtual int}{OnExit}{\void}

Override this member function for any processing which needs to be
done as the application is about to exit. OnExit is called after
destroying all application windows and controls, but before
wxWidgets cleanup. Note that it is not called at all if 
\helpref{OnInit}{wxapponinit} failed.

The return value of this function is currently ignored, return the same value
as returned by the base class method if you override it.


\membersection{wxApp::OnFatalException}\label{wxapponfatalexception}

\func{void}{OnFatalException}{\void}

This function may be called if something fatal happens: an unhandled
exception under Win32 or a a fatal signal under Unix, for example. However,
this will not happen by default: you have to explicitly call 
\helpref{wxHandleFatalExceptions}{wxhandlefatalexceptions} to enable this.

Generally speaking, this function should only show a message to the user and
return. You may attempt to save unsaved data but this is not guaranteed to
work and, in fact, probably won't.

\wxheading{See also}

\helpref{wxHandleFatalExceptions}{wxhandlefatalexceptions}

%% VZ: the wxApp event handler are private and should not be documented here!
%%
%%\membersection{wxApp::OnIdle}\label{wxapponidle}
%%
%%\func{void}{OnIdle}{\param{wxIdleEvent\& }{event}}
%%
%%Override this member function for any processing which needs to be done
%%when the application is idle. You should call wxApp::OnIdle from your own function,
%%since this forwards OnIdle events to windows and also performs garbage collection for
%%windows whose destruction has been delayed.
%%
%%wxWidgets' strategy for OnIdle processing is as follows. After pending user interface events for an
%%application have all been processed, wxWidgets sends an OnIdle event to the application object. wxApp::OnIdle itself
%%sends an OnIdle event to each application window, allowing windows to do idle processing such as updating
%%their appearance. If either wxApp::OnIdle or a window OnIdle function requested more time, by
%%calling \helpref{wxIdleEvent::RequestMore}{wxidleeventrequestmore}, wxWidgets will send another OnIdle
%%event to the application object. This will occur in a loop until either a user event is found to be
%%pending, or OnIdle requests no more time. Then all pending user events are processed until the system
%%goes idle again, when OnIdle is called, and so on.
%%
%%\wxheading{See also}
%%
%%\helpref{wxWindow::OnIdle}{wxwindowonidle}, \helpref{wxIdleEvent}{wxidleevent},\rtfsp
%%\helpref{wxWindow::SendIdleEvents}{wxappsendidleevents}
%%
%%\membersection{wxApp::OnEndSession}\label{wxapponendsession}
%%
%%\func{void}{OnEndSession}{\param{wxCloseEvent\& }{event}}
%%
%%This is an event handler function called when the operating system or GUI session is
%%about to close down. The application has a chance to silently save information,
%%and can optionally close itself.
%%
%%Use the EVT\_END\_SESSION event table macro to handle query end session events.
%%
%%The default handler calls \helpref{wxWindow::Close}{wxwindowclose} with a true argument
%%(forcing the application to close itself silently).
%%
%%\wxheading{Remarks}
%%
%%Under X, OnEndSession is called in response to the `die' event.
%%
%%Under Windows, OnEndSession is called in response to the WM\_ENDSESSION message.
%%
%%\wxheading{See also}
%%
%%\helpref{wxWindow::Close}{wxwindowclose},\rtfsp
%%\helpref{wxWindow::OnCloseWindow}{wxwindowonclosewindow},\rtfsp
%%\helpref{wxCloseEvent}{wxcloseevent},\rtfsp


\membersection{wxApp::OnInit}\label{wxapponinit}

\func{bool}{OnInit}{\void}

This must be provided by the application, and will usually create the
application's main window, optionally calling 
\helpref{wxApp::SetTopWindow}{wxappsettopwindow}. You may use 
\helpref{OnExit}{wxapponexit} to clean up anything initialized here, provided
that the function returns \true.

Notice that if you want to to use the command line processing provided by
wxWidgets you have to call the base class version in the derived class
OnInit().

Return \true to continue processing, \false to exit the application
immediately.


\membersection{wxApp::OnInitCmdLine}\label{wxapponinitcmdline}

\func{void}{OnInitCmdLine}{\param{wxCmdLineParser\& }{parser}}

Called from \helpref{OnInit}{wxapponinit} and may be used to initialize the
parser with the command line options for this application. The base class
versions adds support for a few standard options only.

\membersection{wxApp::OnRun}\label{wxapponrun}

\func{virtual int}{OnRun}{\void}

This virtual function is where the execution of a program written in wxWidgets
starts. The default implementation just enters the main loop and starts
handling the events until it terminates, either because 
\helpref{ExitMainLoop}{wxappexitmainloop} has been explicitly called or because
the last frame has been deleted and 
\helpref{GetExitOnFrameDelete}{wxappgetexitonframedelete} flag is \true (this
is the default).

The return value of this function becomes the exit code of the program, so it
should return $0$ in case of successful termination.


\membersection{wxApp::OnUnhandledException}\label{wxapponunhandledexception}

\func{virtual void}{OnUnhandledException}{\void}

This function is called when an unhandled C++ exception occurs inside 
\helpref{OnRun()}{wxapponrun} (the exceptions which occur during the program
startup and shutdown might not be caught at all).
Note that the exception type is lost by now, so if you want to really handle
the exception you should override \helpref{OnRun()}{wxapponrun} and put a
try/catch clause around the call to the base class version there.


\membersection{wxApp::ProcessMessage}\label{wxappprocessmessage}

\func{bool}{ProcessMessage}{\param{WXMSG *}{msg}}

Windows-only function for processing a message. This function
is called from the main message loop, checking for windows that
may wish to process it. The function returns true if the message
was processed, false otherwise. If you use wxWidgets with another class
library with its own message loop, you should make sure that this
function is called to allow wxWidgets to receive messages. For example,
to allow co-existence with the Microsoft Foundation Classes, override
the PreTranslateMessage function:

\begin{verbatim}
// Provide wxWidgets message loop compatibility
BOOL CTheApp::PreTranslateMessage(MSG *msg)
{
  if (wxTheApp && wxTheApp->ProcessMessage((WXMSW *)msg))
    return true;
  else
    return CWinApp::PreTranslateMessage(msg);
}
\end{verbatim}


\membersection{wxApp::Pending}\label{wxapppending}

\func{virtual bool}{Pending}{\void}

Returns true if unprocessed events are in the window system event queue.

\wxheading{See also}

\helpref{wxApp::Dispatch}{wxappdispatch}


\membersection{wxApp::SendIdleEvents}\label{wxappsendidleevents}

\func{bool}{SendIdleEvents}{\param{wxWindow*}{ win}, \param{wxIdleEvent\& }{event}}

Sends idle events to a window and its children.

Please note that this function is internal to wxWidgets and shouldn't be used
by user code.

\wxheading{Remarks}

These functions poll the top-level windows, and their children, for idle event processing.
If true is returned, more OnIdle processing is requested by one or more window.

\wxheading{See also}

\helpref{wxIdleEvent}{wxidleevent}


\membersection{wxApp::SetAppName}\label{wxappsetappname}

\func{void}{SetAppName}{\param{const wxString\& }{name}}

Sets the name of the application. The name may be used in dialogs
(for example by the document/view framework). A default name is set by
wxWidgets.

\wxheading{See also}

\helpref{wxApp::GetAppName}{wxappgetappname}


\membersection{wxApp::SetClassName}\label{wxappsetclassname}

\func{void}{SetClassName}{\param{const wxString\& }{name}}

Sets the class name of the application. This may be used in a platform specific
manner to refer to the application.

\wxheading{See also}

\helpref{wxApp::GetClassName}{wxappgetclassname}


\membersection{wxApp::SetExitOnFrameDelete}\label{wxappsetexitonframedelete}

\func{void}{SetExitOnFrameDelete}{\param{bool}{ flag}}

Allows the programmer to specify whether the application will exit when the
top-level frame is deleted.

\wxheading{Parameters}

\docparam{flag}{If true (the default), the application will exit when the top-level frame is
deleted. If false, the application will continue to run.}

\wxheading{See also}

\helpref{wxApp::GetExitOnFrameDelete}{wxappgetexitonframedelete},\\
\helpref{wxApp shutdown overview}{wxappshutdownoverview}


\membersection{wxApp::SetInstance}\label{wxappsetinstance}

\func{static void}{SetInstance}{\param{wxAppConsole* }{app}}

Allows external code to modify global \texttt{wxTheApp}, but you should really
know what you're doing if you call it.

\wxheading{Parameters}

\docparam{app}{Replacement for the global application object.}

\wxheading{See also}

\helpref{wxApp::GetInstance}{wxappgetinstance}


\membersection{wxApp::SetTopWindow}\label{wxappsettopwindow}

\func{void}{SetTopWindow}{\param{wxWindow* }{window}}

Sets the `top' window. You can call this from within \helpref{wxApp::OnInit}{wxapponinit} to
let wxWidgets know which is the main window. You don't have to set the top window;
it is only a convenience so that (for example) certain dialogs without parents can use a
specific window as the top window. If no top window is specified by the application,
wxWidgets just uses the first frame or dialog in its top-level window list, when it
needs to use the top window.

\wxheading{Parameters}

\docparam{window}{The new top window.}

\wxheading{See also}

\helpref{wxApp::GetTopWindow}{wxappgettopwindow}, \helpref{wxApp::OnInit}{wxapponinit}



\membersection{wxApp::SetVendorName}\label{wxappsetvendorname}

\func{void}{SetVendorName}{\param{const wxString\& }{name}}

Sets the name of application's vendor. The name will be used
in registry access. A default name is set by
wxWidgets.

\wxheading{See also}

\helpref{wxApp::GetVendorName}{wxappgetvendorname}


\membersection{wxApp::SetUseBestVisual}\label{wxappsetusebestvisual}

\func{void}{SetUseBestVisual}{\param{bool}{ flag}}

Allows the programmer to specify whether the application will use the best visual
on systems that support several visual on the same display. This is typically the
case under Solaris and IRIX, where the default visual is only 8-bit whereas certain
applications are supposed to run in TrueColour mode.

Note that this function has to be called in the constructor of the {\tt wxApp} 
instance and won't have any effect when called later on.

This function currently only has effect under GTK.

\wxheading{Parameters}

\docparam{flag}{If true, the app will use the best visual.}


\membersection{wxApp::HandleEvent}\label{wxapphandleevent}

\constfunc{virtual void}{HandleEvent}{\param{wxEvtHandler}{ *handler}, \param{wxEventFunction}{ func}, \param{wxEvent\& }{event}}

This function simply invokes the given method \arg{func} of the specified
event handler \arg{handler} with the \arg{event} as parameter. It exists solely
to allow to catch the C++ exceptions which could be thrown by all event
handlers in the application in one place: if you want to do this, override this
function in your wxApp-derived class and add try/catch clause(s) to it.


\membersection{wxApp::Yield}\label{wxappyield}

\func{bool}{Yield}{\param{bool}{ onlyIfNeeded = false}}

Yields control to pending messages in the windowing system. This can be useful, for example, when a
time-consuming process writes to a text window. Without an occasional
yield, the text window will not be updated properly, and on systems with
cooperative multitasking, such as Windows 3.1 other processes will not respond.

Caution should be exercised, however, since yielding may allow the
user to perform actions which are not compatible with the current task.
Disabling menu items or whole menus during processing can avoid unwanted
reentrance of code: see \helpref{::wxSafeYield}{wxsafeyield} for a better
function.

Note that Yield() will not flush the message logs. This is intentional as
calling Yield() is usually done to quickly update the screen and popping up a
message box dialog may be undesirable. If you do wish to flush the log
messages immediately (otherwise it will be done during the next idle loop
iteration), call \helpref{wxLog::FlushActive}{wxlogflushactive}.

Calling Yield() recursively is normally an error and an assert failure is
raised in debug build if such situation is detected. However if the 
{\it onlyIfNeeded} parameter is {\tt true}, the method will just silently
return {\tt false} instead.